A Guide To The Scientific Knowledge Of Things Familiar - LightNovelsOnl.com
You're reading novel online at LightNovelsOnl.com. Please use the follow button to get notifications about your favorite novels and its latest chapters so you can come back anytime and won't miss anything.
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?_
A. Because SOUTH and WEST winds come heavily _laden with vapour_; and _vaporized_ air is lighter than _dry air_.
Q. _What effect has WIND on the mercury?_
A. _All_ winds make the barometer _drop_, except EASTERN winds: those winds which blow from the SOUTH, and SOUTH-WEST make it _drop the lowest_.
Q. _Why do WINDS generally make the mercury of a barometer DROP?_
A. Wind is caused by a _partial vacuum_ in some parts of the globe; and as the air _rushes in_ to supply this deficiency, _its general pressure is lessened_, and the barometer falls.
Q. _What is the 3RD SPECIAL RULE in regard to the barometer?_
A. While the barometer stands above 30, the air must be very _dry_ or very _cold_, or perhaps _both_, and _no rain_ may be expected.
Q. _Why will there be NO RAIN if the AIR be very DRY?_
A. If the air be very _dry_ it will _absorb moisture_, and not part with what it has _in rain_.
Q. _Why will there be NO RAIN if the AIR be very COLD?_
A. If the air be very _cold_ it is _so much condensed_, that it has already parted with as much moisture as it can spare.
Q. _What is the 4TH SPECIAL RULE in regard to the barometer?_
A. When the barometer stands _very low_ indeed, there is never _much_ rain, although a _fine day_ will seldom occur at such times.
Q. _What kind of WEATHER will it be when the barometer is UNUSUALLY LOW?_
A. There will be _short heavy showers_, with sudden _squalls of wind_ from the _west_.
Q. _Why will there be VERY LITTLE RAIN if the barometer be UNUSUALLY LOW?_
A. Because the air must be very _warm_, or very _moist_, or perhaps _both_.
Q. _Why will there be little or no rain, if the_ AIR _be very_ WARM?
A. If the air be very warm it will have a tendency to _imbibe more moisture_, and not to part with what it has.
Q. _Why will there be little or no rain if the air be MOIST, and the barometer remains very LOW?_
A. If the air be ever so moist, rain will never fall till _cold air_ has been introduced to _condense the vapour_; and the moment that the _cold_ air is introduced, the barometer will _rise_.
Q. _What is the 5TH SPECIAL RULE in regard to the barometer?_
A. In summer-time (after a long continuance of fair weather) the barometer will _fall gradually_ for 2 or 3 days before _rain_ comes; but if the fall of the mercury be very _sudden_, a _thunder-storm_ is at hand.
Q. _What is the 6TH SPECIAL RULE in regard to the barometer?_
A. When the sky is cloudless, and seems to promise fair weather, if the barometer be _low_, the face of the sky will soon be suddenly _overcast_.
Q. _What is the 7TH SPECIAL RULE in regard to the barometer?_
A. Dark dense clouds will pa.s.s over _without rain_, when the barometer is _high_; but if the barometer be low, it will often rain _without any gathering of clouds_.
Q. _What is the 8TH SPECIAL RULE in regard to the barometer?_
A. The _higher_ the barometer, the greater is the probability of _fair weather_.
Q. _Why is the barometer HIGH in FINE weather?_
A. Because the air contains but _very little vapour_. The _drier_ the air, the _higher_ does the mercury of the barometer rise.
Q. _What is the 9TH SPECIAL RULE in regard to the barometer?_
A. When the mercury is in a _rising_ state, _fine_ weather is at hand; but when the mercury is in a _sinking_ state, _foul_ weather is near.
Q. _Why does the mercury RISE at the approach of FINE weather?_
