Page 95 - 1915, Springs of CA.

HOT SPRINGS. 91
The analyses indicate that the waters of the Sulphur, Belmer, and
Hot springs do not differ greatly in chemical character. All three are
secondary waters in which salinity and alkalinity are about equally
prominent, but the differences in concentration and the unusually
large content of manganese in the Hot Spring are of interest. The
Iron Spring is characterized by somewhat lower concentration and a
higher content of irorj. than the other three, and it differs from them
in properties of reaction chiefly by reason of a greater proportion of
sulphate and a smaller proportion of carbonate. The Sour Spring is
characterized by a still greater proportion of sulphate and absence of
carbonate, and, as is common in waters having tertiary salinity, con-
tains notably large amounts of iron and aluminum. Considering the
springs as a group, it appears that the differences in character
may have been acquired in the passage of water of the Sour Spring
type through calcareous shale and magnesian limestone, the Iron
Spring representing a phase in which the water encountered but
little limestone.
East of Anderson Springs lava covers the surface, but near the Cold
Sulphur Spring a schist is exposed which forms the surface rock west-
ward, and through which the several springs issue. At the group
near the Hot Spring it has been altered by solfataric action to the
characteristic white, siliceous material that is so plentiful at The
Geysers, a few mile^ to the northwest. In a tunnel-like chamber
excavated in it near iihe Hot Spring, quantities of Epsom salt form a
thick efflorescence on] the walls, and on the surface slopes outside a
yellow coating is deposited that has been collected and used as a
catarrh powder. An analysis of a sample of it that was made by
Anderson 1 showed that it consists largely of calcium carbonate,
with the sulphates of calcium, magnesium, and sodium, and the car-
bonates of the latter two bases in smaller amounts.
This small area at Anderson Springs that shows the effects of sol-
fataric action is of especial geologic interest in its resemblance to the
areas at Little Geysers (Sonoma 5, p. 88), and The Geysers (Sonoma
4, p. 83), which are respectively about 4 and 7 miles in a direct line
northwestward across the St. Helena Range.
CASTLE HOT SPRINGS (LAKE 54). j
Castle Hot Springs are situated about 1 mile by steep trail on the
mountain side west bf Anderson Springs (Lake 55, p. 89). Basins
or small reservoirs have been excavated and cemented at two hot
springs that issue a few yards apart in a ravine that is tributary to
Putah Creek. The observed temperatures in these basins were 160°
and 164°. Their combined flow about 8 gallons a minute could
probably be increased by developing two or three near-by seepages
1 Anderson, Winslow, Mineral springs and health resorts of California, p. 88,1892.