The reason why : $b a careful collection of many hundreds of reasons for things which, though generally believed, are imperfectly understood. A book of condensed scientific knowledge for the million — John Stuart Mill — John Shaqi
The reason why : $b a careful collection of many hundreds of reasons for things which, though generally believed, are imperfectly understood. A book of condensed scientific knowledge for the million
John Stuart Mill · en
Because the _hot air_ absorbs a large amount of vapour, and as the
atmosphere is usually calm, there is an absence of currents, by which
the saturated air would be removed. In this, which is called "_the
Region of Calms_," rain falls almost daily.
429. _Why are some parts of the earth rainless?_
Because, being situated in tropical or torrid latitudes, and at a
distance from the ocean, the atmosphere above them is always in a _dry
state_.
[Verse: "Thou, O God, didst send a plentiful rain, whereby thou
didst confirm thine inheritance, when it was weary."--PSALM LXVIII.]
430. _When is air said to be saturated with vapour?_
When it cannot take up _a larger quantity_ than that which it already
holds.
When common salt is dissolved in water, until the water can take
up no more, the water is then said to be _saturated with salt_.
431. _What proportion of water is air capable of sustaining in the form
of vapour?_
The amount of water held in suspension by the air averages the
following proportion: one thousand _cubic feet of air_ contain as much
vapour as, were it condensed to water, would yield about _two fifths of
a pint_.
But _one thousand cubic feet of air_ are capable of holding
_half-a-pint of water_; and this may be regarded as the _point of
saturation_.
Thus, in a room ten feet square and ten feet high, the air, _at
the point of saturation_, would hold in the form of vapour,
_half-a-pint of water_. It must not be forgotten, however, that
the point of saturation necessarily varies with the _temperature
of the air_.
432. _Why are cloudy days and nights not always wet?_
Because the air has not reached the state of _saturation_.
433. _Why does rain purify the air?_
Because it produces motion in the particles of the air, by which they
are _intermixed_. And it precipitates noxious _vapours_, and cleanses
the face of the earth from _unhealthy accumulations_.
434. _Why are mountainous localities more rainy than flat ones?_
Because the mountains _attract the clouds_; and because the clouds
that are flying low are borne against the sides of the mountains and
directed upwards, where they meet with _cold currents of air_.
435. _Why does more rain fall by night than by day?_
Because by night the temperature of the air, heated during the day,
falls to that degree which condenses _its vapours into rain_.
[Verse: "As the hart panteth after the water brooks, so panteth my
soul after thee O God."--PSALM XLII.]
436. _Why do bunches of dried sea-weed indicate the probability of
coming rain?_
Because they readily imbibe moisture, and when they become soft and
damp they show that the air is _approaching the point of saturation_.
437. _Why does the weather-toy, called the "weather-cock," foretell the
probability of rain?_