Geology and Mineralogy. 253 



liberation of heat, in the outer zone from chemical reaction, in 

 the inner from reduction of volume ; and thus metamorphism 

 conforms to the apparent law of the universe of dissipation 

 of energy. 



Chapter II treats in detail of the forces of metamorphism ; chem- 

 ical energy, gravity, heat, and light. Chapter III of the agents, 

 which are gaseous and aqueous solutions and organisms. 



Of great use to the working geologist and mineralogist is 

 chapter V, which treats individually of the geological relation- 

 ships, genesis and alterations of each of the rock-making min- 

 erals. The alterations are ordinarily such as take place in the 

 zone of katamorphism, but the author points out that upon the 

 altered materials being brought again into the zone of anamorph- 

 ism the reactions are reversible and, provided that the results of 

 decomposition are present in suitable proportions, the original 

 mineral may be reproduced. Some of the more complicated 

 reactions have been written out chemically for the first time, and, 

 as pointed out by Van Hise, must be looked upon as first approxi- 

 mations and suggestive for further study. 



The following three chapters, YI, VII, VIII, treat in detail of 

 the belt of weathering, the belt of cementation and the zone of 

 anamorphism. In regard to the belt of weathering besides a 

 statement of the laws governing the changes a number of new 

 features are developed, but special emphasis is placed on systema- 

 tization under laws of physics and chemistry, of a vast number 

 of facts already known. 



In chapter VIII, among other matters are treated the meaning 

 and method of rock flowage, the generalization being arrived at 

 that rock flow is mainly accomplished through continuous solu- 

 tion and deposition, that is, by recrystallization of the rocks 

 through the agency of the contained water, the rocks throughout, 

 with the exception of an inappreciable amount which at the 

 moment is in solution, being crystallized solids. 



The student of metamorphic geology is expected as a matter 

 of course to study carefully the entire monograph and a review 

 should hardly be written for him, but rather for the general 

 student of geology. 



To such, perhaps, the most interesting chapter is the eleventh, 

 upon the relations of metamorphism to the distribution of the 

 chemical elements, and a more extensive review of this chapter 

 will therefore be given. 



Metamorphic processes operating upon the lithosphere have 

 redistributed the elements of the original igneous rocks tending 

 to segregate them into the several groups of sedimentary rocks, 

 the hydrosphere and atmosphere, this redistribution concerning 

 many large questions of geological theory. The author states, — 

 " So far as practicable redistribution is dealt with in a quantita- 

 tive way, . . . made more with a view of stating the various 

 problems which in the future will undoubtedly be satisfactorily 



Am. Jour. Sci. — Fourth Series, Yol. XIX, No. 111. — March, 1905. 

 17 



