378 Reflections on some Mineralogical Systems. 



obvious effects of the sun's varying influence in raising 

 and dispelling vapours, we may, I think, account pretty 

 satisfactorily for the various vicissitudes of weather, which 

 mark the different seasons throughout the year; and, by the 

 relation of the barometer to those causes, be enabled to 

 foresee, with a considerably greater degree of certainty than 

 is commonly supposed, the different'ehanges of weather 

 which are, at all times, about to take place. 

 I am, sir, 



Your obedient servant, 



Queen-street, Oxford, R D . WALKER. 



Nov. 17th, 1810. 



LXX. Reflections on some Miner alooical Systems. By 

 E. Chenevix, Esq. F.R.S. and M.R.LA.,'&c. Trans- 

 lated entire from the French, with Notes by the Trans* 

 lator. 



{ [Continued from p. 303.] 



SUPPOSED DEFECTS OF THE CRYSTALLOGRAPHJCAL 

 SYSTEM. 



1V1. Hauy has been reproached for his principle of speci- 

 fication and his definition of the species : one alleging that, 

 according to him, muriated soda and sulphated lead are of 

 the same species ; another, that the two indications of the 

 species are often in contradiction, and that the same form 

 of molecule does not always accompany the same chemical 

 composition, and vice versa. Some do not like the octaedron 

 for a primitive form, because, to preserve unity of form in 

 the integral molecule, it is necessary to suppose empty spaces ; 

 others, in short, reproach him with the difficulty of finding 

 all the directions of the cleavage (or the construction of the 

 cleft), and the system also with a want of generalization; 

 and finally, as a dernier resource, that we must return to 

 the system of external characters. 



Will it be believed that I have heard the first of these ob- 

 jections made by a celebrated philosopher, a professor who 

 draws around him from all parts of the world the zealous 

 lovers of mineralogy, and who repeats it at least once a 

 year in his public lectures ? that I have seen it printed and 

 published in a work which passes for one of the best on the 

 systems of this professor ? It is of German origin, and 

 proceeds, no doubt, from the circumstance that they have 

 not yet learned to count even to two on their lingers ; a 

 great misfortune for a philosopher. Identity of form in the 

 integral molecule, — this is one condition in order that two 



minerals 



