Reviews—Survey of Colorado. 477 
Tn like manner fresh-water and estuarine conditions are found now 
in one region, now in another, throughout all the formations or 
groups of formations possibly from Silurian times onward; and 
glacial phenomena, so far from being confined to what was and is 
generally still termed the Glacial Epoch, are now boldly declared, 
by independent witnesses of known high reputation, to begin with 
the Cambrian epoch, and to have occurred somewhere, at intervals, 
in various formations, from almost the earliest Paleozoic times down 
to our last post-Pliocene ‘Glacial Epoch.’ 
If the nebular hypothesis of astronomers be true (and I know of 
no reason why it should be doubted), the earth was at one time in a 
purely gaseous state, and afterwards in a fluid condition, attended 
by intense heat. By-and-by consolidation, due to partial cooling, 
took place on the surface, and as radiation of heat went on, the outer 
shell thickened. Madiation still going on, the interior fluid matter 
decreased in bulk, and, by force of gravitation, the outer shell being 
drawn towards the interior, gave way, and, in parts, got crinkled up, 
and this, according to cosmogonists. was the origin of the earliest 
mountain-chains. I make no objection to the hypothesis, which, to 
say the least, seems to be the best that can be offered, and looks 
highly probable. But, assuming that it is true, these hypothetical 
events took place so long before authentic geological history began, as 
written in the rocks, that the earliest of the physical events to which 
I have drawn your attention in this address was, to all human 
apprehension of time, so enormously removed from these early 
assumed cosmical phenomena, that they appear to me to have been of 
comparatively quite modern occurrence, and to indicate that from the 
Laurentian epoch down to the present day, all the physical events in the 
history of the earth have varied neither in kind nor in intensity from 
those of which we now have experience. Perhaps many of our British 
geologists hold similar opinions, but, if it be so, it may not be alto- 
gether useless to have considered the various subjects separately on 
which I depend to prove the point I had in view.” 
II.—Unirep Srares GronogicaL AND GEOGRAPHICAL SURVEY OF 
Cotorapo AND ApsAcENT TRRITORY, 1876. By F. V. Haypen, 
United States Geologist. S8vo. (Published at the Government 
Printing Office, Washington, 1878.) 
HE Tenth Annual Report of this extensive and exhaustive Survey 
is fully worthy of its predecessors, and bears testimony that there 
is no want of care, attention, and energy on the part of the Depart- 
ment over which Mr. Hayden has presided. 
It contains the subsidiary reports of Messrs. C. A. White, F. M. 
Endlich, and A. C. Peale, on the Geology of a portion of North- 
Western Colorado, the White River Division, and the Grand River 
district ; and reports also on the triangulation and survey of the 
districts under examination, the value of the arable and pasture land 
for cultivation, and a most interesting treatise on the archxological 
remains. 
