Milford chronicle. [volume] (Milford, Del.) 1878-1974, 1889-09-13
STEAM FOG HORNS.


Sounds ia the Air.
Point Judith's siren is a damsel Of the first
class. The fog horns extend their long,
black threats from the side Of the fog signal
house, hard by the light tower, and open
their mouths to the sea There are two of
the sisters, each provided with boiler for
lungs and little engine, so that if either
gives out, in lung power, the other may sing
in her place
The governments fog sirens are among the
most interesting creatures Of the lighthouse
service. They have been the subject OF the
study of the services scientists for a good
many years. They have been experimental
with, all sorts of devices have been tried
with view to improving their serviceabil
ity, and their position today IN Importance
is even Of seniority rank TO the lighthouses
themselves. But while the lighthouses are
pretty well perfected establishments, the fog
sirens, with all the acoustic problems which
they give rise to, are subjects Of the most in
teresting research the utilized field of which
is still broad
Each of the sister sirens at Point Judith is
sixteen feet long, tapering from the throat Of
four inches diameter to the mouth, thirty
inches in diameter. There is a diaphragm
across the throat with four square holes in it,
and across this diaphragm and the square
holes whirls, at the rate Of l 200 revolutions a
minute, an arrangement that is like a wheel
without the felly. The steam is sent rushing
between the flying spokes and through the
holes, and goes reveberating along the six
teen feet of cast iron neck and out of the big
mouth with a roar that makes the signal
house jump, and can be heard beyond Block
Island. A cam device on the engine lets
steam into the sirens throat at intervals OF
forty seconds, and then the siren bellows
continuously for six seconds. The fog damsel
at Block Island lets 60 every thirty seconds
instead Of every forty seconds, so that the
mariner who observes his chart can always
tell which shore he is closer on by counting
the intervals between the fog sirens blasts
The Importance Of this difference of interval
may not be fully apparent TO the laudsman,
and is not always regarded by the mariner
guiding his ship blindly through impenetra-
Die fog. Aside from the impossibiity Of
master of a sailing vessel maintaining re-
liable idea Of his position in a fog, where per
haps he is drifting more than sailing, the
contour Of the coast and the make Of the
tides out Of the Sound is such that he may
easily find himself sailing on to Point judith
when he believes lie is close to the Block Isl
and shore.
nc ucNtloIlilellb OF Lut siren mas presented
acoustic problems which, if really explaina-
bic by acoustic and atmospheric principles,
have not been foreseen, and have bothered
the experts when they ran against them, and
are none the less curious now to the lay OBJ
server. Moreover. the experts are completely
foiled in their efforts to make the siren do the
work that it was thought it could do without
any trouble, although they have found ont
what the difficulty is For instance with all
its lung power long throat and big month,
that carry its believing far ont into the sea,
sometimes the ponderous sound disappears
utterly at short distances. The sound from
Point Judith siren that reverberates In tine
mariners ear away across TO Block Island
may not be heard at all by the unfortunate
skipper straining his ear for its warning
blast a mile of shore Then suddenly, when
he has drifted in until Point Jude is too close
on his lee to escape from, the thunder of the
siren bursts upon HIM, and he knows from its
ponderous tone that it is desperately near.
The breakers are roaring on his bow; there
is an ugly crunch, crash and shiver and
he is hard and fast. When the life saving
crew gets him ashore the first thing be does
is to let go his swearing gear, and then he
complains TO the authorities at Washington
that at such an hour on such a night, in
dense fog, the fog signal on Point Judith was
not sounding, and was only sounded when it
was too late TO warn him off. In years gone
by the light keeper would be hauled over the
Goals on the strength Of complaints like this
Now the authorities merely inquire of the
light keeper if his siren was working or not. |
They have found out by experience and de
monstrated 10y bheory that the different cur
rents Of air play the deuce with the SIRENS
call; that the sound which they carry for
miles out over the ocean they may also toss
out Of reach Of the mariners hearing few
thousand or even a few hundred feet off
shore; may play with it as if it we're a foot
ball; kick it here and throw it there, any
where but TO the mariners waiting ear
Providence Journal