484 REVIEWS 



commercial importance. In the chapter on iron, the Lake Superior 

 deposits receive an undue amount of attention in view of the title of 

 the book, and following what seems to have become a convention 

 among those intrusted to teach geology, a large number of stratigraphic 

 columns built up of many formations and members, doubtless of 

 interest to local geologists, have been introduced, but they add little 

 in elucidating the principles of the science. The reviewer would like 

 to see the chapter on iron recast in accordance with the genetic classi- 

 fication adopted in the book. As illustrating the first category of the 

 classification, the descriptions of the districts might then begin with 

 the igneous iron ores of Kiruna, Sweden, which have been carefully 

 studied by many able geologists and concerning which there is, as a 

 result of the attrition of ideas, a solid nucleus of established fact. It 

 seems desirable that this mode of treatment be extended to the other 

 metals also, and that the representative districts be selected regardless 

 of whether they are or are not in North America. Although the author 

 has purposely chosen the illustrative districts almost wholly from North 

 America, the procedure can hardly be commended, as it encourages 

 provinciaHsm and seems rather a concession to our American linguistic 

 laziness. In the chapter on copper seven of the eighteen districts 

 described are those containing disseminated deposits, which adds much 

 to the amount of information presented, but does not increase the num- 

 ber of principles exemphfied. For some of the "porphyry coppers," 

 descriptions of types not now illustrated by the book might profitably 

 be substituted, such as those of Mansfeld, Sulitelma, and Little 

 Namaqualand. 



In naming this volume The Principles of Economic Geology, Professor 

 Emmons has given it a highly attractive title — one which arouses the 

 expectation that the book thus distinguished will deal in a broad and 

 stimulating way with the firmly estabhshed generalizations of the sub- 

 ject. If in places it deviates from the ideal suggested by its title and 

 becomes burdened with details, these departures are after all easily 

 forgotten in view of the general excellence of the book. The subject 

 is accurately, clearly, and succinctly presented, and is well illustrated 

 by numerous carefully chosen text figures. The author has achieved 

 the plan he set himself to accompUsh — to give a conspectus of the sub- 

 ject for advanced students of geology — and for this purpose the book is 

 undoubtedly the best text on economic geology that has yet been 

 written. 



Adolph Knopf 



