A Guide To The Scientific Knowledge Of Things Familiar Part 33

Q. _Why do PERSONS who ASCEND in BALLOONS FEEL PAIN in their eyes, ears and chest?_

A. Because the air in the upper regions is _more rare_ than the _air in their bodies_; and (till the _equilibrium is restored_) great pain is felt in all the more sensitive parts of the body.

Q. _Why do PERSONS who DESCEND in DIVING-BELLS FEEL PAIN in their eyes, ears and chest?_

A. Because the air in the sea is _more dense_ than the air in their bodies; and (till the _equilibrium is restored_) great pain is felt in all the more sensitive parts of the body.

Q. _Why does the SEA HEAVE and SIGH just PREVIOUS to a STORM?_

A. The density of the air (just previous to a storm) is _very suddenly diminished_, but the air in the sea is _not so quickly affected_; therefore the sea heaves and sighs _in its effort to restore an equilibrium_.

Q. _Why is the AIR so universally STILL just PREVIOUS to a TEMPEST?_

A. Because the air is _suddenly and very greatly rarefied_; and (as the _density of the air is diminished_) its power _to transmit sound is diminished also_.

Q. _How do you_ KNOW _that_ RAREFIED _air_ CANNOT TRANSMIT SOUND _so well as dense air?_

A. Because the _sound of a bell_ (in the receiver of an air-pump) _cannot be heard at all_, after the air has been partially exhausted; and a pistol _fired on a high mountain_ would not sound louder than a _common cracker_.

Q. _Why do we FEEL BRACED and LIGHT-HEARTED on a FINE spring or FROSTY morning?_

A. 1st--Because there is _more oxygen_ in the air on a fine frosty morning, than there is on a wet day: and

2ndly--A brisk and frosty air has a tendency to _brace_ the nervous system.

Q. _Why do DOGS and CATS (confined to a room) feel LAZY and DROWSY at the approach of rain?_

A. 1st--Because the air does not contain _its full proportion of oxygen_: and

2ndly--Because the damp _relaxes their nervous system_, and makes them drowsy.

Q. _Why do HORSES neigh, CATTLE low, SHEEP bleat, and a.s.sES bray, at the approach of rain?_

A. 1st--As the air does not contain its full proportion of _oxygen_, they feel a _difficulty in breathing_: and

2ndly--As damp _relaxes their nerves_, they feel languid and uneasy.

Q. _Why do CANDLES and FIRES burn with a BLUER FLAME in WET weather?_

A. As the air contains _less oxygen_ in wet weather, the _heat of fire is less intense_: and the flame is blue, _because the fuel is not thoroughly consumed_.

Q. _Why do HILLS, &c. appear LARGER in WET weather?_

A. Because (when the air is _laden with vapour_) the rays of light are _more dispersed_, and produce a larger reflection; objects, therefore, seen at a distance, _appear larger_.

Q. _Why do TREES, &c. in WET weather appear FURTHER OFF than they really are?_

A. Because the fog or mist _diminishes the light_ reflected from the object; and as the object becomes _more dim_, it seems to be _further off_.

Q. _Why does the SUN seem LARGER when he SETS and RISES, than he does at noon?_

A. Because the rays pa.s.s through _more of the vapoury atmosphere_ which surrounds the earth; and this vapoury atmosphere acts like a _magnifying gla.s.s_.

[Ill.u.s.tration: It is very manifest that the lines D C are shorter than the lines E C: if, therefore, A be the earth, and D G E the boundary of the atmosphere round the earth, then the rays M E C (at the _horizon_) will pa.s.s through _more of the atmosphere_, than the rays S D C, which are more elevated.]

Q. _Why does the MOON appear LARGER at her RISING and SETTING, than when above our heads?_

A. Because the rays pa.s.s through _more of the vapoury atmosphere_ which surrounds the earth; and this vapoury atmosphere _magnifies_ the moon, just like a magnifying gla.s.s.

Q. _Why do CATS RUB their EARS when it is likely to rain?_

A. Either because the _air is full of vapour_, and its humidity (piercing between the hair of the cat) _produces an itching sensation_; or more probably, because the air is _overcharged with electricity._

Q. _How can the ELECTRICITY of air produce a sensation of ITCHING?_

A. If the _air_ is overcharged with electricity, the _hair of the cat_ is overcharged also; and this makes her feel _as if she were covered with cobwebs_.

Q. _Why does the CAT keep RUBBING herself?_

A. Her _hair will not lie smooth_, but has a perpetual tendency to become _turgid and ruffled_; so the cat keeps rubbing her coat and ears, to _smooth the hair down_, and brush away the feeling of cobwebs.

Q. _Why do our HEADS and SKIN itch before rain?_

A. Probably because the _air is overcharged with electricity_; and, therefore, a sensation (like that of cobwebs) _irritates the skin_, and produces an itching.

Q. _Why do we HEAR distant CLOCKS more distinctly when rain is near at hand?_

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

Q. _Why do we hear CHURCH-BELLS further, just previous to rain?_