prevent such growths. [Illustration: Roman Water Pipes made of Bored-out Blocks of Stone] Besides the principal reservoir, each aqueduct had a number of smaller ones at different points in the sections they supplied, to provide that neighborhood with water. It is estimated that all told there were 247 of the auxiliary public reservoirs scattered throughout the city. These reservoirs were supplied from the principal reservoir through pipes of lead, burned earthenware, and in some cases bored out blocks of stone. Burned earthenware pipes were generally used not only on account of their greater cheapness, but because the Romans were aware of the injurious effect of lead poisoning, and looked with suspicion on water that had been conducted through lead pipes. When a number of individuals living in the same neighborhood had obtained a grant of water, they clubbed together and built a private reservoir into which the whole quantity allotted to them collectively was transmitted from the public reservoir. The object of private reservoirs was to facilitate the distribution of the proper amount of water to each person and to avoid puncturing the main aqueduct in too many places. When a supply of water from the aqueduct was first granted for private use, each householder granted the privilege obtained his quantity by tapping a branch supply pipe into the main aqueduct, and conducting the branch to a domestic reservoir within his own house. Later when the system of private reservoirs was adopted, each domestic supply of water was obtained from the private reservoir and piped to the domestic reservoir which was made of lead. [Illustration: Trophies of Marius] The façade of an aqueduct reservoir known as the "Trophies of Marius" may be seen in the accompanying reproduction of a woodcut made in the sixteenth century. The ground plan shows part of the internal construction. The stream of water is first divided by the round projecting buttress into two courses which are again sub-divided into five minor streams that discharge into the reservoir as indicated in the cut. [Illustration: Old Roman Lead and Terra-cotta Pipe]