196 FOUNDERS OF OCEANOGRAPHY 



of deep-sea deposits are present in that part of the crust 

 of the earth which we can examine — with the possible 

 exception of the Polycystina earth of Miocene age at 

 Barbados, which may be a fossil Radiolarian ooze. 



Analogues of terrigenous deposits are to be found in 

 all geological ages, and many calcareous rocks are formed 

 of neritic shallow-water deposits, but we know of no un- 

 doubted analogue of the true deep-water pelagic deposits. 

 Various rocks have from time to time been supposed to 

 correspond to the oozes of the deep sea, since Huxley, 

 in 1858, claimed Globigerina ooze as a modern chalk, but 

 further investigation and consideration of the case has 

 always led to the conclusion that such claims must be 

 rejected as very doubtful. It must not be supposed, 

 because Radiolarian ooze is an abyssal deposit, that 

 ancient highly siliceous sandstones and cherts or shales 

 containing fossil Radiolaria were necessarily formed as 

 deep-sea deposits. Radiolaria can live in comparatively 

 shallow water, or their dead shells may be carried by currents 

 into shallower water, and some of the sandstones and shales 

 in question show evidence (such as contained plant remains) 

 of having been formed as shallow-water deposits near land. 



It was generally held at the time of the " Challenger " 

 expedition, and even by some geologists since, that the 

 Cretaceous formation, or at any rate the Upper Chalk, 

 was formed as a deep-sea deposit, and that, to put it another 

 way, the chalk formation is still being deposited at the bottom 

 of the Atlantic. Hence arose the doctrine of what was 

 called " the continuity of the chalk." But the view is 

 now generally held that in upper Cretaceous times the chalk 

 of England was deposited in warm shallow water containing 

 very little terrigenous material ; and that therefore the 

 Globigerina ooze of the abyssal Atlantic cannot be regarded 

 as its lineal descendant. It may be regarded as estabUshed 

 that at any rate the great mass of the stratified rocks which 

 compose the continents as we see them must have been 



