518 Reviews — Cordier's Classification of Bocks, ^x. 



I. — Description des Roches composant L'Ecorce Terrestre, et de 

 Terrains Crystallins constituant le sol primitif, outrage 



REDIGE d'aPRE LA CLASSIFICATION, LES MANUSCRITS INEDITS, ET LES 

 LE9ONS PUBLIQUES DE FEU P. L. A. CORDIER PAR C D'OrBIGNY. 



Paris, 1868. 



M D'ORBIGNY has rendered a useful service to geology by 

 I publishing a detailed classification and description of Rocks 

 by the late Professor Cordier, who for more than thirty years of his 

 long scientific career, has studied with extreme care, both in the 

 field and the cabinet, the composition, origin, position, and other 

 character of the rocks which constitute the crust of the globe. M. 

 Cordier's collection comprised more than 10,000 varieties of rocks, 

 chosen with special care, and classed according to his own method, 

 which is based on the physical, chemical, mineralogical, and geologi- 

 cal characters that rocks present, giving prominence to that of 

 composition. This colbction is now arranged in the Museum of 

 Natural History of Paris, and the work before us embodies the 

 classification of rocks as defined by M. Cordier, who unfortunately 

 during his lifetime published no treatise on the subject, with the 

 exception of an important memoir *' on the mineral substances which 

 enter into the composition of volcanic rocks of all ages," in the 

 Journal de Phjsique for 1815-16, so that the only knowledge to be 

 obtained of his system was from those who were fortunate enough to 

 attend his courses of lectures. His colleague, M. C. D'Orbigny, 

 published in the Dictionnaire universel de histoire naturelle (article 

 Boches), 1848, a succinct description of rocks from notes taken at the 

 lectures of M. Cordier. The present volume is an enlarged and 

 considerably improved edition of this article, embodying not only 

 the public lectures, but the manuscripts left by M. Cordier, as well 

 as a careful examination of the collection itself. The first part 

 contains the distinctive characters, specification, and classification of 

 rocks ; the second part comprises their detailed description, synom^my, 

 position, and industrial uses, and the third part includes an hitherto 

 unpublished manuscript " on the structure of the terrestrial crust, 

 and a description of the primordial rocks," as well as the memoir on 

 volcanic rocks above mentioned. 



The fundamental principle of the classification is that of composition. 

 Three great divisions are established. 1. Normal rocks, including 

 rocks proper ; 2. Abnormal, mineral veins and irregular deposits in 

 caverns, etc. ; 3. Meteoric rocks. 



The normal rocks are divided into four classes. 



Class I. Roches a base de Silicates. Families, Felspathic, Py- 

 roxenic. Amphibolic, Epidotic, Grenatic, Diallagic, Talcose, Mi- 

 caceous, Quartzose, Vitreous, ArgiHaceous. 



Class 11. Roches a base Acidefere. Families, Calcareous, Rock 

 Salt, Gypseous, Alunitic. 



Class III. Roches a base metallique. Families, Carbonate, Hydrate, 



