AUTHORS’ ABSTRACTS Bus 
composition, has the character of an igneous rock. The Grenville series, 
which appears to rest upon it, frequently has a well-banded character 
with rapid alternations of various varieties of gneiss, which are in 
many places interstratified with heavy bands of crystalline limestone, 
quartzite, etc., has the character of a sedimentary series. A set of 
analyses of the gneisses, some from the Fundamental gneiss and some 
from the Grenville series are given, and it is shown that the former 
have the composition of granite, while the latter have that of sand and 
clay, a composition quite different from that of any igneous rock, but 
like that of ordinary sediments. It is also shown that these rocks do 
not always occur highly inclined, but that over great areas they lie 
nearly flat or in low undulations, suggestive of thin crust buoyed up 
by some semi-fluid or plastic material beneath, probably a great 
batholite granite mass, a portion of which is exposed in one part of 
the area. The effect of pressure acting after the intrusion of the 
anorthosites through the Grenville series, is shown in the development 
of a foliation in the peripheral portion of all the great igneous intru- 
sions, and in the movements which have caused the foliation of the 
gneiss to follow, and to a certain extent the outline of these more 
resistant masses. The Grenville series, therefore, comprises certain 
primeval sediments which have been deeply buried, invaded by great 
masses of igneous rocks and recrystallized. A map of the area and a 
photograph of a cliff of the horizontally banded gneiss accompany the 
paper. 
Relations of the Granite and Porphyry Areas in Southeastern Missourt. 
By CHARLES R. Keyes. Geol. Soc. of Am., Philadelphia, 1895. 
As is well known the granitic rocks of Missouri are the only 
massive crystallines occurring in the Mississippi basin between central 
Arkansas and Lake Superior and between the Appalachians and the 
Rocky Mountains. They are, moreover, the most ancient rocks 
exposed within the limits of the region. As irregular, discontin- 
uous fields they are scattered over a district of about 3000 square 
miles. 
Lithologically the crystalline rocks comprise both acid and basic 
varieties. The latter, however, are unimportant and occur usually as 
narrow dikes; the former comprise two well-marked structural phases, 
one a coarse-grained granite and the other a porphyry. Mineralogic- 
