422 Reviews — Classification of Bocks. 



There is an interesting review of G-eological Maps, and the relation 

 of Geology to AgTiculture and the question of the Coal-supply. 



In the Chronicles of Geology and Palgeontology will be found 

 discussions on several questions of theoretical interest, more par- 

 ticularly an account of Mr. Croll's " Speculations on Cosmical Causes 

 of Changes of Temperature, and on the Submergence of the Northern 

 Hemisphere during the Glacial Period," and of the papers by 

 Messrs. Heath, Carrick Moore, and the Eev. Professor Haughton on 

 the same subject, in the " Philosophical Magazine." 



leiEAT'IE'VT'S. 



I. — EocKS Classified and Described, a Treatise on Lithology. 

 By Bernard von Cotta. An English Edition. By Philip 

 Henry Lawrence, Eevised by the Author. 8vo. pp. 425. 1866. 

 London : Longmans, Green & Co. 



[1st Notice.] 



A TREATISE on Eocks, by Bernard von Cotta, rendered into 

 English by Mr. P. H. Lawrence, and revised by the author, 

 is a book that must of necessity find a place in the library of every 

 geological student. We are not altogether sorry, however, to find 

 that it does not (as M^e anticipated it might have done) supersede 

 our trusty referee, "Bristow's Glossary of Mineralogy,"^ which still 

 holds its own against the veteran invader. 



Dr. Cotta's work consists of three parts. Part I. is devoted to 

 Mineralogy; Part H. to Eocks, and Lithology proper; Part HI. 

 to the mode of formation and metamorphism of Eocks. 



Without any desire to withhold the meed of praise due to the 

 author for Parts H. and III. of this most valuable book, we cannot 

 refrain from offering a few needful critical observations upon Part I. 

 which we hope will undergo great revision in another edition. 



In Part I. chapter the first (p. 3), the author observes : — "As to 

 the much-debated question of classification of the minerals, we have 

 adopted one which appeared to us best suited for our present pur- 

 pose ; it is not exactly that of any one author. We have placed a 

 few of those minerals first which are of the most frequent occur- 

 rence ; otherwise the arrangement adopted will be found to corres- 

 pond in several respects with Dana's ' System of Mineralogy.'" 



This attempt of Dr. Cotta's to combine several systems of classifi- 

 cation in one has given rise, as will presently be seen, to many 

 difficulties, for the media via of mineralogy does not here prove to be 

 tutissima. 



The classification of Minerals, or, in fact, of any other natural 



1 A Glossary of Mineralogy. By H. "W. Bristow, F.G.S., Senior officer of the 

 Geological Survey of Great Britain, 1861. 8vo. pp. 466. (Arranged alphabetically, 

 with numerous woodcuts.) London : Longmans, Green, and Eeader. 



