834 G. H. SQUIER 
operating during a period of subsidence, more or less inter- 
rupted by periods of partial reélevation. 
Torrential action. — Considered in the light of inherent proba- 
bility, as well as in certain general aspects, this agent is doubt- 
less the one we should select. The formations are strictly 
valley deposits. Torrents necessarily existed and must have 
produced characteristic deposits, and some of the beds at least 
might have been so formed. When, however, we take account 
of specific characteristics we find very grave difficulties, such as 
the transverse ridges. To account for these at all by torrential 
action it is necessary to regard them as ridges of erosion, the 
remains of a formation once occupying the entire upper part of 
the valley. The sequence of events which would thus be indi- 
cated is something as follows: (1) Subsidence, unstratified 
deposits; (2) Elevation, erosion ; (3) Subsidence, stratified 
beds and loess, but no unstratified beds; (4) Reélevation, 
erosion. 
A study of local conditions furnishes several reasons why 
such a sequence of events must be regarded as violent and 
improbable. I will mention but one which alone seems to me 
to be fatal to it. As already stated, in the west valley above 
the ridge: 
a. The loess covers everything high and low, even to the 
bottom of recent gullies, within a couple of rods of the upper 
end of the gorge, and a foot or two higher than its rock floor. 
Unless, therefore, we suppose that the gorge has received no 
appreciable deepening since the last elevation we must suppose 
that the early erosion extended deeper above the gorge than in 
the gorge itself. (How much deeper the loess extends, I do 
not know.) 
b. The lateral ridges.— Not to occupy too much space I will 
refer to but one, the ridge marked aon the map. Assuming the 
two valleys to have been filled to the height of the ridge we 
should have to account for the removal of a very large amount 
of material, exceeding in the west valley the amount removed 
from its own gorge, yet its drainage area as compared with that 
