The Waters oe the Rio Grande 
27 
drain-waters is such that an admixture of them with Rio Grande 
waters would reveal itself in the changed composition of the latter. 
We shall have further use for these data, but, for the present, the 
main purpose is to demonstrate the absence of their influence on the 
composition of the river water. 
RELATION OF GREASEWOOD TO SODIC CARBONATE CONTENT 
OF SOIL 
We may observe in passing that the last alkali given was collected 
amid greasewood ( Sarcobatus )* bushes with the expectation of find¬ 
ing large quantities of sodic carbonate present, but we find only 8.3 
percent of this salt in the water-soluble portion of the effloresced mass 
which, as gathered, probably contained 75.0 percent of its weight of 
surface soil. The aqueous extract of this soil, amounting to 1.94 per¬ 
cent of the soil, contained 25.4 percent of this salt, or 0.49 percent 
calculated on the soil. We have presented no sample of ground-water 
from this locality, for we took none. 
The theory that soil about these bushes is rich in carbonates be¬ 
cause of the nature of these plants was advanced by Prof. Hilgard. 
These greasewood ( Sarcobatus ) bushes may have been the cause of 
the presence of this carbonate in the soil but there is also another, and 
perhaps a better, explanation possible in this case, but we shall refer to 
this subsequently. In the following case the debris of the greasewood 
growth may have been the source of the carbonate, I know of no other 
probable source of the salt. The sample is of a virgin soil taken from 
a rather low place, with an abundant growth of greasewood (Sarco¬ 
batus). The surface soil yielded 3.71 percent of soluble salts to water. 
Organic matter was very abundant; there was- no calcium, and only a 
trace of magnesium present. The acid determined and calculated as 
sodic salts corresponds to sodic sulfate 44.8 percent, sodic carbonate 
31.7 percent, sodic chlorid 8.0 percent and organic matter 15.0 percent. 
This sample of soil was not taken to a greater depth than 2 inches. 
The sodic carbonate in this sample amounts to 1.1 percent of the soil 
and its presence may account for the growth of the Sarcobatus. It is 
a question whether any other plant can tolerate so large an amount of 
this salt, owing to its toxic qualities. Another sample of alkali con¬ 
taining sodic carbonate was obtained two miles from the latter. It 
would not be at all unreasonable to attribute the occurrence of the so¬ 
dic carbonate in the two preceding samples to the prevalence of the 
| greasewood, but in this case, I know of no source to* which it could 
reasonably be attributed, therefore, I have considered it as an isolated 
sample of little or no importance, an exception, a curiosity among our 
alkali waters. The dried salt consisted of: 
*Big-elovia is locally called “Greasewood” and this is the reason for the 
1 word, “Sarcobatus” in parentheses. 
