South Bend news-times., 1918-07-08

Your brothers. statement is near
ly right. II would have been en-
tirely so IL he had said that
black surface absorbs light (not
heat), and that the energy of the
light thus absorbed is transformed
into heat. This Is not a mere pc
dantical correction as you will see
IN a moment.
Light and heat are both viora-
tory phenomena which may pass
into one another. Thus, when the
vibrations OF the molecules OF
body reach a certain degree OF in
tensity II becomes perceptibly
warm. Increased intensity OF
molecular vibration increases the
heat.
AS the heat grows part OF it is
given or from the body IN the form
Of ratiations, l. e., OF vibrations set
up in the surrounding ether. When
the body becomes hot enough its
IA adiations become visible. or take
the form OF light, and we say that
the body is led hot. X the heat
rises still higher in temperature the
brightness of the body increases
until it becomes white hot"
Now, let the same body cool off
and the radiations and vibrations
will run down the scale, the body
first sinking TO red heat" again.
and then ceasing TO shine, although
IL will still give of invisible radis-
tions heat.
Keep what has just been said in
mind and go back to the white and
black clothes. A white surface IS
sunlight that falls upon it COR vir-
tually ally, and absorbs none-sun-
light being composed OF rays Of va
rious colors which are separable
under certain circumstances. but
which when mingled together pro-
duce white light.
A black surface. on the contrary,
reflects none OF the sunlight falling
upon il, but absorbs all. The ques-
ton is then: what becomes of the
energy thus absorbed? The reply is
light into heat /: g. the vibrations
which were OF such quality before
they struck the surface as to pro-
duce in the ether the, phenomenon
which the eye recognizes as light
are now used Up in setting the
molecules OF the absorbing sub
stance into the invisible agitation
which the sense OF touch recognizes
as heat.
In this way only 90 black clothes
become warmer than white ones.
They 90 not absorb more heat shan
the others. but they ABSORB light
and slow down its vibrations into
heat, thus gaining in temperature
over white clothes which have not
this power OF transforming the ra-
diant energy that falls upon them.
but instead reflect nearly all OF il
away in the unchanged form Of
light.
BENJAMIN Franklin obtained a
part OF the enormous reputation
that made him one OF the most in
auentiai men % his generation.
l living anywhere in the world BY a
very striking experiment on the ab-
sorbing power or cloth OF various
colors He laid equal-sized pieces
varying in tone from black 20 white
i side BY side on a field OF snow in
the sunshine and measured the
depth 20 which they sank as they
melted the snow beneath them.
/ He found that the black sank
most and the white least, while the
pieces Of other colors sank deeper
roughly in proportion TO the dark
ness OF their hues. The inference,
/ of course. was that the black col
I Iected the most heat and the white
the least. from which Il was easy
TO draw the conclusion that white
clothes in summer and black IN
winter would AFFORD the creates
/ degree OF comfort 20 the wearers
Afterwsrd this conclusion. though
correct in principle. was pushed toe
far because Z was not limited. as