mineral species independent of Phenomena of Isomorphism. 208 
ite, which have the same form, are regarded as different species, 
because they have a slightly different composition. It is true 
that the actual composition of a mineral may vary very greatly 
by the substitution of isomorphous elements, and yet, if the gen- 
eral formula remains constant, the species may not be changed. 
But the extent to which such substitution can + carried without 
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be modified by the substitution of isomorphous elements, was 
first established by Mitscherlich, and has long been an admitted 
Principle in mineralogy. We must now, as I think, still further 
Sciences, we are led to admit the truth of that maxim which 
facie), Savant in true knowledge seems to verify, “Natura non 
It saltus,” - 
hevnile the results of my investigations thus serve to render 
e idea of a mineral species less definite than before, I cannot 
eiePe that they will tend ultimately to simplify the whole 
the number of mineral species, but also, by simplifying the gen- 
eral formule of those which remain, to classify the whole with a 
"son; and it is the chief object of the present paper to call the 
