* Of the Western Wind. l. 430. The principal frosts of this country are accompanied or produced by a N.E. wind, and the thaws by a S. W. wind; the reason of which is that the N.E. winds consist of regions of air brought from the north, which appear to acquire an easterly direction as they advance; and the S. W. winds consist of regions of air brought from the south, which appear to acquire a westerly direction as they advance. The surface of the earth nearer the pole moves slower than it does in our latitude; whence the regions of air brought from thence, move slower, when they arrive hither, than the earth's surface with which they now become in contact; that is they acquire an apparent easterly direction, as the earth moves from west to east faster than this new part of its atmosphere. The S. W. winds on the contrary consist of regions of air brought from the south, where the surface of the earth moves faster than in our latitude; and have therefore a westerly direction when they arrive hither by their moving faster than the surface of the earth, with which they are in contact; and in general the nearer to the west and the greater the velocity of these winds the warmer they should be in respect to the season of the year, since they have been brought more expeditiously from the South, than those winds which have less westerly direction, and have thence been less cooled in their passage.
Sometimes I have observed the thaw to commence immediately on the change of the wind, even within an hour, is I am not mistaken, or sooner. At other times the S.W. wind has continued a day, or even two, before the thaw has commenced; during which time some of the frosty air, which had gone southwards, is driven back over us; and in confequence has taken a westerly direction, as well as a southern one. At other times I have observed a frost with a N.E. wind every morning, and a thaw with a S.W. wind every noon for several days together. Sec additional note, XXXIII.
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