3 J 4 On Professor Jameson's System of Mineralogy . 



but sacrificed facility to precision*: and if mineralogy be doomed 

 to rank amongst the sciences, its foundation must rest on a firmer 

 basis than colour, hardness, and weight. 



As for the discrepancies which are " so trivial as scarcely to 

 deserve attention," they may rest in peace : it is waste of words 

 to argue for mathematical exactness with men who think nothing 

 of an unit or two in specjfic gravities, and eight or ten degree* 

 in the measure of a right angle ! f 



We are reminded how easily I might perceive that the obser- 

 vations to enable a student to distinguish particular minerals 

 from those which they more nearly resemble, are not delivered as 

 essential characters. Tliis 1 did perceive ; and considered that 

 very circumstance a great objection. The principal complaint 

 is, that by " a very absurd adherence to a system " (to use 

 G. M.'s own words) the essential characters are made to depend 

 wholly on circumstances which have frequently nothing charac- 

 teristic in them ; and the discrimination of the species is left to 

 be ultimately determined upon principles which the founder of the 

 system has not the candour to avow. 



Towards the conclusion we are told, that the excellence of a 

 system will consist in " laying down such methods, founded on 

 the external characters of minerals, as shall aiford the means of 

 immediately placing the mineral in the class, order and species 

 to which it belongs." Expunge the word "external" and the 

 sentence will appear unexceptionable ; but, while minerals re- 

 main destitute of organization, and liable to continual variations 

 from accidental contamination with foreign substances, it will be 

 found that a sy&tcn), allogei her dependent on external characters ^ 

 will never impart a degree of knowledge worthy the nfime of a 

 scientific attainment. Of this we have a lamentable proof in the 

 work under discussion, which presents us with groups of earthy 

 minerals without an atom of earth in their composition. 



When the observations which yon honoured by insertion iu 

 your Magazine for January were written, I had not learnt any 



* Facility applied to the obsolete system, which enabled any one within 

 sight of an oak to decide on its belonging to the 1st class, or trees. Linnaeus 

 rejected such misleading facility, and obtained precision by the more careful 

 and scientitic examination which guides the modern botanist in referring it 

 to the class Monoec'a. 



f " By describing a mineral thus" (according to Werner's system, the 

 via v'ltcB of the externalists) " native sulphur, whose specific gravity is 

 2'0232, and telesia, which wei.;hs 3-9941, svould be included in the same ex- 

 pression." — Chenevix in Phil. Mag. vol. xxxvi. p. 420. 



" I have heard M. Werner say (and I have written his lectures as he de- 

 li .-ered them) that a difference of 10° did not prevent him from considering 

 any angle as a right angle." Ibid. 



Other 



