On Draining. 
255 
with several ancient drains six feet deep, placed parallel with 
each other, but at so great a distance asunder as not to have 
commanded a perfect drainage of the intermediate space. The 
author from whom I have so largely quoted is the earliest known 
to me, who has had the sagacity to distinguish between the 
transient effect of rain, and the constant action of stagnant bottom 
water in maintaining land in a wet condition. It is this subter- 
ranean water, as it may not be improperly termed, to which 
excessive and injurious wetness is attributable, and if such water 
be not removed and kept down at a depth exceeding the power of 
capillary attraction to elevate it too near the surface, no drainage 
can be efficient. It is this force combined with the absorbent 
power of the earths which chiefly maintain those soils in a suf- 
ficiently moist state for vegetative perfection, on digging into 
which we do not discover any free water within several feet of 
the surface. The effect of rain is to thoroughly moisten such 
soil, gravity carrying down below the excess, or that portion which 
the soil cannot absorb or retain. Evaporation takes place from 
the surface of the land, and as each atom of moisture is taken up 
into the atmosphere, its place is supplied by another atom com- 
municated by the contact of the particles of soil, the more super- 
ficial acting on the deeper particles like so many pumps to elevate 
the water and supply the loss. In this way the deep rich loams, 
to which I have before adverted, as so rare and so coveted, are 
maintained in a nearly constant condition of moisture suitable to 
the necessities of plants. It may and does, though rarely, 
happen, that even such soils during long-continued droughts 
suffer, that is, become too dry ; but the attentive observer will 
notice a very beautiful and powerful provision of nature to pre- 
vent excessive dryness. During the night evaporation from the 
surface of soil commonly ceases, to commence again when ihe 
rays of the sun impinge upon it ; but capillary action is constant 
and of equal intensity both by night and by day, so that we have, 
on the average, twelve hours per diem of the sun's influence to 
produce evaporation, and twenty-four hours of capillary action to 
supply the loss from below, and maintain a tolerably uniform 
hygrometric or moist condition of the active soil. It is, I believe, 
consistent with the universal opinion that drained lands do not 
burn, nor suffer from drought so soon or so much as those soils 
which are wet at all periods of the year, except during the hottest 
months. This phenomenon is explained by the fact of a retentive 
soil swollen by water contracting so much by the loss of its water, 
that it is almost inaccessible to air from which to obtain moisture. 
After drainage the mechanical texture of such soils becomes gra- 
dually changed ; pulverization takes place in the subsoil in a 
manner precisely similar to the change we see produced in fresh 
