J. G. Goodchild — The Paste of Limestones. 77 



carbonate of lime brought seawards by rivers does not reach the sea 

 as carbonate, but is poured unceasingly into the ocean as sulphate of 

 lime. Hence the sudden disappearance of carbonate of lime at the 

 point where river waters and the water of the sea meet. 



That being the case, what becomes of all the sulphate ? Sulphate 

 of lime is present in all sea-water in proportions per 1000 parts by 

 weight varying from 1-35 to nearly 4. But unless some agency is 

 at work extracting this lime-compound from sea- water as fast as it 

 is brought in, it is obvious that sulphate of lime would go on 

 accumulating until the saturation point were reached, when pre- 

 cipitation would ensue. But, as all the researches that have yet 

 been made have failed to bring to light the smallest proof of the 

 existence of such precipitates in the open sea, it was an obvious 

 conclusion that, in some way or other, the sulphate of lime was 

 extracted by organic agencies, and that it was from this source, and 

 not from carbonate of lime, that corals, molluscs, fishes, — in short, all 

 marine organisms whose hard parts consisted of carbonate of lime, — 

 obtained the supplies necessary for their purpose. And this was the 

 view to which I had been independently led, and which was set 

 forth in one' of the papers referred to at the head of this article, 

 without knowing that the fact had been actually demonstrated already. 



The researches that led to the demonstration referred to were 

 conducted near Edinburgh by Messrs. R. Irvine, F.C.S., and G. S. 

 Woodhead, M.D., in 1888 and 1889. The results were made known 

 in two papers read before the Boyal Society of Edinburgh, the first 

 in May, 1888, and the concluding part in May, 1889. They are 

 published in the Proceedings of that body for 1888-9, part xvi. 

 Their chief conclusions are of great importance to both biologists 

 and geologists. The authors supplied various animals with different 

 lime-compounds, singly, or in combination with other salts ; and 

 they proved by the results that organic beings possessed the power 

 of decomposing all lime compounds during digestion, sulphate of 

 lime amongst others ; and that, through organic agencies, the re- 

 sulting lime, entering into fresh combination with carbonic acid, and 

 temporarily, also with phosphoric acid, is ultimately deposited and 

 is left, while the phosphoric acid is apparently reabsorbed and is 

 utilized afresh (op. cit. p. 340). In this way they consider " carbonate 

 of lime may be secreted by marine animals, which have the sulphate 

 of lime presented to them in the presence of chloride of sodium " 

 (ibid, p. 350). And, lastly, they observe, " the carbonate of ammonia 

 produced by the decomposition of urea, etc., decomposes] a portion 

 of the sulphate of lime of sea- water, with the formation of carbonate 

 of lime equivalent in amount to the carbonate of ammonia thus 

 formed" (ibid, p. 336). The papers referred to .contain a valuable 

 bodj' of facts and observations relating to the formation of carbonate 

 of lime by organic agencies other than those with which this paper 

 is more directly concerned. But apart from these, the authors have 

 unquestionably cleared away the principal mystery that has hitherto 

 surrounded the origin of the organic constituents of limestones. 



To return to the origin of the paste, with whicli Messrs. Irvine 



