352 THE POPULAR SCIENCE MONTHLY. 



tion, for four and a half to five feet, holds unnumbered crystals; at 

 that depth they suddenly and abruptly cease. Abundant explorations 

 demonstrated that none were to be found any lower, and the daily 

 working came to recognize the fact as established. The mud below 

 that was saturated with the salts of soda, such as held by the water 

 of the lake, but no distinct crystals existed. 



The crystals of borax, in the upper portion, were removed by 

 means of coffer-dams. Each dam consisted of a box, without top or 

 bottom, four feet square and six feet deep, made of thin boiler-iron, 

 suitably stiffened with surrounding bands of heavier iron. These 

 dams, suspended above the water, between large pontoons or floats, 

 were allowed to drop suddenly, whereupon their force of descent, 

 drove the sharp lower edge down through the soft mud and into that 

 which was sufficiently firm and tenacious to resist the inrpact, and to 

 render thus the iron walls of each a true coffer-dam, from which the 

 entire contents could be easily removed. 



The water was first pumped or bailed out, till it became too thick 

 to flow easily, and the remaining mud was lifted in tubs, in true min- 

 ing style, and thrown into large troughs, where, being subjected to 

 constant agitation in streams of the lake-water, it was washed away, 

 the borax being retained by its superior gravity. 



No crystals were found until from twelve to fifteen inches in depth 

 of the most fluid mud had passed away. The mud then began to feel 

 " gritty," as the workmen expressed it, the " grit " consisting of multi- 

 tudes of most exquisitely perfect minute crystals of borax. These crys- 

 tals, like all those in the lake, were lying loose, detached from each 

 other, attached to nothing by the base, and consequently perfect at 

 both ends. It is not meant by this that every crystal was absolutely 

 complete in every angle, but that they all had the tendency to the 

 theoretical type, symmetrical at each end (a form which in artificial 

 crystallization we scarcely ever reach, except by accident), and that 

 many of them showed the type in full j)erfection, such as no model 

 could excel or equal. 



With every descending inch through the mud their size increased; 

 the "grit" soon became " sand," in a few inches farther crystals were 

 very manifest to the eye, and shortly a " layer " was reached. It is 

 true that in some places no " layers " occurred, the crystals being scat- 

 tered at random through the mud. But in most instances when from 

 twenty-four to thirty inches of surface-mud had been removed, and 

 the crystals had attained a length of one fourth to one half an inch, 

 one or more " layers " would be found within the four feet square of 

 the coffer-dam. In these " layers " the crystals were so closely packed 

 as to have no mud intermingled with them; they were nearly as clean 

 as though recently washed in clear water, lying closely stowed and 

 loose, like pebbles on a beach. A " layer might be one to four inches 

 thick and two feet, more or less, in length, surrounded on all sides by 



