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words, the principles of the development of ore deposits are the principles 

 of the segregation of those elements which are of importance to man, but 

 which, for the most part, are so rare that they are not included in the dis- 

 cussion in the chapter on the redistribution of chemical elements. 



It is not possible in a summary to give any adequate idea of the scope 

 of this treatise on metamorphism. A very broad range of facts, extending 

 far beyond what might at first be regarded as a part of a treatise on meta- 

 morphism, is considered from the energy point of view. It is believed that 

 the volume marks a great stride in the reduction of the entire subject of 

 physical geology to order under the principles of physics and chemistry, 

 and points out the way for a treatment of the entire subject from this point 

 of view. K. 



The Stone Reefs of Brazil, Their Geological and Geographical Rela- 

 tions, with a Chapter on the Coral Reefs. By John Caspar 

 Branner. (Bulletin of the Museum of Comparative Zoology, 

 Cambridge, Mass., 1904.) Pp. 285, 91 plates. 



This contribution stands almost in a class by itself in that it adds a 

 new variety to the recognized type-formations. While reefs of this class 

 have not been wholly unknown to geologists, they seem to have been 

 regarded rather as individual aberrancies than as expressions of a type 

 dependent on regional conditions and prevalent within the range of those 

 conditions. They have, indeed, been mentioned more or less frequently, 

 but oftenest in such a way as to carry the suggestion that they were coral 

 reefs or some modification of such reefs due to accessions of hardened 

 sand. Their distinctive nature and its peculiarity was recognized by 

 Darwin, Plartt, and a few others, but this comprehensive treatment by 

 Dr. Branner is the first exposition that has brought forth their broader 

 relations and their true significance; indeed, it is the first that has made 

 clear the essential fact that they are not mere aberrant phenomena, due 

 to a fortuitous combination of local conditions, but rather a type of forma- 

 tion, albeit a rare and regional one. While not confined to the coast of 

 Brazil, these sandstone reefs are so limited and peculiar in their distribu- 

 tion, so far as present knowledge goes, as to give special interest to their 

 localization. In the opinion of the author, this regional localization 

 carries genetic significance, and the discussion of this forms a most inter- 

 esting feature of the book. The pecuUarities of these reefs are summar- 

 ized by the author as follows: 



