IMohs^ /System q/' Crystallography 
its remaming characters^ constitutes^ in regard to its form, 
a member in a series of individuals, distinguished only by their 
forms ; and in regard to its colour, constitutes a member in a 
series of individuals, distinguished only by their colours ; in 
that case, the individuals of the former series disagree with 
those of the latter, by the smallest degree of difference, consis- 
tent with the individuals not being simply un form. 
23. Universality of the above. — This conclusion may be pro- 
secuted and extended to all characters, from the varieties of 
which series arise. When any such are found as shew no 
difference, which happens in some cases with respect to hard- 
ness and specific gravity, in those cases series, having terms en- 
tirely equal, may be imagined, concerning which the foregoing 
result is likewise true. By this means it is possible to find in- 
dividuals which, with regard to the properties or characters 
combined in them by nature, may at once be members of all the 
series, which can be linked together in the way already explain- 
ed (23). Though these individuals are not uniform, yet there 
subsists among them the smallest degree of difference, (for by 
the process described above, (19.)? they and their characters 
may be included under the nqtion of uniformity), and they can 
be separated from all others distinctly and accurately. 
24. Species. Homogeneity. — The group of individuals which, 
by the preceding treatment of their series of characteristics, can 
be brought under the notion of smallest differences, or of uni- 
formity, is named a Species, and the individuals belonging to 
the same species are said to be homogeneous. 
25. Logical condition of the Idea of Species. — From what has 
been said, homogeneity in the mineral kingdom, among indivi- 
duals which are not uniform, (for the uniform are of course ho- 
mogeneous,) depends on the connection which reigns among 
their characters. This connection is founded on the consi- 
deration of the various series of characters ; among which, 
that of regular forms is capable of geometrical management. 
Were all the characteristic series possessed of the same property, 
homogeneity in the mineral, and therefore the natural historical 
distribution into series, would be an object of mathematical de- 
monstration, and besides its exactness, would be attended with 
perfect evidence. 
