CHEMICAL COMPOSITION OF INCRUSTATIONS. 
105 
grounds. The Mojave Indians are on the opposite hank of the river, and occasionally these 
latter travel south along this plain to make incursions upon the peaceable Maricopas. 
Along its whole extent it is said to exhibit the same character—sterile where the soil is dry, 
fertile where it can he irrigated, and without timber throughout. 
Saline incrustations. —During the period of visit many of the small basin beds were dried 
up, and presented a rippled sandy surface, easily impressed with the foot, but yet sufficiently 
coherent to resist the action of light winds. Upon the surface a dry whitish efflorescence 
was spread, which tasted alkaline and unpleasantly. Two such efflorescent incrustations were 
collected—one at a spot on the Mojave river known as Uavajo camp, (Camp 3 ;) the other was 
collected from the surface of the dry playa called Soda lake. Portions of each of these were 
subjected to chemical examination, with the following results : 
Incrustation of dry playa called Soda lake. —In mammillary bunches and botryoidal masses, 
efflorescent, readily crumbling under the finger, dull white externally, purer white and semi¬ 
crystalline internally ; readily and completely soluble in cold water. Solution is colorless and 
transparent, and possesses a very faint alkaline reaction. 
While crystallizing under the microscope, two forms of crystals are observable—needle prisms 
and cubes. 
The solution tested with a barium salt gave a light precipitate, and a copious white with a 
silver solution, which is soluble in ammonia. 
The solution was not affected by solutions of oxalate of ammonia or carbonate of soda, and 
did not effervesce on the addition of an acid. 
The salt mass fused readily before the blow pipe and gave a deep yellow tinge to the flame. 
Prom the foregoing it is evident that both sulphuric acid and chlorine are present, with the base 
sodium, and the crystalizations shows that only two salts are contained in the solution. The 
cubes are therefore chloride of sodium and the needles sulphate of soda. There is a mere trace 
of carbonate of soda, and not any lime salt present. The solution on standing deposits traces 
of silica. The amount of sulphuric acid present was determined in the usual way, and calcu¬ 
lated for sulphate of soda ; the difference was set down as chloride of sodium. The mass is not 
homogeneous ; the centre of the nucleus containing the greatest amount of chloride, while the 
sulphate was round the periphery of the crust. Thus, one portion differed a little centesimally 
from another ; but the following is an average of these estimations : 
Chloride of sodium............. 85. 
Sulphate of soda... 14.6 
Carbonate of soda, silica.. .... .4 
100.0 parts. 
The very small quantity of carbonate present in this crust is singular, since an alkaline car¬ 
bonate exists in the well waters at the margin of the playa. The water of the wells at the 
bivouac distintly effervesced and was very unpleasantly alkaline to the taste ; the crust was taken 
one mile out in the middle of the playa which may account for its small quantity of carbonate. 
Incrustation of soil at Navajo Camp. —An earthy powder of a light yellow brown color, and 
without trace of crystallization, of a dull white color, discolored by the surface soil; efflorescent, 
partially soluble in water ; solution transparent, of an amber tint, owing to vegetable matter ; 
highly alkaline reaction to test paper; strong effervescence on addition of nitric acid to solution. 
14 U 
