OF TUE DIATOME.E. ^ 83 



submarine flanks of Mount Erebus, an active volcano 12,000 feet high. From 

 the fact that Diatomete and other organisms enter into the formation of 

 pumice and ashes of other volcunos, it is perhaps not unreasonable to con- 

 jecture that the subterranean and subaqueous forces, which keep Mount 

 Erebus in activity, may open a direct communication between this Diato- 

 maceous deposit and its volcanic fires. Moreover, this bank flanks the whole 

 length of Victoria Barrier, a glacier of ice 400 miles long, whose seaward 

 edge floats in the ocean, whilst its landward extends in one continuous sweep 

 from the crater of Mount Erebus and other mountains of Victoria Land to the 

 sea. The progressive motion of such a glacier, and accumulation of snow on 

 its surface, must result in its interference mth the deposit in question, which, 

 if ever raised above the surface of the ocean, would present a stratified bed 

 of rock which had been subjected to the most violent disturbances." 



But instances of the abundance of silicious organisms in sea- or river- 

 bottoms are to be met with nearer home. Mr. Boper has explored the mud 

 of the Thames {J. M. S, 1854, p. 68) ; and he tells us that, excluding the 

 coarse sand, nearly one-fourth of the finer part of the residuum is entirely 

 composed of the silicious valves of difierent species of Diatomeae, — '' marine 

 forms prevailing." This writer also quotes the experience of Ehrenberg, 

 who, Avith respect to the mud of the Elbe, has established the remarkable 

 fact that at Gluckstadt, a distance of 40 miles, and even above Hambiu'g, 

 upwards of 80 miles above the mouth of the river, marine silicious- shelled 

 Infusoria were found alive, and theii' skeletons deposited in it in such abun- 

 dance, that at the former locality they form from one-quarter to one-third of 

 the entire mass, and that the proportion is stiU about one-half that amount 

 at Hamburg, as far as the flood-tide extends. All his observations gave a 

 great predominance of marine over freshwater species, even when the salt 

 taste of the water was no longer perceptible. His examination of the mud 

 of the Scheldt and Ems fiu-nished similar results, as did that of the marine 

 deposit in various littoral regions of the North Sea and Baltic. 



Reverting to the Thames deposit, Mr. Roper expresses his beUef that the 

 silicious shells " have a perceptible influence in the formation of shoals and 

 mud-banks in the bed of the river. , . . And the great abundance and general 

 chstribution of species serve to illustrate the occurrence of similar dejiosits 

 in a fossil state at localities now far removed, by alterations in the earth's 

 surface, from the streams or harbours in which they were originally de- 

 posited. 



" Another point worthy of attention is the influence of these organisms 

 in the formation of deltas at the mouths of large and slowly- flomng 

 rivers — such, for instance, as the Mississippi, in which the mean velocity of 

 the current at N'ew Orleans is only about one mile and a half per hour for 

 the whole body of water. Sir Charles Lyell, from experiments on the pro- 

 portion of sediment carried down by the river, has calculated that, taking the 

 area of the delta at 13,600 square miles, and the quantity of solid matter 

 brought down annually at 3,702,758,400 cubic feet, it must have taken 67,000 

 years for the whole delta. Now, as the silicious frustules of the Diatomea) 

 are secreted from the water alone, and would most probably be extremely 

 abundant in so sluggish a stream (especially as Prof. Bailey has found both 

 marine and freshwater species abundant in the rice-grounds), there can be 

 little doubt that, without taking the larger proportion noticed by Ehrenberg 

 in the Elbe, even if it were considerably less, it would reduce the above 

 period by several thousand years ; and the same cause would probably apply 

 wnth equal force to the Ganges and Nile. Ehrenberg considered that, at 

 Pillau. there are annually deposited from the water from 7200 to 14,000 



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