Flints of the Upper or White Chalk. 175 



Prof. Rupert Jones and others, account for all the phenomena ? 

 The second : — Is flint, the true black or typical flint of the 

 Upper or White Chalk, a crystalline, or an amorphous and, to 

 a certain extent, colloid body ? 



It has already been stated that, according to Mr. Sollas, 

 ^''flints originate as silicijied chalk'''' [loc. cit. p. 452). "It 

 would appear (he says) that the simple deposition of silex is 

 impossible in the Chalk ; the first STAGE of deposition in this 

 deposit is always that of replacement {ibid. p. 451)." And 

 again : — " Briefly to sum up, a deposit of sponge-spicules 

 accumulated in the chalk oo^e*, and in the presence of sea-water 

 under pressure entered into solution. Keplacement of the cal- 

 careous material of the ooze then ensued, small shells, and many 

 large ones too, being converted into silex ; and siliceous chalky 

 not flint, was the result. The chambers of the Foraminifera and 

 tlie interstices of the chalk were now filled up by a simple depo- 

 sition of silica, and the siliceous chalk became converted 

 into Mack flint, an incompletely silicified layer of chalk remain- 

 ing as the white layer of the surface" {ibid. p. 449). 



It will, I think, be admitted that it is no easy matter to 

 divine, from this extraordinary description, what the distinc- 

 tion is which the author desires to convey between his version 

 of the replacement-theory, that " flint originates as silicified 

 chalk," and the generally accepted view, that " the flints are 

 due to the replacement of carbonate of lime by silica" — apart 

 from the fact that the former is an unnecessarily complicated 

 mode of expressing the latter, which, as it stands, is both plain 

 and to the point. But it will be observed that Mr. Sollas 

 divides the process into two distinct parts, which he dignifies 

 by the name of " stages^'' without in any wise intimating what 

 is to be gained by this division. The first stage (he tells us) 

 commenced with the solution of the sponge-spicules in sea- 

 water under pressure, and ended when the calcareous ooze, 

 with some small shells and many large ones too, became con- 

 verted into silex, through the replacement of carbonate of 



* This is an assumption, since no accumulation of spicules "m the 

 ooze " at all sufficient to account for the flint-formation has as yet been 

 recorded by any deep-sea observer. . I have seen nothing in the North 

 Atlantic that could meet the requirements of the case. I was the first, 

 however, to point out and furnish valid reasons for concluding that the 

 substance called ^^Bathyhius,^^ which from the first I suspected to be no 

 independent living organism, is merely the effete residuum of deep-sea 

 organic life and the protoplasmic nidus of the deep-sea vitreous sponges, 

 whose existence, in inconceivably vast numbers, over the calcareous areas 

 of the sea-bed, had been conclusively demonstrated during the cruises of 

 the ' Porcupine ' and ' Challenger.' (See my paper " On the Cretaceous 

 FHnts," pp. 74-77.) 



13* 



