f the air; their greatest departure from
each other being at the hottest hour of the day, which is two or three
hours after noon, and the least at the coldest hour which is four or
five hours after midnight. The average temperature of the dew-point in
April, May, and June, 1844, was, at midnight, 50-1/2 deg., air, 57 deg.; five
hours after midnight, dew-point, 49 deg., air 54 deg.; three hours after noon,
dew-point, 54 deg., air, 63-1/2 deg.. The average temperature for July, August
and September, was, at midnight, dew-point, 58-1/2 deg., air, 65 deg.; five
hours after midnight, dew-point, 58 deg., air, 62 deg.; three hours after noon,
dew-point, 60-1/2 deg., air, 78 deg.. The average temperature for the year was,
at midnight, dew-point, 42 deg., air, 48 deg.; five hours after midnight,
dew-point, 41 deg., air, 46 deg.; three hours after noon, dew-point, 44-1/2 deg.,
air, 59 deg..

The relative humidity of the atmosphere, or the amount of vapor held in
suspension in the air, in proportion to the amount which it might hold,
was, in the year 1858, as given in the journal of the Franklin
Institute, for

_Philadelphia._ _Somerset Co._
April 49 per cent. -- 2 P. M.
May 59 " 72 "
June 55 " 63 "
July 50 " 61 "
August 55 " 58 "
September 50 " 57 "

The saturation often falls to 30 per cent., but with great variability.
Evaporation goes on most rapidly when the per centage of saturation is
lowest; and, as before observed, the cause of the excess of evaporation
in this country over that of England is the excessive humidity of that
climate and the dryness of this. It has also been said that there is
greater need for drainage in the United States on this account; and, as
the warmth induced by draining is somewhat, in its effect, a
merchantable product, it may be well to consider it for a moment in that
light.

First: The drained land comes into condition for working, a week or ten
days earlier in the Spring than other lands.

Secondly: The growth of the crops is quickened all through the Summer by
an increase of several degrees in the temperature of the soil.

Thirdly: The injurious effects of frost are kept off several days later
in the Fall.

Of the value of these conditions, the farmer, who has lost his crops for
lack of a