REVIEWS. 231 



In a work of this kind, brief and concise statements are necessary 

 in order to confine the volume to its proper size, but the different 

 subjects should receive discussion more or less briefly according to 

 their importance, and the more important subjects should not be 

 neglected while the legs important are treated in detail. The latter 

 course not only prevents a book from containing as much useful infor- 

 mation as it might otherwise do, but it also makes it extremely mis- 

 leading to the student, for it gives him an erroneous idea of the rela- 

 "tive importance of the different branches of the subject. Thus, in the 

 present volume, the discussion of iron covers 27 pages. Of this num- 

 ber only 18 pages are given to the description of iron deposits proper, 

 while nine pages are given to the enumeration of statistics which might 

 have been condensed into a third of that space. Moreover, the great 

 iron region of the Lake Superior country, which supplies more than 

 two-thirds of the iron ore used in the United States, receives only 

 three pages of treatment. The copper region of the Lake Superior 

 country receives only four pages, and the copper and silver region of 

 Butte City, Montana, one of the most celebrated mining localities in 

 the world, receives only two pages ; while other much less important 

 subjects receive many pages. Such inequalities might be justifiable 

 if the geology of certain regions were so simple that it could be 

 described in a few words, even though the commercial features might 

 be of great importance. In the instances cited, however, this is not 

 the case. 



Economic geology, including both the subject of ore deposits and 

 other subjects which properly belong to this branch of geology, is in 

 much need of accurate geological work and careful discussion. This 

 is especially true in the United States, which is preeminently the 

 mining region of the world ; and it is unfortunate that a treatise 

 relating mostly to the ore deposits of this country should have failed 

 to give the subject thorough treatment. The volume, though in some 

 parts it need not be severely criticised, shows in most parts an ex- 

 tremely superficial knowledge of economic geology, and contains many 

 the errors in statements regarding the mineralogical nature of ores and 

 geological nature of ore deposits ; it shows a want of knowledge of the 

 commercial features of the various mining industries, and it bears evi- 

 dence of a lack of the sense of proportion in the amount of space 

 given to different subjects. 



R. A. F. Penrose, Jr. 



