THE BRITISH SCIENCE ASSOCIATION. 320 
that the phenomena of metamorphism of strata had been continued from that 
date all through the later formations or groups of formations down to and 
including part of the Eocene strata in some parts of the world. He had 
also shown that ordinary volcanic rocks had been ejected in Silurian, De- 
vonian and other times, and from all that he had seen and read of these 
ancient volcanoes he had no reason to believe that volcanic forces played 
a more important part in any period of geological time than they did in 
this modern epoch. So also mountain chains existed before the deposition 
of the Silurian rocks, other of later date before the old red sandstone 
strata were formed, and the chain of the Ural before the deposition of the 
Permian beds. The deposition of salts from aqueous solutions in inland lakes 
and lagoons appeared to have taken place through all time and was still going on, 
and in like manner fresh water and estuarine conditions were found now in one 
region, now in another, throughout all the formations, or groups of formations, 
possibly from Silurian times onward, whilst what was termed the glacial epoch 
was now boldly declared to have occurred at intervals from almost the earliest 
Paleozoic times down to our last post-Pliocene ‘‘ glacial epoch.” 
If the nebular hypothesis of astronomers be true—and he had no reason to 
doubt it—the earth was at one time in a purely gaseous state and afterward in a 
fluid condition, attended by intense heat. By and by consolidation, due to par- 
tial cooling, took place on the surface, and as radiation of heat went on the outer 
shell thickened. Radiation still going on, the interior fluid matter decreased in 
bulk, and by force of gravitation the outer shell, being drawn toward the interior, 
gave way, and in parts got crinkled up, and this, according to cosmogonists, 
was the origin of the earliest mountain-chains. This looked highly probable. 
But assuming that it was 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 he had drawn their attention was to all human ap- 
prehension of time so enormously removed from these early assumed cosmical 
phenomena that they appeared to him to have been of comparatively quite 
modern occurence, and to indicate that from the Laurentian epoch down to the 
present day all the physical events in the history of the earth had varied neither 
in kind nor in intensity from those of which we now had experience. Perhaps 
many British geologists held similar opinions, but if that were so, it might not 
be altogether useless to consider the various subjects separately on which he de- 
pended to prove the point he had in view.—/von. | 
