NEOCENE DEPOSITS OF CALIFORNIA 383 
level, or the local sinking of an orographic block bounded by 
faults, such as Professor Whitney adduced in explanation of 
Yosemite Valley. Dr. A. C. Lawson has called to my attention 
that in Europe, particularly in Germany, there are depressed 
areas of no great width which clearly have resulted from a 
‘dropping out of the bottom,” as we may say. The flat bottoms, 
steep walls, and canoe shape of the valleys occupied by the 
Neocene deposits in Trinity county seem to favor this theory, 
but against its adoption I have the following objections : 
1. Outside of the four or five Neocene valleys already men- 
tioned, there is no evidence in Trinity county of Neocene or 
later faulting. We know there have been gentle disturbances, 
broad arching of the strata, but no general ‘breaking up of the 
rocks. The faulting would have to be strictly localized or con- 
fined to these valleys. Where the faults intersected at the cor- 
ners of these valleys they must have terminated abruptly, not 
gradually dying out as is the habit of faults. 
2. The valleys trend in different directions, so that there 
could be no regularity in the system of dropped fault-blocks, as 
there usually is. 
3. The old Trinity valley is rather too crooked, and the 
crooks are not systematic enough to fit into such a scheme of 
dropped fault blocks. 
4. The coarse character of the deposit throughout the Trinity 
area shows that the valley was kept filled up to a river level 
during a progressive sinking, and had there been a sinking of 
the rock floor relative to the walls, the gravel deposit should in 
its lower portions be much disturbed and bent up along the bor- 
ders, a structure which has not yet appeared in the deepest nat- 
ural or artificial excavations. 
5. But the strongest objection of all les in the fact, which 
may be particularly observed in the case of the old Trinity val- 
ley, that these valleys do show the influence on their width of 
the varying resistant properties of the formations traversed. 
The northern portion of the old Trinity valley is narrow (aver- 
aging one mile) because it is trenched into serpentine and the 
