122 



BULLETIN OF THE ESSEX INSTITUTE. 



Higher up on the spur intersected by the western 

 tunnel sandstone dikes outcrop obscurely ; and the south 

 wall of what appears to be the most southerly dike is 

 exposed in two prospect holes, showing, like the greut 

 fault, a strong hade to the southwest. All along this 

 line of contact the granite has a finel}'^ brecciatedor semi- 

 crushed appearance, with much slickensiding along the 

 joints. On the spur above the second tunnel this contact, 

 not well exposed, is found again in the same direct line. 

 Between this contact and the tunnel eight hundred feet 

 to the north is granite with occasional inclosed masses 

 of foliated diorite and numerous dikes of sandstone. 

 About three of the dikes are large (10 to 50 feet) and 



Granite 



W 



■\ + + -^'^ + + 4- + + 



Saiidstone 



these are clearly parallel with the Ute fault. In several 

 of the dikes the sandstone is much coarser than usual and 

 practically indistinguishable from the ordinary brown 

 sandstone of the Potsdam. 



The next spur, which terminates below near the junc- 

 tion of Ruxton and Manitou Avenues (10), is all drift 

 in the first bench south of the railroad, but at the head of 

 this bench, about eight hundred feet from the railroad, the 

 Fountain beds can be seen dipping gently to the east ; and 

 on the steep front of the next bench a large sandstone 

 dike outcrops obscurely. The same conditions were noted 



