History of Sanitation

24 HISTORY OF SANITATION The ruins of a work of this kind that still exist on the Esquiline Hill at Rome, are about 200 feet long by 130 feet wide, and had a vaulted roof that rested on 48 im- mense pillars disposed to form rows so as to form 5 aisles and 75 arches. From the description of this interesting reservoir, the interior must have greatly resembled many of the covered slow-sand fillers re- cently constructed in this country, in which elliptical groined Roman Water Pipes made of Bored-out Blocks arches form the TOOf, of Stone which is carried on brick columns spaced as in the reservoirs at Rome, about 15 feet from center to center. Judging from the fact that not only the aqueducts but also the reser- voirs were covered to exclude light, it seems reasona- ble to conclude that Roman engineers were aware that absence of light prevented or altogether checked the growth of algæ and other objectionable forms of water vegetation. Nowhere in the writings of the early historians is any men- tion made of trouble due to this cause, but as the water supply of Rome was obtained from both ground (spring) and surface sources, which in many cases were mixed together, the resultant mixture would have furnished the best possible soil for algæ, the ground water providing the necessary mineral food and the surface water furnishing the seed. It is quite probable, therefore, that the aqueducts and reservoirs were covered to prevent such growths. 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