456 REVIEWS 



Blake ' refers to the Archean the thick layers of gneiss forming the 

 southern flank of the Santa Catalina Mountains, Arizona. The gneiss 

 is in flat layers representing beds. A part of it is augen gneiss; other 

 layers are quartzose and seemingly quartzites. 



Knight^ in connection with the discussion of the artesian basins of 

 Wyoming gives a brief description, accompanied by a map, of the 

 geology of the state. Algonkian and Archean rocks are present. The 

 Archean rocks consist mainly of granite, in places cut by dikes of 

 porphyry containing mineral ores, which can be seen in typical expos- 

 ure at Sherman, Laramie Peak, east of Whalen Canyon, along the Big 

 Horn, Wind River, Gros Ventre, Medicine Bow, Ferris, Seminoe, and 

 Owl Creek ranges, along the Sweetwater River, a few miles northwest 

 of Rawlins, and north of Clark's Fork, in Big Horn county. 



The Algonkian rocks are for the first time separated from the 

 Archean. They consist of schists in great profusion, marbles, and 

 quartzites, all cut with dikes of eruptive rocks. They occur in granite 

 basins in unconformity with the Archean, and form important bands 

 in numerous localities. The strike of the series varies from north 

 to northeast and the dip of the strata is seldom less than 65-75°. 

 The thickness of the entire series has not been absolutely measured, 

 but including the eruptive band, which does not form an important 

 part; the maximum thickness in Wyoming is about 20,000 feet. Typical 

 areas have been found in the Black Hills in Wyoming, and occasional 

 outcrops from that place to the Hartville hills — one exposure being 

 east of Lusk, another at Rawhide Butte, and a large one in Whalen 

 Canyon. They also occur at Halleck Canyon, Plumbago Canyon, in 

 the Medicine Bow Mountains, nearly all of the Sierra Madre Moun- 

 tains, in the Seminoe Mountains and in the Sweetwater mining district 

 of the Wind River range. None of these localities have been examined 

 in detail ; but sufficient work has been done to prove that these rocks 

 were at one time sedimentary, and that they have been changed by 

 metamorphism to schists. In the Sweetwater districts the rocks are 

 chiefly schists ; but there are many bands of erruptive rock that form 

 dikes which follow the strike of the formation. 



' Mining in Arizona, by Wm. P. Blake : published in report of the Governor of 

 Arizona to the Secretary of the Interior, Washington, 1899, p. 142. 



° A preliminary Report on the Artesian Basins of Wyoming, by Wilbur C. 

 Knight : Wyoming Experiment Station, Bulletin No. 45, 1900. Part on pre-Cam- 

 brian, pp. 111-116. With geological map. This is the first geological map of Wyo- 

 ming that has appeared. 



