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
[Verse: "With clouds he covereth the light, and commandeth it not to
shine by the cloud that cometh betwixt."--JOB XXXVI.]
376. _Why, if they are invisible when they rise, do they became visible
when they have ascended?_
Because the vapours become _cooled_ in passing through the air, and
form a denser body.
377. _Why, when they are condensed, do they not follow the course of
gravitation, and descend?_
Because the vapours form into _minute vesicles_, which we may call
_vapour bubbles_, and these, being warmed by the sun, are specifically
_lighter than the air_.
Because, also, the lower parts of clouds _do partially_ descend, but
again becoming more _rarefied_ by meeting with a _warmer atmosphere_,
they again ascend, and are thus _poised_ upon the air.
Because, also, there is always a degree of atmospheric motion _upward_,
caused by the _convection of heat_ from the earth's surface. And,
although there must also be downward movements of the air to supply the
place of that which has ascended, still _the heat_ of the ascending
air, _combined with its upward movement_, expands and floats the vapour
of the clouds.
378. _At what height do clouds usually fly?_
They fly at every degree of altitude; but clouds of _specific
character_ are said to fly at given altitudes, or to occupy certain
_ranges of altitude_. We will give their probable altitudes when
speaking of the specific clouds.
[Illustration: Fig. 5.--CIRRUS, OR CURL CLOUD.]
[Verse: "Who giveth rain upon the earth, and sendeth waters upon the
fields."--JOB V.]
379. _How many descriptions of clouds are there?_
There are _seven_.
1. The _Cirrus_ (Fig. 5), estimated range of altitude from 10,000 to
24,000 feet.
2. The _Cumulus_ (Fig. 7), from 3,000 to 10,000 feet.
3. The _Stratus_, an extended continuous level sheet of cloud,
increasing from beneath. They fly very low.
4. The _Nimbus_ (Fig. 10), 1,500 to 5,000 feet.
5. The _Cirro-cumulus_ (Fig. 4), from 3,000 to 20,000 feet.
6. The _Cirro-stratus_ (Fig. 6), from 5,000 to 10,000 feet.
7. The _Cumulo-stratus_ (Fig. 9), from 3,000 to 10,000 feet.
[Illustration: Fig. 6--CIRRO-STRATUS, OR WANE CLOUD.]