November 28, 1913] 



SCIENCE 



775 



groundwaters into the crust of the earth is 

 appreciated; when the great restrictions upon 

 their actual amount which have been demon- 

 strated in recent years are grasped in their 

 full significance; and when the great depths 

 to which many veins extend are kept before 

 us; we may justifiably state, as on page 24: 

 " However important these (i. e., magmatic 

 waters) may be in the formation of certain 

 kinds of ore deposits, they are insignificant 

 in quantity compared to the great circulation 

 of atmospheric water." It sometimes seems to 

 the reviewer that even while stating newer 

 facts almost from force of habit we are in- 

 clined to reiterate older doctrines from be- 

 neath which the newer facts have largely re- 

 moved the foundations. Had we known at the 

 outset of the limited vertical distribution of 

 the meteoric groundwaters and of their small 

 amount, it is quite possible that we should 

 have had a less firmly rooted faith in them 

 as the prima facie source of deep-seated 

 circulations, and would have given other 

 kinds of water greater relative importance. 

 The subject is, however, young, and a 

 gradual modification of views may come in 

 time as we escape the hj'pnotic influence of the 

 past. Indeed, as we read Professor Lindgren's 

 subsequent pages, and especially Chapter VI., 

 we feel as if, when the actual phenomena were 

 reviewed, the magmatic waters seemed of 

 greater and greater importance. Indeed, who 

 can affirm that the surface waters were not 

 themselves once magmatic? 



The introductory portion also contains val- 

 uable chapters on faults, folds, openings in 

 rocks, textures of deposits and ore-shoots, on 

 almost all of which Professor Lindgren has 

 previously written in a most illuminating 

 way. The classification of rnineral deposits, 

 which is to form the framework of the later 

 pages, is introduced by a condensed review of 

 other schemes and of agents. 



The scheme of classification is the founda- 

 tion of the treatise. It is fundamentally based 

 on mechanical processes of concentration on the 

 one side, and chemical, on the other. While 

 these two have been emphasized in one way 

 and another by earlier writers, no one else has 



so logically and completely carried out the 

 chemical processes in determining the sub- 

 groups on the basis of temperature and pres- 

 sure. The types of mineral deposits are, 

 therefore, taken up in order, beginning with 

 reactions at the surface at ordinary tempera- 

 tures and pressures, passing to those in the 

 rocks at greater and greater depths and termi- 

 nating in the natural climax of those produced 

 by processes of differentiation in magmas. 

 Perhaps the question will arise in the minds of 

 some, as to whether we are sufficiently well- 

 informed regarding the temperatures and pres- 

 sures at which minerals develop in order to 

 make this grouping sound. The reply may be 

 made, that the associations of minerals in the 

 various types are in contrast; that we have 

 learned much from their artificial production; 

 and that the peculiar etch-figures afforded by 

 quartz, a mineral of wide occurrence, and 

 differing according to its crystallization above 

 or below its conversion point of 575° C, 

 have all given , critical data now of great sig- 

 nificance. 



Professor Lindgren reviews practically all 

 the famous mining districts of the world and 

 in connection with them discusses with full- 

 ness and illuminating insight the questions 

 of secondary enrichment, of persistence of 

 mineral characters with depth, of contact 

 zones, of magmatic segregations and of peg- 

 matites. Indeed, no student of the subject 

 can read these pages without feeling his inter- 

 est quickened and his grasp of the causes 

 which have led to the formation of mineral de- 

 posits greatly broadened. Professor Lindgren 

 has, therefore, as stated in the opening sen- 

 tence of this review, placed his colleagues and 

 students everywhere under a great debt by the 

 preparation of a masterly work. 



J. F. Kemp 



Der Mensch der Vorzeii. Von Dr. Hugo 

 Obermaier, Professor am internationalen 

 " Institut de Paleontologie Humain," Paris. 

 Mit 39 Tafeln, 12 Karten und 395 Textab- 

 bildungen. Allegemeine Verlags-gesell- 

 schaft, M. B. H., Berlin, Miinchen, Wien. 

 1912. 



