SUBTEREANEAN EIVER WALKER AND BOND. 717 



of structures above it. When the tunnel is completed, it will be one 

 of the most durable pieces of work ever constructed by man; for 

 practically nothing but an earthquake can destroy it, and even this 

 possibility is veiy remote, for the rock underl3'ing New York is of 

 very early formation, and not at all liable to seismic disturbance. 

 And so the city tunnel of the Catskill aqueduct is being bored 

 through the rock on an average of 200 to 250 feet below the surface, 

 except in places where the nature of the rock is of such a character 

 as to call for a much greater depth. 



The first dip takes place just above the Harlem River, where the 

 tunnel drops down to 362 feet below the ground level. Then it runs 

 practically horizontally until it passes the dip in the rock under One 

 hundred and twenty-fifth street. Thence it rises again, and main- 

 tains a practically constant level of 200 feet under the city until it 

 arrives at the ancient bed of the East River. A glance at the map 

 of New York City will show that the East River makes a decided 

 turn about the lower east side or " heel " of Manhattan. In pre- 

 glacial times the East River had no elbow in its course, but ran 

 directly across the heel of Manhattan, and it wore away the rock in 

 its bed to considerable depths. However, the large deposits of earth 

 and rock carried by the glaciers caused the river to be pushed east- 

 ward, out of its normal channel and over the solid rock beyond. 

 Wlien borings were made for the aqueduct through this section of 

 the city, it was found necessary to lay it at a depth of about 750 feet 

 below the surface. As indicated in the drawing on page 721, much 

 of the rock through this section is decayed and unfit to form the 

 walls of a high-pressure aqueduct which is being built to last for all 

 time. The present channel of the East River, on the other hand, 

 passes over solid rock, and is comparatively shallow. Seven hundred 

 and fifty feet is an enormous depth, second only to the great siphon 

 under the Hudson River, which is 1,114 feet below the river surface. 

 It so happens that the deepest shaft ever sunk in New York City 

 equals the height of the tallest building in the world. To illustrate 

 this enormous depth, our artist has taken the liberty of building the 

 Woolworth Building topsy-turvy — that is, from the ground down — 

 at the Clinton Street shaft at the west bank of the East River. Enor- 

 mous as is the building, yet it barely reaches the aqueduct at this 

 point. Evidently there will be plenty of cellar room over the tunnel ; 

 and yet it is worth noting, the aqueduct follows the street lines so 

 as not to trespass on private property. 



Arrived in Brooklyn, the aqueduct rises again to within two or 

 three hundred feet of the surface and is pushed as far as it is possible 

 to carry it in solid rock and yet communicate ^ith the surface. This 

 limit was found to be at the junction of Flatbush and Third Avenues. 



