GEOLOGY OF THE NEW YORK CITY AQUEDUCT 169 



very encouraging. The decay is shown not to be confined to mere 

 seams. The doubt raised by so much bad ground has finally led to 

 the adoption of a different plan for crossing Foundry brook valley 

 and no further data are likely to be added by this work. As it now 

 stands the borings at Foundry brook indicate the deepest decay of 

 any yet made in granites or gneisses except those of Pagenstechers 

 gorge on the north side of Storm King mountain. Both cases are 

 of similar origin and history, but Foundry brook is apparently the 

 more complex in occurrence. There are several parallel zones 

 along which there is extensive decay to a depth of more than 300 

 feet. 



