Page:Philosophical Transactions - Volume 096.djvu/311

This page has been proofread, but needs to be validated.
on the Marine Barometer.

of the winds from the east and from the west; for where the vicinity of land is out of the question, the former generally causes an ascent, (from what principle I leave others to determine,) and the latter a descent in the barometer, and I believe this extends to both hemispheres, and all climates* The wind from SE then, which combines something more than half the power, both of the south and of the east wind, will raise the mercury higher than any other, on the south side of the equator, and the wind from NW permit it to fall lower, independently of their effects as sea and land winds; and this allowance requires to be first made upon them: the south-west and north-east quarters should be equal where there is no land in question, and of a medium strength between the power of the south-east, and the deficiency of the north-west wind.

I leave it wholly undetermined, whether the effects of sea and land winds upon the barometer, as above described, extend beyond the shores of the country where these observations were made, and to about one hundred leagues of distance from them; but it seems not improbable, that they may be found to take place near the shores of all countries similarly circumstanced; that is, upon those which are wholly, or for the most part, surrounded by the sea, and situated within the fortieth degree of latitude. In colder climates, where snow lies upon the ground during a part of the year, the wind from off the land may perhaps be so cold, and the air so much condensed, as to produce a contrary effect; but this, and the prosecution of the subject to other important consequences, I leave to the philosopher; my aim being only to supply my