Eastern times. [volume] (Bath, Me.) 1846-1857, 1853-05-12
The Atmospheric Telegraph.

In Boston, the city Of notions, they have
now on exhibition an atmospheric telegraph,
which correspondent Of the Tribune thus
explains for the benefit of those who are not
engineers. Suppose That cylindrical pump
36 inches in diameter, with AS inch stroke,
be connected with pipe IL inches in diam
eter and 36 feet long. The capacities of the
pipe and cylinder will be equal. Ii the pis-
ton then be raised from the bottom OF the
cylinder to the top, the air in the pipe will
have TO expand to double lis space to fill both
The pipe aud the cylinder, and while the pres
ure without is whole atmosphere, or Is lbs.
10 The square inch, The reaction within is
only half an atmosphere, or Z 12 lbs. As
every upward stroke of the piston is sufficient
10 reduce one-haf The density in 36 feet of
pipe by making Is strokes a minute and
working 80 hours, it would rarity 10 the same
extent the air in 200 miles of pipe. AT that
degree of exhaustion, the external pressure
on the piston willbe 1884 lbs. more than the
INTERNAL and there will be pressure OF one
ninth that, or S48 lbs. available 10 propel
load through the pipe. AS the pipe is nearly
level, the resistance from friction is nearly
all that has 10 be overcome by the propulsion,
and consequently mail OF 20, 900 half ounce
letters would be propelled by such force
acting constantly, with enormous velocity
IL would in fact, be shot forward hundred
miles in very few minutes, and then, the
aerial equilibrium being restored, a resistance
would commence which woulI gradually de-
stroy its momentum. If, instead Of one
pump, many should be employed a, once in
exhausting The supposed 200 miles OF pipe, IL
is plain that the work might be done in a
single hour or less: One hundred horse pow
er Of steam, acting at different points, would
undoubtedly be able in an hour to produce a
propelling force approaching much nearer to
whole atmosphere leaving indeed only air
enough in the pipe to answer The important
purpose OF re-acting spring or cushion at
the remote end, so as TO prevent the mail
from mbeing shattered or reduced 10 homo.
genOus pulp by TOO sudden arrival.
So far as the mail itself is concerned, il
will probably cost less tractive force to drag
il bodily through pipe OF pretty smooth bore
than 10 drag II with Its proportion Of lOcomo-
tive apparatus over a railroad. The amount
of horsepower which would in given time
drag it from Boston TO New York, would in
the same time exhaust a pipe Of sufficient
bore to enable atmospheric pressure to put il
through in ten or fifteen minutes. Multiply
ing the horsepower applied 10 The exhaus-
ton will reduce the time consumed ia the
same proportion. And in this way we may
have hourly mails, or half.hourly, with no
greater expense for carrying them than at
present. As 10 IlIe wear and tear, that is
another matter. The friction on the bags
might be little more serious than al present,
yet this difficulty may be reduced to trifie.
As the load is constantly in contact with cold
pipes, the heat from the friction will be alb
sorbed nearly as fast as il is generated, and
there is little danger that The mail will take
fire. The apparatus, OF small scale, which
Mr.. Richardson shows at the Exchange, is
very iDgeniously constructed, and works prel-
lilly. But, of course, no model so diminuye
can demonstrate the feasibility of the opera
ton, in large. Neither does an experiment
OF mile of pipe, three inches in diameter,
which was successfully put in operation on
the line of the Providence Railroad, amount
to demonstration. These experiments,
however, show the nature Of the force, how
the Rria team is TO be harnesseG, and what
are its good points for The mail service.