1891.] Recent Literature. 135 
RECENT LITERATURE, 
Justus Roth’s ‘‘ Allgemeine Geologie ’’ ' treats of the original 
crust of the earth and of the theory of metamorphism. In that part of 
the volume now before us the author maintains his position as one of 
the most indefatigable investigators of geological literature. As the 
result of his labors he has produced a book which at the same time is 
almost a complete index of the literature of metamorphism and a 
cyclopedia of the facts learned or surmised with respect to the 
phenomenon. To the plutonist it serves as a very welcome antidote to 
the great mass of neptunistic doctrine now penetrating the body of 
geological thought. In it is denied i _ oto the possibility of the 
alteration of a sediment into a crystalline-schist. The origin of those 
crystalline-schists that are not members of the original crust is ascribed 
in all cases to the dynamo-metamorphism of plutonic rocks. At the 
same time it is denied that pressure without attendant chemical action 
is able to produce such changes as are necessary in a rock to transform 
it from a granite or gabbro into a gneiss or a hornblende-schist. The 
necessary chemical action is thought to be sometimes the direct con- 
sequence of the pressure, and sometimes to be merely the ordinary 
processes of complicated weathering. No reliance is placed in the 
conclusion that the granulites of Saxony are regularly metamorphosed 
granites, or that the hornblende-schists are (as is supposed to be the 
case by Rosenbusch) ‘‘ metamorphic facies of gabbro.”” 
After discussing briefly the constitution of the original crust, of 
which the crystalline-schist formation is supposed to be the survival, 
the author plunges at once into the subject of metamorphism, which 
he takes up and treats with the same thoroughness as is evinced in the 
first two volumes of his work, The principal topic of the portion of 
the volume before us is the description of metamorphic phenomena, 
under which are described the action of lightning on rocks, the 
products of the action of coal burning underground (Erdbrande), and 
the changes produced in rocks by the intrusion through them of 
eruptives (contact-action). Under contact-action are treated the 
effect of igneous rocks upon coals, their effect upon inclusions caught 
up in them during their progress to the surface, and the result of their 
action upon eruptive and sedimentary rocks through which they break. 
1 Allgemeine und Chemische Geologie. 3 B.1 Abt. Hertz (Besser’ sche Buchhand- 
; lung), Berlin, 1890, 210 pp. 
