Reviews—Prof. Grubenmann—The Crystalline Schists. 329 
igneous rocks, the formation of the mineral components, the structures 
and textures and products of differentiation of the latter group are 
described. Chapter B (24 pages) treats of Metamorphism, under the 
headings of solvent, temperature, pressure, and factors peculiar to 
the substance metamorphosed. Chapter C (41 pages) deals with the 
product of metamorphism in its different forms of development, viz., 
mineral composition, structure, texture, separation planes, and jointing. 
Chapter D (7 pages) is devoted to the geological occurrence of 
crystalline schists, and is followed by a bibliographical list (4 pages). 
In chapter B, under the heading of ‘“ Pressure,”’ the fact is dwelt 
on that under high pressure minerals (and rocks) of high specific 
gravity, and hence small molecular volume, are formed, and numerical 
instances (partly from Professor F. Becke’s papers) of such volume 
changes are given. In chapter C, under ‘ Mineral Composition,”’ 
attention is drawn to the zones of metamorphism in accordance with 
depth proposed by Mr. C. R. Van Hise!; but, whereas Van Hise 
proposes an upper zone of catamorphism and a lower one of anamorphism, 
Dr. Grubenmann proposes three zones—an uppermost zone of moderate 
temperature (heat being liberated), small hydrostatic pressure, great 
stress, and predominating mechanical pressure effects; a middle zone 
of higher temperature (heat being liberated or absorbed), greater 
hydrostatic pressure, very great stress, predominating chemical pressure 
effects (decrease of molecular volume); a deepest zone of very high 
temperature (heat being absorbed), very great hydrostatic pressure, 
weaker stress, predominating chemical pressure effects (recrystallization 
without change of form). Dr. Grubenmann maintains that certain 
minerals and certain rocks are characteristic of each zone, and in his 
second volume he bases his classification on this view. 
Under ‘‘Structure,” in chapter C, many new terms (most of them 
suggested by Professor Becke) are introduced, e.g., crystalloblastic, 
idioblasts, xenoblasts, homceoblastic, heteroblastic, granoblastic, lepido- 
blastic, nematoblastic, peeciloblastic, etc. Professor E. Weinschenk * 
has found fault with these terms, asserting that they are nothing 
more than a re-coinage of old terms used to describe contact rocks. 
Professor Becke, reviewing Professor Weinschenk’s book,* maintains 
that his object was to sharply contrast the structures common to 
crystalline schists with the structures of igneous rocks and give 
appropriate names. 
Dr. Grubenmann’s first volume is interesting, and the 12 photographic 
figures of microscopic structures are instructive, but the rocks 
represented in the figures, their localities, the minerals shown in 
the sections, and the amount of magnification are not mentioned. 
The second volume begins with 9 pages of historical introduction, 
followed by 9 pages on the principles of the classification adopted 
by the author. It is primarily chemical and follows the method of 
1 For full details see his Treatise on Metamorphism (11}”x9"), pp. 1286, with 
13 plates and 32 figures. U.S. Geological Survey Monograph, xlvii (1904), reviewed 
by Mr. A. Harker in Nature, lxxiii (1906), p. 450. 
2 «¢ Spezielle Gesteinskunde,’’ Freiburg i/B, 1905, p. 11. 
5 Tschermak’s ‘‘ Mineralogische und Petrographische Mitteilungen,”’ xxv (1906), 
p- 238. 
