158 
POPULAR SCIENCE REVIEW. 
evidently occupies the cavity of an ancient volcanic vent. The 
waters of this lake are considerably less alkaline than those of 
Owen’s Lake, but bubbles of carbonic acid make their way to its 
surface in almost uninterrupted streams. 
Fifteen miles east from this point are numerous hot springs ; 
the path for the greater portion of this distance lies over lava- 
flows, which render travelling slow and fatiguing. At the 
principal group of springs the ground is covered, over a large 
extent, by innumerable cones of plastic mud, varying in height 
from a few inches to several feet ; these rise above the surface 
of a seething swamp, and give issue to steam and jets of boiling 
water. In some cases the steam and gases, instead of issuing* 
from cones as above described, are evolved under the surface of 
water and mud contained in basin-shaped reservoirs formed in 
the decomposed rock. By these means are produced multi- 
tudes of boiling cauldrons in which violent ebullition keeps clay 
in a constant state of suspension ; this clay varies in colour 
from bluish grey to bright red. The waters of these springs are 
much employed by the Indians as an embrocation for the cure 
of diseases of the eye ; on examination they were found to con- 
tain 48 grains of solid matter to the gallon, of which amount 
26 grains are sulphate of aluminium ; in addition they contain 
lime, soda, potash, and a little free sulphuric acid. 
Borates of sodium and calcium occur in various localities in 
N orth America. The two borax lakes are both situated near the 
shores of Clear Lake in Lake County, California, seventy miles 
north-west of the port of Suscol, and one hundred and ten from 
the city of San Francisco. 
The larger of these lakes is separated from Clear Lake by a 
low ridge of volcanic materials loosely packed together, and 
consisting of scoriae, obsidian, and pumice ; it has an average 
area of about three hundred acres. Its extent however varies 
considerably at different periods of the year, as its waters cover 
a larger area in spring than during the autumnal months. No- 
stream flows into its basin, which derives its supply of water 
partly from drainage from the surrounding hills, and partly 
from subterranean springs discharging themselves into the 
bottom of the lake. In ordinary seasons its depth thus varies from 
five feet in the month of April to two feet at the end of October. 
The borax occurs in the form of crystals of various dimensions 
imbedded in the mud of the bottom, which is found to be most 
productive to a depth of about three and a-half feet, although a 
bore-hole which was simk near its centre to the depth of sixtj 
feet afforded a certain amount of the salt throughout its whole 
extent. 
The crystals thus occurring are most abundant near the centre 
