Q. Why is the barometer highest of all during a long frost?
A. Because long frost condenses the air very greatly; and the more air is condensed, the greater is its pressure on the mercury of the barometer.
Q. Why does the barometer generally rise with a north-east wind?
A. Because north-east winds make the air both cold and dry: the air, therefore, is both condensed, and without vapour.
Q. What is the 2ND SPECIAL RULE in regard to the barometer?
A. The barometer is lowest of all during a thaw which follows a long frost: it generally falls with south and western winds.
Q. Why does the barometer fall lowest of all at the breaking up of a long frost?
A. 1st—Because the air (which had been much dried by the frost) absorbs the moisture of the fresh warm current of wind from the south or south-west: and
2ndly—The air (which had been much condensed by the frost) is suddenly expanded by the warm wind which is introduced.
Q. Why does the barometer fall very low with south and west winds?