The Wilmington daily Republican. (Wilmington, Del.) 1890-1902, 1892-09-22
THE VALUE or DUST,
ITS Partieiss Form Froe Surfaces for a
NJ VanOr

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ITS Parsieiss Form Free Surfaces for the
Collection of vapor.
How can invisible particles be brought
within the range Of our vision? That
was one Of the FIRST of the many MARVEL
GUS discoveries of Mr.. John Astken, r.
r. s., Falkirk, q distinguished physicist,
whose remarkable work has revolution
lied branch Of meteorology. He
showed that without dust in the air
there could be no fogs, no mist, no cloud
and probably no rain. The particles of
dust are the free surfaces, which, under
certain conditions, attract the water
vapor of tho atmosphere to form fog.
Invisible before, they become visible
when clothed all over with the moisture;
unseen as dust, they become distinct as
fog particles.
This can be easily verified. II ordi-
nary air be forced through q filter of
cotton wool into glass receiver, it is
deprived of all its dust particles. Let
steam be introduced into this receiver
from boiler, no change will be OBJ
served; the vessel is quite transparent.
But IL jet of steam be introduced into
similar vessel containing ordinary air,
it will be seen rising in a dense cloud;
then beautiful fog will be formed, 90
dense that 1t cannot be seen through. In
the former case, when there was nc
dust In suspension, the air remained
clear; In the latter case, when the ordi-
nary atmospheric dust was in the yes
sci, fog at once appeared. The invisible
dust then is detected by the introduc-
ton OF water vapor.
Until very lately it was thought that
particles Of water vapor combined with
each other to form cloud particle, but
it is now found that some solid body,
however small, is required for this
formation. In fact, when there are nc
dust particles on which the water vapoi
at proper temperature and pressure
can condense, there is at present nc
knowledge as to the point at which the
change will take place. But the fine
particles Of dust in the air act as free
surfaces on which the water vapor con
denses into fog. When there is abund.
ance of dust In the air and little water
vapor present there is IN overproper.
ton Of dust particles, and the fog par
ticles are in consequence closely packed
but light in form and small in size, and
take the lighter appearance of fog. Ac
cordingly, IL the dust is increased in the
air, there is proportionate increase oil
fog.
But on the other hand If the dust
4 particles are fewer in proportion to the
number of molecules of water vapor
each particle soon gets weighted, springs
into visible existence as if by creative
hand, and falls in mist or rain. If tn,
water vapor had no dust at all on which
to settle, 1t would use the objects on tn,
surface of the ground for the same cid
as the grass, leaves, tree branches o.
house projections. Moisture would thei
be ever dripping. The occasional genia
rain, though at times dashed up to I
biting storm Of sleet, would require t.
give place to o constant wetness on tn
roads and grass.
Umbrellas would not be needed, bu
india rubber protectors for the feet anC
legs would be in constant requisitiou
Even the irritable housekeeper, ever MI
noyed at the unaccountable appearance
of dust in rooms which she left for clean
would prefer the old necessary evil II
this dry dust form than see the wall
dripping and the floor wet. - Coco
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