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
The convection of heat is the transmission of it _through_ a body or
a number of bodies, or particles of bodies, by those substances which
_first received it_; as when hot water rises from the bottom of a
kettle and imparts heat to the cold water lying above it.
CHAPTER VII.
118. _Why does not a piece of wood which is turning at one end, feel
hot at the other end?_
Because wood is _a bad conductor of heat_.
119. _Why is wood a bad conductor of heat?_
Because the arrangement of the particles of which it is composed does
not favour the transmission of _caloric_.
120. _Why do some articles of clothing feel cold, and others warm?_
Because some are bad conductors of heat, _and do not draw off much of
the warmth of our bodies_; while others are _better conductors_, and
_take up a larger portion of our warmth_.
[Verse: "The fining pot is for silver, and the furnace for gold: but
the Lord trieth the hearts."--PROVERBS XVII.]
121. _Which feels the warmer, the conductor or non-conductor?_
The non-conductor, as it does not readily _absorb_ the warmth of our
bodies.
122. _What substances are the best conductors of heat?_
Gold, silver, copper, and most substances of close and hard formation,
&c.
123. _What substances are the worst conductors of heat?_
Fur, eider down, feathers, raw silk, wood, lamp-black, cotton, soot,
charcoal, &c.
124. _Why has the toasting-fork a wooden handle?_
Because wood is not _so good a conductor_ as metal, therefore the wood
prevents the heat from being transmitted _by conduction_ to our hands.
125. _Why has the coffee-pot a wooden handle?_
Because the metal of the coffee-pot would otherwise _conduct the heat
to the hand_; but wood, _being a bad conductor_, prevents it.
126. _Why does hot water in a metal jug feel hotter than in an
earthenware one?_
Because metal, being a good conductor, _readily delivers heat to the
hand_; but _earthenware, being an indifferent conductor_, parts with
the heat slowly.
127. _How can we ascertain that wood prevents the conduction of heat to
the hand?_
By passing the top of the finger along the wooden handle of the
coffee-pot, until it reaches the point where the wood meets the metal.
The wooden handle will be found to be _cool_, but the metal will feel
_very hot_.
128. _Of what use are kettle-holders?_
Being made of _bad conductors_, such as wood, paper, or woollen cloth,
they will not readily _conduct_ the heat from the kettle to the hand.
[Verse: "Wisdom is the principal thing; therefore get wisdom: and
with all thy getting get understanding."--PROVERBS IV.]
129. _Will a kettle-holder, being a bad conductor, sometimes conduct
heat to the hand?_
Yes. But so slowly that the hand will not _feel the inconvenience of
too much heat_.
130. _Why does hot metal feel hotter than heated wool, though they may
both be of the same degree of temperature?_
Because metal gives out heat _more rapidly than wool_, by which it is
made _more perceptible to our feelings_.