160 
POPULAR SCIENCE REVIEW. 
tion of boracic mud was effected by the aid of sheet-iron coffer- 
dams. The only apparatus employed consisted of a raft, covered 
by a shingled roof, provided with an aperture in its centre 
about fifteen feet square, above which were hung, by suitable 
tackle, four coffer-dams, each six feet square in horizontal section, 
and nine feet in depth. This raft, or barge, was successively 
moored in parallel lines across the surface of the lake, and at 
•each station the four dams were sunk simultaneously by their 
■own weight into the mud forming the bottom. 
When they had thus become well imbedded, the water was 
baled out, and the mud and crystals removed, by means of 
buckets, into rectangular washing-vats, into which a continuous 
stream of water was introduced from the lake by Chinese pumps, 
the contents being at the same time constantly agitated by the 
aid of wooden rakes. In this way the muddy water continually 
flowed off, finally leaving a certain amount of crude borax at 
the bottom of each tank ; this was purified by re-crystallization. 
From the density acquired by the 70,000 gallons of water daily 
employed for this purpose, it is evident that only about one- 
half of the borax existing in the form of crystals was thus 
obtained, while the mud was again returned to the lake. 
Instead of the coffer-dams, a small hand-dredging machine, 
worked, like the former, by Chinese labour, was subsequently 
introduced ; but the mud brought up by it was subjected to the 
wasteful process of washing before described. 
The crystals of crude borax thus daily obtained amounted to 
about 3,000 lbs. ; these were dissolved in boiling water, and re- 
crystallized in large lead-lined vessels, from which the purified salt 
was removed to be packed into boxes, each containing 114 lbs., 
in which it was forwarded to San Francisco. The loss of weight 
experienced in the process of purification amounted to about 
13 per cent. 
Shortly after my visit in 1866, the manufacture of refined 
borax at 6e Big Borax Lake ” was suspended, and I am not 
■aware whether it has now been resumed, but the works do not 
appear to have been in operation in 1874. 
Little Borax Lake covers an area of about thirty acres, and 
is usually dry during the months of September and October ; it 
is then covered by a white crust, which is collected by Chinese 
labourers, and carried to the works, where it is refined by re- 
crystallization. Ulexite , a double borate of sodium and calcium, 
is brought to this place from Wadsworth, in the State of 
Nevada — a great distance, with several transhipments — to be 
treated at these works ; it appears that on account of the pre- 
sence of carbonate of sodium, and the cheapness of fuel, this 
can be done more cheaply here than in Nevada. 
Clear Lake is a large and picturesque sheet of water, twenty- 
