REVIEWS 761 
It is particularly in the study of endomorphic contact action that 
the bulletin demands the attention of petrographers. While the slates 
do not seem to have exerted any very pronounced effect on the gran- 
itite except in the way of slightly altering its structure, the limestone 
contact is one pronounced, both from the quality of the changes 
wrought and from their great areal extent, to be the most noteworthy 
phenomenon of the region. By the assimilation of the limestone, the 
granitite successively loses the alkaline feldspars, orthoclase, microcline 
and anorthoclase, and lastly, quartz, and gains other constituents rich 
in lime, the basic plagioclases and hornblende. The result is to pro- 
duce a gradual replacement of the pure granitite magma in the massif 
by secondary mixtures which have crystallized out as hornblende- 
granitites, quartz-diorites, diorites, norites and hornblendites. Biotite 
and hornblende appear in the whole series. When, finally, olivine 
replaces all the feldspars, the resulting rock, though again, the product 
of assimilation in the same way as the more acid rocks just enumer- 
ated, is an amphibole peridotite! The evidences for the fact of mag- 
matic incorporation are exceptionally strong; they may be summarized 
as follows: 
1. Field observations in connection with many localities of actual 
contact and the study of numerous thin sections showed ordinarily an 
insensible transition in mineralogical characters from the normal gran- 
itite to the basic types. 
2. These hornblende rocks are developed only in zones of contact 
between typical granitite and the limestone, or else in bands which rep- 
resent the prolongation of limestone layers stretching out into the 
granitite—a significant mode of occurrence emphasized in the memoir. 
Such basic bands, extending through the granitite from one end of an 
interrupted limestone layer along its strike to the corresponding end 
on the other side of the stock, are interpreted as being the product of 
recrystallization of mixed granite magma and digested limestone 
during a prolonged static condition of the igneous rock—that is, a 
period of quiescence as regards ascensional or lateral movement in the 
mass. It is hard to resist the conclusion that the map and numerous 
cross-sections of M. Lacroix prove such a long continuance of the 
limestone in contact with the particular magma now crystallized and 
visible where erosion has laid bare the zones of passage; and, more- 
over, that this fact explains the peculiarly favorable case for the proof 
of assimilation. ‘The present reviewer is of opinion that the lack of 
