and on the Age of the Cascade Mountains. 175 
tained petrified drift wood. But erect stumps and leaf impres- 
sions, though diligently searched for, were found only at the 
locality first mentioned. 
There is still another fact observed which has an important 
bearing upon the age of the lava-flow. Going ' Tanner's 
Creek, the rising stream-bed reaches the upper surface of the 
conglomerate first about two miles from the main river. From 
above the river, while it comes down to the water's edge at 
from these very trees, certainly from contemporaneous trees. 
The order of events, as I conceive them, was briefly as follows : 
l. The region of the Columbia River was a forest, probably a 
valley, overgrown with conifers and oaks. The subsoil cf this 
forest was a coarse boulder drift. 2 By exces of water, 
either by floods or changes of level, the trees were killed, their 
leaves shed and buried in mud, and their trunks rotted to 
m 
rapidly than the tributaries, and these latter, therefore, ran 1nto 
the river on either side by foaming cascades, until the river 
