REVIEWS. 855 



like that pointed out by the present writer in the greenstone-schists 

 and associated rocks of Lake Superior. (Bull. U. S. Geol. Surv., 

 No. 62). 



Professor Termier of the Ecole des Mines at Saint-Etienne has given 

 in his essay on the constitution of the Vanois massif in Savoy, another 

 excellent contribution to our knowledge of the effects of orographic 

 movement in metamorphosing Alpine sediments of Caboniferous and 

 Triassic age. This is all the more welcome from France where 

 dynamometamorphism has been rather slow to gain recognition, in 

 spite even of the convicting demonstrations by Gosselet in the Ard- 

 ennes. The schistes lustres, which bound the Vanois massiv on the 

 east, considered by Lory as upper Triassic, are made by Termier pre- 

 Carboniferous. The principal horizons which have been studied with 

 reference to metamorphism are the Permian and Trias. The former is 

 represented mainly by quartzites and phyllites, altered and recrystall- 

 ized in proportion to the disturbance they have suffered. In the 

 phyllites rutile, sphene, tourmaline, garnet, zoisite, epidote, glauco- 

 phane, chloritoid, various micas and feldspars, and quartz have been 

 abundantly developed. Many interesting details and figures are given 

 to illustrate the development of these new minerals. Albite crystals 

 by their growth in the phyllite have sometimes displaced all, or only a 

 part of the original schist constituents, while in other cases they have 

 not disturbed their position at all. Various minerals are traced in 

 their gradual development from indistinct nodules to perfect crystals. 

 Only the metamorphism of sedimentary beds is considered, and the 

 general conclusion is reached that their alteration is independent of 

 eruptive action, and entirely conditioned by the heat produced by 

 orographic movements. This heat is supposed to have been very 

 gradually produced and very slowly dissipated. The author thinks 

 that a temperature of 200 to 250 C, continued through ages, would 

 suffice to crystallize new compounds like feldspar, quartz, carbonates, 

 tourmaline, chlorite, micas, ilmenite, rutile, etc., without affecting the 

 bulk composition of the rock. In exceptional cases an intenser move- 

 ment might give a temperature of 300 C, sufficient to produce amphi- 

 bole, which will appear as glaucophane, if, as in his Permian beds, the 

 original sediments are very rich in soda. 



George H. Williams. 



