336 Count de Bournon's Observations on a new 
merely the chemical combination of a particular acid with a par- 
ticular basis which forms the species, but the mode in which that 
acid is combined with the basis. Perhaps, in many cases, the 
formation of the species may depend upon the introduction of a 
third principle, which, either from its mode of combination or 
from its nature, has hitherto eluded the investigations of che- 
mistry. Thus, in the analysis of two plants, or of two animals, 
of totally different species, chemistry, in most cases, is not able 
to discover any thing but the same ingredients combined with 
each other. In these instances, therefore, it is evident that the 
mode of combination, and not the combination itself, is what 
determines the species. 
The science of mineralogy is indebted to the Abb£ Hauy, for 
having ascertained the primitive form of the slightly attractable 
oxide of iron, formerly known by the name of specular iron 
ore, to which he has given the name of fer oligiste. That 
form was supposed to be derived from the cube ; but the Abb6 
Hauy, directed thereto by the secondary crystals, has shown 
that it belongs to a rhomboid of 87° and 93 0 . Nevertheless, 
the cube must not be excluded from among the forms be- 
longing to the oxides of iron. On the contrary, it constitutes a 
particular species, which has hitherto been entirely overlooked 
by mineralogists. 
Between the slightly attractable oxide of iron, (or specular 
iron ore,) and that kind which no longer crystallizes, except in 
a very indeterminate form, nature has placed another species, 
the surface of which is of a gray colour, and has a specular ap- 
pearance, pretty much like the iron ore from the island of Elba, 
This kind is not at all acted upon by the magnet; and seems to 
be in the last degree of oxidation in which iron retains the pro- 
perty of crystallizing in a regular form. 
