The Fixation of Nitrogen. 55 
this term but to the presence of azotobacter and nitrates which 
do not come from the adjacent land or the ground water, nor from 
the water that flows in the ditch, but are developed in the soil, and 
the controlling factor in this case is the constant and abundant 
supply of moisture. To some the facts given may not be fully 
convincing that the nitrates are formed in situ —to me they are, 
but we will give, in the proper place, further proof that this is so. 
This is true, too, of the sample which we are discussing; the 
ground is not seeped but there is a ditch perhaps ten feet away 
which probably furnishes the necessary moisture. I do not know 
why this had not developed in this place prior to 1909, but it was 
there in 1909 and I had not seen it there before. This and the 
next following samples were taken during a shower and I have 
made no notes of how the samples were taken. They may have 
been, and probably were, shoveled up hastily as it was not a good 
time for making notes. The samples were taken to learn the 
character of these surface salts. This accounts for the high con¬ 
tent in water-soluble which amounts in No. 826 to 16.30 percent, 
and in No. 822 to 32.07 percent. The latter sample, No. 822, was 
taken a mile or more south of sample No. 826 and near to the 
edge of an alfalfa field which was in good condition at the time, and 
so far as I know is at this time. There was, however, a depression 
immediately south of this which is, at times, filled with water. 
ANALYSES 
LX VII 
LXVIII 
Water-Soluble 
Water-Soluble 
laboratory 
laboratory 
No. 826 
No. 822 
Percent 
Percent 
Calcic sulfate . 
. 16.044 
7.973 
Magnesic sulfate . 
. 8.411 
7.911 
Potassic sulfate . 
. 1.074 
0.999 
Sodic sulfate . 
. 49.623 
73.105 
Sodic chlorid . 
. 22.345 
9.074 
Sodic nitrate . 
. 2.394 
0.839 
Iron and Aluminic oxid. 
0.040 
Silicate acid . 
. 0.109 
0.059 
100.000 
100.000 
The territory from which the last five samples were gathered 
is above the shales which were described and analyses of which were 
given in Bulletin 155 pp. 28 and 29, Laboratory No. 645, and 
while this locality is not the one referred to in explaining the 
occurrence of nitrates in certain waters and in the shales themselves 
in which I state, “The occurrence of nitrates in the waters and 
apparently in the shales is susceptible of an easy explanation, i. e., 
the nitre spots which are only exaggerated instances of a general 
condition, occur in lands above the shales,” it exemplifies the con¬ 
dition described in a most satisfactory manner. 
The following analyses of a soil and its aqueous extract will 
