SOILS AND ALKALI. 
19 
what is called ‘ alkali ’ of the Western plains. It was in the 
form of a dry, milk-white powder, mixed with bleached 
leaves and coarse grass. It did not effervesce with acids, nor 
did it exhibit an acid reaction to test paper. It contained: 
Water_ 3.6 
Insoluble clay_ 1.5 
Chloride of sodium_traces 
Sulphate of sodium_94 6 
99.7 
“ It is consequently a native sulphate of soda, which, 
from the small amount of water present, may be classed 
as anhydrous. There is no evidence to show that it is a 
product of volcanic action. It differs from the varieties of 
mirabilite of Dana in the small amount of water, which 
we may conjecture, has been lost during the prolonged 
heat of summer. It may owe its origin to the decompo¬ 
sition of sulphate of lime, which is so largely present in 
the soils at the foot of the Rocky Mountains and Sierra 
Nevada series, by means of carbonate of soda occurring as 
efflorescence on soils. The usual origin of sulphate of soda 
is either directly from volcanic sources, or by the delivery 
of springs containing the salt derived from pre-existing 
sedimentary beds. In a few cases it is derived from the 
t j 
oxidation of sulphur in bituminous strata, or in pyritifer- 
ous beds, which, reacting on common salt, produces the- 
nardite or other forms of sodic sulphate.” 
The sample of alkali analyzed in the laboratory came 
from Mr. Black’s farm, three miles north of Fort Collins, 
and it contained: 
Water at 100° C_53.8 per cent. 
Silica (Si 02)_12.72 per cent. 
Iron and alumina oxides_traces 
Lime (Ca 0)_ .10 “ 
Magnesia (Mg O)_ 1.16 “ 
Chlorine (Cl)_ 5.23 “ 
Sulphuric acid (S 03)-48.92 “ 
Soda (Na2 0)_31.97 “ 
100.10 “ 
