PETROLOGICAL ABSTRACTS AND REVIEWS 279 



upon, the authors group deposits as fragmental, chemical, and organic. 

 The various types of these are described, and much space is devoted to 

 their origin. An attempt is made to present criteria by means of which 

 the terrestrial deposits may be distinguished from each other and from 

 marine deposits. These criteria include the form and size of the grains, 

 and the presence or absence of certain minerals, but, as is pointed out by 

 the authors, there are such insufficient data on many of these points and 

 the exceptions are so numerous that safe conclusions can scarcely be 

 drawn. The absence of mica in wind-blown sand is notable, but this 

 criterion could not confidently be applied to cemented deposits where 

 mica might have been developed by slight metamorphism. 



The statement is made that because of variations in the chemical 

 composition of coals "they must have originated under widely different 

 conditions." This is hardly a necessary conclusion, since varying 

 amounts of inorganic matter must have been transported by wind and 

 water into the many basins of accumulation. The analyses of different 

 kinds of coals quoted are neither average nor typical analyses of their 

 types. 



The authors seem to accept the idea that the fusion of sediments on 

 a large scale is due to the great pressure of accumulated overlying matter, 

 but it is to be greatly doubted whether fusion on a large scale has ever 

 taken place, although there are undoubtedly many places where local 

 fusion has gone on. The thickness given for the Laurentian gneisses as 

 some 50,000 feet may be the result of complex duplication of beds by 

 faulting and folding. 



The geology of the Scottish Highlands, which has been so minutely 

 worked out in recent years, is presented in some detail as an illustration 

 of regional metamorphism. 



A final chapter on the systematic examination of the loose detrital 

 sediments is given under the authorship of T. Crook. 



Field data and abundant references to geological literature enhance 

 the value of the book and it is well adapted to elementary courses. The 

 figures are numerous and clear. 



E. A. Stephenson 



Iddings, Joseph P. "The Petrography of Some Igneous Rocks of 

 the Philippines," Philippine Jour. Sci., V (1910), 155-70. 

 Describes both plutonic and eruptive rocks. Andesites make up the 

 great bulk of the volcanic rocks of the island, basalts are next in impor- 

 tance, while dacites and rhyolites, so far as known, are rare and occur in 



