250 



On Mr, Chenevix^ Attack 



[April, 



ing for it without being under the necessity of giving up his ^ 

 opinion. When minerals cr37stallized, says he after Dolomieu, 

 they were enveloped in foreign bodies. Hence they usually 

 eontaio a variety of foreign matter mechanically mixed. Now, 

 as chemistry is not in possession of a method of distinguishing 

 betv/een those ingredients which are chemically combined^ and 

 tliose which are mechanically mixed, both together are stated as 

 belonging to the constituents of the mineral ; and hence a varia- 

 tion is exhibited in its constitution, which would disappear if we 

 could get rid of all the ingredients that are only mechanically 

 mixed, and of course in reality foreign. Were we to grant the 

 truth of this explanation, still it would follow that the composi- 

 tion of stones is insufncient to enable us to arrange them into' 

 spp'/ses, since by the confession of Mr. Chenevix himself we 

 have ii ) means of discovering what that composition is. Thus 

 a fitted l>y Mr. Chenevix that chemical analysis (in the 

 vr st^ate of the art) is not sufficient to enable us to divide 

 . - i-'dh into species. 



1 c:v ;i . iV',.id noticing here Mr. Chenevix's remarks regard- 

 in;; vV- (iRi's conduct with respect to chemical analysis. When 

 i: ; ;, i^''S with his previous classification, says Chenevix, he 

 ;t to be of weight; but, when it disagrees with it, he 

 GisLards it altogether, and will not allow it to be a sufficient 

 reason for altering his arrangement. This accusation must be 

 taken witli some limitation. Werner has been induced in some 

 cases, by cheinical analysis, to separate into two species minerals 

 which had l)een formerly considered as constituting only one. 

 Mr. Chenevix himself acknowledges that this was his reason for 

 separating sulphate of strontian from sulphate of harytes. But 

 when the results of chemical analysis and the eX-ternal characters 

 a^e completely at variance, in that case he is induced to hesitate. 

 He has concluded, and 1 cannot avoid embracing the same 

 opinion, that identity of composition will generally be attended 

 by identity of characters. When chemical analysis gives us 

 identity in the one, while there exists diversity in the other, it 

 is reasonable to suppose that from the imperfect state of che- 

 mistry some important ingredient may have been overlooked by 

 the analyst, which occasions the difference so conspicuous in the 

 characters. What two substances in nature possess properties 

 more; different from each other than charcoal and the diamond ? 

 Yet, as far as chemical experiments have gone, the composition 

 of both is absolutely the same. It is not possible to avoid sus- 

 pecting that sorne essential difference exists between the com po-^ 

 sition of these bodies, though the art of analysis is not yet far 

 enough advanced to enable us to find it out. Fontana made a 

 great many experiments on the poison of the viper, and, as far 

 as chemical properties went;, he found it the same as gum arahic. 



