138 
A. FRAGMENT OF GEOLOGY. 
Where the Coiumbia River breaks through the 
Cascade Mountains there are found, beneath 
the overlying lava: First, Along the water’s 
edge, and for about fifteen feet upward, a very 
coarse conglomerate of rounded _porphyritic 
pebbles and bowlders of all sizes up to five or 
six feet in diameter, cohering by an imperfectly 
lithified earthy paste. 
Second, Above this conglomerate is a very 
distinct, irregular, old ground surface bed, in 
which are found silcified stumps, with their roots 
spreading out over twenty feet in diameter and 
penetrating into the bowlder material beneath 
evidently 2 sé#z, This is undoubtedty an old 
forest ground surface, 
Third, 
surface, and therefore inclosing the erect stumps, 
Resting directly on this ground 
is a layer of stratified sandstone, two or three 
feet thick, fiiled with beautiful impressions of 
leaves of several kinds of forest trees, possibly 
of the very trees about whose silicified bases 
they are found. ‘Tnis layer is not continuous, 
like the ground surface on which it. rests, 
Fourth. 
layers, rests a coarse conglomerate similar to 
the 
Above this stratified leaf-béaring 
that beneath at water-level, Scattered 
about in the 
conglomerate and in the stratified sand-stone, 
lower part of this upper 
and sometimes lying in the dirt-bed beneath it, 
are fragments of trunks and branches of oaks 
and conifers, in a silicified or lignitized condi- 
tion, They are evidently silicified drift-wood. 
Fifth, and 
resting upon it, rise the layers of lava, mostly 
columnar basalt, one above another, to a 
height of more than 3,000 feet. 
All these facts were noted and studied by 
Professor Le Conte, who drew the following 
order of events from them. 
First The region of the Columbii River 
was a forest, probably a valley, overgrown by 
Above this last conglomerate, 
conifers and oaks. The subsoil of this forest 
was a coarse bowlder drift produced by erosion 
of some older rocks. 
Second. By excess of water, either by ‘loods 
or changes of level, the trees were killed, their 
THE OREGON NATURALIST. 
leaves shed and buried in mud, and their trunks 
rotted to stumps, 
Third, 
coarse drift containing drift-wood, covered up 
Tumultuoas and rapid deposit of 
the forest ground and the still rem vining stumps, 
one hundred, perhaps several hundred, feet in 
thickness. 
Fourth. Thesurface thus formed was ero- 
ded into hills and dales. 
Fifth. Then followed the outburst of lava 
in successive flows, perhaps for a long period of 
time, and the silicification of the wood and the 
cementation of the drift by the percolation of 
the hot alkaline waters containing sil.ca, as 
happens so commonly in sub-lava drifts. 
Sixth .Finaily followed the process of erosion, 
by which the present stream channels, whether 
main. or tributary, have been cut to their enor- 
mous depth. 
The great masses of sediment sent down to the 
sea from the primary Cascade range, forming a 
thick off-shore deposit, gave rise in its turn at the 
end of the Miocene to the upheaval of the Coast 
range, and, coiuc: feutiy Lierewith, the Cascade 
Mountains were rent along the axis into enor- 
mous fissures from which outpoured the grand 
lava floods, buitding higher the mountains and 
covering the country for great distances. 
This is probably the grandest and most 
extraordinary lava flow which ever took place 
in the world, covering as it does an area of 
about 200,000 square miles of the Western 
States and Territories. Commencing in Mid_ 
dle California as separate streams, in Northern 
California it becomes a flood, completely mant- 
ling the smaller inequalities, and flowing a- 
round the greater inequalities. In Northern 
Oregon and Washington it becomes an absol- 
utely universal flood, beneath which the whole 
original face of the conntry, with its hills and 
dales, mountains and valleys, lie buried several 
thousand feet, {[t covers the greater portion of 
Northern California and Northwestern Nevada, 
nearly the whole of Oregon Washington, and 
Idaho, and runs far into British Columbia on 
the north. The average thickness of this tre- 
mendous flood is probably not far from 2,000 
feet. This is shown where the Columbia, Des- 
