404 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 
lith and soil. Such springs, as a general rule, had their flow increased at the time of 
the earthquake. ‘The tendency to compression in firm rocks would not be so effective 
as in the case of noncoherent sediments, but it would make itself manifest in the gen- 
eration of an elastic stress which would die out and merge with the normal gravitative 
stress very gradually. ‘There would also be an effective tendency to bring together the 
walls of cracks and fissures whose planes lay transverse to the path of propagation of 
the compressive wave. Both of these tendencies would make for an expulsion of the 
water. The expulsion could not, in most cases, be effected suddenly, however, owing 
to the great frictional resistance; and simply resulted in an increased flow of the 
springs at the surface, which would continue during the life of the abnormal elastic 
stress. The duration of this stress appears in some cases to have lasted but a few days; 
in other cases it continued for 2 months, as inferred from the abnormally large flow of 
the springs. This variation would depend on local conditions, such as the superficial or 
deep source of the water, the character of the rocks, the degree to which it was seamed 
with cracks, ete. 
This same general explanation would apply to artesian wells, in which the water 
acquired and maintained an increased head for some time. In some such wells, where 
the water stood normally at some little distance below the surface, it overflowed and 
flooded the ground in some instances. In other cases, where the supply was not arte- 
sian, but shallow wells reached the ground-water, the level of the latter rose. This 
general tendency was complicated in some instances by other effects of the earthquake. 
Several surface wells had their level lowered, and others went dry. This sudden drop 
in the level of the ground-water can be explained only by a sudden draining off of the 
underground waters to lower levels, and this might be effected by the opening up of 
the ground superficially, in consequence of -the shock. A similar explanation would 
apply to the few springs which had their flow diminished or cut off altogether. This 
draining off of the waters of higher levels would also augment the flow of springs and 
wells at lower levels and may in some cases have been the principal cause of observed 
increases of flow. The noteworthy case of the spring near Ukiah, described below, 
which ceased flowing and remained dry thruout the following summer and fall, but 
resumed its flow with the advent of the winter rains, suggests that the fissure in the 
rock from which the spring welled served as the limb of a siphon and that the water in 
the siphon was drained off in consequence of the agitation and opening of the ground 
at the time of the shock. The winter rains refilled the siphon limb and so brought 
about a resumption of the flow. 
One of the most common reports regarding the shallower wells was the roiling of the 
water by the admixture of earthy matter, doubtless due to the agitation of the ground 
and the loosening up of.the incoherent material at the bottom of the wells. 
RECORD OF SPRINGS AND WELLS AFFECTED. 
A brief and partial record of springs and wells affected by the earthquake follows: 
Montague, Siskiyou County (C. H. Chambers). — A sulfur spring was formed at a point 
2 miles south of the town of Montague. Hot water ran from it for 2 days, after which 
it cooled off. A soda spring 9 miles east of the town doubled its flow. The water of 
many springs was muddy for several days after the quake. 
Denny, Trinity County (P. L. Young). — At a small quartz mine near Denny the shock 
doubled the amount of water flowing from the tunnel. 
Peanut, Trinity County (Mrs. E. Diller). -—'There was an increase in the water in the 
ditch which comes from a small gulch. The increased flow had not diminished up to 
May 6, 1906. 
