136 INTRODUCTION. 



the villages of Sing-Sing, Tarrytown, Dobb's ferry and Yonkers, where, leaving 

 the Hudson and crossing the valley of Sawmill river and Tibbitts brook, it gains 

 the summit between the Hudson and East rivers, and continues on that summit 

 to the Harlem river, a distance of 32*880 miles of continuous masonry. Iron 

 pipes are then laid 1450 feet, on an arched bridge, across the valley of the 

 Harlem river, at an elevation of 114 feet above high tide. After crossing the 

 valley, the aqueduct of masonry is resumed and continued two miles to the Man- 

 hattan valley, which is passed with iron pipes, descending 102 feet to the bottom 

 of the valley, and continued rising again to its opposite side, the distance across 

 the valley being 0*792 mile. The masonry conduit is again resumed, and cross- 

 ing the Asylum ridge and the Clendinning valley, is continued 2 '173 miles to the 

 receiving reservoir at Yorkville. This basin is 1826 feet long and 836 feet 

 wide, and including its embankments, contains an area of thirty-five acres divided 

 into two parts ; from thence iron pipes are laid beneath the surface of streets 

 2 '176 miles, to the distributing reservoir at Murray hill, three miles from the 

 City Hall. 



This reservoir is 420 feet square, and covers four acres. It is divided 

 into two equal parts, and has an average elevation of 44 '05 feet above the 

 level of the adjacent streets. The length of the aqueduct, including the iron 

 pipes and reservoir, from the Croton dam to the receiving reservoir, is 45*562 

 miles ; and including the elevated surface of the Croton river, and the large 

 mains conducting the water from the distributing reservoir through the central 

 parts of the city, the entire length is 50 miles, of which the masonry conduit 

 constitutes 37 '067 miles. The rocks through which the line of the aqueduct 

 passes are two marble quarries in Westchester, and for the residue of the route 

 gneiss of many varieties. A large portion of the open cutting, and nearly 

 all the tunnel cutting, have been made through rocks, more than 400,000 feet 

 of which have been excavated. The formation of the ground is very irre- 

 gular. There are on the line sixteen tunnels, varying in length from 160 feet to 

 1263 feet, and being in aggregate length 6841 feet. The height of the ridges 



