1908-9.] On THE ORIGIN OF THE CANADIAN APATITES. 501 
JAWS 
EVIDENCE FROM THE CHEMICAL CHARACTERISTICS OF APATITE. 
19. ‘‘Searcely any other economic mineral occurs in such diverse 
forms as mineral phosphate.’’!® In the guano and bone beds we see 
the substance of modern or recent deposition and clearly organic. The 
nodular phosphates from which most of the fertilizers are made give 
ample indication of their origin in the fragmentary fossils which they 
contain. The presence of phosphoric acid in some phosphatic limestones 
is less easily explained, but it is conceded to have been due to the numerous 
animal remains which would accumulate at the bottom of the teeming 
Silurian seas. 
20. When we turn our attention to the phosphorites which differ 
from the above in a comparative fixity of composition, the problem of 
referring them to their origin becomes much more difficult. This mineral 
occurs in irregular crevices and cavities in rocks of various ages and 
kinds, very frequently in limestone regions it occurs also as an incrustation 
on the sides of caverns. To explain the presence of the phosphorite two 
hypotheses have been proposed; firstly “‘the hypothesis of ascending 
water,” secondly, “‘the hypothesis of descending water.” 
21. According to the hypothesis of ascending water, the presence 
of phosphorus is accounted for by the equally hypothetical occurrence 
of phosphides in the abysmal depths. Water coming in contact with 
these at high temperatures causes their dissociation and as the solution 
reaches points nearer the surface it attacks any limestone present and 
precipitates calcium phosphate on the surface. Two facts militate against 
this hypothesis. In the first place the deposits are usually shallow and 
superficial. In the second place as Filtol has pointed out'* when they 
are fully worked out they do not show any necks or leads of phosphorite 
pointing towards a deep seated origin. 
22. The hypothesis of descending water accounts for the phos- 
phorites on the supposition that they were originally in a bedded form 
and derived from the animal remains. ‘These beds acted upon by thermal 
water, Were dissolved or leached away and the calcium phosphate was 
reprecipitated in a purer form in caves and crevices. ‘This according to 
13 Penrose, p. 10. 
19 Recherches sur les phosphorite du Querey—Annales sci. geol. 7; 1-120, 1876. 
