Water supply and water management in Rome



Water supply and management in Rome.

A work in progress (16th-20th Century)

By Paolo Buonora

1. Introduction

This paper stems from an hypothesis: the visible water, flowing in the Tiber river or appearing in the beautiful fountains of Rome, finished for hiding by the time a more complex hydraulic network. This happened not only for physiological reasons (pipes run usually underground), but also for cultural reasons (functional uses are often hidden), and for the urban development of the city (streams were covered and diverted).

Literature written in crucial periods of crisis in water supply or in hydraulics emergencies related to river floods is thought to have influenced also the historical interpretation of these aspects of the city life. In fact, this literature was often produced by erudite men and not by technicians, and had always dealt with the Tiber River. Is it really true that the city could not survive without the mills floating in the river and without restoring ancient aqueducts? Also, about the system created by the popes starting with 16th century, is that only the restoration of an ancient system or another one, different in structure and purposes?

On the contrary, this paper will try to show how the river represented mostly the final discharge of a more complex system of water circulation within the body of the city, and that the center of this system can be placed outside the river. The genesis of this system can be found in the modern age, in the period of more intense demographic growth of the 16th century. Also if the old structures of the ancient Rome had their importance, the characters of the hydraulic system of the modern Rome have a different function, that can be related to a model of water supply common to most part of the cities of Center Italy. Finally, an outline of a hypothesis will be attempted on the evolution of the system during a long period, disregarding the chronological limits of the archive research currently in progress.

2. Ancient aqueducts

It is difficult discuss Roman aqueducts without telling their often-repeated, long story, concerning both their ancient building and their modern restoring. But as it’s just upon this element that I will try to single out the differing aspects between the ancient and the modern system of water supply, it will be necessary to deal thoroughly with the subject. Another reason for this, is that several new studies have appeared in the last ten years, and they present many suggestions that exceed the terms of the problem as had been established by the classical works by Lanciani and Ashby. Anyway, it can be stated that one of the most important examples of emancipation of humanistic disciplines from dependencies with literary sources, is indeed the study of ancient Roman aqueducts. Distinguishing research based upon the mere literary reconstruction from the scientific topographic relief started with Lanciani’s studies and is one of the milestones of archeological science[1]. Also Ashby, understanding the relevance of leveling ruins, worked side by side with the engineers of the Scuola d’Ingegneria dell’Università di Roma: Reina, Corbellini, Ducci[2].

A brief summary of the history of aqueducts: the first Roman aqueduct was the Appio (312 b. C.); it was followed by the first one coming from the Aniene river valley, the Anio later named Vetus (272-269 b. C.), running underground for defense purposes. In 144 b. C., Q. Marcius Rex brought in the city and then up to the Capitolium some springs by the upper Aniene valley, with the Aqua Marcia aqueduct. In 125 b. C. the less important Aqua Tepula arrived, by the Colli Albani, and in 40 b. C. Agrippa, curator aquarum, added the Aqua Julia, restoring also the main conducts. In 19 b. C. Agrippa again joined near springs of Aqua Virgo near Salone in a conduct without raising parts, that turning beside the city hills entered the town by the Flaminia road bringing water in Campo Marzio. In the Empire period, the building of new public baths proceeded along with the building of new aqueducts to bring water to the thermae. After Agrippa’s death the 240 specialized slaves employed in hydraulic works went under the management of the emperor and the State, forming a familia publica that under Claudius the emperor reached 700 units. These workers were anyway employed in the usual management and supporting, while the new buildings were made under contract[3].

Augustus the emperor carried out works of restorations and added new springs, and in 2 a. C. carried the Aqua Alsetina, a bad quality one, to supply a naumachia on the right side of the Tiber. In 52 a. C. Claudius had the two aqueducts built that Caligola had designed in 38 d. C.: the Aqua Claudia, supplied with the same springs of the Aqua Marcia; the Anio Novus, that drew its waters directly from the river. The subsequent emperors engaged themselves in important works of distribution of waters inside the city and of restoration. Only Traianus, in 109 a. C., built a new aqueduct on the right side of the river “to supply the industrial part of the town”, as Ashby says. Alexander Severus finally built the Aqua Alexandriana, later restored with the name of Aqua Felice by Pope Sixtus V.

Procopio’s evidence (14 aqueducts) can be justified either as an exaggeration, or as to include three secondary branches of the existing aqueducts[4]. Neglecting ancient aqueducts came about very gradually: several evidence affirm the continuation of restoration activity – in particular between the 7th and 9th century for the Aqua Traiana, supplying St. Peter’s basilica and the mills on the Janiculum[5]. Only after the 9th century the failure of water supply would have prompted to abandon the upper parts of the town for using wells – not only the river – situated in the lower parts near the Tiber.

Hence let’s consider in a more specific way what a Roman aqueduct was and what were its purposes: This analysis will be performed following the many suggestions that T. A. Hodge’s book contains[6]. He remarks that only the raising parts of aqueducts captured attention, and not the longer parts underground; not enough of this has been considered in Hodge’s opinion “the water supply system as a whole. In a word, the aqueducts have generally been studied rather as archeological monuments than as functioning machines”[7]. Roman aqueducts in fact were not built for drinking and washing: these basic needs were just satisfied, and continued to be, with the system of springs and private cisterns. They were instead a sign of luxury and urban status that satisfied civic pride, a matter the symbolic interest of which is underlined by a series of monumental and artistic uses of their water.

In other words, there were “two quite separate water systems operating in parallel and independently, fulfilling different purposes and observing different rules”, and the primary role of the aqueduct is still to demonstrate[8]. What is really important is the public and civic relevance of the aqueduct as an enterprise, compared to the private character of the cisterns. Public baths were the sign of civil living, and Romans often made this aspect in colonial cities perceivable: aqueducts were for their own needs, not for native inhabitants who continued to employ springs and cisterns[9].

Let’s now examine the structural elements of the aqueduct as a system. When designing an aqueduct the quality of waters was firstly examined; afterwards difficulties in the road were appraised: it was neither possible to build very high arches nor very deep galleries, and often the choice was to border the hills. It was possible also to pass under the valleys by employing siphons, but in the Ashby’s opinion, Romans never realized the capacities of their own cement pipes: “resistance to compression of their hydraulic cement exceed the safety standard accepted today”[10]. In fact, they did not need pressure aqueducts as on the contrary the distribution system avoided high pressure carefully.

Hodge remarks that the aqueduct in Roman age was not a closed pipe: from a hydraulic point of view it must be considered an open channel, an artificial river. It is not true that lead pipelines could poison people: the internal surface of pipes was quickly covered with limestone to isolate them, and water never stayed inside for a long time[11]. It is important to underline this problem of aqueducts service: the “tartaro” in the Italian term, or “sinter” in the German one. Romans never solved this problem that produced a progressive reduction in supplying capacities. Deposits found in the archeological works are very impressive: the carefully worked calcareous stone was employed to replace travertine in churches – and in fact its chemical structure is very similar to the “natural” one in marble[12].

For the distribution in town, waters were often filtered in multiple reservoirs; it was afterwards distributed by the means of principal castella (247 at the time when Frontinus writes) and still after to the secondary and private ones, the number of which is unknown. This cascade distribution allowed to control pressure in some critical points – not the pipes, but taps. The measurement of water, calculated in quinarie (40 m3 in a day), was practically reliable: the copper intakes, the pipe’s regular size and mostly the water level in the castellum, regularly kept at the same height, leaving exceeding water to flow away guaranteed good results.

Exception made for some few private houses with their own pipeline, domestic supply was assured by public fountains. In Pompei, where it is still possible to precisely reconstruct their locations, fountains were placed in a number and in places as no house had a fountain more than 50 meters distant; of course, the arrival of an aqueduct nearby modified everyday life: no more queues to take water and to irrigate gardens. Pipes, connections and other pipelines distributed waters: usually every user had his own pipe from the castellum to his house, as many parallel pipings have been found, and not a network distribution system[13]. Also a castella with a tank separated in three parts has been found, as Vitruvius recommended, in Rome a distribution of the water of the same aqueduct relating to the profile of users has never been made: different supplies were performed relating to different parts of the town. The division suggested by Vitruvius (public fountains, public baths, private users) was not necessary in Rome because there were many aqueducts and different employments could be performed – as will be shown further on – in a more sophisticated way, specializing an entire aqueduct to some users and not to others.

There were taps, but usually the system worked with a continuous flowing of water. From the hygienic point of view, the great amount of water arriving in Rome (Frontinus affirms it was almost 1 million m3 in a day) was not useless at all, even if many cities functioned well without sewers. In other words, the continuous flow could not be considered a waste of water: “the only guarantee for public health remained the continuous washing of drains”[14]. As concerns rain drainage, water was collected in the impluvium of the roman house, it was kept and used; also human dejection was often kept, but there were anyway drains along the roads, and sometimes open sewers.

Relating to water supply inside Rome, no reconstruction can be made without considering the evidence of Vitruvius and Frontinus. Hodge remarks that Vitruvius is often not the best teacher on this subject; moreover, he does not tell how ancient Romans built, but how they should build: for instance he was absolutely contrary to lead pipes, that we nevertheless find very frequently. As for Frontinus, he was not an engineer but a functionary, not very interested in technical subjects: he saw flowing water as an administrative object, a service supplied following a general map of the system; this mental map is not an engineer map, but rather the diagram of a manager.

Frontinus was born at the end of Tiberius kingdom and died in 103-104 a. C.; he was appointed to the cura aquarum in 97 a. C., and he is considered a sympathizer of the senatorial party. His text does not deal with the course of single aqueducts, but focuses on problems of measuring waters and the needs for supply.

From his own survey, the water furnished was more than the disposable amount, and moreover measured at the springs it seemed to be almost double the quantity that the water really supplied in town. As he used a mere geometrical method of measuring the final pipes (fistulae), his evaluation of flow was not reliable; a modern evaluation[15] assigned to the roman quinaria a value of 0,48 liters per second for an amount of a million m3 in a day, supplied but the 8 aqueducts functioning at the time of Frontinus[16]. This value is surprisingly similar to the modern roman oncia. Probably measuring at the beginning and at the end of the aqueduct was not comparable, but anyway Frontinus tried to eliminate many abuses and irregularities in the previous administration of the cura aquarum. They concerned irregular diversions and the respect of public property of the terrain where an aqueduct was placed; he carefully assured a different use for waters relating to their characteristics, separating domestic, industrial, hygienic and irrigation uses.

In spite of the declared purposes of his Commentari, presenting guidelines for the administration of roman waters, political purposes of the pro-senatorial Frontinus appear by the repeated criticism to the previous management, by often comparing himself with Agrippa and by the preparation of maps: “Frontinus therefore presents in his treatise an image of himself as a loyal lieutenant of an enlightened princeps determined to correct the abuses of the past”[17]. Also if his evidence is the source for all studies on roman waters, his text is “a document presented to celebrate its author and the policies of the emperor who appointed him”[18].

A study by Evans remarks how few are the things we know about water supply inside ancient Rome, and tries to answer some questions on the basis of the evidence of Frontinus himself, as it remains the only statistic we have. There has been a long discussion about the amount of the waters flowing in the ancient aqueducts, calculated either in a million m3 in a day, or only in 5 or 600 thousands m3. However his text gives also some information upon the water supply of suburban region, as he claims that almost one third of the water was distributed before getting in the city walls.

As stated, water arrived flowing to castella, whence it was distributed. Vitruvius’ theory, the main tank should be divided in three parts to supply separately fountains, public baths (he considered that they brought in relevant taxes to the state treasure) and private houses. It must be noted that in his classification there are no mills or industrial users. As for the public users, Frontinus indicates public buildings (thermae, circus, etc,), the castra, the munera (that were both monumental fountains and emergency basins), and the lacus (where exceeding water flowed and could be drawn). Let ‘s review again every aqueduct, considering the specific uses.

The Aqua Appia was brought in the lower parts of the town that were only supplied by springs, also for supplying the river harbor (an example was the port of the roman-Etruscan site of Cosa) and commercial activities of the Campo Boario. It followed a low course and brought in a medium amount of water, supplying many lacus. Its maintenance up to medieval period in fact is not clearly distinct by the Marrana stream, that arrived under Aventine hill and near St. Maria in Cosmedin, as will be seen further on. The Anio Vetus flowed higher (it was provided with 35 castella), but not so much to supply the highest parts of the town; its function seems to be limited to the new expanding eastern districts, Esquiline hill. The modest quality of its waters convinced Frontinus to suggest a general use of it, to keep the better drinking water of other aqueducts[19].

The Aqua Marcia, for its quantity and higher level of distribution (51 castella) succeeded in supplying with several branches almost every district of the city, including the highest hills. Its excellent quality supported its utilization as drinking water for private users and public lacus, and kept its fame up to the restoration of Marcia-Pia aqueduct in 1870. The Aqua Tepula, an adding stream coming from the Castelli Romani using the rising arches of the Marcia with its own pipeline, was worse in quality and was distributed to private users mixed with the Julia and with some Marcia for general purposes. The Aqua Julia, in spite of its similar quality to the Tepula, was mostly employed for public buildings.

The Aqua Virgo was instead an important aqueduct for distribution; it didn’t worked for the high parts of the city but just for the lowest ones of the Campo Marzio: a relevant part of it supplied the suburban districts. In Rome it supplied mostly public buildings.

Aqua Claudia and Anio Novus flowed parallely in separate pipelines, and integrated one another in a some complex way furnishing both the emperor’s palace (Domus Aurea and Palatinus hill) and a spreading private network, arriving in Transtiberim to increase the modest supply of other aqueducts. Their remarkable branches were the Arcus Celimontanus and a branch flowing high to supply the Marius Trophy on the Esquiline[20]. Claudia’s quality was excellent, and the amount of water of the two aqueducts together was a special reason of pride for Frontinus.

The Aqua Alsietina of the Martignano Lake was driven to town especially for the naumachia in Transtiberim, and was forgotten after the arrival of the Aqua Traiana. The latter finally supplied good drinking water directly to the districts of the right side of the Tiber; the discovery of channels and mill stones confirm the reconstruction made by Lanciani in his Forma Urbis[21]. Its quantity was enough to distribute it on the other side of the Tiber, in the opposite direction than before. Without Frontinus’ evidence, we cannot exactly affirm the aqueduct purposes, although the demographic growth of Transtiberim created of course needs in water supply.

Aqua Claudia/Anio Novus are the main water suppliers both for private and for public users: this system appears to be the backbone of water supply of the imperial city. Exception made for many springs inside the town that continued to play their role, other aqueducts showed particular specialization. This specialization is organized for functions and for geographic areas: some waters had a wide spreading (the Marcia as drinking water, the Tepula and the Julia for more general purposes); others had concentrated supply for a less number of users, especially public ones (the Virgo, the Anio Vetus). To private uses prevailing in water supply and irrigation of suburban districts corresponds inside the city a slight prevailing of public uses (44%) on private ones (40%), and an important presence of imperial uses (20% in nomine Coesaris). The older republican aqueducts continued to play their role supplying public basins, the lacus.

A separate problem concerns special uses. Irrigation first of all, as it is known to have been relevant in the suburban area: the amount of water necessary for irrigation is an enormous quantity compared to the basic needs of drinking and washing, also considering that in ancient times it was used for continuous flowing. Mechanical irrigation was not practiced, for the high costs and because it was not possible to raise waters very high. There is evidence about the Aqua Cabra coming down by the Tusculum hill, which was employed in an irrigation channel: maybe it was utilized with a rotation system among users, as it had become common practice in the middle age. But Roman agriculture was in fact dry farming; it seems that the Romans diverted water employed by Berber farmers to supply thermae in their colonial cities[22].

The most interesting subject anyway concerns industry: it will give us the essential point to appreciate the differences between ancient and medieval-modern situation[23]. In Hodge’s opinion – but Evans too seems to be very interested in this matter – water was employed in mines to wash minerals and in town by fullers, but especially to move the hydraulic wheels of mills. The role of hydraulic mills was not as secondary as historical tradition believes, and it is also uncertain if the vertical “roman” wheel is an evolution of the “greek” horizontal one: a simple mechanism could be more important than power, in those times. Anyway, a vertical wheel is particularly efficient if moved by an upper flow, not if moved only by a flowing stream. Hodge is not convinced by arguments to justify a rare utilization of mills in the roman world (the only discoveries in Rome are at the Janiculum and at the Thermae of Caracalla): the Romans knew the structure and function of hydraulic mills very well[24]. Moreover, aqueducts were an ideal supply for mills. In other words: “the only reason that we think water-mills were rare is that we have not found many, and this may reflect simply a failure either of archeological evidence, or of our interpretation of it”[25]. However, how many among the hundred of mills cited in medieval documents have archeologists discovered? As the water used by the mill could be introduced in the aqueduct, this utilization could be have been practiced at the birth of the aqueduct and Frontinus would never have talked about it; so, there could be a wide hydraulic network for mills, completely unknown to us. In fact, ruins of a serial mills construction have been found in Barbegal, supplied by their own aqueduct, different by the parallel one used for the water supply of the city of Arles. In the archeological reconstruction, it seems to be a system of eight buildings with two wheels each, a truly industrial system: “how many Barbegals are there awaiting discovery?” Hodge asks, affirming “this may well be the largest and most important question raised by this book”[26].

His thesis must be discussed carefully, not only for the importance that author himself place in it: is it only a provocation, or a fantasy? In fact the discovery of millstones in 1990-1991 under the American Academy on Janiculum confirms the existence and the importance of those mills[27]. Anyway, the fact that not a lot of mills have been found does not prove, and does not exclude, that they really existed; even if wooden parts can disappear in time, mill stones are a durable part, and it’s easy to discover it. While it is usual to find marble parts from ancient buildings employed again in modern ones, no ancient mill stone has yet been found, let’s say, on the ground floor of a medieval church.

Hodge’s opinion seems to be restricted too much to the technological aspects of the problem: adopting a technology is not only a technical matter, but also an economical one. The main argument of economic historians on this subject is that the presence of so many slaves made the labor saving use of mills not necessary, and that the different conditions made it an essential element of development in the urban medieval economy. In fact, the same number of mills would have a quite different relevance in imperial Rome with one million inhabitants and in the pope’s city, with a modest population.

3. Modern aqueducts

We will now examine the events concerning water supply after the ancient age[28]. In 537 a. C. the Gothic army of Vitige besieged the Byzantine troops of Belisarius, and interrupted the aqueducts to deprive the city of water. Two years after they entrenched themselves at the crossing point of the arches of Aqua Claudia and Marcia: the Byzantine also made some walls inside the pipelines to prevent their attacks inside the town. But we know that a war was not necessary to stop the water supply of a Roman aqueduct: the limestone was sufficient to stop it in time, if maintenance was performed frequently. In fact, after the war, aqueducts were restored and maintained until the 8th or 9th century. After that time only some Aqua Virgo continued to arrive in town, also because the majority of the conduct was underground and it was not exposed to damage of arches. In my opinion, an important factor of its long survival was due to the minor quantity of limestone, as the quality of its water was different from the one of the main ancient aqueducts.

As said, the Aqua Virgo went a long way to get in town from the northern part, passing under Pincio hill and arriving in Due Macelli street behind the modern Trevi fountain, to the terminal reservoir in Seminario street. At the time there was of course some maintenance on it, but the drawing of waters was made in a lower point, near Boccadileone, with a stream of water less than before. It must be considered that in the humanistic discovery of ancient roman techniques the city of Rome does not have a special role. Siena for instance was a more important center for the rise of new hydraulics: Leonardo da Vinci also can be placed in this tradition. But Taccola and other engineers of Siena in the 14th-15th century studied as an example not a Roman aqueduct, but mostly the Segovia one, as it was well known for the intense commercial relations between Italian and Hispanic ports[29]. Stopping the ancient aqueducts also influenced the evolution shape of the city: Rome in medieval age was rebuilt in the northern part, that was better supplied by vatican springs, by the river and by the medieval Virgin aqueduct.

D’Onofrio, following Lanciani, often talks about the discussion between Bacci and Modio about the water quality of the Tiber River. In his opinion the river had an important role in supplying the city: an inadequate policy in restoring aqueducts was justified with the belief of a healthier quality of the river waters[30]. In other words a necessity would be presented as a choice. In fact not having real drinkable water was the origin of a lot of diseases and also made children wine consumers. But maybe the literary evidence of discussion between Bacci and Modio is not enough to demonstrate that the inhabitants of Rome drank the river water: in town there were many other springs to satisfy in a better way the needs of drinkable water. The political essence of these writings is confirmed by the circumstance that Pope Giulius III in that time took a part of the Virgin water for his own needs i. e. to supply Villa Giulia. In Bacci’s opinion, who claimed the healthy virtue of the Tiber water, sounds in fact like a justification for his action.

The works of Lanciani represent an excellent point of view not only for ancient situation, but also for modern water supply: sometimes old structures were still working at his time. It must be considered that on the one hand he was trying to distinguish ancient ruins from the modern structures, and on the other, he could see a long period situation, not yet destroyed by the changes of the Capital city of Italy. First of all, he can perceive in a very concrete way the quantity of the “underground” water of Rome: “it is difficult to conceive an idea of these underground waters. In 1875, during the works for building the main sewer in Babuino Street, drainage machines took away sixty days’ time six hundred and fifty thousands m3 of spring waters”. In Rome, he wrote, it was enough to “descend at a 5 meters deep, in the lowest parts of the town, to find the beneficial stream”[31].

There were many more springs in town[32] than the ones named by Frontinus, as he talked only about the medical ones. There was Aqua Mercuri, that originated from Celius hill and arrived in modern times to supply the St. Giorgio mill by the basin of St. Anastasia: in the same place there was, by that time, a lavatory, then a paper mill, finally a fuller. The conduct along the Circus Maximo was in part a modern, in part an ancient construction, and until 1750 it was an open channel; at Cerchi street it flowed almost 9 meters higher than the Cloaca Maxima. There was Flumen Almonis, with several springs joining it, which I will discuss later; there was a fons Juturnae on Palatinus hill[33]; springs Lautolae, Lupercale, Pico Spring, a public tank that existed before the Aqua Appia, the Tullianum spring, the Fontinalis waters, the fontis arae, the Esquiline spring, the damasian water between Janiculum and Vatican, Vatican springs, Janiculum springs and some others.

Anyway, as regards Modio’s argumentation[34] or the real needs of the city, it was finally decided to begin the restoration of the Virgin aqueduct. An unsigned project with a relevant urban meaning[35] planned the drawing of Salone springs, the restoration of the aqueduct and the building of a certain number of fountains to distribute water in the center part of Rome. Works were begun in 1562 by Pope Pius IV: there are evidences of these works in civic councils of 1560-1570; the network pipelines, originally planned in stone, were made in clay[36]. The network of beautiful renaissance fountains, made mostly under pope Gregorius XIII, supplied the whole center of the city. The traditional falling system of distribution forced Giacomo Della Porta to build the Campo de’ Fiori fountain under the ground level, to attain enough pressure; but in Spagna square it was necessary to wait until the Paola water arrived, to let Bernini install the Barcaccia fountain.

There was in fact the problem of other sources of supply. Between restoring the ancient Aqua Alexandriana and the Traiana one, the first was chosen to support both the pope’s residence in Quirinale and the Villa of Pope Sixtus V on the Esquiline hill. The work was planned under Pope Gregorius XIII and performed by Sixtus V (Felice Pieretti, whence the name of Felice for this water). From the spring point of Pantano dei Grifi between Montecompatri and Colonna the water was brought to Rome with a lot of difficulties and money. Since the technician Giovanni Antonio Nigrone performed wrong leveling, the architect Matteo Bartolani failed in tracing the aqueduct and only his substitute Giovanni Fontana succeeded in carrying water up to the Esquiline hill in 1587[37]. Starting from the terminal tank and fountain, water spread in the direction of Monte Cavallo, Madonna dei Monti, Campo Vaccino, Santi Apostoli, Colonna Traiana and also towards Villa Medici on Pincio hill. In 1588 Campidoglio hill, which since roman times had been supplied only by cisterns, had a part of the new water, and at the beginning of 17th century the Felice water appeared also in front of Laterano palace, to supply the fountain underneath the obelisk.

In 1612 a lot of new water arrived on the Gianicolo hill: it was the Paola water, named by Pope Paulus V. Why so much water in a part of the city with a few aristocratic palaces and wealth? The Discorso sopra i profitti da cavarsi dall’acqua di Bracciano[38] of Pompeo Targone answers this question in a very clear way: keeping water in closed pipelines (“it should never touch the ground”) to avoid pollution, the water would be employed before to supply mills of a unique system, then it would have brought in the city pipelines.

Until then, the town on the right side of the river could employ several springs: those irrigating gardens of Belvedere and the Vatican spring that Pope Damaso (366-384) discovered and closed in a pipeline. Only in 1601 a little part of Felice water arrived in Transtiberim, because of the ultimate ruin of the St. Maria Bridge (or Ponte Rotto). So after some time the problem of supplying Transtiberim was worked out by restoring the Aqua Traiana. The nature of this new aqueduct was in fact different: “even if Traiana and Paola waters are usually considered the same thing, there is a big difference concerning their origin, their nature, their quality. The Aqua Traiana was supplied by very clear and healthy springs”[39], while the Paola water brought mostly the water of Lake Bracciano.

The water of this lake was bought by duke Orsini with the money of the city (Camera Catitolina): but in fact it was managed by the State Administration (Camera Apostolica). In the construction, work was performed by Pompeo Targone, Giovanni Fontana and Carlo Maderno. Finally the Paola water, as the Traiana in ancient times, crossed the Tiber to supply fountains in Giulia street arriving up to Montegiordano, Orsini’s residence, and later passing on the Tiberine Island up to the Marcello theatre and to Savelli’s houses.

The choice of employing the lake waters directly instead of ancient Vicarello springs, the quantity and power of the flow itself, too much for the weak structure restored by the popes, all prove that the main purpose was to supply energy. Mills were finally built between 1678 and 1682 with the clear aim to support the entire mill activity of the city if the Tiber and the Marrana had failed[40].

Aqueduct work were almost 270.000 scudi for Felice water and 397.000 scudi for Paola water; there is uncertain information about the Virgin water, as it was usually managed by the Camera Capitolina. Works and management were supported by luoghi di monte and specific taxes; Felice water in 1590 depended on the sixtine Congregatio super viis, pontibus et fontibus, but in 1612 the Paola water depended on its own Congregatio. Also if management was different, the Camerlengo had a central role, for its being directly subordinate to the pope, in coordinating politics of supplying[41]. In 1701 a unique management for Virgin and Paola water was decided, mostly for supporting the Virgin with the higher resources of the Paola; only in 1742 there was a unique Presidenza for all three waters.

The precise work of Paola Scavizzi[42] clearly shows how the hydraulic network worked to distribute water inside the city and the administrative management. Of course it is very difficult to describe the whole as a static system: the network expanded in time both for public and for private enterprise. To promote its development, private diversions would be free if the owner built a fountain on an external wall of his house.

As mentioned before on the unit of measurement, the oncia, is very similar to the ancient quinaria employed by Frontinus. The amount of water was measured with the diameter of the initial pipes (fistole) without considering the speed that was not possible to calculate yet[43]. Only in the 19th century a reliable evaluation was made, showing a bigger flow, with pipes of the same diameter, of the Felice and Paola water compared to Virgin water[44]. How could papal technicians assure a correct distribution to every single user? Differences were in part balanced by a different measure of initial pipes or a different price for oncia: in practice the price of an oncia of Virgin water was half an oncia of Felice or Paola water. The main uncertainty in distribution was in fact the diversion point: pipes section could be round or square, they could be placed or oriented in a different way and more than this they could work as a siphon[45]. The siphon system of distribution was abandoned after the arrival of the Felice water, as its flow was faster than the Virgin one. This difference prompted a more precise measure to be made by introducing measure boxes for single users after the main tanks[46], or also on the main conducts. In a tax division of 1756 for works on the pipelines of Felice water, the 194 pipes counted are joined to conducts, to main tanks, to secondary ones, to the waters just employed by public fountains: the amount of water was 1.127 once.

We have a description for the Paola water, concerning 204 users, by a similar tax calculation. Here we can notice the presence of industrial users: a branch of the aqueduct goes to the fuller of the Ospizio Apostolico of St. Michele, to the state tobacco manufacture, to colors mills and to the grain mill of Sixtus bridge discharging these waters in the river. Another part of the water went to a tank under the mills of the Gianicolo – it must be noticed - after supplying them: as they were state mills, they were free of charges. On the amount of 1.802 once, only mills employ 370, but also the remaining water supplied mills, first of all. For the Virgin water a tax calculation of 1789 marks 494 users for an amount of 1.143 once; even the Ripetta mill is considered.

Manufacturers employment grew in time: a report in 1789, assured that the Paola water moved at that time 6 grain mills with 12 millstones, 2 bran mills, 2 valonia oak mills, 1 color mill, 1 paper mill, 1 draw iron manufacture and 2 fullers[47]. Finally there were irrigation uses for gardens, cultivation and villas. A visit to Paola water in 1658, made to evaluate the diversion to Vatican affirms en passant that a lot of water did not arrive to the fountain of St. Pietro in Montorio but was employed in villas and gardens.

Pipelines were made with clay, lead and sometimes with stone. Scavizzi informs us precisely about the building techniques, the cost of plastering, welding and binding operation that were employed for maintenance: but the administrative costs (officers, taxes, notary) seem to be anyway higher than the cost of installing or modifying a diversion[48].

Although the management throughout the two centuries was precise, at the end of the 18th century the situation appeared chaotic for the spreading of irregular diversions: “it is clear enough that a big part of the distribution in spreading the network, failed any control”[49]. The water agency was in hard financial difficulties: debts did not allow, of course, a good technical management. In fact almost 74.000 scudi of the enterprise had been spent not only for the Trevi fountain (44.833 scudi) and for other artistic works, but also for building the Gianicolo mills (18.850 scudi) made on commission for Pope Innocenzo XI in 1678, and their revenues were taken by the Camera Apostolica. In 1818 the debt was paid and water management in Rome began to work better[50].

Finally, when Rome was the Capital City of Italy, the ancient Aqua Marcia was restored, with the name of Pia water. Also in this case, the structure and function of the aqueduct were completely different compared to the ancient times: the new aqueduct of the ending 19th century first employed for Rome a pressure pipeline in cast iron to overcome differences of level instead of restoring ancient arches[51].

4. Secondary streams

Some years ago, working to reconstruct the mill network in the Umbrian Valley during modern age, I saw some interesting documents; these compared the “Marrana” stream in Rome to a small regular river, the Clitunno, supplying most of the urban mills in this valley. The roman technician sent by the Congregazione delle acque to make peace between the two little towns disputing about the Clitunno water, G. B. Contini, declared sincerely that “it cannot be found, and I cannot adopt any rule, for justifying my opinion, and for comparing exactly waters in a plain and regular stream and waters in a fast flowing one”. For this reason he could only take as an example the experience in the Marrana stream, as it looked very similar in section, course and outlet[52].

It was said before that the Tiber River, supplying energy to floating mills, after building (or rebuilding) the Gianicolo mills was no longer the only energy resource for milling in the city. In fact there was another resource, more ancient and maybe more important, but it was less evident and more widespread: the mill network on secondary streams, sometimes far from the center of the town, but anyway connected to urban functions. It must be considered that the land extension of Rome is very wide.

When the Tiber is dry, said the officers of the Congregazione delle acque for shutting up the Bevagna inhabitants, “Rome itself has to be go for milling its needs in Tivoli”[53]. But without arriving in Tivoli, there were other resources nearer to town. Very near: we saw the Marrana arriving in ancient times to Circo Massimo, under the Aventine hill. In fact the first channel, not precisely an aqueduct, to be restored in medieval-modern age was not the Virgin, but the “Mariana” channel, brought in Rome by Pope Callisto II in 1122. It gathered the ancient waters of Tepula and Julia in an open channel starting from the Valle della Molara near Squarciarelli down to Morena, were the water flew in subterranean conduit that had been a part of the Aqua Claudia. At Porta Furba it turned toward Porta St. Giovanni and entered in town at Porta Metronia, arriving at the Circo Massimo. Lanciani had very clear in mind that it was an artificial channel of medieval origins, not an ancient one, and it had nothing to do with the Aqua Cabra[54].

The owners of rights upon the Marrana stream were the Laterano basilica, that was at the time the pope’s residence. In 1723 and in 1856 new springs were flowed in the channel and in emergency events ( dry periods or the holy year in 1824) water from the Felice aqueduct was directly diverted in it[55]. This system was often protected by papal dispositions until the 19th century[56]: for instance in 1820 cardinal Camerlengo Bartolomeo Pacca proclaimed[57] that works, derivations and bridges were forbidden if not previously authorized. Drinking and passing was forbidden for animals, and flaw cultivation too (in modern age it was particularly polluting); in general, tree cultivation was forbidden also.

This stream was so regular and important that Dutch engineer Meyer, who arrived in Rome at the end of 17th century to solve many hydraulic problems in the Papal State, suggested to make it navigable from the Torre di Mezza Via under the village of Marino to Porta St. Giovanni. He remarks that bringing a river, or better a channel to outlet in an harbor is the best way to keep it free from the mud: his proposal was in fact useful also for maintaining the river harbor in Ripa[58].

Route and mills of Marrana are marked, for the part outside the town, in two maps of the Catasto Alessandrino where we can see its flow and two mills near St. Giovanni with a “monte del grano” (a deposit of grains) [59]. In the 16th century some Spanish craftsmen controlled the most part of the fullers: an urban market of wool clothes developed, rich enough to attract capitals[60]. In some tax reports, made in 1740, 1798, 1821 and 1895 a precise situation is outlined: mills are in different moments 11 or 13, and their utilization is sometimes changed from grain mills to fullers or specialized manufactures or back to grain mills. In general, inside the city a grain mill use prevailed and outside a fuller employment was more frequent[61].

Ancient rights of the Laterano basilica were by the time inherited by private owners gathered in a society. The important role of the Marrana ended when the new banks of Lungotevere were built, as they stopped the river outlet to the stream: in 1897 Marrana waters were declared public property and the appeal of ancient owners did not prevent water use from changing from an energetic to an irrigation use. In 1910 the dispute was over accepting state property of waters by the owners and granting them waters only for irrigation uses.

Moreover, there were other secondary “Marrane”[62]. There is a detail in the map that Gio. Paolo Ferreri drew in 1599 planning a derivation of Tiber River[63]: the “Amarana” stream follows the course previously described: the “Acquataccio” stream is the ancient Almone, that supplies a small lake-basin just before the Appia bridge near Quo Vadis, where a fuller was placed. In fact there were three fullers: upper, middle (near the Redicolo temple) and lower (on the Appia street). The Almone stream turned then toward a St. Paolo fuller[64]. A fuller of Caffarella valley is mentioned in a document in 1470 and marked in a map of Eufrosino della Volpaia in 1547[65]. During the plague in 1656 these fullers worked as laundries to satisfy hygienic needs of the town in that moment[66]. These mills are well evident in the maps of the Catasto Alessandrino some time later: we can see the Acquataccio course with two fullers[67] and more precisely the fuller of the Tenuta of Caffarella[68]. As Lanciani remarks, the water of the Nynphaeum of Egeria was kept in a separate channel to supply alone the medium mill. Lower down the same stream it supplies energy to a fuller and a “little fuller” on the Ostiense street near St. Paolo[69]: they were named after a property (“Tenuta della valchetta”) [70].

In spite of the long use as fullers, these mills were at the beginning grain mills and then, in the 19th century, were used again as grain mills: they followed, as in the case of the Marrana of St. Giovanni, the development of the city, sometimes in a commercial direction, sometimes a demographic growth[71].

Finally there was a remarkable spread of mills around the roman land. Some of them have been studied, as the Pantano[72] mills mentioned above: we can see them in the Catasto Alessandrino on two different but similar maps[73]. In one of them it is very clear that they were placed in the falling point where the ancient aqueduct of the Aqua Alexandriana, now broken, begins. This case could be typical, and similar ones could be found near the ruins of ancient aqueducts coming from Aniene valley.

These mills of Pantano in particular employed the water of the same spring used before by the Aqua Alexandriana and after by the Felice aqueduct to supply Rome, collected in a “rifolta”, a reservoir: the same built by Matteo Bartolani, maybe using a further structure, to try to raise springs up to the pipeline he built. These mills were owned firstly by the Colonna family, then by the Borghese, who had the rights of milling (the “privativa”) in the neighboring land: they were a good revenue for the owners, who had granted also rights to use waters for irrigation.

In 1585 the Camera Apostolica decided that spring water was a public property; owners had granted the use of only one of the existing mills, to be supplied with the water raising “inside” the reservoir. From that moment a long dispute began, in which the pope’s technicians Cornelio Meyer, Luigi Vanvitelli and his substitute Ermenegildo Sintes were hired. One problem was the installation of another reservoir (“botte”) by the Camera Apostolica to supply the aqueduct: as this reservoir was connected with the other, both mills and aqueduct tried to collect the same water. Of course everybody would like to use the same water to move several wheels of mills and after draw it into the pipeline; but the pipeline had a certain level, and it could not be lowered without loosing the slope necessary to bring water in Rome. In fact it was not the quantity of water to be disputed, but the energy that the initial difference of level supplied.

At the middle of the 18th century the Camera Apostolica reached an agreement with the Borghese family: a new mill would have been built to replace the old ones, after which the activity of the old one would be halted if the new one would show that it worked well. Also milling rights concerning Montecompatri and Monteporzio villages would go to the new mill. Work was authorized in 1767 and consisted of collecting water from upper springs, bringing them in Valle Marchetta to a new mill with a big vertical wheel with boxes, that would produce the same amount of flour than the older ones (10 rubbia in 24 hours). The new building appeared to the technicians more similar to an “aristocratic cottage” than to a country mill. But even if it was very expensive its production revealed to be insufficient to reach the original aim, and the dispute was finally worked out only when the Camera Apostolica bought it to use it for different employment. This experience demonstrated that there were limits in the technology of those times which were not possible to overcome (the diameter of wheels, the structure of machines). On the other hand, it showed that water which stayed for a long time in a mill reservoir and passed then in its wheels maybe is not the best water that could be drawn in an aqueduct.

Finally, a fuller often marked in the maps of the Catasto Alessandrino is St. Pietro’s fuller, placed on Flaminia Street near Grottarossa on a small stream coming from the right side into Tiber[74]. We can then arrive to the sea near Via Ostiense, where we find at the house and property of St. Lorenza two mills supplied by a secondary stream flowing into the sea, and near them a “grain deposit on the beach”[75]; it was not difficult from this place, with small boats pulled from the beach, to go upstream along the river up to the city.

5. The right branch of the river at the Tiberine Island

After the walls of Tiber River were built, the existing situation of the Tiberine Island seems to be a natural scenario. In reality it is not: engineer Canevari, first suggested to eliminate the island itself closing the right branch and sizing the left one to the rest of the river bed. Only later did he accept to keep the island by creating an equal section to both branches, widening in a considerable way the right branch.

In ancient times, and up to modern age, the branch was much narrower than we can see today. The floating mills beside the island placed in Procopio’s evidence by the Byzantine general Belisario, were usually on the right branch: this fact confirms its characteristic of a narrow channel, while the left one was functioning better for exceeding flow. The left branch would be so prevailing in medieval times to be navigable, and to allow “galere” built in the shipyard of St. Spirito to leave the shipyard itself and to get down the river passing left beside the island[76].

Other mills that were until 1473 near the ruins of Ponte Sisto were probably placed at St. Spirito and at the Fiorentini Church when the bridge was restored. The aqueduct water supplied some mills from above; these mills employed the Tiber only to release waters (the Ripetta mill, with Virgin water; the Ponte Sisto, with Paola water) [77]. In 1563 and in 1575 there were about 20 mills on the urban part of the river[78]. As clearly noticed in the comments made in 1744-1745 by Chiesa and Gambarini, the pope’s engineers[79], the riverbed between Ripa and Ripetta harbors was simply an artificial system of small lakes and streams, functioning as mills and basins. This milling system worked anyway in a river that looked like a channel: from the Piazza del Popolo down to Ponte Sisto the houses on the river were built along the ancient Aurelian walls, and they looked as a unique wall facing the river[80]. From this point of view the “big banks” of the Tiber have always existed: they were the compact front of houses or better their back, because the front was on the main street, opposite the river. Not only the basic needs of houses were facing the river, but also factories: only when the “big banks” were built and these activities stopped, the city finally entered a new administrative and bureaucratic context[81].

It must be noticed that the so blamed floating mills were not taken away from the river up to the banks building. Now, if evidence confirm the existence and importance of hydraulic mills in the hydraulic network upstream the river, why was the river never abandoned for milling? I think that non-technical aspects were not considered enough: the Gianicolo mills were state property; a private willing to gain “industrial” revenue could anyway be allowed to install a floating mill. Of course a river flood could damage mills but flour and bread were always sold, differently from other goods: a river mill revenue touched 10% and was superior to house to let revenues[82]. Mills’s owners were city aristocracy, and later religious orders, but already in the 15th century there were some “capitalistic” efforts[83].

Now, how did the geographic context changed around the Tiberine Island in the course of ages? Drilling made recently by the Tiber Watersheds Agency confirm that the island is a moving sandbank formed by successive layers; its shape has changed in the time and transformed by the flowing water[84]. If this is the nature of the island, I think it is justified made the following hypothesis.

1. The Ponte Rotto was built on the edge where at that time the sand bank ended; the two branches of the river had then no communication upstream the bridge.

2. The right branch seems to be the partially artificial consolidation of a natural diversion opened by the river itself during floods. In fact the shape of the island was artificially protected from the river current transforming it in a stone ship: the end of this ship was very close to the left bank of the river and forced the water to go in the right branch[85].

3. The existence of the bridge would produce a greater growth of the deposits and of the dimension of the island itself. By the time the river current eroded the natural edge, both toward and beside the bridge, separating it from the island and eliminating the narrow diaphragm between the two branches. The bridge, abandoned to his fate, would be ruined after the river current, more whirling than before the elimination of the diaphragm, had undermined its foundations; later its ruins began a physiologic part of the milling system.

The interaction between the two branches has always been the key to understand and control the river around the island: it must be considered that actually the strategy to defend from erosion of the riverbed is centered on artificial thresholds. The latter would be moving, to allow by adjusting its height to distribute in an equal way the river current in the two branches, in the same way in which the old dikes of floating mills did to address more water from the left branch to the right one[86].

In other words: we should consider the right branch as a diverted channel or anyway an artificial maintained channel, more than a natural branch of the river: a way to see that approach in the case of Rome to the model of urban hydraulic network

6. Future researches and contemporary events

Even if bibliography discussed and documents mentioned seem to confirm the interpretation suggested, a complete reconstruction of the hydraulic network of Rome and its territory is still to be done. The many elements cited at the beginning arrived in time to hide the shape of this network and the evolution of urban function obliterates its memory.

A necessary instrument of this research is cartography, especially land office maps. Although urban context appears as an anonymous series of walls and roofs, these maps can shape the underground circulation of water and the spreading of manufactories deriving from it[87]. When a real map of the hydraulic network is not found, it is always possible to use the land office registers (“brogliardi”) to locate the constructions which use water and the hydraulic branches along which a network is established.

Anyway land office maps in the Papal State at the beginning of the 19th century, the Catasto Gregoriano, are a precious source for the study of waters in urban context, because they are always carefully interested in springs, drains, channels, reservoirs. Surely this is the consequence of a special and long interest of cartography for hydrographic aspects; maps often remark details which are not marked on the land register. Maybe the register remarks a “public spring”, or mentions a basin useful for a garden, but only on the map is it possible to see all visible elements (springs, aqueducts, drains) of the urban hydraulic system. Special attention must be placed in these elements: gardens, oil and grain mills, fullers and “cellars”: some researches suggest that with this name a laboratory is often suggested rather than a stotage for wine and other goods[88]. The utilization of waters in the cities of ancien régime is characterized by many manufactories employing decomposition processes: “technique requires a lot of water and turn a town in a little Venice, or in the Renaissance in a true archipelago”[89]. The consequent sickly situation lasted until the end of the 18th century: only in the new century soaking is removed and placed outside the town. Then a non organic chemistry is employed; channels and drains are turned along the city walls and more and more distant, following the progressive expansion of the city.

The case of Rome is in part more complex for a researcher as the system spread in a wider territory than other cities in Italy: in these cities the system is entirely enclosed within the urban walls, or maybe extended to some mill at the nearest stream in the plain. In Rome instead it is necessary to consider the whole territory (the “Agro”) until the border of the nearest municipal communities of the Comarca. At this moment only a complete investigation on the Catasto Alessandrino maps has been done: these maps, drowned for paying taxes on main roads to Rome, gives proof about the land outside the city walls. In the next few months, an investigation will be done on maps and registers of the land office dating from the beginning of the 19th century (Catasto Gregoriano) for the city inside the walls. Later maps (“Cessato Catasto Rustico”) will provide a complete and more recent survey on suburban area and the territory of the Agro.

I hope that from the elements exposed there, seems to be a way to see Rome and its waters separately from the tradition that described the city much more dependent, in good or bad fortune, to the river as a “natural” element. On the contrary the scenario is similar to a model of an urban hydraulic system with original characters facing the ancient one and rather common to many other cities in modern age. The element of this model are: the character of a system integrating in a whole origin, circulation, functions, drain of waters; the complete separation of clear waters and dirty waters; the alternate utilization of waters in domestic and irrigation supply, and for moving mills[90].

The ancient water supply system was somewhat different: a roman aqueduct could supply much more good water than a modern one, but it was a machine working only with a massive maintenance assured with hundreds of slaves. The restoration of aqueducts that the popes performed gave up carrying water from the karst mountain, and so avoided limestone problems. Popes were satisfied with the springs along Via Collatina (Virgin water), with those from the secondary mountain of the Castelli Romani (Paola water), and water from the natural volcanic basin of Lake Bracciano (Paola water). Another difference concerns the importance of energy supply for mills: although some ancient mills existed in the same place where the popes rebuilt them, Gianicolo hill, only in the medieval and modern city a system of hydraulic manufacturers appears. Only in the pope’s city, mills play a key role in the origins and the development of the hydraulic network.

The case of Rome appears to be in fact a late conforming to the general model of hydraulic system common in Center Italy. This delay can be explained with several factors: a scarce population, the nature of urban center devoted to financial and manufacturers functions, the complex geographic context, the balance with manufacturers placed outside the city, but whose functions were integrated to the city economy. Of course, Rome would perform this model in its own way, for the existence of several different aqueducts, and not one only. In Rome the double and separate circulation of clear and dirty waters has always been carried out specializing single aqueducts.

Contemporary events give other evidence about these aspects. The functions of the Virgin aqueduct remained the same until late 19th century, when extending distribution obliged to install a raising pump. The expanding city anyway posed new problems, that the complete rebuilding of this aqueduct in 1936 did not work out. In 1961 its waters, beside the drinkable waters of the New Virgin aqueduct, were classified not drinkable[91]. The same declassing process happened for the Felice water, because of many irregular derivations: also its waters were classified not drinkable in 1963-68 and were substituted by the waters of a new Appio-Alessandrino aqueduct. Both these aqueducts are thus devoted to a mere archeological conservation. Low classification of waters for the Paolo aqueduct dates much earlier, at its birth, for the decision in 1672 to draw in Bracciano Lake water. Anyway later events are remarkable. The Paola water remained not drinkable until some emergencies in water supply (in 1968 and 1979) obliged to perform treatment installation to make this water drinkable; but then the non drinking users had to be content by drawing water from the Tiber River in Grottarossa. For these emergencies a new aqueduct from Bracciano Lake had been prepared[92].

Contemporary events confirm also the close connection between domestic supply, irrigation and energy supply. The civic agency ACEA accepted at its birth in 1937-38 the double traditional employment of aqueduct, for supplying water and energy (now hydroelectric energy) [93]. It must be noticed that the first raising pumps of the New Virgin aqueduct, in 1901, worked with electric energy produced by the Paola aqueduct; only in 1930 a new installation was performed to raise waters near the sources of Salone[94]. To the big demographic expansion of Rome and to the origins of the civic agency is connected also the origin of the Peschiera aqueduct, that today supplies 60% of present needs with waters from the watersheds of Velino Mount. A part of this system is the hydroelectric installation of Salisano (built in 1937-1940), where since 1980 it joins waters of the Capore aqueduct, after employ in water supply. From this point two separate pipelines, on the right and on the left side of the Tiber River, arrive to the several basins in the city[95].

The evolution of the water supplying system of Rome in the 20th century poses a problem: is it the complete realization of the model discussed before or its failure? We cannot deny that technology suggests very different solutions than the falling distribution by slope common both in the ancient city and in the modern one. Events show also that growth, sometimes sudden and dramatic, of demographic context, force to employ less clear resources than spring waters brought in a pipeline from a long distance to Rome: lakes, the Tiber River itself. But even if demographic events play their role, I think in Rome to employ the lake or river water can be considered historically a secondary resource compared to springs, or an emergency resource due to demographic crisis, to be overcome. Didn’t the ancient Anio Vetus aqueduct also draw its waters in the Aniene River?

More generally, we could ask if the case of Rome corresponds to the model outlined in an interesting book by Dora Crouch about water supply in ancient cities of the Mediterranean area, strongly dependent on the presence of the karst mountain[96]. The Simbruini Mountains whence in time most of the water came to Rome, are a typical karst mountain. Another model regarding this is the supplying system of the biggest European cities in rapid demographic growth during modern age, that were far from the mountain and dependent mostly on a large river[97]. This different context attracted attention in the modern world and excited fantasy to find out, in the 16th and 17th century, inventions to raise water from the river to houses, palaces and gardens of the city. But everywhere in Europe there have been roman aqueducts: also in these situations we can ask ourselves how much supplying water and treating water of a river for drinking is to be considered an emergency, or a physiologic event.

Appendix

Pompeo Targone, Discorso sopra i profitti da cavarsi dall’acqua di Bracciano, da C. D'Onofrio, Acque e fontane, cit., pp. 296-7, note 2.

“… né meno s’averà l’intento, volendo d’una parte di essa far mulini l’uno sotto l’altro, e l’acqua che s’impiegasse a questo servizio, dovendo venir per terra, e scoperta per tanto transito, sarebbe soggetta à molte immonditie, et per la caduta persa inutile all’uso delle fontane. Io ho pensato di proporre alla S.tà di Nostro Signore un’inventione, con la quale si potrà non solo cavar’il possibile da questa acqua, vendendola per fontane, ma si potrà con pochissima spesa far un’entrata perpetua di parecchie migliaia di scudi. Il modo che io propongo è che, condotta l’acqua alla Porta di San Pancrazio, ivi stando sempre coperta, e non toccando mai terreno, coll’inventione, che si vede nel mio disegno facci macinare tutta quella quantità di grano ch’ha bisogno la città di Roma. Doppo che l’acqua haverà servito questo effetto, restando nella sua stessa purità, senza aver ricevuto immonditia alcuna, e con caduta più alta di tutte le case di Roma, e ridotta tutta insieme in una sola botte si venderà a’ particolari per le fontane. E non trovandosi a vender tutta, d’una parte d’essa si potranno far artifitij per carta, ò da follar i panni, o macinar mortella etc. che saranno di grandissimo guadagno et à Roma di moltissima comodità. Oltre questi benefitij suddetti se ne caveranno ancora degli altri di grandissima importanza. Il primo sarà che dal Tevere si leveranno tutte le mole, scale e parete ch’impediscono il corso del fiume, e sono in parte causa dell’inondazione, che ben spesso arreca a questa Città. L’altro sarà che dove hora per le crescenti del Tevere questa Città patisce del macinare, fatti che saranno questi molini, in un istesso modo, et in ogni tempo sarà sempre ben servita; oltreché questi molini non saranno esposti ad esser portati via dal Tevere, né haveranno bisogno ogni giorno d’esser risarciti, come accade à questo, ch’hora vi sono, ma con la mia intenzione duraranno molti e molti anni senza bisogno di cosa alcuna.. Di più essendo tutti questi molini in un corpo, non potranno li molinari falsificar i grani, e dove adesso vi sono molti Ministri dell’Abondanza sopra questo effetto, e non possono ben rimediarvi, essendo ciaschun molino diviso, e lontano dagli altri, all’hora un Ministro solo, ch’assiste in detta fabrica, senza andar correndo per le strade rimediarà à tutti questi inconvenienti. Quella parte d’acqua che servirà alle fontane di Belvedere doppo ch’haverà fatto l’effetto, gli restarà una buona caduta e potrà far macinare un poco de molini ò più, ò meno la quantità che sarà, e doppo potrà ancor servire alle fontane della Piazza San Pietro, e di Borgo”.

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[1] R. Lanciani, Le acque e gli acquedotti di Roma antica, Roma, 1975: reprint of R. Lanciani, Topografia di Roma antica: i commentarii di Frontino intorno le acque e gli acquedotti: silloge epigrafica aquaria / memoria di Rodolfo Lanciani, in Atti Lincei, Ser. 3., Mem. scienze morali, storiche e filologiche, Vol. 4., seduta 18 genn. 1880, Roma 1880.

[2] T. Ashby, Gli acquedotti dell'antica Roma, Roma, 1991, note to translation and forewords.

[3] A. M. Liberati Silverio, for the X Ripartizione del Comune di Roma, drew a general map of the Campagna romana 1:100.000, representing the most complete and upgraded outline of the aqueduct lay-out: Il trionfo dell'acqua. Atti del convegno "Gli antichi acquedotti di Roma. Problemi di conoscenza, conservazione e tutela", edited by di A. M. Liberati Silverio, G. Pisani Sartorio, Roma 1986, pp. 35-46.

[4] Differently from Ashby, A. Betocchi, Le acque e gli acquedotti di Roma antica e moderna, in Monografia della città di Roma e campagna romana, Roma 1881, try to indicate three others “waters” for matching with the total number given by Procopio.

[5] T. Ashby, Gli acquedotti, cit., p. 32.

[6] T. A. Hodge, Roman acqueducts and water supply, London, 1992. Hodge does not mean to offer a chronological survey of roman aqueducts, as they changes in time, nor a repertory to use in a geographical order: he follows the course of the water inside the parts of the typical roman aqueduct. About ancient aqueducts in general see also T. A. Hodge, (edited by), Future currents in aqueduct studies, Leeds, 1991; R. Tolle-Kastenbein, Archeologia dell’acqua. La cultura idraulica nel mondo classico, Omegna 1993; Utilitates necessaria: sistemi idraulici nell'Italia romana, a cura di I. Riera, Milano, 1994. About roman aqueducts in particular, see G. Panimolle, Gli acquedotti di Roma antica, Roma, 1963; P. Pace, Gli acquedotti di Roma e il "De Acqueductu" di Frontino. Contesto critico, versione, e commento, Roma, 1983 e quelli più recenti C. Bruun, The water supply of ancient Rome: a study of Roman imperial administration, Helsinki, 1991; P. J. Aicher, Guide to acqueducts of ancient Rome, Wauconda, 1995.

[7] T. A. Hodge, Roman aqueducts, cit., p. 4

[8] Ibid., p. 48.

[9] Ibid., p. 50.

[10] T. Ashby, Gli acquedotti, cit., p. 52; the case of Alatri, that in fact he mentions, seems to affirm the contrary.

[11] T. A. Hodge, Roman aqueducts, cit., p. 2

[12] Ibid., cit., p. 231. See the limestones of the Aqua Marcia in Il trionfo dell'acqua. Atti del convegno, cit., fig. 3 a p. 38. For some examples of calcareous deposits, see I. Riera, Le testimonianze archeologiche, in Utilitates necessaria, cit., pp. 234 e 250.

[13] T. A. Hodge, Roman aqueducts, cit., p. 320

[14] T. Ashby, Gli acquedotti, cit., p. 53.

[15] C. Di Fenizio, Sulla portata degli antichi acquedotti romani, in «Giornale del Genio civile», 14 (1916), pp. 227-331. See also P. Branchini, Nota sulla misura adottata in Roma per la dispensa delle acque, Roma, 1857.

[16] As the Aqua Alexandriana e Aqua Traiana did not existed yet, only evaluations for the Aqua Virgo can be compared: their order of measuring is similar: 2.504 ancient quinaria versus 3.840 modern roman oncie in the evaluation made by Betocchi for the papal aqueduct. In his calculation, the amount of water for each Rome ancient inhabitant was still higher than the disposable supply for the Romans in the new Capital City of Italy.

[17] H. B. Evans, Water distribution in ancient Rome: the evidence of Frontinus, 1994, p. 61.

[18] Ibid., cit., p. 63.

[19] Evans talks about an irrigation and industrial employ: ibid., p. 81, and further at p. 82: “used primarily for industrial purposes”. But the text of Frontinus, 92, talks only about gardens and of “baser needs of the city” (in the same translated version by Evans), not about industrial uses. His interpretation seems to be a misunderstanding: original text say: “in hortorum rigatione, atque in ipsius Urbis sordidiora exiret ministeria”. In the ‘800 version of B. Orsini it sounds: “all’innaffiamento degli orti, e che finisse ne’ più lordi servizi della medesima Città”, Sesto Giulio Frontino, "Commentario di S. G. Frontino degli acquedotti della città di Roma" con note di B. Orsini, Perugia, 1805, pp. 148-149. I will turn back further about the meaning of these “industrial” interpretations.

[20] G. Tedeschi Grisanti, Primo contributo a una livellazione urbana sistematica degli antichi acquedotti di Roma, in Il trionfo dell'acqua. Atti del convegno, cit., pp. 59-72, affirms that the Trophy of Mario could not be supplied by the Aqua Julia, and was probably the terminal point of a branch of the Claudia.

[21] R. Lanciani, Forma urbis Romae, Roma 1990, pl. 27.

[22] T. A. Hodge, Roman aqueducts, cit., p. 252.

[23] Ibid., pp. 254 onward.

[24] Exception made for Vitruvius, see the archeological evidences in Il trionfo dell'acqua. Acque e acquedotti a Roma (IV sec. a. C. - XX sec.). Mostra organizzata in occasione del XVI Congresso ed Esposizione internazionale degli acquedotti, Roma 31 ottobre 1986 - 15 gennaio 1987, edited by Comune di Roma e IWSA-ACEA, Roma 1986.At the beginning of the volume, at tab. IX, we see a fresco of 3rd century, placed in St. Agnese catacombs, representing the vertical wheel of a mill.

[25] T. A. Hodge, Roman aqueducts, cit., p. 256

[26] Ibid., p. 261

[27] H. B. Evans, Water distribution, cit., p. 130. References by Evans are the followings: O. Wikander, Water mills in ancient Rome, Opuscola Romana, 12 (1979), pp. 13-36, 1979; Id., Water mills and aqueducts, in Future currents, cit., pp. 141-148, 1979; M. Bell, III, Dig we mustn't during the World Cup, AMACADMY, Newsletter of the Academy of Rome, fall 1990, 8; Id. The mills of the Janiculum, Classical Society of the Academy of Rome Newsletter, December 1990, 9; L. Richardson, The aqueduct of the Transtiberim and the American Academy in Roma, Classical Society of the Academy of Rome Newsletter, December 1990, 6-8. About the ruins on the Janiculum, see also T. Ashby, Gli acquedotti, cit., p. 363:Ashby believed that the main channel was not the one named by Lanciani, as later a specus was found under the American Academy, see A. W. Van Buren; G. Ph. Stevens, Memoirs of the America Academy of Rome, I, 1917, pp. 59-61. Images and information concerning the conduit discovered under the American Academy are in Il trionfo dell'acqua. Acque e acquedotti, cit., pp. 118-119: it is a derivation parallel to the Aqua Traiana, with channels and reservoirs; there have been found the mill stones mentioned above.

[28] For a popular history of these facts, see C. D'Onofrio, Acque e fontane di Roma, Roma 1977. Coeval sources and bibliography on this subject are many, also if sometimes they are not original; see: L. Peto, De restitutione ductus acquae Virginis, Roma, 1570; R. Fabretti, De acquis et acqueductibus veteris Romae, Roma 1680; F. Fontana, Relazione sullo stato vecchio e nuovo dell'Acqua Felice, Roma, 1696; C., Fontana, Utilissimo trattato delle acque correnti, diviso in tre libri, Roma, 1696: Book III was devoted to the aqueduct from Bracciano Lake; A. Cassio, Corso delle acque antiche portate da lontane contrade fuori e dentro Roma sopra XIV acquedotti e delle moderne in essa nascenti, Roma, 1756-1757; N. M. Nicolai, Sulla Presidenza delle strade ed acque e sua giurisdizione economica, Roma, 1829; C. Fea, Esame storico-legale-idraulico dei sifoni impiegati pei condotti dell'acqua Paola, Roma, 1830; Id., Storia delle acque antiche sorgenti in Roma, perdute, e modo di ristabilirle. Dei condotti antico-moderni delle acque Vergine, Felice e Paola, e loro autori, Roma, 1832; N. Cavalieri San Bertolo, Sulle acque della moderna Roma e sui metodi usati nella distribuzione di esse pei pubblici e pei privati commodi della popolazione, Roma, 1859; R. Marchetti, Sulle acque di Roma antiche e moderne, Roma, 1886; F. Mastrigli, Acque, acquedotti e fontane di Roma, Roma, 1928 (s. d.); P. Pecchiai, Acquedotti e fontane di Roma nel Cinquecento, Roma 1944; M. Pediconi, L'approvvigionamento idrico di Roma, Roma 1967; A. Betocchi, Le acque, cited above.

[29] Gli ingegneri del Rinascimento da Brunelleschi a Leonardo da Vinci. Catalogo della mostra, Firenze 1996-97, edited by P. Galluzzi, Firenze 1996; this exposition was first edited in Siena with a similar title: Prima di Leonardo. Cultura delle macchine a Siena nel Rinascimento. Catalogo della mostra, Siena 9 giugno - 30 settembre 1991, edited by P. Galluzzi, Milano 1991.

[30] It is the thesis of C. D’Onofrio, Il Tevere, Roma 1980, p. 77: “as in general every water, especially streams, it had a purifying character and value ”.

[31] R. Lanciani, Le acque, cit., pp. 217-218.

[32] Ibid., pp. 220 ss..

[33] Probably it is the same water employed in the saltpeter manufactories in the modern age: the manufactory had basins to wet the saltpeter ground, and in the boiler room there was a big basin supplied by a continuous spring: P. Scavizzi, La salnitriera al Palatino. Il luogo e la fabbrica fra metà Cinquecento e inizio Ottocento, «Archivio della società romana di storia patria», 120, pp. 211-258, especially pp. 218-220.

[34] G. B. Modio, Il Tevere, di M. Gio. Battista Modio. Dove si ragiona in generale della natura di tutte le acque, et in particolare di quella del fiume di Roma, Roma 1556.

[35] In the opinion of C. D'Onofrio, Acque e fontane, cit., p. 48, the manuscript was made in 1535-1536 by the pope’s librarian Agostino Steuco, who in fact wrote De aqua Virgine ad Urbem revocanda, Roma 1547.

[36] See the epigraph dated 1726 showing the spreading of water from the main tank, C. D'Onofrio, Acque e fontane, cit., p. 57, fig. 37.

[37] L. Quilici, Il sistema di captazione delle sorgenti, in Il trionfo dell'acqua. Atti del convegno, cit., pp. 47-58, affirms that the strange leveling mistake of Matteo Bartolani, in 16th century, was depending upon the purpose to use the ancient catchment basin of the Aqua Alexandriana; after he tried to raise the water level of the spring hoping it would flow into the new aqueduct, Giovanni Fontana worked out the problem using higher springs, and the first tank was employed for supplying some mills. These mills are the subject of a study by Scavizzi, about which I will discuss further.

[38] For this text, see the appendix; it is referred in C. D'Onofrio, Acque e fontane, cit., pp. 296-7, note 2.

[39] R. Lanciani, Le acque, cit., p. 375.

[40] C. Cancellieri, L’acquedotto Paolo (secc. XVII-XX), in Il trionfo dell'acqua. Acque e acquedotti a Roma, cit., pp. 225-21: see the project of dom. Giuseppe Paglia.

[41] M. Morena Donnici, Evoluzione storico-legislativa delle magistrature preposte al rifornimento idrico di Roma (secc. XVI-XIX), in Il trionfo dell'acqua. Atti del convegno, cited; see E. Marconcini, La “magistratura delle acque” e la sua evoluzione dal XVI secolo al 1860, in Il trionfo dell'acqua. Acque e acquedotti a Roma, cit., pp.259-265, referring the work of Morena in M. G. Pastura Ruggiero, La Reverenda camera apostolica e i suoi archivi (secc. XV-XVIII), Roma 1984.

[42] P. Scavizzi, La rete idrica urbana in età moderna, in «Storia della città», IX, n° 29, pp. 77-96. See also M. Casciato, S. Mornati, C. P. Scavizzi, Il modo di costruire. Atti del 1° seminario internazionale (Roma, 6-8 giugno1988), Roma 1990.

[43] About the measure of current waters and the birth of modern hydraulic, see C. S. Maffioli, Out of Galileo. The science of waters (1628-1718). Foreword by Richard S. Westfall, Rotterdam 1994 e P. Buonora, Gli ingegneri e il Tevere: il percorso della teoria idraulica, in I rischi del Tevere: modelli di comportamento del fiume di Roma nella storia, Atti del seminario di studi (Roma 23 aprile 1998), in course of publication.

[44] P. Scavizzi, La rete idrica, cit., note 17, p. 91: by information of the enterprise ACEA, slope is m. 4 on km 18, 500 for Virgin aqueduct (0, 2 per km); m. 11 on km 27 for Felice aqueduct (0, 4 per km); m. 88 on km 32 (2, 75 per km) for Paolo aqueduct, that however has several different slopes. Evaluations about flood, complicated by the difference between the “double” oncia of Virgin and the “simple” oncia of Felice and Paola (usually accepted as modern roman oncia), are different between authors: oncia flood is evaluate about 0,46 liters per second, but evaluations about the entire flood are different. For Betocchi Virgin aqueduct brought once 3.840 in 24 hours, Felice 535, Paola 2.000. For Corsetti Virgin aqueduct brought 40 m3 in 24 hours, Paola aqueduct 20 m3. Prony e Scaccia give similar evaluations, but Rondelet affirms that the amount was much bigger: m3 180.500 in total in 24 hours: 94.181 for Paola, 65.782 for Vergine, 20.537 for Felice.

[45] See the drawing in P. Scavizzi, La rete idrica, cit., p. 84.

[46] This method was suggested by the “chierico di Camera” mons. Biscia; see the map of the tank of Montecavallo in P. Scavizzi, La rete idrica, cit., p. 81. It would be important to understand if this important moment of planning in the management of the hydraulic network was an original innovation or just a new employ of an ancient roman method, that planned secondary castella both for ruling supply, both for controlling pressure.

[47] Relazione sul condotto dell’acqua Paola ordinata da Monsig. Ill.mo e Rev.mo Giuseppe Vai Presidente dell’acqua, Roma 1789, f. XII; see C. Cancellieri, L’acquedotto Paolo, mentioned above, who use a report of the architect Vici of 1789.

[48] P. Scavizzi, La rete idrica, cit., tab. p. 88.

[49] Ibid., p. 89.

[50] Ibid.: information is in a report by C. Fea of 1784, published by Scavizzi in app. III. See also: A. Cambedda, L’Acquedotto Vergine (secc. XVIII-XX), in Il trionfo dell'acqua. Acque e acquedotti a Roma, cit., pp. 208-213, who mentions documents in Archivio Capitolino, Fondo servizio idraulico, especially b. 132; R. Motta, L’acquedotto Felice, ivi, pp. 220-225, mentioning maps in the Archivio di Stato di Roma and a map by G. Rainaldi of 1609; D. Cattalini, Acquedotti antichi: vicende e restauri nei documenti d’archivio, in Il trionfo dell'acqua. Atti del convegno, cit., pp. 73-82, about sources relating maintenance activities after Rome was the Capital City of Italy, in the Archivio Centrale dello Stato.

[51] A. Mastrobuono, Gli acquedotti contemporanei, in Il trionfo dell'acqua. Acque e acquedotti a Roma, cit., pp. 277 ss.; see the civic proud expressions employed by A. Betocchi, Le acque, cit., pp. 572-573, both concerning the quality of the water and concerning pressure pipeline techniques using cast iron.

[52] Archivio di Stato di Roma, Congregazione delle acque, b. 106, report by G. B. Contini, 18 June 1712.

[53] Ivi, b. 234, disposition 8 August 1756.

[54] G. Bodon, I manufatti idraulici di età romana nella storia e nella cultura antiquaria, in Utilitates necessaria, cit., p. 21: evidences in 14th century refer of some pipelines near the Coliseum called “forme” and water basin of Capocce. This "forma Claudiana" or "Lateranensis" is clearly represented in Dittamondo written and designed in 1447 by Fazio degli Uberti, in the Bibliothéque Nationale in Paris; see also a Dupérac drawing, ibid. p. 38.

[55] M. L. San Martini Barrovecchio, La Marrana o Acqua Mariana, le sue mole e i suoi opifici. Notizie dell'archivio del Consorzio conservato presso l'Archivio di Stato di Roma, in Gli archivi per la storia della scienza, Roma, 1995, p. 1282.

[56] R. Motta, La decadenza degli antichi acquedotti e la conduzione dell’Acqua Mariana, in Il trionfo dell'acqua. Acque e acquedotti a Roma, cit., pp. 203-205.

[57] Referred in the appendix of M. L. San Martini Barrovecchio, La Marrana, cit. p. 1289.

[58] C. Meyer, L'Arte di restituire a Roma la tralasciata navigatione del suo Tevere, Roma 1685, fig. 34.

[59] Archivio di Stato di Roma, Catasto Alessandrino, 429/23 e 24.

[60] M. Vaquero Piñeiro, Artigiani e botteghe spagnole a Roma nel primo '500, «Rivista storica del Lazio», a. III, n° 3 (1995), pp. 99-115, especially pp. 108-111.

[61] M. L. San Martini Barrovecchio, La Marrana, cit.; see also R. Lanciani, Le acque, cit., pp. 325-327.

[62] Moreover the mentioned streams, also a stream on the left side of the Aniene river is marked as “Marrana”; it supply a mill in a tower at the Casale del Cervaro, Archivio di Stato di Roma, Catasto Alessandrino, 430/30.

[63] See La valle della Caffarella. Catalogo della mostra (Roma, 14 marzo - 5 aprile 1981), Roma, 1981, p. 85.

[64] See the study by S. Ranellucci, made long before these manufactories began to be exploited creating the Appia Antica Park, in La valle della Caffarella, cit., pp. 121 e 128. He used maps of 18th century in Archivio di Stato di Roma, Collezione prima disegni e piante, 91/688, 689, 700 e 92/ 717 e 718, e Catasto Gregoriano, Agro 39; in appendix there are some reports from the Archivio Pallavicini.

[65] A. P. Frutaz, Le piante di Roma, Roma 1962, tav. 159.

[66] La valle della Caffarella, cit., pp. 139 ss.: there are detailed information in an engraving about the plague in 1656.

[67] Archivio di Stato di Roma, Catasto Alessandrino, 433a/5.

[68] Ivi, 433/38.

[69] Ivi, 432/I.

[70] Ivi, 423/74.

[71] La valle della Caffarella, cit., pp. 25-26: at the beginning there is the entire report about the property of Caffarella in Archivio Centrale delle Stato, Archivio Torlonia. Here there are no maps, but a precise description of every building including mills, that were then used for milling grains.

[72] P. Scavizzi, Nota su tre mulini idraulici da grano: i mulini di Pantano e Valle Marchetta (secc. XVI-XIX), «Rivista storica del Lazio», 2 (1994), pp. 205-244.

[73] Archivio di Stato di Roma, Catasto Alessandrino, 430/2 e 430/24.

[74] Ivi, 433/IV, 433/7, 14 e 39.

[75] Ivi, 432/20 e 28.

[76] I. Ait, Un aspetto del salariato a Roma nel XV secolo: la fabrica galearum sulle rive del Tevere (1457-58), in Cultura e società nell'Italia medievale. Studi per Paolo Brezzi, Studi Storici, fasc. 184-187, Roma 1988.

[77] There are many useful images in C. D'Onofrio, Il Tevere, cit.: see the engravings by a Holland anonymous, beginning of 18th century, of the floating mills at Ponte Rotto (p. 220), and some details by the Falda plan (pp. 232-233).

[78] I. Ait, I mulini e l’Isola Tiberina, Atti del Convegno “Roma e il Tevere. L’Isola Tiberina e il suo ambiente”, «L’acqua», 3/1999, pp. 61-66; see also U. Mariotti Bianchi, Roma sparita :'I Molini del Tevere', Roma 1976, expecially for the relationship between river mills and and other mills in Rome, p. 38.

[79] A. Chiesa, B. Gambarini, Delle cagioni e dei rimedi delle inondazioni del Tevere, Roma 1746.

[80] See the 1879 photograph in C. D'Onofrio, Il Tevere e Roma, Roma 1968, p. 190.

[81] R. Sorbello, Il Tevere prima dei muraglioni, in L’Ingegno del Tevere attraverso vicende storiche, valori ambientali, progetti e risorse inespresse, edited by S. Polci, Roma, Mediocredito, 1996, p. 81.

[82] I. Ait, I mulini, cit., p. 63.

[83] See the example of Leni family, ibid., p. 66.

[84] G. Margaritora, S. Magnaldi, L’Isola Tiberina. Introduzione alla idrografia dell'isola, in Atti del Convegno “Roma e il Tevere”, cit., pp. 11-16.

[85] Ibid., fig.2, p. 12 and Falda plan, fig. 3, p. 13; ruins of the “ship” would after obstruct the left branch maintaining thus the right branch.

[86] G. Santariga, Il piano urbanistico di recupero dell'isola Tiberina, in Atti del Convegno “Roma e il Tevere”, cit. pp. 25-26.

[87] Carlo Poni and others practiced a similar approach in the case of Bologna: Paesaggio e strutture produttive. La città di Bologna e il suo contado in età moderna, in Paesaggio: immagine e realtà, Catalogo della mostra, Milano 1981.

[88] See Regolamento sulla misura dei terreni e formazione delle mappe del catasto generale dello Stato ecclesiastico dall'art 91 del moto proprio de' 6 luglio 1816, Roma, Poggioli 1817. Chapter IV, Del brogliardo, sez. III, descrizione delle case (pp. 52-53), explains how to conform property denominations: “La casa abitata dallo stesso proprietario, si dirà, casa di propria abitazione. Se affittata o solita ad affittarsi, casa d'affitto. Se alla casa vi sono unite botteghe, magazzini etc., casa con botteghe colle rispettive enumerazioni, specificando se di proprio uso, o affittate [...]. Gli edifici di qualunque genere con macchine, siano animate a forza di uomini, o animali, siano a forza d'acqua, o di vento, o di qualunque altra specie, si segnaleranno sotto il nome particolare esprimente il proprio uso”: this description allow to get out from an anonymous classification every building.

[89] A. Guillerme, Les temps de l'eau. La cité, l'eau et les techniques, Champ Vallon, 1983, p. 8.

[90] This model came out from my work about several cities in Umbria: P. Buonora, La Valle Umbra. Genesi e trasformazione di un sistema idraulico (secoli XVI-XIX). Quaderni monografici of «Proposte e ricerche», n ° 17/1994; e Id., Il sistema idraulico delle città umbre nel catasto gregoriano, in In primis una petia terrae. La documentazione catastale nei territori dello Stato Pontificio, Atti del convegno (Perugia 30 settembre - 2 ottobre 1993), in «Archivi per la storia», a. VIII, n° 1-2 (1995).

[91] See also C. Terzano and M. P. Martinico, Acquedotto Vergine: tutela delle sorgenti, in Il trionfo dell'acqua. Atti del convegno, cit. pp. 249-258. Time and erosion took away the tuff layer protecting the springs from the surface pollution, obliging to adopt measures in the NPRG (the city planning) and by the ACEA agency to control damage produced by irregular development of the area.

[92] G. De Caterini, L’attuale gestione degli acquedotti Vergine, Paolo e Felice: prospettive future, in Il trionfo dell'acqua. Atti del convegno, cit., pp. 225-228.

[93] About the Azienda Comunale Elettricità ed Acque (ACEA), see S. Battilossi, ACEA di Roma, 1909-1996: energia e acqua per la capitale, Milano 1997.

[94] A. Mastrobuono, Gli acquedotti contemporanei, cited.

[95] A. Paglia, Sistema acquedottistico Peschiera-Capore, in Il trionfo dell'acqua. Acque e acquedotti a Roma, cit., pp. 296-304.

[96] D. P. Crouch, Water management in ancient Greek cities, New York - Oxford 1993.

[97] For Paris, were since 16th century were employed both pumps for drawing water from the river and aqueducts for a better supply, see L. Beaumont-Maillet, L'eau a Paris, Paris 1991; for London, C. F. Antonelli, Acque sporche. Londra e il 'Metropolitan Board of Works', 1855-1865, «Storia Urbana», 61 (1992): in London also the two traditional supply resources were raising water from the Thames and bringing spring water in aqueducts; about metropolitan cases of late 19th century see finally L. Anderson,, Fire and disease: the development of Water Supply System in New England, 1870-1900, in Technology and the rise of networked city in Europe and America, edited by J. A. Tarr and G. Dupuy, Philadelphia 1988.

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