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III. Remarks on a Pctpcr oji Isomorphism, by Prof. Whewell of 

 Cambridge, inserted in the preceding Number of this Journal. 

 By H. J. Brooke, Esq. F.R.S. L.S. S^- G.S* 



AS I have not contemplated engaging in any contro- 

 -^^ versy respecting the doctrines of isomorphism, having 

 merely thrown out the few facts and arguments contained in 

 the paper referred to by Mr. Whewell, for the consideration 

 of the supporters of those doctrines, I should not have been 

 induced to discuss the subject further at this moment if I had 

 not been misunderstood by Mr. Whewell, relative to the che- 

 mical constitution of aniphibole. 



By the expression to which Mr. Whewell refers, I intended 

 merely to put the hypothetical case, that amphibole had been 

 ascertained to consist of one atom of trisilicate of lime. J had 

 no intention whatever of assuming that to be its true constitu- 

 tion ; and I must regret that the ambiguity which I conclude 

 must exist in the expression I used, should have led to the 

 occupation of any portion of Mr. Whewell's attention in com- 

 menting upon that part of the paper. 



From the short third section of Mr. Whewell's " remarks" 

 " on the principles of the doctrine of isomorphism," I apprehend 

 that our notions even of those jorinciples do not agree. 



I have supposed the theory to imply that different bodies, 

 a, b, c, d, may mutually replace each other because they are 

 isomorphous; and tliat their isomorphism being once esta- 

 blished by their being found to replace each other in combi- 

 nation with X, their capacity is established of becoming iso- 

 morphous substitutes generally : and hence that when any two, 

 as a and b, are admitted by the theory to be isomorphous in 

 relation to Y, or c and d, in relation to Z, a, and b, and c, 

 and d may mutually replace each other in their combinations 

 with either Y or Z. 



Tliis, however, does not appear to be Mr. Whewell's view 

 of the theory; and indeed the fact stated in his paper, that 

 bodies which are isomorphous in combination with silica are 

 only plesiomorphous in relation to carbonic acid, seems to be 

 fatal to the doctrine of isomorphous substitution as a general 

 law of cliemistry, which the new theory professes to be, and 

 would seem to retjuire one theory for silica, and another for 

 carbonic acid, and perhaps others for the other acids, unless 

 the plesiomorphous adjustments of the bed of Procrustes 

 should be found capable of fitting any one theory to every 

 case. 



* Coiiiniiinicatcd by tlic Aullior: sec Phil. Mag. and Annals, N.S. vol. x. 

 1)1). IGl and 401. 

 " The 



