i66 



NATURE 



[June 12, 1890 



secreting animals die at the surface of the water and their bodies 

 fall to the bottom, the shell is exposed to solution from the 

 action of the sea-water through which it passes, and it may be 

 to that of carbonic acid produced b/ the decomposition of its 

 own organic matter. If the shell be thin, as in the case of 

 Heteropods and Pteropods, it may be wholly removed before 

 reachin;^ the bottom, but the thicker shelled varieties tend to 

 accumulate even in depths of 2000 fathoms, where they are soon 

 covered up by other shells ; and being surrounded by sea-water 

 already saturated with carbonate of lime, are preserved from 

 solution, and form vast beds of calcareous ooze. It is found that 

 the amount of carbonate of lime present in such ooze is greater 

 or less according to the depth of water through which the shells 

 pass from the surface to the bottom, and also to the slow re- 

 newal of the water in contact with these great lime deposits. In 

 the red clay area the carbonate of lime is almost entirely absent. 

 The deeper waters which cover such areas are more active in the 

 removal of carbonate of lime, not only because of the larger 

 amount of carbonic acid they contain, but doubtless to the 

 deoxidation of alkaline sulphates by organic matter, which, we 

 have already pointed out, gives rise to sulphuric acid, &c. At 

 the same time account must be taken of the great pressure at 

 such abysmal depths, and the fact that the substance of the shells 

 being less compressible than sea- water, they would fall more 

 slowly, and hence would be longer exposed to the action of the 

 deeper layer of water than those near the surface. 



What calcareous remains do reach the ocean floor at such 

 abysmal depths represent the hardest and crystalline varieties of 

 carbonate of lime which resist the solvent action of sea-water to 

 the greatest extent. 



In this way we appear to have a perfectly rational explanation 

 of the partial disappearance of carbonate of lime shells from the 

 shallower depths, and their total disappearance from all the 

 greater depths of the ocean. It is to be observed that all those 

 shells in which a considerable quantity of organic tissue is asso- 

 ciated with the carbonate of lime disappear in solution more 

 rapidly than the shells of the Foraminifera, which contain little 

 organic matter. (During the whole of the Challenger cruise only 

 two bones of fishes, other than the otoliths and the teeth, were 

 dredged from the deposits, and all traces of the cetacean bones 

 were removed, except the dense ear- bones and dense Ziphioid 

 beaks.) The remains of crustacean animals were almost wholly 

 absent from deep-sea deposits, with the exception of Ostracode 

 shells and the hard tips of some claws of crabs. 



Turning now to the lagoons and lagoon channels of coral 

 islands, it is believed that large quantities of carbonate of lime 

 are in the same way being dissolved from these shallow basins as 

 well as from the deposits of the deep sea, but under somewhat 

 different circumstances. In the case of a shell falling to the 

 bottom of the sea, it is continually brought in contact with new 

 layers of water, which has the same effect as if a continuous 

 stream of water were passing over the shell. In the case of the 

 lagoons this last is what takes place. The water which flows in 

 .and out of the lagoons twice in twenty-four hours passes over 

 rgreat beds of growing coral, and from all the observations we 

 'have is largely charged with carbonic acid, owing probably to 

 the large number of living animals on the outer reef over which 

 the water passes on its way to the lagoon. This water passes 

 -continually over the dead coral and sand of the lagoon, and takes 

 up and removes large quantities of carbonate of lime in solution 

 (as well as suspension), for in these lagoons the spaces covered 

 by dead coral debris always greatly exceed the patches of growing 

 coral. Owing to the fact that the water of the lagoon is con- 

 tinually in motion, and constantly renewed, the layer in contact 

 with the bottom of coral sand can never become saturated or 

 unable to take up more lime, as is apparently the case in the 

 layers of water in contact with the Globigerina ooze and other 

 -calcareous deep-water deposits. 



From the foregoing discussion and observations it is evident 

 that a very large quantity of carbonate of lime is in a continual 

 state of flux in the ocean ; now existing in the form of shells and 

 •corals, but after the death of the animals passing slowly into 

 solution, to go again through the same cycle. 



On the whole, however, the quantity of carbonate of lime that 

 is secreted by animals must exceed what is re-dissolved by the 

 action of sea-water, and at the present time there is a vast 

 accumulation of carbonate of lime going on in the ocean. It 

 has been the same in the past, for with a few insignificant ex- 

 ceptions all the carbonate of lime in the geological series of 

 Tocks has been secreted from sea-water, and owes its origin to 



NO. 1076, VOL. 42] 



organisms in the same way as the carbon of the carboniferous 

 formations ; the extent of these deposits appears to have in- 

 creased from the earliest down to the present geological period. 



At the present time most of the carbonate of lime carried to 

 the ocean by rivers has been directly derived from calcareous 

 stratified rocks formed by organic agency in the sea in earlier 

 geological ages, but the calcium in these formations was in the 

 first instance derived from the decomposition of the lime-bearing 

 silicates of the earth's original crust, and this decomposition, 

 which is still going on in the sea and on the land surfaces, is a 

 continuous additional source of carbonate of lime. 



In considering the analyses showing the average composition 

 of sea salts, one is struck with the relatively small quantity of 

 those very substances which are extracted so largely from sea- 

 water by plants and animals, viz. carbonate of lime and silica. 

 Siliceous deposits are of vast extent, yet silica occurs merely in 

 traces in sea-water ; carbonate of lime deposits are of vastly 

 greater magnitude, yet carbonate of lime makes up only ^Jj^th 

 part of the saline constituents of sea-water, and only ^Vr<r'h part 

 of the whole bulk of sea-water. Sulphate of lime is ten times 

 more abundant than the carbonate in sea-water ; on the other 

 hand, the river water that is poured into the ocean contains 

 about ten times as much carbonate as it does of sulphate of 

 lime.i 



The total amount of calcium in a cubic mile of sea- water is 

 estimated from analyses to be 1,941,000 tons, and the total 

 amount of calcium in the whole ocean is calculated at 

 628,340,000,000,000 tons. The total amount of calcium in a 

 cubic mile of river water is estimated at 141,917 tons, and the 

 total amount of this element carried into the ocean from all the 

 rivers of the globe annually is estimated at 925,866,500 tons. At 

 this rate it would take 680,000 years for the river drainage from 

 the land to carry down an amount of calcium equal to that at 

 present existing in solution in the whole ocean. Again, taking 

 the Challenger deposits as a guide, the amount of calcium in these 

 deposits, if they be 22 feet thick, is equal to the total amount of 

 calcium in solution in the whole ocean at the present time. It 

 follows from this that if the salinity of the ocean has remained 

 the same as at present during the whole of this period, then it 

 has taken about 680,000 years for the deposits of the above thick- 

 ness, or containing calcium in amount equal to that at present in 

 solution in the ocean, to have accumulated on the floor of the 

 ocean. From the data here furnished a number of other inte- 

 resting speculations might be indulged in, relating to the amount 

 of carbonic acid that has been abstracted from the atmosphere 

 and fixed in carbonate of lime deposits ; the total amount of dis- 

 integration of lime- bearing siliceous rocks measured in terms of 

 the calcium at present existing in solution in water and fixed in 

 calcareous deposits ; the relative proportions of substances secreted 

 from the ocean as compared with other materials derived from 

 the direct disintegration of the land-forming deep-sea deposits ; 

 and the apparent accumulation of carbonate of lime formations 

 towards the equatorial regions of the globe. These various 

 matters will, however, be discussed in another place. 



UNIVERSITY AND EDUCATIONAL 

 INTELLIGENCE. 



Cambridge. — The event of the week has been the achieve- 

 ment of Miss Philippa Garrett Fawcett, of Newnham College, 

 who, in Part I. of the Mathematical Tripos, is declared to be 

 " above the Senior Wrangler," Mr. Bennett, of St. John'.". 



Mr. Sedley Taylor, the delegate from Cambridge to the 

 Sexcentenary Festival of the Montpellier University, in a letter to 

 the Vice-Chancellor on the subject of his mission, writes: — 

 " We had the great satisfaction of seeing Prof, von Helm- 

 holtz, Delegate of the University of Berlin, publicly received 

 with much cordiality, and of learning that, on account of his 

 optical researches, which have given such a beneficent impulse to 

 modern ophthalmology, he was subsequently made the object of 

 a special ovation by the Medical Faculty for which the Uni- 

 versity of Montpellier has long been famous." 



Dr. Butler, Master of Trinity College, was on June 2 again 

 elected to the office of Vice-Chancellor for the ensuing academical 

 year. 



The John Lucas Walker Research Studentship in Pathology 

 is vacant by the resignation of Dr. William Hunter, of St. 

 John's College, recently elected to a Research Scholarship in 



' Murray, •' Total Rainfall of the Globe," Sect. Geogr. Mag., 1887. 



