It may vary as much as a pound and a half to the square inch at the level of the sea.
703. When does the barometer stand highest?
When there is a duration of frost, or when north-easterly winds prevail.
704. Why does the barometer stand highest at these times?
Because the atmosphere is exceedingly dry and dense, and fully balances the weight of the column of mercury.
705. When does the barometer stand lowest?
When a thaw follows a long frost; or when south-west winds prevail.
706. Why does the barometer stand lowest at those times?
Because much moisture exists in the air, by which it is rendered less dense and heavy.