1891.) Mineralogy and Petrography. 367 
the earth’s crust nearly as large as that of Europe. Volcanic dust fell 
on an island ninety-five miles to the windward in such quantities that 
trees were crushed to the earth by the weight of its mass. During the 
eruption subterranean noises were heard at Caracas, and in the midst 
of the Llanos, which cover a space of 36,000 square miles. (Proc. 
Phila. Acad. Nat. Science, 1890.) ' 
MINERALOGY AND PETROGRAPHY.* 
Petrographical News.—The protogine of Mont Blanc isshown by 
Lévy? to be a true eruptive, apophyses from which penetrate the surround- 
ing schists and alter them, and break from them fragments which they 
hold as inclusions, These fragments have been regarded as basic 
segregations, and the surrounding schists have been looked upon as 
dynamo-metamorphosed phases of the protogine. Both of these views 
the author combats. Among the schists he finds eclogites, with diop- 
side in micropegmatitic intergrowths with quartz and feldspar, amphi- 
bolites and mica-schists, each of which classes is briefly described. The 
segregations mentioned oecur most frequently near the contact of the 
granite with the schists. Many of them resemble so closely certain 
phases of the schists that Lévy is compelled to regard them as frag- 
ments of these caught up by the eruptive during its passage from below. 
A microgranite from the periphery of the main mass of granite con- 
sists of corroded crystals of the first generation cemented by a granitic 
ground-mass. This fact is thought to be an indication of the correct- 
ness of the view that the constituents of granite are mainly of the 
second generation, those of the first consolidation having disappeared. 
To the southeast of Mont Blanc are quartz-porphyries which, accord- 
ing to Graeff,3 are genetically related to the granite composing the 
body of the mountain. Like the latter, the porphyries have been 
subjected to pressure, by which process much sericite has been devel- 
oped, resulting in sericite-schists. The present contact of the erup- 
tives with the gneisses and mica-schists of the Mont Blanc « massif ” 
is thought not to be an original contact, but one brought about by 
dislocations. The conclusions of Lévy and Graeff are thus seen to be 
in accord in some particulars, while in others they are at variance. 
Fuller discussions are promised later.—In the first part of a general 
_ 1 Edited by Dr. W. S. Bayley, Colby University, Waterville, Me.. 
2? Bull. des Serv. d. 1. Carte. gèol. d. la France, No. 9, 1890. 
. ie phys. et nat., Nov., 1890. 3 
