The Washington critic., 1888-01-14
PNEUMATIC MOTIVE POWER.
Successful systems for the Propulsion
of MnlInr hA Air Erna.mrc-

Successful Systems for the Propulsion
of Matter by Air Pressure.
The first attempt to use air pressure
or air suction us a motive power for
the propulsion of objects was made by
a Frenchman named Ador, in 1852, in
the Park of Monceau. The following
year, 1858, Mr.. Latimc. Clark, at that
time engineer in charge of tho Iilcc.
trio and international Telegraph Com
pany in London, put it into practical
use by building the tube line between
the Central and Stock Exchange sta
tions of the above company Since
then countless schemes for transport
ing telegrams, mail matter, express
packages and passengers have been
given birth TO and have died.
THE LONDON SYSTEM.
In 1858 Mr.. G. +. Narley, then n
the head of the London telegraph sys-
TEN, instituted some very important
improvements, which consisted in
using compressed air TO force the car
riers in one direction, Il partial vacuum
being still used to draw them in the
other direction.
This improvement enables single
lines of pipe TO be used, both
for sending and receiving car
riers between central station
with pumping machinery and out
lying stations not SO supplied. This
system has been brought TO very
great perfection in London, in con-
nection with the telegraph depart
ment of the postofIicc. The first
tnbes used were in lengths of 10 to 20
feet, made of iron, but the English
shortly adopted leaden pipe inclosed
| in an iron one, for the reason that
lead is much more air tight than iron
| and its surface can be worn much
smoother. The iron outside pipe was
for protecting the lcaden one from ac-
cident.
The inside diameter is usually two
| and q quarter inches, though three
| inch is sometimes used. The greatest
| single length of any of the London
! lines is II ,Gl0 feet. In most cases a
| single tube serves to send and receive
carriers, but, where the traffic is
heavy, pair of tubes are used--one
TO send by pressure, the other to re-
Ceive by vacuum. The carriers are of
| gutta percha about six inches long,
! and covered with felt, which is al
lowed to project loosely at the back,
so that the pressure makes it expand
and fit the tube closely. The
engines and pumps are generally
located at the central station, though
relay machines are put in at some OF
| pt gfo In
lines there are intermediate stations
and the sections are worked on the
Block system as used on railways.
During business hours the carriers
are incessantly passing through the
tubes. With pressure of 10 pounds
to the square inch, or vacuum of
pounds, the time of transit through ;
% inch tube is | minute for l,00l
yards and 81 minutes for 5000 yards
THE PARIS SYSTEM.
Another method of working is useC
in Paris and other continental cities
This is the circuit system, in whicl
stations are grouped on loop lines o
tubes, around which the carriers trave
in only one direction. Very large area
are covered in Paris by the pneumati
tube system. Trains of carriers
coupled together like railway cars, ar
u dispatched at intervals of Is minutes
! These trains are stopped at the mail
stations of the outer loops, to leav
! off the carrier destined for that par
ticular loop, and to take on the car
rier containing the dispatches for tn
rest of the system.
i The Paris system was inaugurate,
in 1865, and has since then been YER
much extended The tubes are O
wrought iron in lengths of 10 feet
$500 inches in diameter. They ar
laid about 40inches below the surface
The carriers are cylindrical, and mad
of sheet iron covered with leather
Each one holds from 80 to 80 dis
patches. The combination of iroi
and leather is found good to eXclud
moisture, often present in the tubes
from the dispatches. A carrier vii
travel about 200 miles before it
leather covering has to be renewed
The Berlin and Vienna systems ar
very similar to the Paris one, an
need not be here described. Tn
Vienna system is now believed to b
the longest and most extensive il
Europe.
THE WESTERN UNION SERVICE.
The tube service of the Wester
Union Telegraph Company in NeV
York is much more extensive than j
generally supposed. The centre fror
which the tubes run is the big build
ing of the company at the corner o
Dey street and Broadway. From thi
point a series of four brass tubes thre
inches in diameter run up unde
Broadway to the company's buildin
at Fifth avenue and Twenty-thir
street. Two of the tubes are fo
through carriers and two are for wa,
carriers, or the branch offices locate,
along the line.
A second series of brass tubes, .
inches in diameter, runs down Broad
way, from Dey street, connecting tht
company's building at 16 and is Broat
street, and also the Cotton and Pro
duce Exchanges.
Still third series Of six tubes, L
inches in diameter, starts from De,
street and connects various newspape
Offices with the Western Union build
| ing.
The tubes are from four to six fee
under the ground, to get below tn,
frost line, which is four feet 81,
inches in this neighborhood. In tn,
cellar of the Dey street building arr
four 50-horse-power air compressors
run from a Knowles pump, who's
cylinders are is by SO inches, Tw,
of the compressors are for all th
down town lines, and two for up town
IL. 4 l.. ~ i