36 
Bulletin 72. 
on the 11th, while well D, probably due to accidental inflow of 
water from the surface, fell. The nitric acid rose in the mean¬ 
time by 7 parts per million in A, 13 parts in B, 18 parts in C, 
and 1 part in D. The largest increase, however, was observed in 
a well sunk in an adjoining plot which had been manured and 
which chanced to receive an irrigation at this time. This well 
showed 3.59 parts of nitric acid per million on June 27th and 
475.63 parts on July 9th. The water table was raised, in this 
case, almost to the surface. 
§ 101. The duration of the effects of this irrigation upon the 
amount of nitric acid in the water was quite different in the dif¬ 
ferent wells. The greatest increase in my plot was shown in the 
case of well C, which, throughout the season, proved to be the rich¬ 
est in nitric acid of any of the four wells here considered, and also 
of all the wells on my plot of ground. The water of this well car¬ 
ried on the 8th of July 2.69 parts nitric acid per million ; this rose 
to 21.18 parts just after the irrigation and fell to* 2.51 parts by 
August 1st. The nitric acid in well B did not increase to the same 
extent as in well C, but it fell a little more slowly, and on this 
date, August 1st, showed more than either of the other three wells. 
The quantities for all the wells ranged from 1.8 to 6.1 parts per 
million. 
§ 102. The rate of decrease was quite rapid at first, and while 
it gradually grew slower, it was quite abrupt at the end. The well 
alluded to as being in an adjacent plot may serve as an illustration 
of both the rapidity of the rise and the rate of decrease. On July 
4th, before irrigation, and with a low water level, it carried only a 
trace; on the 9th, after irrigation, and with the water plane near the 
surface, it carried 475.63 parts per million. In the next two days 
this fell to 242.0 parts, in the succeeding seven days it fell to 89.74, 
in seven days more to 35.89 parts, and in seven days more to what 
may be expressed as within the range of its constant content. 
This well behaved unlike the others, for while mine showed a tem¬ 
porary increase in nitric acid about August 8th, this one continued 
to decrease until there was less than 1 part of nitric acid per 
million. 
§ 103. As a rule the nitric acid was lower when the water 
plane was low, but there were variations which showed no relation 
to either the height of the water level or to the amount of the total 
solids present; for instance, the nitric acid in the water of well C 
on August 1st was 2.5 parts per million, on the 8th 8.4 parts, on the 
22d 2.7 parts; the total solids on the 1st were 2.0143 parts per 
thousand, on the 8th 1.9143 parts, and on the 22d 1.8000 parts. 
The height of the water table on the 1st was 7.75 feet, on the 8th 
7.67 feet, and on the 22d 7.15 feet above the reference plane. The 
