REVIEWS. 531 



Utah, South Dakota, Minnesota, Iowa, Wisconsin, and Michigan. 

 They are known, but their areas not defined, in various other localities. 

 The summaries of the several chapters, or their sections, the final 

 chapter, and the maps, should serve as a text-book on"-pre-Cambrian 

 geology for all advanced students in our universities. Not only will 

 the best information available be thus put into their hands, but the 

 whole treatment of the subject is such as give an intelligent insight into 

 the methods of geology, and into the methods of science as well. 



Rollin D. Salisbury. 



