The Washington herald., 1911-05-07

there were no heat. Now, every temperature
between the freezing point and boiling point
can convert water into vapor. As the AIR
gets colder again part OF the vapor 1t contains
Is turned into water. II the air Is very full
Of vapor, a slight increase OF cold will cause
it to deposit wet When hot day Is fol-
lowed by cold night. then the dews are
most abundant, for the heat has turned much
overcharged with it, and the chills OF evening
speedily reconvert it into dewdrops.
A gentleman once put glass cup INTO
silver basin when the night was very dewy.
Next morning the silver basin was found dry
while the glass cup was wet with dew. The
reason was that the glass became cooler than
the silver (rarting with its latent heat more
readily, and as the glass, therefore. cooled the
neighboring air more than the silver. the glass
had dew on it while the silver mad none
Grass, too, parts with its heat sooner than
many other substances, and therefore dew Is
deposited on it sooner than on them.
Cloudy nights are not dewy nights, Tor the
clouds act as a heat screen acts-they sehu
the escaping heat back again. and prevent the
earth from becoming cold enough 10 eAtrac'
moisture from the air.
Some materials conduct heat from bodies
more rapidly than others do. Linen conducts
rapidly. flannel slowly. Therefore hannci
shirt keeps us warmer, as we say, than a
linen one. Stone conducts more rapidly tnan
CARPET as we feel when We put one bare loot
on the hearthstone and the other on rug.
Metals conduct heat quicker than pottery, pot
terry than wood. ,,-,,
Why is the air colder as We ascend high
mountains: Because it becomes iarer, thinner,
less compressed. and it requires greater heat
to warm il, and the heated air from below
does not rise fast enough to meet the dih-
Guilty.
Different substances when burning give out
different degrees OF heat. Charcoal gives out
about twice as much heat as wood. and one
sort of coal will be twice as hot when klndled
as another. Dry wood is better for heat than
damn, because much OF the heat generated by
[ he damp wood when burning Is used up IN
turning it's dampness into vapor. And the
smoke arising from coal when first put on
the fire is in great measure caused by the
vapor of the water in the coal. AS 1t dries.
those blue and yellow flames, which show
where the different gases are burning.
The flame OF a candle Is worthy OF study.
The tallow is melted, and drawn up to the
top OF the wick, where 1t Is boiled and turned
into vapor. which when at a white heat COM
bines with the oxygen in the air about 1t.
Everything that will burn does not begin to
burn until it is raised to a heat that suits
it.. Thus, spirits OF wine will burn at
lower heat than oil.
Coal gas, or fire damp. often ignites in mines,
and causes terrible accidents As it requires
strong heat before it infames, the Davy lamp
was invented to prevent the gas taking fire.
The flame inside the lamp loses Its heat in
passing through the wire gauzc OF which the
lamp is made, and is too cold to set tire to
the fire damp outside.
Heat il not only made by the sun and by
burning, but also by rubbing things together,
iron on an anvil, and so on. Damp
hay sometimes ignltes from fermentation.