3G0 
THE GEOLOGIST. 
most eminent writers on this subject have fallen into this mistake. 
It almost appears as if they had forgotten that the expression vein 
only distinguishes the form of an occurrence, by no means its nature ; 
and that particular species of ores (native metals, sulphides of 
metals, oxides and hydrates) are found in veins with very varied 
combinations, and under veiy diveree circumstances. 
Another mistake of early geologists was that they were always 
prone to consider geological events as caused by a wholly peculiar 
state of things belonging to an anterior world concluded with the 
appearance of man. This doctrine was but too favourable to the 
growth of the most unsound and gToundless hypotheses. Nothing 
was at that time impossible in the eyes of geologists ; they had no 
regard to the analogies of existing causes ; scarcely much indeed for 
the essential laws of nature. It was chiefly Sir Charles Lyell who 
successfully combated this doctrine. He showed that the magni- 
ficence of the result was extraordinarily heightened by the per- 
manency of the causation ; and that we had not necessarily to assume 
new sets of causes, different from those now in action, in order to 
account for the earth's surface as we now see it. According to this 
geologist, existing causes acting through periods of unlimited dura- 
tion are sufficient to explain all geological phenomena. But he and 
his school have evidently carried this doctrine to an extreme, since 
he insists that there exists no recognizable proofs of any progressive 
development in the state of our earth, only a constant metamor- 
phism ; while an immense mass of facts affords very sti-ong evidence 
of a iirogressive development of the earth, arising from its continued 
gradual cooling. Of these, I shall here merely point to the very 
i-emarkable differences in composition and structure that exists be- 
tween the older and newer eruptive rocks, and to the succession of 
the various types of organic life recog-nized by fossil remains. This 
succession most undoubtedly leads, by its convergence, to a vanish- 
ing point, when as yet there existed no organic life on the earth. 
The acceptance of the doctrine of a gradual development of the 
caith by slow cooling is supported by many facts, and suffices to 
explain the totality of geological phenomena and the general forma- 
tion of the solid crust of the earth, although isolated cases of 
obscurity still remain. 
