"2-34 Scientific Intcl/iyence. 



the analyses of the same mineral, (as there recorded) by different 

 chemists; how much do they sometimes differ; and how differently 

 will they be placed, according to our confidence in one or other of 

 the authorities. How many minerals, too, are there, of which we 

 have still reason to suspect the recorded analyses as erroneous; and, 

 how frequently does the detection of such errors subject us to the 

 annoyance of transferring a specimen, both in the collection and the 

 catalogue. But, 2d, (supposing the analyses to be correct), will the 

 same elements, united in one instance by igneous, in another by 

 aqueous action, form the same mineral species? In the case of 

 aragonite and calc spar, (and others might be quoted, if we could de- 

 pend upon the published analyses), isomerism is produced by the 

 same action (aqueous) on both sides ; and we have yet all to learn of 

 the causes and extent of this phenomenon in mineralogy ; of which, 

 however, the incoveniencc in the chemical system will not be great. 

 But it is otherwise with the 3d case, Isomorphism, the micas, the 

 hornblendes, the garnets and several other species, mineralogically 

 all but identical, must be chemically dispersed in different parts 

 of the collection ; and some will apply to the 4th case ; their proper 

 places, upon fixed principles, being difficult to decide. 



III. My third practical objection to chemical arrangement, that 

 by diverting our attention from the physical distinctions, minerals 

 are mistaken for one another, is of not less importance. How many 

 instances may be referred to of the analyses of one mineral being 

 recorded under the name of another, by chemists of the first eminence. 

 And, in your Number for December, a foot note at page 445 makes 

 it appear that a specimen examined by Berzelius, and given to him 

 by Haiiy, was a different mineral from what both those philosophers 

 understood it to be. Now, their mineral systems, although differing 

 in arrangement, are both chemical, and, therefore, subject to this 

 charge, of fixing the attention on other than the natural distinctions. 

 And of a method which leaves the greatest masters liable to mistake 

 their specimens, when deliberated, noticed for analyses, or examina- 

 tion for the purpose of publishing their distinctive properties ; how 

 can the student expect such a method to facilitate his attainment of 

 the power of recognizing and distinguishing them ? 



For such reasons, which may he amplified on a future occasion, 

 the natural appears to me preferable to the chemical arrangement of 

 a public mineral collection. But a chemical arrangement, on paper, 

 as an index, or catalogue raisonnee, symbolically elucidated, and suc- 

 cinctly explained, I conceive to be an accompaniment of essential 

 importance in a scientific point of view. Such a book was wanted 

 in our language, ar d the first volume of Dr. Thomson's work seems 

 just to supply the deficiency. It may be applied to any collection 

 by putting in, with the pen, the order and genus in the margin of 

 each article, both in the synopsis and the text ; making, at the same 

 time, responding references in the catalogue of the collection to the 

 class and genus of the book. Thus, I think, the practical and 

 scientific progress of the student would be at once promoted ; and 

 the knowledge of mineralogy facilitated in a degree much beyond 

 what it has vet reached in this country. P. 





