34 
Bulletin 72. 
nearly 3 per cent, in this respect. In this case we almost certainly 
had an admixture of water from points above that at which we 
endeavored to collect the water, for with our appliances we could 
not prevent it. The drain waters, in which we have a better sep¬ 
aration of the waters, show a still greater difference, both in the 
amount of the total solids and in the percentage of the sodic sulfate. 
We are justified in extending our statement that the ground water, 
in so far as it is # a solution of salts, differs from the alkalis which 
effloresce, from the solution obtained by exhausting the soil with 
distilled water as previously described, and also from the drain 
water flowing from under the area. 
LITHIA IN THE GROUND WATER. 
§ 96. Reference has been made in a preceding bulletin to the 
failure of an attempt to determine the lateral movement of this 
salt through the soil, or the rate and direction of the flow of the 
ground water. The detection of lithia in the samples of water tested 
to ascertain with certainty that my experiment was actually a 
failure, led me to test a considerable number of samples of the 
ground water and also samples of drain water to ascertain whether 
its presence was accidental or whether its occurrence was general 
and constant. The result was that its presence was established 
qualitatively in every sample tested, and these represented samples 
taken during a period extending over more than two years. The 
quantity present was as a matter of course not large, but sufficient 
to be readily detected by the aid of the spectroscope, and in some of 
the samples sufficient for quantitative determination without great 
trouble. This element seems to be present in all of the water in 
this basin. Its presence was detected in the ash of beets grown 
upon this plot, and also in the ash of their leaves. This is peculiar 
for I have tested a number of ashes of alfalfa; some of it grown 
within this same swale and have never succeeded in detecting it. 
NITRATES IN THE GROUND WATER. 
§ 97. The results of the only determinations of the nitrates in 
the soil are given in Bulletin 65, page 45. The variation in the 
amount present in the different portions of the plot and also in the 
first and second two inches of soil is very considerable. The deter¬ 
minations are entirely conclusive that the conditions obtaining do 
not prevent the formation of nitric acid, and further, that its distri¬ 
bution in depth as well as from place to place throughout the plot 
is very uneven. The minimum quantity of nitric acid in a million 
parts of the air dried soil of the first two inches was 32 and the 
maximum 162; of the second two inches the minimum was a trace 
and the maximum was 9 parts. In A, the section of the plot where 
the conditions were most unfavorable to cultivation, there was 32 
