520 
ProcGGciings of the Royal Society 
In this manner, then, it is shown that the remains of calcareous 
organisms are completely eliminated in the greatest depths of the 
ocean. For if such he not the case, why do we find all these shells 
at the bottom in the shallower depths, and not at all in the greater 
depths, although they are equally abundant on the surface at both 
places There is reason to thinlv that this solution of calcareous 
shells is due to the presence of carbonic acid throughout all depths 
of ocean water. It is well known that this substance, dissolved in 
water, is an energetic solvent of calcareous matter. The investiga- 
tions of Buchanan and Dittmar have shown that carbonic acid 
exists in a free state in sea water, and in the second place, 
Dittmar’s analyses show that deep-sea water contains more lime 
than surface water. This is a confirmation of the theory which 
regards carbonic acid as the agent concerned in the total or partial 
solution of the surface shells before or immediately after they reach 
the' bottom of the ocean, and is likewise in relation with the fact, 
that in high latitudes where fewer calcareous organisms are found at 
the surface, their remains are removed at lesser depths than where 
these organisms are in greater abundance. It is not improbable 
that sea water itself may have some effect in the solution of carbonate 
of lime, and further, that, the immense pressure to which water is 
subjected in great depths, may have an influence on its chemical 
activity. We await the result of further researches on this point, 
which have been undertaken in connection with the “Challenger” 
Keports. We are aware that objections have been raised to the 
explanation here advanced, on account of the alkaliuity of sea 
water, but we may remark that alkalinity presents no difficulty 
wdiich need be here considered.* 
This interpretation permits us to explain how the remains of 
Diatoms and Eadiolarians (surface organisms like the Foraniinifera) 
are found in greater abundance in the red clay than in a Globigerina 
ooze. The action which suffices to dissolve the calcareous matter 
has little or no effect upon the silica, and so the siliceous shells accu- 
mulate. Nor is this view of the case opposed to the distribution of 
the Pteropod ooze. At first we should expect that the Foraminifera 
shells, being smaller, would disappear from a deposit before the 
Pteropod shells ; but if we remember that the latter are very thin 
* Dittmar, Pliys. Chem. CJutU. Exp., Part i., 1884. 
