230 W. CROSS — INTRUSIVE SANDSTONE DIKES IN GRANITE. 



detailed study is necessary before a plausible theory as to the origin of 

 these dikes can be advanced. 



The coincidence in direction between the dike system and the struc- 

 tural axis of the Front range would indicate that the dike fissures were 

 formed during some period of orographic movement; but as movements 

 parallel to this axis are known to have been repeated at intervals from 

 very remote geologic periods clown to the Tertiary or even more recent 

 time, this coincidence is of no value in ascertaining the age of the dikes. 



