TRANSACTIONS OF SECTION E. 617 



Within 300 or 400 miles of the shore, whether in deep or in shallow water, 

 formations are being laid down, whose materials are derived mainly from the disin- 

 tegration of shore rocks, and which consequently depend for their structure and 

 composition upon the nature and composition of the rocks which supply their 

 materials. These deposits imbed the hard parts of the animals living ou their area 

 of deposition, and they correspond in every way with sedimentary formations with 

 which we are familiar, of every age. In water of medium depths down to about 

 2000 fathoms, we have in most seas a deposit of the now well-known globigerina- 

 ooze, formed almost entirely of the shells of Foramiuifera living on the sea sur- 

 face, and which after death have sunk to the bottom. This formation, which 

 occupies a large- part of the bed of the Atlantic and a considerable part of that of 

 the Pacific and Southern Seas, is very like chalk in most respects, although we are 

 now satisfied that it is being laid down as a rule in deeper water than the chalk of 

 the Cretaceous period. 



In depths beyond 2500 or 3000 fathoms no such accumulations are taking place. 

 The shores of continents are usually too distant to supply land detritus, and although 

 the chalk-building Foraminifera are as abundant on the surface as they are else- 

 where, not a shell reaches the bottom ; the carbonate of lime is entirely dissolved 

 by the carbonic acid contained in the water during the long descent of the shells 

 from the surface. It therefore becomes a matter of very great interest to determine 

 what processes are going on, and what kind of formations are being laid down in 

 these abyssal regions, which must at present occupy an area of not less than ten 

 millions of square miles. 



The tube of the sounding instrument comes up from such abysses filled with an 

 ■extremely fine reddish clay, in great part amorphous, but containing, when exa- 

 mined under the microscope, a quantity of distinctly recognisable particles, organic 

 and inorganic. The organic particles are chiefly siliceous, and for the most part the 

 shells or spines of Radiolarians which are liviDg abundantly on the surface of the 

 sea, and apparently in more or less abundance at all depths. The inorganic par- 

 ticles are minute flakes oi* disintegrated pumice, and small crystalline fragments of 

 volcanic minerals ; the amorphous residue is probably principally due to the de- 

 composition of volcanic products, and partly to the ultimate inorganic residue of 

 decomposed organisms. There is ample evidence that this abyssal deposit is taking 

 place with extreme slowness. Over its whole area, and more particularly in the 

 deep water of the Pacific, the dredge or trawl brings up in large numbers nodules 

 very irregular in shape, consisting chiefly of peroxide of iron aud peroxide of man- 

 ganese, deposited in concentric layers in a. matrix of clay, round a nucleus formed 

 of a shark's tooth, or a piece of bone, or an otolith, or a piece of siliceous sponge, or 

 more frequently a fragment of pumice. These nodules are evidently formed in the 

 clay, and the formation of the larger ones and the segregation of their material 

 must have taken a very long time. Many of the sharks' teeth to which I have 

 alluded as forming the nuclei of the nodules, aud which are frequently brought up 

 uucoated with foreign matter, belong to species which we have every reason to 

 believe to be extinct. Some teeth of a species of Carcharodon are of enormous 

 si/e, four inches across the base, and are scarcely distinguishable from the huge 

 teeth from the tertiary beds of Malta. It is evident that these semi-fossil teeth, 

 from their being caught up in numbers by the loaded line of the trawl, are covered 

 by only a very thin layer of clay. 



Another element in the red clay has caused great speculation and interest. If 

 & magnet be drawn through a quantity of the fine clay well diffused in water, it 

 will be found to have caught on its surface some very minute magnetic spherules, 

 some apparently of metallic iron in a passive state, and some of metallic nickel. 

 From the appearance of these particles, and from the circumstance that such 

 magnetic dust has been already detected in the sediment of snow-water, my col- 

 league, Mr. Murray, has a very strong opinion that they are of cosmic origin — 

 •excessively minute meteorites. They certainly resemble very closely the fine gra- 

 nules which frequently roughen the surface of the characteristic skin of metorites, 

 and from their composition and the circumstances under which they are found, 

 there is much to be said in favour of this view. I cannot, however, hold it entirely 



