Flints of the Upper or White Chalk. 163 



a medium for indulging in a number of unwarranted comments 

 (for they cannot be called criticisms) upon my paper " On the 

 Physical History of the Cretaceous Flints " (published in 

 the ' Quarterly Journal of the Geological Society,' vol. xxxvi. 

 No. 141, Feb. 1880)*, I shall first reply to his strictures, and 

 then avail myself of the opportunity to furnish some additional 

 facts and arguments in support of my views, which want of 

 space debarred me from bringing forward in the paper just 

 referred to. 



That Mr. Sollas or any other professed geologist should have 

 hesitated to accept my explanation as to the mode of formation 

 of the Flints, and should freely canvass my facts as well as 

 my conclusions, was not only perfectly legitimate, but no more 

 than I expected when giving utterance to an hypothesis both 

 novel and opposed, in some most important particulars, to all 

 preconceived ideas concerning a difficult and avowedly un- 

 solved geological problem. But I likewise expected, from a 

 writer whose previous researches on kindred subjects (so far 

 as T was acquainted with them) had yielded me both pleasure 

 and instruction, at least a precise and impartial recital of such 

 of my .statements and conclusions as he felt called upon to 

 impugn — together with some better results than a laboured 

 and, as I venture to think, futile attempt to improve upon the 

 well-known doctrine that " the flints are due to the replace- 

 ment of carbonate of lime by silica " f- 



Speaking generally, Mr. Sollas's paper contributes very 

 little that can be considered original to our knowledge on the 

 flint question — unless it be the interesting fact that the silica 

 of the Trimmingham flints may^ in part, have been derived 

 from spicules belonging to, but now missing from, certain 

 fassiiized sponge-remains in the Trimmingham Chalk. For, 

 although he devotes a considerable space in his paper to the 

 chemistrj' of the subject, it is obvious that he has derived his 

 inspiration, on almost every material point relating to the pro- 

 duction of flinty from the splendid researches of Graham, to 

 which, in common with myself, he appears to be indebted for 

 whatever information he possesses regarding the colloidal 

 properties and combinations of silicic acid and colloidal sub- 

 stances in general |. Yet he offers no explanation of the cha- 



• This paper was read before the Geological Society in December 187'J. 



t See paper by Prof. Rupert Jones, F.R.S. &c., " On Quartz. Flint, 

 and other forms of SUica" (Proc. Geol. Assoc, vol. iv. no. 7, Apr. 187G, 

 p. 447). 



I Mr. Sollas mentions Mr. Graham's name only in relation to " the 

 fact," if it be one, " that silicic acid has the property of actually combining' 

 with such substances as albumen and gelatin to form with them silicate 

 of albumen and silicate of gelatin" (loc. cit. p. 452). 



