Plate 29 



Photomicrograph of Yonkers gneiss of the type to be used in the new 

 Kensico dam. Dinnan quarries. Magnified 30 diameters 



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^ Photomicrograph of diorite gneiss from " Garden quarry." JNIagnifica- 

 tion 30 diameters. The constituents are hornblende, biotite, feldspars 

 and quartz. 



