Mineralogical Evolution. 245 
” 
called ‘Notes on Inorganic Evolution,” speaks of the pro- 
duction and conservation of more stable species, as above 
described, as a gradual “selection of inert forms,” and fur- 
ther, as “a survival of the most inert.” But as inertness 
consists in stability, and in fitness to resist alike the chemi- 
cal and the mechanical agencies which destroy other spe- 
cies, it is evident that this phraseology is but another state- 
ment of the formula of ‘‘the survival of the fittest.” 
The great principle of the change of the mineral matters 
which existed in former conditions of our planet, into other 
forms more stable under the altered conditions of later ages, 
is but an extenston to the mineral kingdom of the laws 
already recognised in astronomical and biological develop- 
ment. As was written in 1884, “That a great law presided 
over the development of the crystalline rocks was from the 
first my conviction, but until the confusion which a belief 
in the miracles of metamorphism, metasomatism, and vul- 
canism had introduced into geology had been dispelled, the 
discovery of such a law was impossible.” To this we may 
add that “ the great successive groups of stratiform crystal- 
line rocks mark necessary stages in the mineralogical evo- 
lution of the planet ;” and that the principles which we 
have elsewhere laid down will help us “to recognise the 
existence and the necessity of an orderly lithological devel- 
opment in time.” The reader who desires to follow the 
questions here raised will find them discussed in the au- 
thor’s “Mineral Physiology and Physiography,” (Boston, 
1886,) at much length, in chapters v., vi., vii. and viii., 
and further noticed in the Appendix, p. 688, where will be 
found references to previous pages here cited. 
