PETROGRAPHICAL ABSTRACTS AND REVIEWS 185 



peripheral "diorite" even before that mineral was individualized. The 

 transformation of augite to amphibole, accompanied by crystallization 

 of quartz, is considered to have been the final reaction, effected mainly 

 by the water and boric acid in which the vapors became relatively richer 

 as the consolidation of alkalies and silica progressed. 



M. de Lapparent believes that the action of the kind here described 

 is common, and especially, that it has occurred in certain American rocks. 



F. C. Calkins 



Michel-Levy, Albert. "Les terrains primaires du Morvan et 

 de la Loire," chap, v, "Etude petrographique et chimique des 

 roches eruptives du faisceau synclinal du Morvan," Bulletin 

 des Services de la Carte Geologique de la France, XVIII (1908), 

 209-68. 

 The area described is part of the central plateau of France, made 

 classic by the thorough studies of the elder Michel-Levy and others. 

 Its rocks furnished the basis for some important principles of the science, 

 and some of them are illustrated in the beautiful plates that accompany 

 the "Mineralogie Micrographique." A historical summary and bibliog- 

 raphy relating to these early researches is given in the present work. 

 The petrographic descriptions in this work are brief; its principal con- 

 tribution is a series of chemical analyses, twenty-five in number, which 

 are used to show the position of each rock in the American quantitative 

 classification and in that of Michel-Levy. 



The principal deep-seated rock is a coarsely porphyritic granite 

 (alaskose) with potash distinctly more abundant than soda. The pheno- 

 crysts of potash feldspar are the last constituents to crystallize. This 

 rock passes into microgranite and "microgranulite." Associated diorite 

 (hessose) and amphibolitic porphyries (andose and tonalose) are said 

 to have been formed by digestion of calcareous sediments in the granite. 

 No full argument in support of this assertion is made, the author evi- 

 dently considering that previous work by Michel-Levy and Lacroix 

 has established the frequent occurrence of this- type of endomorphism. 

 The exomorphic action of the granite has affected limestones, shales, 

 sandstones, and conglomerates. The most interesting result of the meta- 

 morphism has been the introduction of albite and orthoclase in all these 

 rocks, especially in close proximity to contacts, by "alkaline fumaroles" 

 from the magma. 



The volcanic rocks — of Paleozoic age — comprise: (1) Upper Devo- 



