DETAILED STUDY OF SECTIONS 



165 



from Long Island City to the Bronx. * Diamond drill borings have been 

 made for piers at the crossing of Hell Gate, f Gneiss was found on the 

 Long Island side at a depth of about 100 feet below mean high water. 

 On the Wards Island side of this crossing the rock is hornblende gneiss. 



MWrHtoftMte tL. 



mtTmrmm 





Stj 



Figure 11.— Section across Harlem River, 

 Along line of Second Avenue bridge. 



Between Wards and Randalls islands the gneiss surface was found at a 

 depth of only a few feet below tide. X 



Hell Gate reefs. — The government works at the entrance to this channel 



Center Pier 

 Caisson 

 Mor+h 



Figure 12. — Section across Harlem Ricer. 

 Along line of Willis Avenue bridge. 



included the removal of large masses of reef a considerable distance out 

 from Hallets point, a shelving ledge extending into the ship channel 

 from Mill rock, and the removal of the cap of Flood rock in the middle 



*See Engineering Record, vol. xli, 1900, p. 453. 



tSee plate xix for location of bridge. 



X Information furnished by Mr A. P. Boiler, chief engineer. 



