THE DEPOSITS OF THE SEA-BOTTOM. ^ 



presence of submarine rocks. Near the coasts this presence will not be so easily pointed out, as the 

 coarser ingredients of the specimens may as well have been derived from the land. From the ridge 

 between Iceland and Greenland, unfortunately, no specimens have been obtained; it would otherwise 

 have been of great interest, if by such we should have been able to show where the border is found 

 between the Greenlaudic and Icelandic rocks. The before mentioned ridge stretching from Iceland 

 towards the southwest, is likely to be completely covered by sediment; if this was not the case larger 

 quantities of mineral ingredients would surely have been obtained, and the specimens would not be 

 so rich in carbonic acid, as they are seen to be. From this may again be drawn the conclusion that 

 a comparatively large period of time must have elapsed, since the ridge was above the surface, if 

 upon the whole it ever was so. On account of this comparatively complete covering with loose 

 layers, nothing can be said of the petrographic nature of the ridge. 



Those factors produced in the foregoing, may be regarded as the factors being of most im- 

 portance with regard to the transportation of mineral material from the land, or eventually from the 

 sea-bottom, and the depositing of it on other places of the bottom. The description will, I think, have 

 conveyed the impression, that the different factors may in many ways counteract each other, and that, 

 in most cases, it will be difficult, if not quite impossible, to state how much each factor has contri- 

 buted to give the specimen in question its precise character. But the case is even more difficult, 

 when we come to regard the fact that the above named factors are not the only ones that are of 

 importance as to the deciding of the amount of carbonic acid in the specimen, and through that of 

 the species of this specimen; one circumstance more has to be taken into consideration, viz. the larger 

 or smaller number of calcareous organisms deposited on the place in question, and here again a 

 number of different circumstances are of importance, as, besides the depth, also the temperature and 

 the salinity, as well in the surface as at the bottom, and moreover the dashing of the waves, the cur- 

 rents, and perhaps still more. As the conditions of life of the Foraminifera and the still smaller cal- 

 careous organisms are scarcely so well known that it is possible to clear up the single facts, I shall 

 not here discuss this question more particularly; perhaps in a later section I may find an opportunity 

 of entering upon some details regarding it. Here I shall only add that the same circumstances that 

 are favourable to the growth and deposition of the calcareous organisms, will as a rule also be favour- 

 able to the siliceous organisms, by which fact the case becomes still more complicated, the amount 

 of lime not being so large, as otherwise was to be expected. 



The Ingolf-Expedition. I. 3. 



