172 J. LeConte on the great Lava-flood of the West, 
I have indicated these also in the figures. The dark line, b, 
was certainly, therefore, an old forest-ground surface. 
3. Resting directly on this ground surface, and therefore 
enclosing the erect stumps, was a layer of stratified sandstone, 
e, two or three feet thick, filled with beautiful cmpressions of 
leaves of several kinds of forest trees, possibly of the very trees 
about whose silicified bases they are found. This layer is not 
continuous like the ground surface on which it rests. 
4, Above this stratified leaf-bearing layer rests a coarse con- 
glomerate, d, 100 feet thick, similar to the conglomerate a, but 
less coarse, and differing in being coarsely and irregularly strat- 
ified in places, like modified drift; in fact, undistinguishable 
from much of what is called northern drift except that.it is par- 
tially cemented. Scattered about in the lower part of the con- 
glomerate, d, and in the stratified sandstone, c, and sometimes 
lying on the dirt-bed, 6, are fragments of trunks and branches 
of oaks and conifers, in a silicified or lignitized condition. They 
are evidently silicified drift-wood. 
5. Above the conglomerate surface, ¢, and a little back from 
the river, rise the layers of lava, mostly columnar basalt, one 
above another, to a height, at this point, of 3,300 feet. 
Such is a brief but accurate description of the cliff exposed 
by the Columbia River at the Cascades. My interpretation of 
these facts was then, as it is now, that the conglomerate under- 
les the lava, and, therefore, that the leaf-bed determines approx- 
imatively the age of the Cascade Range. But, as the actual 
contact of the basalt and the 
asalt and concealing the lower portion of its face, as shown in 
the diagram, fig. 4. Which of these diagrams (fig. 3 or fig. 4) 
basal 
mined first to settle this point definitely. d 
With this object I revisited the locality in August last; an 
after confirming my previous observations and collecting be 
number of fine leaf impressions and fragments of silicifi : 
wood, I went up the stream-beds of three of the creeks — 
run into the Columbia River at this point; one of them, Roe! 
k, from the north, and two, Tanner's Creek and Deadman’s 
