18/0.] 



Deep-sea JResearclies. 



201 



99. But further, when we come to enquire into the source of these sus- 

 pended particles, the progressive subsidence of which gives rise to the fine 

 muddy deposit that covers all the deeper parts of the Mediterranean, we 

 fiud that (so far, at least, as the Western basin is concerned) they have 

 been in all probability brought down into it by the Rhone. The upper 

 part of that river, as is well known, is constantly transporting a vast mass 

 of sedimentary matter into the Lake of Geneva ; and while the deposit of 

 the coarser particles of the sediment at the upper end of the Lake is causing 

 a progressive formation of alluvial land, the water which passes off at the 

 lower end, though apparently clear, is still charged with particles in a 

 finer state of division. " Scarcely," says Sir C. Lyell*, "has the river passed 

 out of the Lake of Geneva, before its pure waters are again filled with sand 

 and sediment by the impetuous Arve, descending from the highest Alps, 

 and bearing along in its current the granitic sand and impalpable mud 

 annually brought down by the glaciers of Mont Blanc. The Rhone after- 

 wards receives vast contributions of transported matter from the Alps of 

 Dauphiny and the primary and volcanic mountains of Central France ; and 

 when at length it enters the Mediterranean, it discolours the blue water 

 of that sea with a whitish sediment for the distance of between six and 

 seven miles, throughout which space the current of fresh water is percep- 

 tible." — Thus the Western basin of the Mediterranean stands in the same 

 relation to the lower part of the Rhone and to the tributaries which dis- 

 charge themselves into it, that the Lake of Geneva does to its upper part. 

 And a like universal diffusion of fine sedimentary particles through the 

 Eastern basin is probably effected by the transporting agency of the Nile. 



100. The very slow, but constant, subsidence of these minute sedimen- 

 tary particles, then, is the source of a large part of the material of that fine 

 tenacious Mud which, mingled with a larger or smaller proportion of Sand, 

 partly calcareous and partly siliceous, constitutes the deposit at present in 

 progress on the deeper parts of the Mediterranean sea-bed. The source of 

 the Calcareous sand, which is itself in a state of very minute subdivision, is 

 probably to be found in the abrasion of the Calcareous Tertiaries which 

 form the shore-line round a large part of the Western basin. This abra- 

 sion is specially noticeable at Malta, where, for the security of the fortifi- 

 cations, it has has been found necessary to check it by artificial means. 

 The singular barrenness of this deposit in regard to Animal life forced itself 

 upon our attention during the whole of our dredging-operations in the 

 Mediterranean (§§ 48-52) ; and whilst disappointed as Zoologists in not 

 meeting with the novelties we hoped to encounter, we venture to hope that 



itself to us : and it was with great satisfaction, therefore, that we found our notion so 

 fully confirmed by Prof. Tyndall's investigations ; whilst it was not a little interesting 

 to him to find that our independent inquiries had led us to affirm the presence of these 

 suspended particles through the whole mass of Mediterranean water, and to attach so 

 much importance to the fact in its Geological and Biological relations. 

 * Principles of Geology, 10th ed. vol. i. p. 427. 



