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Lead and its importance for the archaeological research

by John Foss and Egenia Salza Prina Ricotti

by John E. Foss and Egenia Salza Prina Ricotti

LEAD IN ARCHAEOLOGICAL SITES
John E. Foss and Eugenia Salza Prina Rcotti

Before exposing how much the results of the work of Prof. John Foss sz Per prima cosa egli aveva stabilito were important for my work on Villa Adriana, and how much they helped archaeological research I will rapidly resume them. Prof. Foss established which were the metals present in the samples of soil of the different archaeological sites examined and in what quantities. Among other things he discovered that the amount of extractable lead found in these samples considerably exceeded that in the ground of the surrounding fields and agricultural areas. It was clear that the presence of such a large amount of lead had to be connected with the ancient use of leaden pipes in irrigation. These data varied from place to place, and they were certainly governed by a certain number of variables. For what I can judge they are certainly tied with three of them, the more important of all:

1 - the length of time during which the site had been irrigated;
2 - the kind of trees, shrubs or plants grown there;
3 - the quality of the water and the kind of compounds it made with lead.

Thus, for instance, among the sites examined by Prof. Foss we find a minimum of extractable lead content in a farm of Boscoreale where, from archaeological researches done by prof. Jashemski, we know that there was a large vineyard (in Italy vines don't need to be irrigated) plus a small orchard set around a well and surely watered with pails lifted from it. There was therefore a minimum of irrigation during the limited time before the eruption of 79 A.D.
Looking the other archaeological sites taken in consideration we still find a limited amount of lead in another important place: Oplontis, the villa which, probably, belonged to Poppea. Apart from the fact that also this villa was destroyed in 79 A.D. by the Vesuvius, the building doesn't seem to have been connected with an aqueduct. Therefore the irrigation had to be furnished by cisterns and wells and the use of leaden pipes must have been very limited. Moreover the garden, accurately studied by Prof Jashemski, consisted mainly of box trees, bushes which dont need much watering, and plane trees, which, with their deep rooting, didn't need any.
More lead is found in Pompeii where, starting from the Augustan period, an aqueduct had been in function and where big leaden pipes have been found. Moreover the peristyle gardens of the place certainly favored the kind of plants which needed much watering. Thus it is small wonder if here the content of lead is higher than in Boscoreale and Oplontis. The same must be said from other Campanian sites destroyed in the erupìtion. But the place which was really the most interesting and illuminating for this kind of research was, without any doubt Villa Adriana, and this not only because its soil contained far more lead than any other place, but because the different parts of its extensive area had not been occupied for the same length of time, thus it was possible to tie the different concentration of lead with the length of irrigation..
The map of the imperial residence on which Prof. Foss marked with contrasting bright colors the different concentrations of extractable lead, give a clear and immediate view of what had happened there through the centuries and give a better insight into the life of this imperial residence.
And now we enter the archaeological part of the study. It is important to note that Prof. Foss's results validated what had emerged from archaeological research. First of all, they confirmed the long life of the central part of the site. As a matter of fact, even if nearly all the buildings present in Villa Adriana had been built at the beginning of Hadrian's reign, his project was centered around an ancient republican villa which was inhabited from the end of the III cent B.C.. Many scholars think that the property belonged to the Ælian family and that Hadrian already knew the place and cherished it. Certainly he preserved and restored the original building and made it his private quarters, but he also had to occupy grounds in which there had not been any previous settlement, and probably he also had to buy many plots of neighbouring land to have an area large enough to host the imperial residence he had long dreamed of.
This situation is reflected on Prof. Foss's map. We can see that the higher concentration of lead is to be found around the republican villa where the Hadrianic settlement implanted itself on the republican one, and where the succeeding emperors chose to stay, as is clearly shown by the presence of restorations with late masonry in the walls, the cutting of large halls into small cubicles, the removal of the marble slates which lined the walls and their replacement by cheap painted plaster datable to the late empire. Consequently the higher concentration of extractable lead is found in the very places where the settlements went on from the III cent. B.C. up to the Barbarian invasion.
Very indicative of the situation is the garden set between the Small Baths and the "Edificio a Tre Esedre" where the extractable lead reaches the incredible level of 1234 mg/ kg. Therefore this place must have been irrigated more than any other part of Villa Adriana. The explanation of what happened here is given us by the ruins of a fine nymphaeum of the Augustan period (fig.1; 4. a) set on the north side of the Piccole Terme. It is evident that this monument could not have existed if behind it there had not been a large water reservoir, probably dating from the beginning of the republican settlement - a large cistern embellished afterward by the monumental fountains. In Hadrianic times the water reservoir was displaced by the Baths, but water continued to get there from the big piscina limaria that furnished both Thermae. Thus water must have always been plentiful and therefore plants which needed to be frequently watered could be grown here. Plentiful irrigation with leaden pipes must have lasted at least eight centuries to produce the high lead concentration in this soil.
Apart from this special garden and the Palace with the "Villa repubblicana" which continued to be used from the Republic through the end of the Empire, places in which the quantity of extractable lead varies from 500 to 1000 mg/kg of the soil, we find a blue zone which still contains a very high quantity of the mineral, around 200 to 500 mg/kg. This part includes the Canopus Valley with the Great Entrance Hall down to the back of the Pecile. It extends itself in back of some lodgings for the staff on the other side of the Pecile, and south of the barracks under the Venus of Cnidus terrace. The same quantity of lead is also found in a beautiful pavilion on the Southeast side, which was probably also used after Hadrian's death. All these places are peripheral to the republican landed property, as one can plainly see by looking at the map, areas that may or may not have been part of the ancient estate, but that had probably been kept as pastures for the cattle and where Hadrian was the first to build. Because of their beauty, these parts of the Hadrianic residence seem to have been kept in order up to the end of the empire and at least used as gardens--four centuries as opposed to the eight of the red zone, with the half content of extractable lead in the soil implying half the time of irrigation.
After this there is the yellow zone, where the lead content varies from 50 to 200 mg/kg. It is evidently a part that was scantily cultivated, which corresponds to a kind of belt to keep people away from the Emperor's private quarters, a belt we find in all imperial residences beginning with the Domus Aurea, around which Suetonius describes a vast extension of woods and meadowland; the same zone which also existed in the Villa Albana of Domitian.
But the most astounding fact is that there is no lead in a building of Villa Adriana which had been indicated as a Palace and could probably have been prepared for Sabina. In reality history makes clear what must have happened: Hadrian took his wife with him on his second journey. When they started, the Academy was still not ready. They found it finished on their return in 135 A.D., but Sabina, who died shortly after in 136 A.D. and was probably already ailing, never went there. Hadrian himself died in 138 A.D. and, as we have seen, his successors used only a part of this overly large residence. The Academy was far away from everything and not very convenient. While Sabina and Hadrian, who hated each other and did not particularly like to meet, could find it desirable to live as far apart as possible without creating too much scandal, other emperors preferred to live at closer quarters with their spouses. Thus the Academy was never lived in, and the lead content of the soil now proves without doubt a hypothesis which until now was only a supposition.
Summing up what has just been demonstrated, we have seen that analysis of the extractable lead content of the soil may prove to be a valid tool for archaeological research. Apart from the fact that it can indicate where there was a garden or a farm--which is already important for reconstructing ancient life--if we can succeed in determining such variables as the species that were probably cultivated there, we can probably also get some indications of the length of the settlement and the kind of exploitation of the area. For Villa Adriana at least the findings of Prof. Foss have proved an invaluable help, and have allowed us to determine the truth of many hypotheses.


Bibliography
Bibliografia
J. E. FOSS e E. SALZA PRINA RICOTTI, "Lead Pipes Use in Ancient Roman Irrigation System and Content of Pb in the Soil of Archaeological Sites" in Bullettin of the Metal Museum, Vol. 26 (1996-II) pp. 37-47.