6 BULLETIN 447, U. S. DEPARTMENT OF AGRICULTURE. 
3 inches. In all of the tubes containing soil taken from below the 
first 3 inches the water level fell less than one-eighth of an inch in 
48 hours, and part of this was due to evaporation. 
The smallness of the tubes used may have caused some compact- 
ing during the process of sampling; also the plat sampled was un- 
doubtedly more compact than one that had not been continuously 
fallowed. For this reason a part of the experiment was duplicated 
on land that had been fallow for only a few months. Samples were 
taken with tin cans 5 inches in diameter and with thin cutting edges. 
By this means samples were taken from the surface and from depths 
of 3 and 6 inches without any mechanical compacting of the soil in 
sampling. -The penetration in these cans was then studied in the 
same way as in the brass tubes. Water passed through the surface 
3 inches at the rate of 1 inch in two hours. For the other sections 
the rate was at least as slow as in the brass tubes. Evidently the soil 
in the brass tubes was not compacted enough to make any material 
difference in the rate of penetration except in the surface section. 
Even in this section the difference in the rate was probably due in 
part to the fact that in the field the surface soil in the second plat 
was considerably looser than in the first one sampled. 
The extreme slowness with which water passed into these sections 
proves that water movement in a wet soil of this type in the field 
is exceedingly slow. That this slowness is partly due to the natural 
compacting of the soil by swelling is shown by a comparison of the 
rate at which water moved through soil under natural conditions 
with the rate at which it moved in a saturated soil that was allowed 
to expand freely, as is shown in the first experiment. At any rate, 
water movement in this soil when it is wet is so slow as to be prac- 
tically negligible in field practice. 
PENETRATION OF WATER INTO DRY SOIL IN THE FIELD. 
The experiments already described indicated that in this type of 
soil a dry condition was most favorable for water movement. In 
order to measure the maximum water penetration in the soil, a num- 
ber of experiments were made on a plat that was extremely dry. The 
plat was covered with a very thin dust mulch. Beneath the mulch 
the soil was cracked into very small lumps to a depth of 15 inches; 
below 15 inches it was very hard, dry, and compact. 
The first experiment in this series was made for the purpose of 
determining the permeability of the soil at various depths. For this 
purpose, borings 8 inches in diameter, extending below the surface to 
depths of 6, 9, 12, 15, 18, 21, and 24 inches, were made. Two gallons 
of water was then poured into each hole. A like quantity of water 
was applied to an equal area at the surface by means of a tin can set 
1 inch into the soil. . 
