Mr. J. S. Bowerbank on the Siliceous Bodies of the Chalk. 251 



destroyed, the spicula should be but veiy sparingly found in the 

 fossil, and what more to be expected than that they should be 

 found imbedded in the surrounding chalk ? 



After some passing observations the author says : " If it is 

 once admitted that flint is ever, or may be even in a single in- 

 stance, found elsewhere, the theory ceases to be an explanation 

 of the phsenomena, and becomes of no value to the philosophical 

 inquirer*/^ This is really so richly dogmatical that one cannot 

 suppress a smile : does the author seriously think that he can 

 thus fetter by a syllogism those who differ from him in opinion ? 

 But even in the face of this denunciation, I will at once admit 

 that flint has been and is continually found elsewhere. It abounds 

 in the mountain limestone formation of England, and I have it 

 through the kindness of Mr. Lyell from the newest freshwater 

 tertiary beds, from Egypt from Prof. Ansted, and out of the late 

 Capt. Clapperton^s collection from the neighbourhood of Tini- 

 buctoo, and from other parts of the world through various chan- 

 nels ; and in all these cases it abounds in animal remains which 

 are under the same conditions as those of the chalk flints. 



The author continues, '^ Now, can it be shown that silex has 

 any peculiar affinity for either the animal substance or the horny 

 skeleton of the sponge ? The contrary is known, as matter of 

 fact, to be the case. Facts palseontological as well as recent might 

 be cited in abundance in disproof of this necessary postulate of 

 the sponge theory. I have undoubted sponges in my possession 

 from the chalk, which, instead of being wholly silicified, are in 

 part so, and in part still in the chalk, while the flint is otherwise 

 extended beyond the boundary of the sponge.^' The author is 

 evidently unacquainted with the second paper which I published 

 in the ' Annals and Magazine of Natural History ' in September 

 and October 1842, or he could scarcely have seriously asked the 

 question contained in the first sentence of the last quotation. If 

 he will take the trouble to consult that paper, or to examine a few 

 thinly sliced specimens of moss agates or green jaspers, as they 

 are termed, from India, he will see abundant proofs of the strong 

 predisposition of siliceous matter for the horny skeletons of the 

 Spongiadse. Every separate fibre which is inclosed forms a di- 

 stinct nucleus, from which the chalcedonic crystals of the silex 

 spring. 



The author states, that the contrary of this predisposition is 

 known to be the fact, but does not adduce a single proof of the 

 correctness of this assertion, although he professes to have an 

 abundance of such ; nor does he even attempt to disprove the rea- 

 soning which I have advanced in the first paper to prove the ex- 



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