386 Reflections on some Mineralogical Systems. 



somewhat specious. In the present age natural philoso- 

 phers cannot admit it. 



Specific gravity may he viewed in two points : — where 

 the molecules of all the bodies have the same density, and 

 then the variation of specific gravity between one mass and 

 another depends on their particular arrangement with re- 

 spect to each other, which admits of more or less empty 

 spaces in the different bodies in nature; or where the mole- 

 cules themselves have a different density in each substance, 

 the relative disposition being the same in all. It is evi- 

 dent that, on the first supposition, the molecule and the 

 body which it contributed to form would have properties 

 different in this respect, and that we could never learn 

 any thing of the true specific gravity of the molecule, 

 however correctly we knew that of the body. Platina, 

 for example, which I estimate at nearly 21*437, might 

 have a molecule ten times (100 times if it is wished) more 

 dense than it; and the lightness of the aggregate would 

 result from the space, in which 214370~ molecules of 

 platina might lodge, if the arrangement was the most fa- 

 vourable possible for' this effect, containing only 21437. 

 The specific gravity of cork has been estimated at 0*24. 

 A space therefore which contains 21437 molecules of pla- 

 tina could contain but 240 of cork, in this hypothesis ; 

 yet a molecule of platina loses in water the same quantity 

 of its weight as a molecule of cork. 



In the second supposition we discover the weight of 

 the molecule having that of the mass ; and the number of 

 molecules in a given volume of platina would be equal to 

 that which the same volume of cork would contain. 



There exists, indeed, a third hypothesis, composed of 

 these two, and which supposes at the same time a variation 

 in the density of the molecules and in their arrange- 

 ment. I shall not discuss what hypothesis should be pre- 

 ferred in sound philosophy. 1 speak at present like those 

 mineralogists who judge all by their senses, and I admit 

 every thing which they wish, in order to refute all. 



In the hypothesis where the density of the molecules is 

 supposed variable, it is evident that the objection falls of 

 itself; for I am able to give those molecules whatever 

 density I choose, within reasonable limits. Now when 

 in fiuated lime there would be the two thirds vacant which 

 form the subject of reproach, the density of the mole- 

 cule would be but three times greater than that of the 

 mass. Yet the density of a molecule of gold would be 

 six times greater than in this supposition. Thus, by ad- 

 mitting 



