MINOR GEOLOGICAL EFFECTS OF THE EARTHQUAKE. 407 
a short time. The postmaster gave 4.5 feet as the measured rise of the water in his well. 
The spring which furnishes the town supply is said to have been diminished by one- 
fourth of its flow. ‘Two other changes in water supply were reported: one being the 
starting of a new spring near one of the western Pacific camps in Niles Canyon; the other 
the rejuvenation of an old sulfur spring near Sunol, which had not flowed for many years. 
Calaveras Valley, Santa Clara County (G. F. Zoffman). — The springs near Mr. Robert 
Ingleson’s house, in section 22 on the ridge east of Calaveras Valley, became muddy 
after the shock and remained so for two or three days. The volume of water discharged 
by the springs increased to about four times the usual amount. 
Alvarado (KE. W. Burr). — At the Alvarado Sugar Mill, in several wells, formerly flowing 
artesian wells, the water-table is now a few feet below the surface, the water-level having 
risen at the time of the earthquake. In the accompanying table are given the heights 
of water in a number of wells about the mill, referred to an assumed level 30 feet above 
an assumed base. ‘These wells were observed daily before and after the earthquake. In 
most of them the water suddenly rose. The readings show that in a few cases the water 
rose from | to 2 feet. A well which used to be considered nearly dry began showing daily 
fluctuations, overflowing nearly every morning for some weeks after the earthquake. 
The figures here given are for measurements made on April 9 and 14, preceding the 
earthquake of April 18, 1906, and the measurements made on April 21 and 28 of the 
same month, and May 5 subsequent thereto.’ 
Heights of water referred to an assumed level 30 feet above assumed base. 




hye etn eck: “April 9. | April 14, .| April 21. | April 28, | May 5. 
1 470 22.89 24.81 26.14 26.31 26.56 
2 Shi be 26.64 26.81 28.14 25.48* 28.23 
4 318 26.22 25.47 28.05 27.97 27.30 
4 402 1) 26,02 26.87 28.37 28.20 28.28 
5 405 26.67 28.17 28.34 28:20 28.42 
6 402 26.70 28.28 28.37 28.03 28.45 
ef 399 26.79 26.87 28.45 28.04 28.45 
8 45 26.79 26.87 28.45 28.04 28.45 
9 544 25.36 25.36 26.69 26.94 ZiaG 





* No. 2, April 28. House pump was taking water from this well when measurement was taken. 
San Francisco Peninsula (R. Anderson). — Thruout the central portion of the San 
Francisco Peninsula, the chief geological effects, aside from the actual displacement along 
the fault and the slumping and settling of alluvial ground, were the increased circulation 
of water and its discharge at the surface. The normal flow of water from springs was 
much disturbed. The water was usually muddy or milky. It is reported to have flowed 
salty from one spring for 2 days after the earthquake; after this it returned to its usual 
purity. Streams were considerably swollen temporarily, and water frequently came 
to the surface where it had not made its appearance before. 
(R. Crandall.)—At Mr. Ebright’s place, at the lower end of the lake in Pilarcitos Can- 
yon, the spring water used for house supply is said to have been milky white the day 
of the earthquake. At Byrne’s store, on the Half Moon Bay road, 0.5 mile west of 
Crystal Springs Lake, it was reported by the keeper that the water from their spring on 
the day of the shock was muddy and was not tasted; on the second day it had a very 
salty taste, and on the third day was again normal. 
Santa Clara Valley (J. C. Branner). — At Menlo Park, a mile nearer Fairoaks Station, 
an artesian well flowed faster after the shock. At the Seale place, on the Embarcadero 
1 Since the wells in this district fluctuate in level with the rise and fall of the tide in the bay, a cor- 
rection would have to be made for this influence before the effect of the earthquake upon the under- 
ground water could be inferred from the figures given in the table. If the hour at which the level of the 
water in the wells was measured is known, the correction may be ascertained and applied at any time. 
INNO. AR 

