The weekly democratic statesman. [volume] (Austin, Tex.) 1871-1883, 1873-12-18
pAvis's MAJoRfrIEs.
The Pneumatic Dispatch.


The London Times of November 10, has
an article which gives an account of the orr
gin and development of the pneumatic dis.
patch system in England, and then goes on
to describe the great pneumatic dispatch
tube in the heart of London. Itsays: The
pneumatic tube extends from the London
and Northwestern railway station at Euston
square to the general postoffice in st. Mar
tin's-le-Grand. The central station IS in
Holborn, where is also the machinery for eff
fecting the transit of the trains. Here the
tube is divided, so that in effect there are
two tubes opening into the station, one from
Euston to Holborn, and the other from the
postofiice. The length of the tube between
Holborn and Euston is three Thousand and
eighty yards, OF exactly a mile and three
quarters, greater length than was original
ly contemplated, but which was rendered
necessary by the avoidance of certain pro-
perty on the route. The tube is of a fiat
tened horseshoe section five feet wide and
four feet six inches at the center, having a
sectional area of seventeen square feet. The
straight portions of the line are formed of a
continuous cast-iron tube, the curved lengths
being constructed in briekwork, with a
facing of cement. The gradients are easy /;
the two chief arc one in forty-iive and one
in sixty, some portions of the line being on
the level The sharpest curve is that near
the Holborn station, which is seventy feet
radius. The tube between Holborn and tho
postoffice is sixteen hundred and fiffy-eight
Yards in length, or one hundred and two
yards less than mile, and is Of the same
section and similarly constructed TO the first
length.
Two gradients Of one in fifteen occur on
the postoffice section, but this steep inclina-
ton is in no way inimioal to the working of
the system. The Holborn station is stu
ated at right angles to the line Of the tubes,
which are therefore turned toward the sta
ton into which each opens All through
trains, therefore, have to reverse there, and
this is effected in a very simple manner by
a self-acting arrangement. A train upon its
arrival runs by virtue Of its acquired mo-
mentum up short incline, at the summit Of
which it momentariiy stops, and then
quickly descends ly gravity. In its descent
it is turned on to pair of rails leading to
the other tube, into which it enters and
through which It continues its journey, the
whole process Of reversing occupying barely.
thirty seconds. Trains containing goods
for the Holborn station arc simply run down
from the TOP Of the incline on to d siding.
The wagons, or carriers, as they arc
termed, weigh twenty-five hundrcd-weight,
are ten feet four inches in length, and have
traverse contour conforming to chat Of the
tube. They are, however, Of a slightly
smaller area than tho tube itself, the differ
ence-about an inch all around being oc-
cupied by a flaDge Of india-rubbef, which
causes the carrier to ft the tube exactly, and
so as to form piston upon which the air
acts. The machinery for propeiling the
carriers consists Of a steam engine having a
pair Of twenty-four inch cylinders with
twenty-inch stroke This engine driycs D
fan twenty-five feet six inches in diameter,
and the two are geared together 81 such q
manner that one revolution Of the former
gives two Of the latter, or, IN technical
terms, the engine IS geared at two to enc
with the fan. The trains are drawn from
Euston and the postofIicc by exhaustion,
and are propelled to those points by pressure.
The working Of the fan, however, is not
reversed 70 suit these constantly varying
conditions it works continuously, tho
alternate action Of pressure and exhaustion
being governed by, valves. The engine
takes steam from three Cornish boilers
each thirty feet long and six 'fcst SIX inches
I in diameter TclcgTaphic signaling IS
carried on between the three stations by
means Of heedlc instruments.