502 TRANSACTIONS OF THE CANADIAN INSTITUTE. [Vov. VIII, 
Dieulafait °° offers the most reasonable explanation. ‘Thus the absence 
of any stringers of phosphates along joint planes, and the absence of a 
marked increase of action towards the bottom of the deposits is accounted 
for. Also it suggests a more natural origin for the cavities in which the 
phosphorite is deposited. It is not necessary to suppose that these are 
the result of the thermal waters themselves, but they are conceived as 
being open before the waters came. ‘The theory also accounts for the 
presence of gypsum and iron ore as referred to subsequently. Another 
point of interest is the fact that the deposits are richer in phosphoric acid 
near the walls. It is only when the solution of phosphoric acid becomes 
neutralized that the calcium phosphate can be deposited, and the zone 
of precipitation is that point of contact between the solution and the 
limestone. 
23. It would thus appear that all known facts tend to prove that 
the phosphorites—that form of phosphate which with the exception of 
apatite, shows the least indication of organic origin,—are like all other 
forms the product of the decay of organisms. We may judge from analogy 
that all deposits of phosphate in sedimentary rocks are secondary and 
have a similar origin. 
24. Thus, as has been pointed out by Dawson, all deposits of phos- 
phate at present in process of formation are of unquestionably organic 
origin. Those of earlier periods, while not so obviously so, still have 
the evidence of the included fossils. But the very earliest possess no 
indications, either in themselves or by means of fossils, of an organic 
origin. However, when we consider the beds in process of deposition, 
the earlier formations, and the very oldest, it is apparent that we have, 
with some considerable hiatuses, a series. If these breaks can be bridged 
a chain of life is established. 
25. The fundamental step in the establishment of such a series is 
to account for the presence of phosphoric acid. ‘The amount of phosphorus 
in animal tissue is comparatively small, and yet there are beds of very 
great extent which have become phosphatized by decaying animal matter. 
De Lapparent had early pointed out that living organisms possess the 
power of appropriating to themselves such elements as are necessary for 
the maintenance of life, even though the proportion of these elements 
in the surrounding medium be imperceptible traces. The application 
of this fact to the case of phosphoric acid was made by Carnot. A number 
20 Origine et modes de formation des phosphates de chaux en amas dans les terrains sedimen- 
taires. Leur Unison avec les minerals de fer et les argiles des terrains siderolitiques par M. Dieulafait 
Ann, de Ch. et de Phys, 6: 5: 204. 
