136 BULLETIN OF THE ESSEX INSTITUTE. 



but the gray limestone is south of the white, as before. 

 The sandstone dike can be traced by float across the lower 

 slope of the next spur toward the mountain road. Be- 

 yond the Cheyenne Mountain road my observations have 

 not extended, and 1 have no information as to whether or 

 not the Ute fault, with or without the accompanying sand- 

 stone dikes, can be traced farther in that direction. The 

 topographic indications are certainly very favorable to 

 their occurrence, at least as far as Deadman's Caiion ; but 

 probably the extensive mesa and slide deposits make 

 satisfactory outcrops few and far between. 



The Ute fault series of sandstone dikes has been proved 

 for a distance of over twenty miles, and an extreme 

 length of thirty miles or more is certainly by no means 

 impossible. Professor Stone's observation, cited by Cross, 

 demonstrates the existence of another extended system of 

 dikes in the Pike's Peak region. This occurs in the valley 

 of Turkey Creek, south of Cheyenne Mountain, and is 

 quite certainly not connected with the Ute fault. Ac- 

 cording to Stone, the Turkey Creek system has been 

 located for about twelve miles, and through his courtesy 

 I am able to cite a third system, since he writes me that 

 a short sandstone dike occurs about half a mile east of 

 Nipple Mountain, near Wilbur Station, southeast of Crip- 

 ple Creek. These facts indicate the probable discovery 

 of other systems, as the region is more thoroughly studied. 



ORIGIN OF THE SANDSTONE DIKES. 



Mr. Cross has briefly discussed this topic, without 

 arriving at a definite conclusion. He recognizes that 

 these sandstone dikes are radically distinct in character 

 and origin from those described by Diller in California, 

 and asserts that the known facts do not indicate the source 



