ANNIVERSARY ADDRESS OF THE PRESIDENT. Ixxi 



of a nature unsuited for the existence of life over the original sea- 

 bed. It is now evident that the absence of Hfe in the depths of 

 the ^gean is due to the fine tenacious mud (which, by the by, E. 

 Forbes likened to chalk), iu the same way that those areas of the 

 Mediterranean, discovered by Capt. Spratt, and of the Atlantic at 

 the entrance of the Straits of Gibraltar, discovered in the ' Porcu- 

 pine ' expedition, to be covered by fine mud, apparently in a state 

 of continual slow deposition, were found to be almost entirely barren. 

 On the other hand, where the rocks consist of sandy strata, any 

 fossils composed of carbonate of lime may have been dissolved 

 out, and all traces of them lost by the percolation of rain-water, 

 after their elevation into dry land, as happens in the Bagshot Sands, 

 in which it is only by chance in the few instances where the sand 

 happens to be consolidated by a ferruginous cement that the im- 

 pressions and casts of shells are preserved. Another well-known 

 cause for the absence of fossils in a sedimentary deposit is the 

 circumstance of the strata having undergone metamorphic action. 

 I should hardly have thought it necessary to mention these various 

 causes to account for non-fossiliferous rocks, but for a recently 

 expressed opinion of a presumed more general acceptance of Porbes's 

 hypothesis amongst geologists than has been at all the case. 



As bearing also upon the distribution of life in the same stratum 

 at points in near proximity, Dr. Carpenter notices that there are 

 areas in the North Atlantic in which the temperature varies con- 

 siderably at the same relative depths ; and he infers that there are 

 permanent warm and cold areas, distinguishable not only by differ- 

 ences of from 10° to 15° of temperature, but also by a difference of 

 marine life, such as might present a geological difficulty. He notes 

 the presence of Globigerince and abundance of vitreous sponges on 

 a fine muddy bottom in the one, and of northern forms of Echi- 

 nodermata and Crustacea on a bed of sand and stones in the other. 

 Mr. Jeffreys, however, did not find the same difference in the Mollusca. 

 He states that the result of his examination shows that there are 

 forty-four species in the warm area and fifty-five species in the cold 

 area, and these latter included all the forty-four of the former ; and 

 he accounts for the absence of Glohigerina on the ground that " the 

 strength of the submarine current in the cold area is sufficient to 

 sweep away and remove these slight and delicate organisms," which, 

 from later observations by other naturalists and himself, he believes 

 inhabit only the superficial stratum of the sea. The slight difference 

 in temperature seems hardly sufficient to account for the absence of 



