Year: 1873

What is thecause of the sensation


called cold? When we feel cold


heat is drawn from our bodies.


When do substances feel neithe'


hot nor cold? When they are Of the


same temperature as our bodies.
j Is water good or bad conductor


Water is an indifferent conductor, bat


it is better conductor than air.


What is the cause of the sensation


called heat? When We feel hot, ouI


bodies are absorbing heat from exter-


nal causes.


Do some substances absorb heat ?
Yes, those substances which are the
best radiators are also the best abb
sorbers of heat.


Why are wooden fabrics bad con-
ductors of heat ? Because there is a
considerable amountof airoccupying
the spaces of the texture.


What is radiation? The radiation
of heat is motion of the particles,
in series of rays, divergingi in every
direction from heated body.


What sources of radiation are there
besides the sun and fire? The earth,
and all minor bodies besides, are in
some degree radiators of heat.
+ Which are the better conductors of
heat, fluids or solids? Generally
speaking, solids; especially those of
them that are dense in their sub
stances.


Why do iron articles feel intensely
cold in winter? Because iron is one
of the best conductors, and draws of
heat from the hand very rapidly.


Why are dense substances the best
conductors of heat? Because the
heat most readily travels from par
ticle to particle until it pervades the
the mass.


Why is it said that snow keeps the
earth warm? Because snow is bad
conductor, and prevents the frosty air
from depriving the air of its warmth.


Why are furs and woolens and fam
nels worn in winter? Because being
they prevent the
warmth of the body from being taken
up by the cold air.


Is the air ever hot enough in any
part of the world to destroy life?
The hot winds of the Arabian deserts,
which are called simoons, frequently
destroy both man and beast.


How is warmth provided for in an
imals that have no such coats? They
are furnished with q layer of fat
which lies underneath the skin. Fat
consists chiefly of carbon, and is a
a non-conductor.


What substances are best and worst
radiators All rough and dark sub
stances and surfaces are the best, and
all smooth, bright and light colored
surfases are the worst radiators of
heat.


Why, when we place our hands in
water, which may be of the same
as the air, does the water
feel some degrees colder? Because
water, being better conductor than
air, takes up the warmth of the hand
more rapidly.


Why does a bright metal teapot |
produce better tea than a brown or
black earthenware one? Because |
bright metal radiates little heat, |
therefore the water is kept hot much |
longer, and the strength of the tea is
extracted by heat.


How is the greater warmth of ami |
mails provided for in the winter? 1t |
s observed as winter approaches,
there comes a short woolly or downy |
growth, adding to the non-eonduct-
ng property of their coats, confines |
their animal warmth.


Why would not a dark earthen-
ware jug keep the water hot as long |
IS the bright metal one? Because
.he particles of earthenware being |
rough, and ofdark color, they radiate
leate freely, and the water would
thereby be quickly cooled.


But if the earthenware teapot /
we're set by the fire, why would it
hen make the best tea? Becaus
,he earthenware tea Dot is a good abb
'orber of heat, and the heat it
would absorb from the fire would
more than counterbalance the loss by
'adiation.


Why, when we take our hands out
If water, do they feel warmer? Be
,ause the air does not abstract the
leat of the hand so rapidly as the
water did, and the change in the de-
,ree of rapidity with which the heat
S abstrated produces a sensation of
increased warmth.