1908-9.] On THE ORIGIN OF THE CANADIAN APATITES. 499 
III. 
EvIDENCE FROM THE NATURE OF THE DEPOSITS. 
12. In the search for evidence as to the origin of apatite, one natur- 
ally commences by a careful examination of the tectonic characteristics 
of the deposits themselves. If on the one hand these are invariably in 
the form of undoubted veins or dykes or if on the other they occur without 
exception interbedded with evident clastic rocks, the problem of their - 
origin would be beset with few difficulties. This phase of the question 
naturally occupied a large proportion of the attention of the earlier inves- 
tigators. Unfortunately the circumstances of their occurrence were 
so varied that no uniformity of deduction was possible. 
13. Brégger and Reusch noted the fact that the apatite deposits 
maintain their course quite irrespective of the nature or structure of the 
country rock. Also, many of the deposits are coarse grained at the 
centre becoming finer towards the outside, a peculiarity of trap dykes. 
Where this is so prominent as to give rise to a roughly banded structure 
it could readily be explained as the result of slow cooling of such an in- 
trusive mass. Again the deposits frequently contain large irregular masses 
of foreign rock, quite different from that of the surrounding strata, and 
supposedly brought up from greater depths. In short these authors 
- decided that all deposits in their country are eruptives, having the char— 
acteristics of dykes. 
14. Harrington in commenting upon this conclusion points out 
two ways in which the Canadian deposits differ from those described. 
In the first place the Canadian apatite deposits are clearly influenced 
by the surrounding strata. It is among limestones for instance that: 
the deposits are calcareous. In the second place the granulated structure,. 
so important in showing the deposits to be dykes, is scarcely ever observed 
in Canadian examples. 
15. The theory that the Canadian deposits of apatite are in the 
form of true veins has been vigorously supported by Bell in 1885'* and 
Dawkins in 1889.14 Our attention was called by Dr. Bell to the fact 
that phosphoric acid is a constituent of nearly all rocks, and that the 
small quantity which is present is offset by its extraordinary powers. 
of segregation. Professor Boyd Dawkins referred to the strikingly 
13 Eng. Min. Jour. 1885 j 
14 Man. Geol. Soc. 1889. 
