The Charlotte Democrat., 1892-01-15
Curious Things About Dust.
Without it There Would be no Rain or Snow
or HAIL

Without it There Would be no Rain or Snow
or Hail.
A highly interesting article on "Dust"
by J. G. Mcpherson describes the discov-
cry made few years ago by Mr.. John
Aitken, of Falkirk, Scotland, in regard to
the presence and behavior OF dust particles
in air and water, and especially in the
atmosphere. He found that without such
dust there could be no rain, nothing but
continuous dew in moist climates. There
would be no need for umbrellas, but also
no means of preventing the skin and
clothing from being constantly wet. In
visible dust is absolutely necessary for the
production of fog, cloud, mist, snow, sleet,
hail and rain, their fine particles acting
each as a nucleus around which the vapor
in the air clusters to form a cloud particle.
By means of an ingenious apparatus these
dust particles have been counted, and
found to range from about $1,000, 900
down to "a in the cubic inch of air. The
greatest number was found in room
after crowded meeting, and the least
on the top of Ben Nevis, which is the
highest mountain in Scotland. This ex-
plodes the old theory that the particles
of water vapor have to combine with each
other to form cloud particle, and perhaps
may lead up to revision of the theory of
artifcially producing rain, unless that be
abandoned altogether. 1t leads up to the
idea that granting suficiency of moist
ure in the air it may be made to condense
by scattering among it large number of
dust particles, each of which will attract
around it the material for part of a cloud,
that being the first step in the process Of
producing rain, tor which mere detona-
tion however great, is Intellectual.
Mr.. Aitken has also shown that the
brilliancy and variety of the coloring often
observed at sunset are due to suspended
dust in the atmosphere. He argues that
in the upper air there must always be
dust, for without it no clouds could be
formed to shield us from the suns scorch.
ing rays, and of cosmic dust there must
be considerable quantity suspended in
the air, which is produced from the waste
of the millions of lneteors that daily fall
into it. The tremendous eruptions at
Krakatoa, in the Straits of Sunda, are
computed to have thrown up no less than
10000 cubic yards of dust which actually
fell around the volcano, while the decks
Of vessels hundreds of miles away were
covered with it. Much of this dust re-
mained in the air for several years, and
gave the brilliant sunsets so often describ-
ed. If our atmosphere were perfectly
| devoid of dust, the suns light would
simply pass through without being seen,
and total darkness would ensue soon
after the sun dipped below the horizon.
The length of our twilight, therefore,
depends upon the amount of dust in the
| atmosphere. And this leads up to
| IN ho 10
that the argument adduced to prove that
the moons atmosphere is not sufficient
to balance more than the 30th of an inch
of mercury in the barometer may be
bad one. If much larger quantity of
there would be an absence OF the refraction
which has hitherto been supposed insep-
| arabic from an aerial envelope. Hence
the moon may have more air surrounding
her than she has hitherto been credited
with, but there would be no opportunity
for the snowfall which some have fancied
to occur recently on our satellite.
The sources of the dust in our atmos.
phere are numerous, in addition to those
previously mentioned. On and near the
sea the air is impregnated with brine
dust. But burned sulphur is the most
active of all substances as fog producer
in the cities. No less than $50 tons Of
the products of the combustion of sulphur
from the coal used are thrown into the
atmosphere fLondon every day in winter.
But the powerful deodorizing and anti
septic properties of the sulphur assists in
sanitation, and the winter hints that it
may be better to bear the Inconvenience
of fogs than be subjected to the evils of
pestilence. This smoke can, however,
be dissipated by electric discharges, and
the air is in this way cleared by lightning.
The organic germs that float in the air
are also causes Of disease as we'll as filth,
but they are less harmful than they
would be if not repelIed from the lung
surface of the healthy human being who
breathes air containing them.-Chicago
Tribune.