12 
Bulletin 72. 
soluble salts with it into the ground water, and an increase in the 
salts dissolved in the ground water is simultaneous with the rise of 
the water table. It is evident that this rise is due to the piling up 
of water on a portion of the general water plane represented by the 
irrigated plot, and would not take place if the water could flow per¬ 
fectly freely through the soil, which it does not do. This does not 
fully state the facts in regard to the increase and decrease of the 
salts in the ground water; for while it is true that there is an in¬ 
crease in the salts concurrent with the rise of the water table when 
it is due to the application of water to the surface, and a subse¬ 
quent fall, usually quite a rapid one, we have the solids in the 
water of two of the wells showing a different course. The solids in 
that of wells B and D began to increase immediately, or very soon, 
after the irrigation of August 18th to 20th, and continued to increase 
for several weeks, though the water table was steadily falling dur¬ 
ing this time, which in the case of well D was six weeks. This is 
the more remarkable for in both these cases the maximum reached 
was the maximum for the season. In the case of the other two 
wells the results were in the opposite direction. In the waters of 
these wells the amount of the dissolved salts reached their maxi¬ 
mum for the season immediately after the irrigation and fell within 
four weeks to their minimum for the remaining months of the year, 
and within 0.1571 parts per thousand of the minimum for the whole 
season. The cause of this difference is not suggested by a consid¬ 
eration of the rate at which the water table fell. The height of 
the water table above the reference plane was not the same in the 
different wells, and there were slight variations in the rate of fall, 
but neglecting these irregularities, the rate of falling was very 
nearly the same, so that the rapid decrease in the amount of the 
total solids in the water of wells A and C was not probably due to 
any drainage, affecting these wells to a greater extent or in a dif¬ 
ferent manner than it did the wells B and D. The conditions of 
diffusion obtaining in the different wells probably contributed to 
the observed results. The composition of the solids contained in 
these waters will be given subsequently. 
§ 32. In this irrigation, as well as in the preceding, the head 
of water at our disposal would not permit of our attempting to flood 
off any salts, and practically all the salts which were on the sur¬ 
face- at any given place were carried back into the soil, so that 
there was but little, if any, transporting of salts even for a few feet 
in the direction of the flow of the water. It follows that any re¬ 
moval of salts during this season was by drainage. 
§ 33. In the following season, 1898, the conditions were quite 
different. During April, and especially during May, there were 
frequent light rains. The water table was rather higher at the west 
