202 peesident's addeess. 



sea had a uniform temperature below a certain depth, of 39° P., 

 and that the zero of animal life was reached at a depth of 300 

 fathoms. But the deepest soundings show a lower temperature 

 than that. Indeed the temperature of 39° would appear to be 

 confined to a depth hot exceeding 1000 fathoms. 



The average depth of the ocean, as ascertained from the 

 "Challenger" observations, is two and a half miles, or 13,000 

 feet. The deepest sounding of the "Challenger" was 4,475 

 fathoms, but this has since been exceeded off the coast of South 

 America by a recent American observation. These long-extended 

 and most varied and accurate enquiries have thrown a new in- 

 terest around the subject of the dwellers in ocean depths, and 

 have very widely extended the range of our knowledge. 



Mr. Murray, in the "Proceedings of the Royal Society,"'^' has 

 classified the deposits met with during the "Challenger" Toy age 

 under the heads of Shore Deposits, Grlobigerina Ooze, Radiolarian 

 and Diatomaceous Ooze,, and Red Clays. The shore deposits are, 

 of course, of less consequence and interest than those of the 

 deep seas. The most interesting feature, probably, in the shore 

 deposits is the abundance of Glauconite, or other green Silicate, 

 which occurs as grains and as casts of the interior organisms 

 whose tests have disappeared. The phenomenon is mainly con- 

 fined to depths of less than 700 fathoms. Possibly there may 

 be some connection between these Silicates and the Red Clays 

 of the deeper ocean. 



The Globigerina Ooze is' not met with south of 50°, nor, pro- 

 bably, much beyond 60° IN". ; but within these limits it is, after 

 the Deep-Sea Clays, the most abundant of oceanic deposits. It 

 consists largely of the dead shells of Globigerina, Orbulina, and 

 Pulverulina, etc. With regard to the rest of the calcareous ele- 

 ments of Globigerina Ooze much of it consists of "Coccoliths" 

 and "Rhabdoliths." I^o one appears to know much about the 

 organic position of these things. The Botanist and the Zoologist 

 seem to regard them with equal suspicion. Whatever they are 

 they secrete a large quantity of Carbonate of Lime. 



I^ext we have the Radiolarian and Diatomaceous Ooze. The 



*Vol. XSIV., p. 578, 



