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Messrs. Carpenter and Jeffreys on 



[Dec. 8, 



the negative result of our sedulous investigations may have an important 

 Geological bearing. 



101. It will be borne in mind that our previous researches have fully 

 demonstrated the fact that the Depth of from 600 to 1200 fathoms is not 

 per se inconsistent with the existence of a varied and abundant Fauna ; and 

 that the reduction which shows itself at from 1200 to 2435 fathoms seems 

 to depend as much on depression of Temperature, as on increase of Depth. 

 Hence it was fairly to be expected that a varied and abundant Fauna — 

 probably containing a number of Tertiary types supposed to have been 

 long extinct — would have been found between 500 and 1500 fathoms, on a 

 bottom of which the temperature seems never to fall below 54°. Now 

 the question as to the cause of the deficiency of Animal Life on this 

 bottom naturally connects itself with the old Geological difficulty, of which 

 the inquiries of Prof. Edward Forbes were long supposed to afford a 

 satisfactory solution ; viz. the existence of vast thicknesses of sedimentary 

 strata, almost or entirely destitute of Organic Remains. The explanation 

 which has been accepted for many years, — that these deposits were formed 

 in Seas too deep to allow of the existence of Animals on their bottom, — 

 having been now shown to be untenable, the old difficulty recurs ; and it 

 is obvious that if it can be shown that a condition prejudicial to Animal 

 Life now prevails on the Mediterranean bottom, which also prevailed 

 when other azoic deposits were formed, a great step will have been gained. 

 Such a condition is to be found — we are disposed to think — in the turbidity 

 of the bottom-water. All Marine animals are dependent for the aeration 

 of their fluids on the contact of water either with their external surface, 

 or with special (branchial) prolongations of it. Now if this water _be 

 charged with suspended particles of extreme fineness, the deposit of these 

 particles upon the respiratory surface will interfere with the aerating 

 process, and will tend to produce asphyxia. This is not a mere hypothesis. 

 It is well known that Oyster-beds cannot be established in situations to 

 which fine mud is brought by any fluvial or tidal current. And our 

 Colleague Mr. Jeffreys, when dredging some years ago in the neighbour- 

 hood of Spezzia, having on one occasion passed a little out of the Bay, from 

 a sandy bottom rich in Animal life to a muddy bottom (this mud being 

 doubtless a part of the Rhone deposit), without any considerable increase 

 of depth, was forcibly struck by the barrenness of the latter. 



102. It will be for Geologists to say how far this explanation can be 

 applied to the case of the azoic sedimentary deposits of former epochs. 

 One very notable case of the kind has been communicated to us by Dr. 

 Duncan, that of the Fleisch, a stratum not less than 6000 feet thick, 

 extending from Mont Blanc to the Styrian Alps, which must have been 

 deposited in the condition of extremely fine arenaceous mud, and in which 

 there is an almost entire absence of Fossils. We are disposed to believe, 

 also, from the results of such inquiries as we have been able to make, that 

 the extremely fine Calcareous sandstone of Malta, though reputed to be 



