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, in the act of congealation a great deal of heat is given out,
and _taken up by the air_, and thus _the severity of the cold is in
some degree moderated_.
164. _Why is it frequently colder when a thaw takes place?_
Because, in the process of thawing, a certain amount of heat is
_withdrawn from the air_, and enters the thawed ice.
165. _What benefit results from these provisions of Nature?_
They moderate both the _severity of frosts_, and _the rapidity of
thaws_, which, in changeable climates, would be seriously detrimental
to _life_, and to _vegetation_.
166. _Why are furs and woollens worn in the winter?_
Because, being non-conductors, they prevent the warmth of the body from
being _taken up by the cold air_.
167. _Why are the skins of animals usually covered with fur, hair,
wool, or feathers?_
Because their coverings, being _non-conductors of heat_, preserve the
warmth of the bodies of the animals.
[Verse: "He sendeth out his word, and melteth them: he causeth his
wind to blow, and the waters to flow."--PSALM CXLVII.]
168. _How is the greater warmth of animals provided for in the winter?_
It is observed that, as winter approaches, there comes a short woolly
or downy growth, which, _adding to the non-conducting property of their
coats_, confines their animal warmth.
In small birds during winter, let the external colour of the
feathers be what it may, there will be found a kind of _black_
down next their bodies. Black is the _warmest colour_, and
the purpose here is to _keep in the heat_, arising from the
respiration of the animal.
169. _How is warmth provided for in animals that have no such coats?_
They are furnished with a layer of _fat_, which lies underneath the
skin. Fat consists chiefly of _carbon_, and is a _non-conductor_.
170. _Why are summer breezes said to be cool?_
Because, as they pass over the heated surface of the body, they bear
away a part of its heat.
171. _Why is a still summer air said to be sultry?_
Because, being heated by the sun's rays, _and being a bad conductor_,
it does not relieve the body by _carrying off its heat_.
172. _Why does fanning the face make it feel cooler?_
Because, by inducing currents of air to pass over the face, a part of
the excessive heat is taken up _and carried away_.
173. _Why does perspiration cool the body?_
Because it takes up a part of the heat, and, evaporating, _carries it
into the air_.
174. _Why does blowing upon hot tea cool it?_
Because it directs currents of air over the surface of the tea, and
these currents take up a part of the heat _and bear it away_.
175. _Why does air in motion feel cooler than air that is still?_
Because each wave of air _carries away a certain portion of heat_ and
being followed by another portion of air, _a further amount of heat is
borne away_.
[Verse: "Though I walk in the valley of the shadow of death I will
fear no evil, for thou art with me."--PSALM XXIII.]