ble
to the thermometer. The heat rendered latent by converting ice into
water is about 140 deg.. There are 7.4805 gallons in a cubic foot of water
which weighs 62.38 lbs."

We have seen that a sea of water, more than three feet deep over the
whole face of the land, falls annually from the clouds, equal to 4,000
tons in weight to every acre. We would use enough of this water to
dissolve the elements of fertility in the soil, and fit them for the
food of plants. We would retain it all in our fields, long enough to
take from it its stores of fertilizing substances, brought from reeking
marshes and steaming cities on cloud-wings to our farms. We would, after
taking enough of its moisture to cool the parched earth, and to fit the
soil for germination and vegetable growth, discharge the surplus, which
must otherwise stagnate in the subsoil, by rapid drainage into the
natural streams and rivers.

Evaporation proceeds more rapidly from a surface of water, than from a
surface of land, unless it be a saturated surface. It proceeds more
rapidly in the sun than in the shade, and it proceeds again more rapidly
in warm than in cold weather. It varies much with the culture of the
field, whether in grass, or tillage, or fallow, and with its condition,
as to being dry or wet, and with its formation, whether level or hilly.
Yet, with all these variations, very great reliance may be placed upon
the ascertained results of the observations already at our command.

We have seen that evaporation from a water surface is, in general,
greater than from land, and here we may observe one of those grand
compensating designs of Providence which exist through all nature.

If the same quantity of water fell upon the sea and the land, and the
evaporation were the same from both, then all the rivers running into
the sea would soon convey to it all the water, and the sea would be
full. But though nearly as much water falls on the sea as on the land,
yet evaporation is much greater from the water than from land.

About three feet of rain falls upon the _water_, while the evaporation
from a water surface far exceeds that amount. In the neighborhood of
Boston, evaporation from water surface is said to be 56 inches in the
year, and in the State of New York, about 50 inches; while, in England,
it is put by Mr. Dalton at 44.43 inches, and, by others, much lower.

Again, about three feet of water annually falls upon the _land_, while
the evaporation from