472 J. LeConte—Formation of the Features, ete. 
fissure-eruptions and volcanoes are usually associated with 
mountain chains. 7. Many other phenomena—such as fissures, 
slips, earthquakes, and the subsidence preceding the elevation 
of mountains, it equally accounts for. 
It will be remarked that the theory, though in its general 
features, not dependent upon, yet strongly inclines toward and 
is powerfully supported by, the views of Rose, Bischof, Hunt. 
and others as to the metamorphic origin of granite and even of 
igneous rocks; the view that surface materials have passed 
by perpetually repeated cycles, through all the stages of rocks 
and soils ; igneous rocks disintegrated to soils, carried away and 
deposited as sediments, consolidated into stratified rocks, meta- 
morphosed into gneiss, granite or even into lavas, to be again 
_ after eruption reconverted into soils and re-commence the same 
eternal round; and thus we look in vain for the original ma- 
terial. I confess I lean strongly to this view. 
I am fully aware that there are some phenomena of move- 
ment of the earth’s crust which are not explained by the fore- 
going theory. I refer especially to those great and wide-spread 
oscillations which have marked the great divisions of time, and 
have left their impress in the general unconformability of the 
tangible which may be attacked and overthrown by facts an 
by physical reasoning. We have had enough of vague theoriz- 
ing in geology ; of vague shadows through which the trenchant 
sword of science passes with no effect. It is time that the more 
perfect methods of physics were applied to geology. 
Oakland, Cal., May 15, 1872. 
