A Guide To The Scientific Knowledge Of Things Familiar Part 34

A. Because the _air is filled with vapour_, and vapour is a better conductor of sound than dry air.

Q. _Why do DOORS SWELL, when RAIN is at hand?_

A. Because the _air is filled with vapour_, which (penetrating into the pores of the wood) _forces the parts further apart_, and swells the door.

Q. _Why do DOORS SHRINK in DRY weather?_

A. Because the _moisture is absorbed from the wood_; and, as the particles are _brought closer together_, the size of the door is _lessened_, (or in other words, the _wood shrinks_).

Q. _Why is the AIR filled with offensive SMELLS previous to a coming RAIN?_

A. Because the volatile parts, (which rise from dunghills, sewers, &c.), being _laden with vapour_, are unable to rise so readily, as when they are rarefied by a bright sun.

Q. _Why do FLOWERS smell SWEETER and STRONGER just previous to RAIN?_

A. Because the volatile parts (which const.i.tute the _perfume_ of flowers) are _laden with vapour_; and (being unable to rise) are confined to the lower regions of the air.

Q. _Why do HORSES and other animals stretch out their necks, and SNUFF up the AIR, just previous to a fall of RAIN?_

A. Because they _smell the odour of plants and hay_, and delight to snuff in their fragrance.

Q. _Why does SMOKE FALL when RAIN is at hand?_

A. The air being less _dense_ in wet weather, _cannot buoy up smoke_ so readily, as when _more dry and heavy_.

Q. _Why do SWALLOWS FLY LOW when RAIN is at hand?_

A. Because the _insects_ (of which they are in pursuit) _have fled from the cold upper regions of the air_, to the _warm_ air near the earth: and as their _food is low_, the swallows _fly low_.

Q. _Why do these INSECTS seek the lower regions of the air in WET weather, more than in FINE weather?_

A. Because they are forced downward, by some current of cold air which _drives them down_.

Q. _Why does a DOWNWARD current of COLD AIR bring RAIN?_

A. Because it _condenses the warm vapour_; which then descends in rain.

Q. _The proverb says, "A SINGLE MAGPIE in spring, FOUL WEATHER will bring:" why is this the case?_

A. In cold stormy weather, _one magpie alone_ will leave its warm snug nest _in search of food_, while the other stays with the _eggs or young ones_; but in _fine mild_ weather (when their brood will not be injured by cold) _both the magpies will fly out together_.

Q. _Why is it UNLUCKY for ANGLERS to see a SINGLE MAGPIE in spring?_

A. Because when _magpies fly abroad singly_, the weather is cold and stormy; but when _both birds fly out together_, the weather is _warm and mild_, which is _favourable for fis.h.i.+ng_.

Q. _Why do SEA GULLS fly about the SEA in FINE weather?_

A. Because they _live upon fish_, which are found near the _surface of the sea in fine weather_.

Q. _Why may we expect STORMY RAINS, when SEA GULLS a.s.semble on the land?_

A. Because the fish (on which they live) leave the _surface_ of the sea in stormy weather, and _go down too deep for the gulls to get at them_; they are obliged, therefore, to feed on the _worms and larvae_ which are driven out of the _ground_ at such times.

Q. _Why does the PETREL always fly to the SEA during a storm?_

A. Because the petrel _lives upon sea insects_, which are always to be found in abundance _about the spray of swelling waves_.

(The Petrel is a bird of the duck-kind, which lives in the open sea.

They run on the top of the sea, and are called Petrels, or rather Peter-els, from "St. Peter," in allusion to his walking on the sea, to go to Jesus.)

Q. _Why do CANDLES and LAMPS SPIRT when RAIN is at hand?_

A. Because the _air is filled with vapour_, and the humidity _penetrates the wick_; where (being formed into _steam_) it expands suddenly, and produces a little explosion.

Q. _Why does a DROP of WATER sometimes ROLL along a piece of hot iron without leaving the least trace?_

A. If the iron be _very hot indeed_, the _bottom_ of the drop is turned into _vapour, before the drop can evaporate_; and the vapour thus formed _buoys the drop up_, without allowing it to touch the iron at all.

Q. _Why does it ROLL?_

A. The _current of air_ (which is always pa.s.sing over the heated surface) _drives it along_.

Q. _Why does a LAUNDRESS put a little SALIVA on an IRONING-BOX to know if it be hot enough?_

A. If the saliva _sticks to the box and is evaporated_, the box is _not_ hot enough; but if the saliva _runs along the box_, it _is_.

Q. _Why is the BOX HOTTER if the saliva RUNS ALONG THE BOX, than if it adheres to it till it is evaporated?_

A. If the saliva _runs along the box_, the iron is hot enough to _convert the bottom of the drop_ of spittle into _vapour_; but if the saliva _will not roll_, the box is _not_ hot enough to convert the bottom of the drop of spittle into vapour.