AQUEDUCTS. 



33 



aqueduct on the west side of Rome ; and Sixtus V. (1585) restored 

 the aqueduct of Trajan by mistake for the Marcian. These two, the 

 former called Paola, and the latter Felice, continued to be the only 

 means of supply until 1870, when the real Marcian was restored by a 

 company of Englishmen and Romans. The water is brought as far as 

 Tivoli in a stone conduit, and the rest of the way in cast-iron pipes. 

 It has sufficient pressure to supply the tops of all the houses. 



Fig. 3. Eeservoik of Aqua Marcia. (Interior.) 



Reference has been made to the aqueduct now building for Paris. 

 The supply of water required is 22,000,000 gallons per day, and the 

 aqueduct was designed to convey that quantity. It is intended for 

 household use only, the existing supply, which is abundant for other 

 purposes, having become somewhat polluted. It was calculated that 

 the aggregate yield of the three rivers which are to be turned to ac- 

 count would be 28,000,000 gallons per day ; but subsequent observa- 

 tion has shown that in very dry seasons it falls considerably below 

 the quantity required. It was therefore found necessary to sink wells 

 or shafts into the chalky formation in which the rivers have their rise, 

 to artificially increase the supply. The plan comprises conduits for 

 collecting the waters from the several soiirces called " conduits of 

 derivation," and a main aqueduct to which these converge. The 

 former are together about 50 English miles long, and the latter is 110. 

 The main aqueduct has a fall of 73f feet, and terminates in service- 

 reservoirs at Belleville 83f feet above the level of the city. Along 



VOL. XI. 3 



