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
131. _Which would become cold first--the metal or the wool?_
The _wool_, because, although the metal conducts heat more rapidly, to
a substance in contact with it, it does not _radiate heat_ as well as a
_black and rough substance_.
132. _Why do iron articles feel intensely cold in winter?_
Because iron is one of the best conductors, and draws off heat from the
hand very rapidly.
133. _What is the cause of the sensation called cold?_
When we feel cold, heat is being _drawn off from our bodies_.
134. _What is the cause of the sensation called heat?_
When we feel hot, our bodies are _absorbing heat_ from external causes.
The condition here implied is that of health, and of ordinary
circumstances. A person in a condition of fever, suffering from
intense heat arising from a diseased state of the blood, could not
be said to be _absorbing heat_. Nor could such a description apply
to a person who, by a very rapid walk, has raised the temperature
of his body considerably above its natural state, by the _internal
combustion_ which has already been described. A person feeling hot
in bed, from excessive clothes, feels hot from the _development of
heat internally_, which is not _conducted away_ with sufficient
rapidity to maintain the natural temperature of the body.
135. _If a person, sitting before a fire-place, without a fire, were
to set one foot upon a rug, and the other upon the stone hearth, which
would feel the colder?_
The foot on the stone, because stone is a good conductor, and would
_conduct the warmth of the foot away from it_.
[Verse: "The earth is the Lord's, and the fulness thereof; the
world, and they that dwell therein."--PSALM XXIV.]
136. _What does the hearth-stone do with the heat that it receives?_
It delivers it to the surrounding air, and to any other bodies with
which it may be _in contact_--and as it parts with heat, _it takes up
more from any body hotter than itself_.
137. _When there is no fire in a room, what is the relative temperature
of the various things in the room?_
They are all of the same temperature.
138. _If all the articles in the room are of the same temperature, why
do some feel colder than others?_
Because they differ in their relative powers of _conduction_. Those
that are the best conductors feel coldest, as they convey away the heat
of the hand most rapidly.
If you lay your hand upon the _woollen table cover_, or upon the
_sleeve of your coat_ or mantle, it will feel _neither warm nor
cold_, under ordinary circumstances. But if you raise your hand
from the table cover, or coat, and lay it on the marble mantel
piece, the mantel-piece will feel _cold_. If now you return
your hand from the mantel-piece to the table cover or coat, _a
sensation of warmth will become distinctly perceptible_. This will
afford a good conception of the relative _powers of conduction of
wool and marble_.