38 
Bulletin 72. 
ditions of the soil were most unfavorable and where the water plane 
was the nearest to the suiface at all times. This last fact may have 
effected a more regular removal of the nitric acid as it was formed 
than in the other cases. Whether this is the explanation or not, 
the water from this well showed uniformly as much nitric acid as 
that of any of the other wells, though the first two inches of the 
soil was lower in nitric acid than the corresponding samples from 
the other sections, but irrigation did not increase the nitric acid in 
the water of this well as it did in some of the others. 
§ 107. Well C is located in the next most unfavorable section 
and the water level is in round figures 1 foot further below the 
surface than in well A. The nitric acid varied greatly in the 
water from this well, and its amount was immediately and greatly 
affected by irrigation or rainfall, even a light rainfall being fol¬ 
lowed by a marked increase in the amount of nitric acid. 
§ 108. I have said nothing about well G, a shallow well near 
well A, in connection with the nitrates. This well was separated 
from the gravel stratum by two feet of soil and was only 12 feet 
from A. There was mo more relation between the quantities of 
nitric acid in these wells, nor in its variations, than between it and 
wells farther removed. 
§ 109. A careful consideration of the results at my disposal do . 
not justify me in making any comparison or assuming any relation 
as existing between the nitric acid in the waters of these different 
wells. There is a general similarity in their conduct, but it is greatly 
modified by, if not wholly dependent upon, the soil conditions in 
the immediate neighborhood of the well. Well A, on July 8th, be¬ 
fore irrigation, showed the presence of 1.79 parts per million and 
well G only a trace; on the 11th, after irrigation, A showed 15.2 
parts and G 19.2 parts of nitric acid per million; by the 25th inst., 
the nitric acid in A had fallen to 6.59 parts per million, and in G 
to 2.69 parts. The water plane was nearly the same in the two 
wrnlls, it being 0.18 of a foot higher in G than in A. 
§ 110. The relation between the amount of nitric acid and the 
total solids is even less intimate than that of the chlorin to the total 
solids, which is practically equivalent to stating that there is no 
relation between them. 
§ 111. An examination of the 300 determinations of the 
nitric acid in this ground water does not permit us to draw any con¬ 
clusions in regard to the effect of either the physical condition of 
our soil or of the amount and character of our alkalies upon the 
formation of nitric acid in the soil. The average of the soil sam¬ 
ples taken to a depth of two inches indicates the presence of 469 
pounds of potassic nitrate or its equivalent in every acre of soil 
