ADIRONDACK BASIC INTRUSIVES wa, 
which was developed around the inclusions during their movement 
through the magma and just before its solidification. The very 
presence of the inclusions or xenoliths proves that the process of 
stoping or rifting off of blocks from the chamber vault or sides 
actually did take place to a certain extent at least, and this when 
the magma had cooled to a highly viscous condition and hence had 
comparatively little power to stope and too low a temperature to 
assimilate the blocks. Thus the occurrence of these xenoliths is 
quite in harmony with Daly’s hypothesis. 
SIGNIFICANCE OF THE MORE ACIDIC MASSES WITHIN THE STOCKS 
As already mentioned, lighter colored, more acidic patches or 
masses sometimes occur within the gabbro stocks. These patches 
lack the diabasic texture of the inclosing gabbro and, instead of 
being in sharp contact with the gabbro, they rapidly grade into it. 
A good example is the stock 1$ miles north-northeast of The Glen 
and represented by Nos. 7 and 8 in Table I, and another is stock 
No. 1 (see map) and represented by Nos. 9 and to in Table I. 
Harker™ admits the probability of stoping, but sees ‘“‘no evi- 
dence of concomitant assimilation,” and Iddings? says: ‘‘ Evidences 
of absorption by the igneous magma of material from adjoining 
mocks are very Slight. .... It commonly happens that blocks, 
or fragments of rocks, are inclosed in molten magma without 
exhibiting evidences of solutional reaction between the magma and 
anclosed' rocks. ... . Few statements as to signs of solution and 
diffusion of rock by igneous magmas have been substantiated by 
chemical evidence of a change in the intrusive magma due to such 
a reaction.”’ Now, the writer believes that the more acidic patches 
or masses within the North Creek gabbro stocks do furnish strong 
evidence of chemical change within the intrusive igneous magma 
due to solution or partial solution and diffusion of blocks of country 
rock. In such cases the magma was just hot enough to melt or 
partially melt and only partially diffuse the blocks of country rock. 
Acidic masses formed in this way would not be expected to show 
t Natural History of Igneous Rocks, p. 86. 
2 Igneous Rocks, I (1909), 281. 
