Evening star. [volume] (Washington, D.C.) 1854-1972, 1892-02-27
Fogs Over Great Cities,
From the Youths Companion.

IEOin tne fOutn - companion
Among the practical questions with which
men Of science are called upon to deal few are
more interesting than that of the origin and
nature of great fogs. 1t is only about eleven
years since the true cause of fogs was discov-
cred Mr.. Aitken, an Englishman, demon
strated by experiments in 1880 that fogs arise
from the presence of dust floating in the air.
Each minute particle of dust, too small in
itself to be visible to the eye. serves as a point
of condensation for the moisture of the atmos-
phere. and as the moisture gathers the particle
becomes a visible speck of mist. Millions and
millions of such particles, each loaded with
condensed vapH, constitute fog.
Careful investigations have shown that even
the clearest AIR contains an astonishing amount
OF dust, while, as everybody can see at a glance.
the atmosphere in the near cities is filled with
microscopic floating particles that frequently
rob it OF much OF its transparency; but while
perfectly clear air seems a thing earnestly to
be desired, yet Mr.. Aitken' experiments showed
that but for the dust in the air we should prob
ably find existence far more trying than it is
now.
The dust particles being absent, the atmos-
pheric moisture would condense upon the trees
the grass, the ground, upon our clothes and
faces, upon the walls. floors and ceilings of
houses. inside and out. SO that during such
times as the air is charged with an unusual
amount of humidity We should be covered and
ure.
That would probably be the form in which
we should then get rain. instead of having it
fall in showers from the sky it now does.
Still, although 1t can thus be shown that dust
in the air serves admirable purposes it has. of
course, many disagreeable and injurious fea-
lures. Not the least of these its effect in pro-
duclng such phenomena as the celebrated fogs
Of London.
Such fogs are not confined to London, but
occasionally make their appearance over all
large and busy cities, especially those where a
great deal OF smoke exists. The smoke parti-
cles not only form excellent little fog condens-
ers, but they give to the fog that black and
gloomy color which is especially noticeable in
the fogs of London. More or less poisonous
ingredients, such as sulphuric acid, are also
found IN the fogs of great cities.
1t is natural to suppose. and it has often been
asserted. that such logs largely increase the
death rate of the cities afflicted by them; but
recent Investigations by W. j. Russell indicate
that while many more deaths occur in London
just after great fog, yet II is probable that the
real cause Of the increase is not SO much the
fog itself as the sudden fall of temperature BY
which it is ordinarily accompanied. He finds
that fogs not accompanied by fall of tempera-
ture are not followed by an increase in the
death rate.
By cutting off the sunshine, however. CITY
| fogs cause great injury to health, and their
destructive effects upon some of the plants
In the great botanic gardens at Kew have proved
/ so alarming that Prof. Thiselton-Dyer the
| director of the Kew Gardens, fears that refined
| horticulture may become impossible in the
| vicinity of London if the fogs continue to in
| crease in number and intensity.
| One remedy recommended is the substitu-
/ ton Of some fuel In the place of coal which
Will not MI the atmosphere with SCOT and dust