efore described, attains the
proportions of a strong wind. As the sun begins to sink, the earth's
surface pours forth its heat; the radiation being assisted by the
extended surfaces of the plants, cooling rapidly takes place.
Meanwhile the sea, because of the great heat-storing power of water,
is very little cooled, the ascent of the air ceases, the temporary
chimney with its updraught is replaced by a downward current, and the
winds blow from the land until the sun comes again to reverse the
current. In many cases these movements of the daily winds flowing into
and from islands induce a certain precipitation of moisture in the
form of rain. Generally, however, their effect is merely to ameliorate
the heat by bringing alternately currents from the relatively cool sea
and from the upper atmosphere to lessen the otherwise excessive
temperature of the fields which they traverse.

Although characteristic sea and land winds are limited to regions
where the sun's heat is great, they are traceable even in high
latitudes during the periods of long-continued calm attended with
clear skies. Thus on the island of Martha's Vineyard, in
Massachusetts, the writer has noted, when the atmosphere was in such a
state, distinct night and day, or sea and land, breezes coming in
their regular alternation. During the night when these alternate winds
prevail the central portion of the island, at the distance of three
miles from the sea, is remarkably cold, the low temperature being due
to the descending air current. To the same physical cause may be
attributed the frequent insets of the sea winds toward midday along
the continental shores of various countries. Thus along the coast of
New England in the summer season a clear, still, hot day is certain to
lead to the creation of an ingoing tide of air, which reaches some
miles into the interior. This stream from the sea enters as a thin
wedge, it often being possible to note next the shore when the
movement begins a difference of ten degrees of temperature between the
surface of the ground to which the point of the wedge has attained,
and a position twenty feet higher in the air. This is a beautiful
example to show at once how the relative weight of the atmosphere,
even when the differences are slight, may bring about motion, and also
how masses of the atmosphere may move by or through the rest of the
medium in a way which we do not readily conceive from our observations
on the transparent mas