A Retrospect of Oceanography 29 



consisted mainly of the dead and comminuted shells of fora- 

 minifera. Deeper soundings which had been reported by 

 earlier observers were generally discredited at this time. 

 Many of them were obviously faulty in execution and untrust- 



hv in result, but there were several soundings which 

 -bowed that depths of over 2500 fathoms were to be found 

 in the ocean. Thus Sir James Clark Ross, in the course of 

 his memorable Antarctic voyage, found 2677 fathoms in 



52 21' S. and long. 9 E. He also made a remarkable 



ding in lat. 68 34' S. and long. 12 49' W., when, under 

 favourable circumstances, he ran out all his sounding- 

 line without having touched bottom in 4000 fathoms. Opinions 



i with regard to the importance to be attached to this 



Bounding, but if his lead had touched bottom in anything 



under 3500 fathoms, Sir J. Ross would certainly have known it. 



effect of the "Bulldog's" work, and of Dr Wallich's 



report on it, was to produce the belief which was generally 



expressed by saying that at the present time chalk is being 



laid down all over the deep ocean ; that, therefore, geologically 



speaking, the bottom of the ocean is a cretaceous forma- 



was undoubtedly the prevalent belief when the 



tllenger" sailed from Portsmouth on December 22, 1872. 



1 Wwille Tin m,*<>n's Depths of the Sea was published only a fc\\ 



weeks before the "Challenger" sailed, and tin- last chapter of it is entitled 



"Continuity of the Chalk." After pointing out that, whereas the chalk 



ts of almost pure carbonate of calcium, with no silica. 



i.alk mud of the Atlantic contains as much as twenty or thirty per 



hat the Kn^lis!) chalk is the very purest of its kind. 



he goes on to say (p. 470), "There can be no doubt whatever th. 



it the bottom of the present ocean a vast sheet of rock 



i very closely resembles chalk; and there < an be as little doubt 



the old chalk, the Cretaceous formation which, in some parts of 



nd. has been subjected to enormous denudation, and which is over- 



v the beds of t ry series, was produced in the same manner 



and under closely M umstanccs; and not the chalk only, but 



most probably all the great limestone for; 



(p. 495) he says. "I have said at the beginning of this 



I believe the doctrine of the continuity of the chalk, as 



i stood by those who first suggested it, now meets with very general 



acceptance; and m idencc of this l -A ill <pi..t<- two passages in two 



consecutive anniversary addresses by presidents of the Geological So* 



and we may have every confidence that the statements of men of so great 



