flow Cultivation Acts. 139 
particles are so separated that the mutual connection of the 
minute interspaces no longer exists. But if it be roughly 
broken up, so that the disturbed layer takes the form of coarse 
clods, the air has free access to the upper surface of the firm 
soil beneath them, in which the capillary condition still exists, 
and evaporation proceeds in the same way, though in a some- 
what less degree, than if there had been no cultivation. It 
becomes evident, then, that the pulverization of the disturbed 
layer must be so complete that the particles are separated and 
capillarity destroyed, and, farther, that the free access of air to 
the lower point, where capillarity exists, must be prevented. 
This is accomplished by the fine loose earth which acts as a 
mulch. When this is attained, only that moisture in the upper 
surface which comes in immediate contact with the air is evap- 
orated, and the balance is retained for the use of the plant. 
Plants growing, then, in a well-cultivated soil, have the water in 
the lower soil held for their use, and as fast as they use it the 
supply is replaced from the firm soil below; or else, evaporation 
being stopped, their roots extend freely through the moist soil, 
seeking the nourishment they need. 
Such is a brief outline of the theory which explains the re- 
sults gained by thorough cultivation of the soil, so far, at least, 
as retention of moisture is concerned. The practical demonsctra- 
tion of this retention is easy. Go into a well-cultivated orchard 
or vineyard, push aside the soil with the foot, and moisture will 
be found two or three inches from the surface, or even less in 
some soils, while on uncultivated land adjacent, digging to the 
depth of several feet will show nothing but hard earth, baked 
and arid. In such hard-baked earth, moreover, the sun heat is 
conveyed or conducted downward very rapidly during a hot day, 
so that in some cases the roots are seriously injured. When 
the surface is well tilled, it will act like a blanket, preventing a 
too rapid conveyance of heat downward, and thus also diminish- 
ing the intensity of evaporation. 
Accurate demonstration of these facts has recently been se- 
cured as the result of many moisture determinations in culti- 
vated and uncultivated soil by the University of California 
Agricultural Experiment Station.* Very striking exhibition of 
the condition of trees with and without cultivation is found in 
the engravings which are reproduced herewith. Upon the dem- 
onstration, the practise in the uncultivated orchard was radically 
changed. The exact determination of moisture present at vari- 
cus depths of the soil beneath these contrasted orchards in the 
month of July is as follows:— 
*Bulletin r2r. 
