The sun., 1894-02-15
WEIGHING AND MEASURING.
Proof 0f AIR Currents by Means of q
Rotating Globe.

Rotating Globe.
Continuing his Christmas lectures at
the Royal Institute, Frof. Dewar, show
ed, In the first place, how 1t Is possible
W weigh and measure air or gas under
high pressure. Air was compressed
into small iron vessel until 1t became
thirty times denser than ordinary air,
and the vessel was weighed OH 4 steel
yard. A further compression to sixty
times the ordinary density was made,
and the weight was found to have cor
r6spondingly increased. Then the com
pressed air was turned off into gas
holder for measurement, and was seen
10 be 3 IL cubic feet. Next Prof. De
war turned to the subject Of the cir
culation Of air. By means Of q dia-
gram. he showed how air is always
moving from the equator to the poles
and then returns. 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 a
which was heated, and so caused to OK
pand and rise. When currents met
ard crossed, they had tOrnadoes and
waterspouts, the same thing happening
in air as they might observe in pools
when whirls and cddies occurred.
Some Of the effects of a whirl Of air
were illustrated by the familiar ex-
pnriments of spinning coins, and saw.
dust ON glass. Thus. the audience
could see, he said, what happened in
the case of ships caught in a tornado.
They might also note the effect of the
use Of a fan on the movement of air,
causing pressure on one side and di-
minution on the other. The tempera-
ture of that thertre was kept equal by
fresh air being famed into it from be-
low, the outlet being through the roof.
Before leaving the subject he gave
demonstration of the effect Il rapidly
rotating globe would have upon the cir
cumambient air, the air being repealed
from the equator and sucked under the
poles. No wonder he said, that when
wind travelled at fifty or sixty miles
an hour ships were helpless. The ex-
pertinent of keeping a ball poised ON
nothing but a current of air was also
shown, and then two interesting expert
ments were made with sand. Sand
was placed before a current of rapid
ly-mOving air and carried with such ra-
pidity (but not more rapidly than the
current itself moved that in ten sec
Onds holes were cut through a sheet
of glass. In the same way a beauti-
full lace pattern was cut upon another
piece of glass by the air and sand alone,
the pattern being secured by placing a
substance over the glass, leaving ex-
posed only the parts to be cut.
Prof. Dewar then vent on to the
chemistry of air, which, as he explain
ed, was connected with what took place
in the combustion. Producing a can
die, he remarked that it would need air
to burn as a man would need air to live.
Put under glass the candle soon burn
cd out, but it left some liquid on the
side of the glass, just as man would
on breathing into it. Lime water on
being introduced into the glass; became
turbd, and lay around the glass under
the deposit or liquid left by the candle
This showed that new air had been
produced. Therefore they were con-
fronted by the fact that in combustion
new air was produced, and the question
was, What? They might burn candle
away, and yet it's products by burning
would be heavier than the candle it
self originally. This was proved to be
the case also with magnesium wire
when burned. The solid which remain
ed was not metallic in character; old
chemists called it calyX Of the material.
Now the increase Of weight following
combustion could only coare from some
material in the air used up in the pro-
cess of combustion, and that must be
oxygen. Oxygen intensified combustion
and was completely taken up by the
burning body. Air, however, was not
completely taken up, but only to the
extent of about fifth of its volume.
The burning of carbon, phOspho MS and
metal in oxygen all went to show that
air was a 1lixt,l"e containing only a
fifth of its substance as oxygen, which
alcne had the property of maintaining
combustion.-London Daily News.