The Bossier banner., 1894-06-21
WEIGHING AND MEASURING AIR.
Proof of Air Currents by Means of Rota-
ting Globe.

Proof of Air Currents by Means of Rota-
ting Globe.
In his recent lectures at the Royal
Institution, Prof. Dewar showed how
it is possible to weigh and measure air
or gas under high pressure. Air was
compressed into small iron vessel un-
til IT became thirty times denser than
ordinary air, and the vessel was
weighed on a steelyard. A further
compression to sixty times the ordi
nary density was made, and the weight
was found to have correspondingly in
creased. Then the compressed air was
turned off into a gasholder for meas
urement, and wss seen to be three and
half cubic feet. Next Prof. Dewar
turned to the subject of the circulate
OF air. By means of diagram he
showed how air is always moving from
the equator to the poles and then re-
turns, Midway between the poles and
the equator, of course, were the calms.
The fact that air rises from the equator
in consequence of heat he demonstrated
by means of a very thin paper balloon,
the air in which was heated, and sc
caused to expand and rise. When cur
rents met and crossed they had lorna
does and waterspouts the same thing
happening in air as they might observe
in pools when whirls and eddies oc-
Cured. Some of the effects of whirl
of air were illustrated by the familiar
experiments of spinning coins and
sawdust on glass. Thus the audience
could see, he said, what happened in
the case of ships caught in tornado.
They might also note the effect of the
use of a fan on the movement of air,
causing pressure on one side and
diminution on the other. The temper
ature of that theater was kept equal
by fresh air being famed into it from
below, the outlet being through the
roof.
Before leaving the subject he gave
demonstration of the effect rapid
ly rotating globe would have upon the
circumambient air, the air being re-
PEELED from the equator and sucked
under the poles. No wonder, he said.
that when the wind travelled at fifty
or sixty miles an hour ships were help
less. The experiment of keeping
ball poised on nothing but current
of air was also shown, and then two
interesting experiments were made
with sand. Sand was placed before
current of rapidly moving air and car.
ried with such rapidity (but not more
rapidly than the current itself moved)
that in ten seconds holes were cut
through sheet of glass. In the same
way a beautiful lace pattern was cut
upon another piece of glass by the air
and sand alone the pattern being Sc
cured by placing a substance over tho
glass, leaving exposed only the parts
to be cut.
Prof. Dewar then went on to the
chemistry of air, which, as he ex-
planned, was connected with what took
place in combustion. Producing a can.
die, he remarked that it would need
air to burn as a man would need air tc
live. Put under glass, the candle
soon burned out, but it left some liquid
on the side of glass, just as mar
would on breathing into it. Lime
water, on being introduced into the
glass, became turbid and lay round the
glass under the deposit or liquid left
by the candle. This showed that new
air had been produced. Therefore,
they were confronted by the fact that
in combustion new air was produced,
and the question was: What? They
might burn candle away, and yet its
products by burning would 5e heavier
than the candle itself originally. This
was proved to be the case also with
magnesium wire when burned. The
solid which remained was not metallic
in character; old chemists called it
calyx of the material. Now the in
crease of weight following combustion
could only come from some material in
the air used up in the process of com.
bustion, and that must be oxygen.
Oxygen intensified combustion, and
was completely taken up by the burn
ing body. Air, however, was not com
pletely taken up, but only to the ex.
tent of about a fifth of its volume.
The burning of carbon, phosphorus
and metal in oxygen all want to show
that air was a mixture containing only
a fifth of it's substance as oxygen.
which alone had the property of main
tanning ombustion.-London News.
The Best Fashions.
With regard to silks and satins, tht