ACADEMY OF SCIENCES. 129 
rain, and the crashing shocks of the earthquakes The snow and ice period 
of the northeast was contemporaneous with the flood period of the Pacific 
coast. £ 
No continental glacial system covered the Pacific portion of the United 
States, notwithstanding the altitudes were much greater; the glaciers were 
local, and more or less isolated, clustering around the higher peaks of the 
mountains. 
The valleys and basins of this western volcanic region were filled with hot 
water, hissing steam, and volcanic products. No ice beds could form in the 
valleys of the Pacific; the hot rocks and escaping gases were busy, vaporizing 
the waters for the glacial supply of the east. No gentle snow-flakes could 
find a resting-place upon the table lands and valieys of the volcanic belt; but 
floods of rain descended, and plowed deep gorges down the steepened flanks 
of the recently elevated mountain ranges, thus establishing a new river 
system for the Pacific coast. 
The most prominent examples of this are seen on the western slopes of the 
Sierra Nevada range, in the State of California, where the old river system 
has been completely buried, first by ashes and debris, brought down by the 
floods of water from the vents along the higher portions of the range, and 
secondly by broad streams of lava extending from such vents, to the plains of 
the valley. Notable instances occur in Tuolumne, Sierra, and Plumas coun- 
ties. The portions of the old river system that were covered by the lava 
outflows were protected by them from subsequent denudation, and are now 
the summit lines of long ridges that divide the waters of the newly formed 
river cafions. 
Under these immense fields of volcanic ashes and lava beds are found the 
relics of the tertiary life; and nota trace of such life has been found any- 
where existing on the Pacific coast since this period of uplift and volcanic 
activity which closed the tertiary age. 
The next notable changes were the development of the new river system, 
by the changes of the water-sheds and the enormous floods of water that fell 
for many years near the lines of escaping heat, and the formation of glaciers 
on the higher portions of the mountain ranges. In some places the glacial 
action has been traced down the slopes of the granite peak to the lava beds, 
and for considerable distances on their upper surfaces, thus showing that as 
the lavas became cooled, the ice pushed its way over their higher portions. 
Here we find events well marked in the order of their occurrence: 
1st. An undulating, fertile country, of subtropical or temperate climate, 
teeming with the living forms of tertiary times. 
2d. <A violent and sudden outbreak of volcanic activity, accompanied by 
great changes ot level. 
3d. The destruction of nearly all life, followed by floods of rain to an 
extent nowhere possible except near the sources of vaporization. 
4th. The formation of glaciers on the higher mountains toward the close 
of the flood period, and as soon as the local temperature was sufficiently 
reduced to permit their formation. 
These characteristic changes were not confined to the California coast. 
The line of volcanic activity extended from Cape Horn to Behring Strait. In 
