The Stourbridge Observer, Cradley Heath, Halesowen & District Chronicle.
Stourbridge, West Midlands, England, 1871-11-18 00:00:00

THE PNEUMATIC DESPATCII TUBES.

The opening meeting of the new session of the In-
stitution of Civil Engineera was held in Great George-
street, London, on Tuesday evening, when the paper
read and discusso Witlloll "Pneumatic Despatch Tubes
--The Circuit System," by Mr. Carl Siemens, M.
104. C. E. The chair was occupied by Mr. Vignoles,
KRA, the President.

After referring to the pneumatic tubes laid by the
Electric and International Telegraph Umpany to con-
nect their central st talon in Telegraph-street with their
nearest branch stations in the city, a system of tubes de-
signed and carriel out by Mr. Latimer Clark, M. Inst.
C. K. and Mr. Farley, M. Inst. C. K , which had been
considerably extended since the telegraphs has ps.sseil
into the hands of the postal authorities, Mr. Siemens
stated that in April, 18631 the Prussian 1 lovern-
ment applied to Messrs. Siemens and Halske, of
Berlin, to suggest a system of pneumatic tubes for
that city. That firm proposed laying tubes, arranged
111 circuit, to lie traversed by a continuous air current
always kept flowing in the mune directii in, The
peculiarities id this system namely, the continuous
current id air and the power if putting carriers into
the tubes at any point---gave it great superiority over
previous systems in the amount of work it was callable
of doing. The Central Telegraph Station and the Ex-
change at Berlin were connected together on this system
in ISO, bymeans of two parallel lines of drawn wrought..
iron tubing, of two and a half inches internal dia-
meter, one tube being used exclusively for the passage
of carriers in one direction, and the other for carriers
going in the opposite direction. The continuous cur-
rent of air for these tubes was produced by means
of a steam-engine working a double acting air-
pump in the lusement of the telegraph station.
Allusi ~,, was then made to the circular pneumatic sys-
tem in Paris, in which a continuous current of air was
not nsed, an.l to the pneumatic line in London from
Euston station cia Ibillairn to the tieneral Post-Oftice,
designed for the conveyance 14 large parcels. A minute
account was then given of the experimental circuit
laid by Messrs. Siemens between the Central Tele-
graph Station and the General Post-office in St. Mar-
tin's le-Grand, which was openel for traffic in Feb.,
WO, and had subsequently been extended to Fleet-
street and to the West Strand office. The different
stations were connected by two lines of wrought-iron
tubing, having an internal diameter of threesinchea
Both lines were laid in the same trench, at a
depth of about 12 inches below the pavement,
and parallel to one another. The tales forming
the circuit were of an average length of 18 feet
inches, a common lead-and-yarn jonit making the
einnection between each tube. A current of air was
kept constantly circulating through thetubes by means
iif a steam-engine and double-acting air-punip placed
in a basement of the I'entral Telegraph Station. Each
station on the circuit had two sending and receiving
instruments, one in the up and one on the down
line of tubes. The carriers for the reception of
telegrams, letters, ite., consisted of small cylinders
made of gutta-perclia, papiermachie, or tin,
covered with felt, drugget, or leather. It WM
found in practice that the carriers need not fit
the tubs-sot all aecurately. Mr. Culley, M. Inst.C.E.,
chief engineer of the Post Office Telegraphs, hail
adopted the block system, such as was used on railways
for working the tubes. The bital length of line now
working hi Is intim, from Telegraph-street to the West
Strand tithe- and back, W:131; MN/ yards. It was found
by experiment that the specs liii the carrier was much
greater as itamiroached the vacuum end thetube than
it was at the other end. The necessity of having a
steam-engine with air pumps and reservoirs was
a great hindrance to the general introduction
of pneumatic tubes, but this inconvenience had
been successfully removed by the construction
of an exhausting apparatus working by the direct
action of steam upon a current of air. In this ex-
hausting apparatus the steam from a boiler was
made to issue, in the form of a hollow cylinder,
fri on an angoular nozzle placed in the centre of the
apparatus, the opening having a width of about Inc
millimeter all retina. The steam issuing in this form
had the greatest possible surface, both inside all.l out,
for contact with the air in the apparatus, which air was
in connection with, 11,12 a was drawn from, the pneumatic
tubes. With one cif these exhausters a vacuum equal
to a column of 23 inches of mercury was obtained
with a less expenditure of steam than would be
required to work a steam engine and lump to effect
the same object. The principal recommendation of
the steam exhauster, besides its extreme simplicity and
the small space it occupied, was its cheapngss if con-
struetion, DA the cost only amounted to about one
twentieth part if an engine and pumps. Up to the
present time, so far as the public was concerned, the
pnemnatic tubes in London, Berlin, and Paris had
only been used for the conveyance of telegraphic
messages, but the British Post Office authorities hail
alreuly considerel the quest* whether it would not
Is' advantageous to have the letter post service in
London executed by means of pnenmatic tubes. With
such a system of distribution an accumulation of letters
at principal offices would be entirely avoided.