Dr. Carpenter's Lecture. 91 



down by the rivers, using up the oxygen. These unfavourable con- 

 ditions are primarily due to deprivation of the general oceanic 

 circulation, which maintains life at such great depths. 



There seems, however, to be a limit, in respect of depth, to the 

 preservation of animal remains; due possibly, as conjectured by Prof. 

 Thomson, to the solvent power of sea- water at pressures below 2200 

 fathoms. This may serve to explain the passage of true Globigerina 

 ooze, first into grey ooze, poorer in calcareous matter, and finally at 

 great depths into red ooze devoid of lime. Moreover, this dissolving 

 of calcareous skeletons at great depths may serve to explain the pro- 

 duction of G-reensands, such as is now going on along the line of the 

 Agulhas current. These consist largely of the internal casts of 

 foraminifera, the sarcode of which has been replaced by glauco- 

 nite). The importance of such facts to geologists is immense. It 

 was the examination of a series of casts of similar bodies in a 

 green silicate, that, years ago, formed the foundation for the lecturer's 

 interpretation of the structure of Eozoon, where there is a replace- 

 ment of its sarcodic body by a green silicate, viz. serpentine. If 

 the sea-water, under this tremendous pressure, has dissolved away 

 the sheik of Foraniinifera, after their sarcode has undergone the sub- 

 stitution alluded to, a beautiful application of this kind of research 

 to geological phenomena has been brought forward. 



Keferring to Ed. Forbes's limitation of marine life to 300 fathoms, 

 the lecturer observed that the statement was true of the iEgean, as 

 of the whole of the Mediterranean, where there is abundant life in 

 the littoral zone, diminishing rapidly towards 250 fathoms, below 

 which Animal Life is almost at zero. Finally it is not a limit of 

 pressure, of heat, or even of food, but the limit of oxygenation, as 

 determined by the presence or absence of a thermal circulation, 

 which affects the life of animals. So that deposits forming in 

 inland seas, excepting in the shallower portions, we must expect to 

 be destitute of fossils. This is well illustrated by the Miocene strata 

 of Malta, where certain coarsish beds, representing shallow water 

 conditions, are full of fossils in a fine state of preservation ; whilst 

 the very fine building stone, corresponding closely with the finest 

 calcareous deposit of the Mediterranean, contains hardly any re- 

 mains but such as would fall in from above, e.g. the teeth of sharks. 

 This may explain the paucity of fossils in many strata, especially in 

 the Eed Sandstones of inland seas. Much depends upon the depth 

 of the communication, supposing there to be one, with the oceanic 

 circulation ; and the level of this may be often inferred from a 

 knowledge of the line of permanent temperature of such inland sea. 

 To the general paucity of animal life under such conditions the 

 Eed Sea appears to be an exception, notwithstanding the shallow- 

 ness of the Straits of Babelmandel. This is probably due to the 

 absence of the sediment and oxidating matter of large rivers, 

 and to the rocky nature of its shores, conditions which insure a 

 clear water ; whilst a certain circulation, producing oxygenation, is 

 kept up to supply the enormous evaporation, which, if the Straits 

 were closed, would desiccate the basin in three or four hundred years. 



