316 Proceedings of Boyal Society of Ediribiirgh. [may 7 , 
calcium salts in one form, and eliminate them in another. We 
would guard against committing ourselves to the positive statement 
that birds can easily assimilate sulphate of lime and elaborate it in 
the form of carbonate, and we admit that all our results are not 
conclusively in favour of this view, for the decomposition must be 
very complex. However, it may be quite otherwise with marine 
animals and plants, which have sulphate of lime presented to them 
in presence of chloride of sodium, between which salts there may 
be interaction, and possibly the production of chloride of calcium 
and sulphate of soda, the former of which may be almost directly 
assimilated. 
2. On the Solubility of Carbonate of Lime under different 
forms in Sea-Water. By Robert Irvine, Esq., 
F.R.S.E., and George Young, Esq. 
It is well known that carbonate of lime is soluble in water in a 
slight degree, sufficiently so to give a distinctly alkaline reaction. 
Fresenius gives this solubility at one part of ten thousand, although 
in the presence of carbonate of ammonia, this is decreased to one 
in sixty -four thousand. 
The solubility of carbonate of lime had almost been overlooked ; 
but Dittmar, in his memoir in vol. i., “ Physics and Chemistry,” of 
the Challenger Reports, in dealing with the question of carbonic 
acid in sea water, writes as follows : — “As a general result of my 
experience, I presume that the water of the ocean in its present con- 
dition, and even where it contains its minimum of carbonic acid, is 
not yet saturated with carbonate of lime, but is ready to dissolve 
whatever of this compound the rivers send into it. Mr Murray 
tells me that extensive deposits of pelagic foraminiferal and mol- 
luscan shells are found in the ocean bed only at depths not exceed- 
ing a certain limit for each latitude, with similar surface tempera- 
ture conditions. For instance, in the tropics, pteropod shells are 
abundant at the bottom in depths of 1200 or 1400 fathoms, but in 
latitudes higher than 45° they are not met with in the deposits. 
The same remark applies to the more delicate foraminiferal shells. 
