498 TRANSACTIONS OF THE CANADIAN INSTITUTE. {Vov. VIII. 
(b) Various analyses made indicate in most instances a composition 
almost identical with that of ordinary shale or slate. 
(c) Under the microscope the appearance and arrangement of the 
component minerals are often suggestive of contact zones bordering granites. 
(d) Almost invariably these rocks are associated with limestones. 
Their conclusion as to the Grenville series was that ‘‘the relations are 
such as to suggest that in the Grenville series we have a truly sedimentary 
group of strata which has sunk slowly down into, and has been invaded 
by great intrusions of igneous rocks of the Fundamental gneiss, when these 
were in a molten or plastic condition.”!° 
9. No line of demarcation is observable between the Grenville and 
Hastings, although the limestones while in the latter were less altered, 
yet the change is so gradual that it is often impossible to determine in a 
given case to which series it should be referred. ‘‘Finally,” they con- 
clude, ‘‘in the region in question, the Hastings series probably represents 
the rocks more nearly in their original form, and that the same rocks when 
invaded, disintegrated, fretted away, and intensely altered by and mixed 
up With the underlying gneissic magma into which they had sagged 
down became identified with the Grenville series. In short we have in 
the Grenville series an extremely metamorphosed portion of the Hastings 
series.’’!! 
1). Now it has been observed that in the rocks below the Cretaceous 
and above the Devonian there is practically no phosphoric acid. ‘This, 
Shaler suggests,!? is to be explained by the absence of those animals 
whose shells contain phosphorus. Below the Devonian the percentage 
appears to increase as we descend in the series until the maximum is 
reached in the Grenville with its beds of Apatite. 
11. This then is the geological horizon in which the apatites occur. 
Among metamorphosed rocks whose clastic origin is yearly becoming 
more definitely proved; in a series whose position at the foot of an un- 
interrupted scale is gradually being settled; and below that line down 
from which the remains of phosphorus-bearing animals steadily increase 
in quantity, the theory of their organic origin is one that admits of no 
a prvort objection. 
10 Idem. p. 49. 
11 Idem, p. 48 
12 Intro. to Penrose Phosphates. 
