Recent Literature. 



EECENT LITERATUKE. 



■Williams's Manual of Lithology 1 is written for the "begin- 

 ner in the subject who wishes a thorough knowledge in the presenta- 

 tion of the subject, in a fuller and more compact arrangement than 

 can be obtained in geological text-books. The arrangement is such 

 that those who wish to continue the work in the microscopic analysis 

 of rock forming minerals, as taught in petrography, will have nothing 



The latter statement of the author is notquite true, for, in his clas- 

 sification of the rocks discussed, he places among the crystalline schists 

 quartzite, pyroxene rock and olivine rock that present no traces of 

 foliation. In the main, however, the classification is good. The rocks 

 are divided into Primary Rocks and Secondary Rocks, and each of 

 these groups is separated into "Divisions" in accordance with their 

 chemical composition. Of the different families or "divisions" the 

 efTusive rocks are first described and then the intrusive ones. The 

 Secondary Rocks embrace the Debris, the Sedimentary and the Meta- 

 morphic divisions, the first of which differs from the second in consist- 

 ing of unconsolidated materials. 



Nearly all the rock varieties recognized by petrographers are briefly 

 described, and even many that are no longer recognized as distinct 

 types. The descriptions are all based on macroscopic characters, but 

 they are, in most cases, full enough to enable the user of the book to 

 identify the type. 



The terminology made use of in the description is somewhat differ- 

 ent from" that used in petrographical text-books, but, since it is em- 

 ployed in the description of hand specimens and not of their sections, 

 this is to be expected. All the terms used are clearly defined, and 

 many of the new ones introduced are perhaps needed. 



The main faults to be found with the volume are that it attempts to 

 discriminate between too many rock types, and that it contains too 

 many rock names that have long since gone out of use. In spite of 

 these faults, the treatise is a valuable one, and it should meet with 

 success. The typographical work is excellent. The plates are from 

 photographs, and are illustrative of rock structures.— W. S. B. 



1 Manual of Lethology : Treating of the Principles of the Science, with Special 

 Reference to Meguscopic Analysis. By Edward H. Williams. 2d Ed. New- 

 York : John Wiley & Sons, 1895. Pp. ri, 418; plates 6. Price, |3.00. 



