18 The Alhaline Lakes of California. [Jan., 



dried, affords (including the enclosed crystals) 17 '73 per cent. 

 Anotlier sample, analyzed by Mv. ]\Ioore of San Francisco, afforded 

 him 18*86 per cent, of crystallized horax. 



In addition to this the deposit at the bottom of the other 

 portions of the basin, although less productive, still contains a large 

 amount of borax, and it has been ascertained by sinking numerous 

 pits on the lake shore, that clay containing a certain proportion of 

 this salt exists in all the low ground around it. 



The borax at present manufactured is exclusively prepared 

 from the native crystals of crude salt, whilst the mud in which 

 they are found is returned to the lake, after the mechanical sei^ara- 

 tion of the crystals by washing. The extraction of mud from the 

 bottom is effected by the aid of sheet-iron coffer-dams, and drcdging- 

 machines worked by manual power, the whole of the labourers 

 being Chinese. Until 1866 the only apparatus employed con- 

 sisted of a raft covered by a shingled roof", with an aperture m 

 its centre, about 15 feet square, and above which were hung, by 

 suitable tackle, four iron coffer-dams each 6 feet square and 9 feet 

 in depth. This raft or barge was moved in parallel hues 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 embedded, the water 

 was baled out, and the mud removed in buckets to large rectangular 

 washing-vats, into which a continuous stream of water was intro- 

 duced from the lake by means of Chinese pumps, the contents of the 

 cisterns being at the same time constantly agitated by rakes. 



At the present time dredging-machines are employed for 

 bringing up the mud and crystals from the bottom of the lake, and 

 these are introduced into cisterns and washed as above described. 

 In this way the turbid water continually flows off, and a certain 

 amount of crystallized borax is finally collected in the bottom of 

 each tank. This is subsequently re-crystallized, but from the density 

 acquired by the washing water, of which some hundred thousand 

 gallons are daily employed, it is evident that less than one-half the 

 borax existing in the form of crystals is thus obtained, whilst that 

 present in the mud itself is again returned to the lake. 



In 1866, when I visited this locality, the crystals of crude 

 borax daily obtained amounted to about 3000 lbs., and after being 

 carefully washed, they were dissolved in boiling water and re-crys- 

 tallized in large lead-lined vessels, from which the crystallized borax 

 was removed into boxes each containing a hundred- weight. 



The amount of refined salt dady obtained varied from 2500 to 

 2600 lbs., which was produced, as nearly as I could calculate, at a 

 cost of about 18Z. per ton. 



It is evident from the foregoing description that the system of 

 working employed is exceedingly crude, and by no means calculated 



