Reviews. 



Geology and Mming Industry of the Cripple Creek District, Colorado. 

 By Whitman Cross and R. A. F. Penrose, Jr. Extract 

 from the Sixteenth Annual Report of the Survey, 1894-5. 

 Part II : Papers of an Economic Character. 



This report of Messrs. Cross and Penrose is to be classed as one of 

 the most valuable of the publications on economic subjects issued by 

 the Geological Survey. Though less elaborate and accompanied by 

 fewer maps and illustrations than the bulkier monographs of past 

 years, these considerations are largely offset by the timeliness of 

 appearance and the handiness of the separate form in which the report 

 was first issued. For no matter how great the intrinsic merit of the 

 publication or the labor devoted to its preparation, its value lies to a 

 great extent in its appearing at the right time and in a form suitable 

 for readv usq, and this particularly with a work relating to mining in 

 a new camp. The report is the outcome of the joint field labors of 

 the authors, prosecuted during three months in the autumn of 1894. 

 It was written, printed, and issued in 1895, and the edition of the sep- 

 arates, as well as of the related Pikes Peak folio, was exhausted before 

 the end of 1896. 



The combined report covers about 200 pages of the large octavo 

 size of the annual reports. It is illustrated by thirty-seven figures, 

 seven plates, and one supplementary geological and topographic map 

 which is inserted at the end of the report. The report is divided into 

 two parts. The first, of 109 pages, by Mr. Cross, treats of the general 

 geology and is in great part devoted to the' important subject of the 

 petrography of the district; Part second, by Mr. Penrose, deals with 

 the mining geology of the district. The latter is exclusively the sub- 

 ject of this review, Mr. Cross' valuable report requiring the attain- 

 ments of a specialist for adequate treatment. 



Chapter I. of Mr. Penrose's report consists of a brief outline of 

 the history of mining in the camp. Operations were practically begun 



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