Dr. G. J. Sinde — Organic Origin of Chert. 437 



they made up the larger part of the Chert. Another fact, also 

 bearing on the probable organic character of the Irish Carboniferous 

 Chert, was the discovery by Messrs. Wright and Stewart of Belfast 

 of beds of siliceous clay, apparently resulting from decayed Chert, 

 which were described by Mr. H. J. Carter, F.E.S.,^ as in some 

 parts nearly entirely composed of sponge-spicules. 



In a paper'* showing the derivation of the Chert in the Lower 

 and Upper Greensand of the South of England from the remains 

 of siliceous sponges published in the Phil. Trans, for 1 885, 1 ventured 

 to suggest that the facts above stated justified the conclusion that 

 the Carboniferous Chert of Ireland would be found to be likewise 

 of organic origin, and that therefore Messrs. Hull and Hardman 

 were probably wrong in regarding it as of inorganic derivation. 

 This suggestion has been warmly combated by Messrs. Hull and 

 Hardman in two short papers brought before the Royal Society,^ 

 and lately published in its Proceedings. Prof. Hull states, in the 

 paper referred to, that there is absolutely no evidence that the 

 silica of the Irish Carboniferous Chert has been derived from 

 sponge-spicules ; that there is only a fanciful analogy between 

 the Carboniferous Chert-beds and the sponge-beds of the Cretaceous 

 formation ; that as sponges were rare in the Carboniferous rocks, 

 it is clear that they could have taken no important part in the 

 formation of the Chert-bands in the Carboniferous Limestone ; and 

 the assertion I made is therefore unfounded, and I must have 

 mistaken sections of crinoid stems for sponge-spicules. Prof. Hull 

 still maintains and reasserts his original proposition, that the beds 

 and nodules of siliceous material in the Carboniferous Limestones 

 of Ireland have been formed by a direct replacement of the original 

 calcareous substance of the limestone itself by silica held in solution 

 in the sea- water, without the intervention of siliceous organisms. 



It is somewhat remarkable that neither Prof. Hull nor Mr. Hard- 

 man make any mention whatever in these papers of the fact, 

 published by Prof. Sollas, that in at least two of the specimens of 

 Chert in Prof. Hull's own possession, sponge-spicules make up the 

 larger part of its substance. This fact alone is quite sufficient 

 foundation for the assertion I made, and Prof. Hull was in duty 

 bound to give some explanation of it, before accusing me of making 

 a statement on absolutely no evidence. It is manifest that * Prof 



1 Ann. and Mag. Nat. Hist. s. 5, toI. vi. (1880) p. 213. 



2 On Beds of Sponge-Eemains in the Lower and Upper Greensand of the South of 

 England, Phil. Trans, pt. ii. 1885, pp. 405-453, pis. 40-46. 



•^ Proc. Eoyal Soc. vol. xlii. p. 304, et seq. 



^ I regret to have to make another serious complaint against Prof. Hull of having 

 misquoted a passage from my published paper in the Phil. Trans., leaving out words 

 essential to its meaning, and then stating that he has quoted the entire passage to 

 avoid the possibility of misinterpretation, and that it is altogether unintelligible ! 

 The passage in question, at the bottom of page 432 in my paper, is as follows, 

 ' ' Thus Dr. Bowerbank held that the sponges imbedded in the Chert of the Greensand 

 possessed horny and not siliceous skeletons, and that the silica of the Chert in which 

 they were imbedded was attracted from the exterior medium by the animal matter 

 and not secreted therefrom by the living sponge." In Prof. Hull's quotation the 

 last paragraph runs thus, " The silica in the Chert in which they were imbedded was 



