The Irish standard. [volume] (Minneapolis, Minn. ;) 1886-1920, 1892-11-19
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How can INVISIBLE par les be hrpugh
within the range off our 'visionl
was one Of the first Of the many q aryelssS
lous discoveries Of Mr. ] ohm sisalken,
r. s., Falkirk,a disting uish he'd phi sicist,
whose remarkable work has reyolutlo
lied q branch Of meteorology He
showed that without dust II the or
| 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 the atmosphere to form fog.
Invisible before, they become visible
when clothed all over with the moissure;
unseen as dust. they become distinct %
fog particles.
This can he easily verified. II ordi-3
nary air be forced through filter OF
cotton wool into glass receiver, It IL
deprived Of all it's dust particles. Let
steam be introduced into this receiver
from boiler, no change will be OBJ
served; the vessel is quite transparent.
But if jet OF steam be introduced int
a similar vessel containing ordinary ar,
it will be seen rising in q dense cloud;
then beautiful fog will be formed, So
dense that it cannot be seen through. La !,
the former case. when there was ne
dust in suspension, the air remained
clear; in the latter case, when the ord1-
nary atmospheric dust was in the YES
sci, fog at o1lce appeared. The invisible
dust then is detected by the introduce
ton Of water vapor.
Until very lately it was thought that
particles Of water vapor combined with.
each other to form 1. cloud particle. but.
it is now found that some solid body.
however small, is required for this
formation. In fact, when there are no
dust particles on which the water vapor
at proper temperature and PRESSURE
can condense, there is at present no
knowledge us to the point at which the.
change will take place. But the fine.
particles OF dust it, 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 al overpropor-
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, if the dust is increased in tho
air. there is proportionate increase OF
fog. a..
But on the other hand it the dust
particles are fewer il, proportion to the
number of molecules of water vapor,
each particle soon gets weighted, springs
into visible existence as it by creative
hand. and falls in mist or rain. It the
water vapor had no dust at all on which
to settle, it would use the objects on tho
surface of the ground for the same end,
as the grass, leaves, tree branches or
house projections. Moisture would then
he ever dripping. The occasional genial
rain, though at times dashed up to q
biting storm of sleet. would require to
give place to constant wetness on the
roads and grass. & ..s.
Umbrellas would not be needed, but
india rubber protectors for the feet and.
legs would be in constant requisit'on.
Even the irritable housekeeper, ever IN,
moved at the unaccountable appearance
of dust in rooms which she left for Clean
would prefer the old necessary evil In
this dry dust form than see the walls
dripping and the floor wet. - Good
Words