INTRODUCTION. 141 



termediate piers that' are 14 feet wide at the spring line. On the south of this 

 range of large arches, there is one, and on the north, there are sL\ arches, each 

 of 50 feet span, resting on piers seven feet wide at the spring line, and two abut- 

 ments that terminate the arch work of the bridge. From the abutments a con- 

 tinuous line of wall of dry stone work is extended to the gate chambers on each 

 side. The length of the bridge is 1450 feet. The height of the river pier above 

 high water line, is 60 feet to the spring of the arches, and 95 feet above the 

 lowest foundation. The arches are semicircular, and the height 100 feet to the 

 soffit or under side at crown ; to the top of the parapets 114 feet above ordinary 

 high water, and 149 feet above the lowest foundation. The widtli on the top of 

 the parapets is 21 feet. The space between the parapets is arranged to receive 

 and protect from frost two cast iron pipes, each four feet in diameter, and lying 

 12 feet below the grade line of the aqueduct, and connected at each end of the 

 bridge with the masonry aqueduct by gate chambers. To make the capacity 

 of the pipes for conveying water equal to that of the aqueduct, an extra fall of two 

 feet has been given across the bridge, and the aqueduct on the southern side 

 is depressed two feet below the grade to accommodate this arrangement. The 

 utmost care and skill have been bestowed in securing durable foundations for the 

 piers. The material of the bridge is well dressed granite. While the bridge 

 remains unfinished, the water is conveyed in iron pipes in the shape of an in- 

 verted syphon. The immense and expensive structure which has been de- 

 scribed, was deemed necessary, by the legislature, to prevent obstruction of 

 navigation of the Harlem river. 



The greatest depression of the Clendinning valley is 50 feet below the top of 

 the aqueduct, and the valley is 1,900 feet across. Streets cross the line of the 

 aqueduct in this valley at right angles. The aqueduct passes the valley on a 

 bridge, and archways are constructed over three of the streets. The archways 

 for each street are one for carriage way of thirty feet span, and an arch on each 

 side for side walks of ten and a half feet span. The style of masonry is the 

 same as that of the Sing-Sing bridge. That part of the bridge which has no 



