Weed and Pirsson — Highwood Jits. Laccoliths. 7 



and there is here afforded a good opportunity to observe the 

 effect of the contact metamorphism. The fissile, platy sand- 

 stones at the contact, are changed to a dense, flinty rock of a 

 blue color, which is generally but a few inches in thickness and 

 the total effect about a foot ; in places, however, the change to 

 the blue rock, the maximum effect, may be as much as two 

 feet. Thus the actual amount of metamorphism produced in 

 the sediments is very limited. The igneous rock at the con- 



Fig. 4. 

 right. 



Mouth of dissectiDg gulch. Shonkinite resting on sandstones on the 



tact is very dense and dark, filled with augite and altered leu- 

 cite phenocrysts ; it is similar to that described in the outer 

 columns above. It maintains this character for a height of 

 about fifteen feet and then passes into an evenly granular, 

 coarse-grained shonkinite. This has a columnar parting which, 

 as one approaches nearer the center, is less evident than in the 

 outer cliff wall. The branching drainages now lose their per- 

 pendicular canyon-like character and widen out into V forms 

 with broader spurs between them, in places grassed over but 

 often showing wide expanses of naked rock. In other places 

 they are covered with heapings of morainal drift whose rounded 

 pebbles are composed in part of what appears to be rocks of 

 Bearpaw types and in part of Canadian. It is thus not local 

 but general in character, and thus possesses a peculiar signifi- 

 cance, which will be adverted to again in another place. It is 

 the most southern point reached by the drift in this place, and 

 marks the limit in this direction of the terminal moraine. 



