1818.] Crystalline Form, and Chemical Composition. 263 



It appears that the first regular classification of minerals on 

 the principle of chemical analysis, was published by Bergman, in 

 1782, in his " Manuel du Miheralogiste," in which the superio- 

 rity of this mode of classification over that which had been 

 previously used, was very conspicuous ; and it is true that this 

 principle has been since generally adopted in separating the 

 species into varieties. 



Since Bergman's treatise, many other systems have appeared, 

 founded more or less upon his principles, arid niodified according 

 to the existing state of chemical science. 



In all these there were found many species of minerals inca- 

 pable of being otherwise than vaguely defined by chemical 

 distinctions, and the number is continually increasing. Berze- 

 lius, however, has very recently proposed a new and more 

 methodical classification, in which he considers the oxides of 

 aluminum, of silicium, &c. as performing the office of acids in 

 the composition of mineral substances'. His treatise is unques- 

 tionably the most ingenious and perfect of all that have been 

 founded on chemical analysis, and it will doubtless be improved 

 by a more perfect state of chemical science. 



In general, in the proposed classification founded on chemical 

 characters, minerals of the same species are defined to consist of 

 such substances as are similarly composed. It cannot be denied, 

 however, that, owing to the irregularity in the proportions of the 

 constituent parts of minerals, this definition becomes uncertain 

 in its application, and the chemical determination of a species 

 will frequently be arbitrary. 



About the time that Bergman was employed in constructing 

 his method of classification, Rome Delisle, in comparing together 

 variously formed crystals of the same substance, discovered that 

 they might all be referred to some simple fundamental form, of 

 which they might be considered modifications resulting from the 

 truncation of its edges or angles ; but he did not pursue this 

 idea further, so as to apply it to the determination of a species. 



M. Ha'uy at length appeared, and not only multiplied the 

 observations on crystals, but was the first who applied to crystal- 

 lography the consideration of physical character, combined with 

 the calculations of the geometrician. By a method equally inge- 

 nious and exact, he was enabled to demonstrate that all the 

 crystalline forms were related to one single system of geometry, 

 that this system varied in relation to different substances, but 

 was uniform in its application to all the varieties of the tame 

 species ; and he thence concluded that crystallization was the 

 character on which the greatest reliance might be placed in the 

 determination of a mineral specie's. 



Fpom this has resulted a new classification, in which a mineral 

 species is defined to be a collection of substances, of which the 

 integrant molecules are similar, and composed of similar elements, 

 and in similar proportions. 



