24 
MEMOIR OF WERNER. 
these primary bases. The mysterious force of crys- 
tallization is the only one that presents any resem- 
blance to the generative power: it determines in like 
manner the composition ; but this is only within cer- 
tain limits. Recent experiments have evinced that 
there are substances whose crystalline virtue is such, 
that they constrain very considerable quantities of 
different substances to accommodate themselves to 
their form ; and it has been long observed in nature, 
that crystals, in all respects alike, those of sparry 
iron, for example, may contain more or less of iron 
or of lime, as there may be in two animals of the 
same species a greater or less quantity of fat, of ge- 
latine, or of the earth of the bones. 
In mineralogy, therefore, crystallization must be 
regarded as the fundamental principle of the species, 
as far as it addresses itself to our sight ; but in an 
immense majority of minerals, the crystalline form 
is not visible, and, in such cases, the composition is 
very far from enabling us to determine it ; for the 
latter is more variable than in the crystals, and im- 
pure intermixtures corrupt it more easily. No al- 
ternative, then, is left, but to have recourse to the 
properties which are most closely connected with 
the fundamental principle, viz. cleavage, which is 
only one of its phenomena, fracture, hardness, lustre, 
and the effect of the body on the touch, which are its 
more or less immediate consequences. 
This plan Werner has pursued, not perhaps proceed- 
ing exactly upon these reasonings, but led by that 
