Atmospheric and Pneumatic Railways

Mark Brader

This is an article by Mark Brader about Atmospheric and Pneumatic Railways. I am maintaining this copy on the WWW for him, and when I get a chance, I will convert it to HTML.

Please note that Mark's email address has changed again, to <>.

The following canned article about atmospheric and pneumatic railways
was originally written in 1991 and has been edited to add information
and correct some errors in the original.

[Last modified April 8, 2003]

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The ultimate responsibility for this web page :-) belongs to George
Medhurst (1759-1827), of England.  During a period of a few years
about 1810, he invented three distinct forms of air-propelled
transport.  None of them was implemented during his lifetime;
but all of them saw use eventually, reaching their greatest extent
in the reverse order of their original invention.

Medhurst's first method involved moving air through a tube a few
inches in diameter, pushing a capsule along it; this simple idea
was the pneumatic dispatch tube.  Next he realized that if the same
system was built much larger, it could carry passengers (or freight
items larger than letters); it was natural to run the vehicle on
tracks, and so this became known as a pneumatic railway.

But would anyone actually want to ride along mile after mile inside
an opaque pipe?  Not likely.  So he then thought of having only a
piston moving within the pipe, somehow dragging along a vehicle
outside it.  He proposed several versions of this idea; in most of
them the vehicle ran on rails, so this became known as an atmospheric
railway (though a distinction between that term and the pneumatic
railway was not always observed).  The key feature of all versions
of the system was a longitudinal valve: some sort of flexible flap
running the length of the pipe, which would be held closed by air
pressure except when the piston was actually passing.  Medhurst
did try to raise capital to implement this system, but failed.

Now, while the first operable steam locomotive was built about 1804,
steam-powered trains did not see regular use for passengers for some
25 years after that.  It was in the 1830s and 1840s that the steam
railway was shown to be practical in both engineering and financial

But the same technical developments that made possible the practical
steam railway also made the atmospheric railway, if not certainly
practical, at least worth a try.  And it offered the prospect of
considerable advantages.  Since the trains wouldn't have to carry
their prime mover, they would be lighter; therefore the track could
be built cheaper, and the trains' performance would be better.
The trains wouldn't trail smoke wherever they went (and into the
passenger cars in particular), and they would also be quiet.
And if one section of the route was hilly and required more motive
power, all that were needed would be more or larger pumping stations
along that section; no need to add extra locomotives.  In short,
very much the same advantages that electricity gave a few decades
later.  (Plus one more: a derailed train would tend to be kept near
the track by the pipe and piston.)

The success of the 1830s railways gave rise to the Railway Mania
of the 1840s, when interest in railway shares reached absurd levels.
In that climate the proposers of atmospheric lines could find the
backing they needed, and four atmospheric lines opened in a period
of about 3 years.  In order of opening, these were:

     * The Dublin & Kingstown, from Kingstown to Dalkey in Ireland,
       1.5 miles long; operated 1844-54.
     * The London & Croydon, from Croydon to Forest Hill in London,
       England, 5 miles, then extended to New Cross for a total
       of 7.5 miles; operated 1846-47.
     * The Paris à St-Germain, from Bois de Vezinet to St-Germain
       in Paris, France, 1.4 miles long; operated 1847-60.
     * The South Devon, from Exeter to Teignmouth in Devonshire,
       England, 15 miles, then extended to Newton (now Newton Abbot),
       20 miles altogether; operated 1847-48.

I note in passing that while I (as a fan of his) might like Isambard
Kingdom Brunel to have invented the atmospheric system used on the
South Devon, it is wrong to say that he did so, as is sometimes done.
He did choose it for the line and actively promoted it (well, "actively"
is redundant with Brunel).  It was actually developed by Samuel Clegg
and Joseph and Jacob Samuda.

Both of the longer, if shorter-lived, English lines used atmospheric
propulsion in both directions of travel, whereas the French and Irish
lines were built on hills and their trains simply returned downhill
by gravity.  Since all were single-track lines, the one-way system
simplified the valves needed to let the pistons in and out of the
pipes at their ends (possibly while traveling at speed).

All four lines were converted to ordinary steam railways in the end.
For one thing, steam locomotive technology had too much of a head
start in development over the atmospheric system; steam railways
might have delays due to engine failure but they never had to shut
down for 6 weeks while a new design of longitudinal valve was
installed along the entire length of the route!

(The valve involved metal and leather parts and a greasy or waxy
sealant "composition".  Although stories were told about rats
eating the composition, and this probably did happen sometimes,
it wasn't really a serious thing; the biggest problems in fact
were freezing and deterioration of the leather, and corrosion
of the metal parts.)

Also, the atmospheric system was inflexible, in that if the power
requirements for a section of route were greater than estimated,
very little could be done short of splitting the section and adding
a whole new pumping station.  (All the lines used vacuum rather
than positive pressure in the pipes, which limited the pressure
differential to about 0.9 atmosphere in practice; but the valve
designs were marginal anyway and likely wouldn't have stood up
to greater pressures if they could have been used.)

What today might be seen as the most serious disadvantage of all,
the requirement for long interruptions of the motive power at
junctions, was not so noticeable in those days.  If the train
didn't have enough speed to coast across the gap, well, the
third-class passengers could always get out and push, or maybe
there would be a horse conveniently at hand.  At some stations
a small auxiliary pipe was used to advance the train from the
platform to the start of the main pipe.

There were many other proposals in those days for atmospheric
lines, but in view of these early failures, none of them were
ever built as atmospheric railways, and the atmospheric system
appeared dead.  In fact, it was nearly 130 years before another
atmospheric railway appeared!

While the first atmospheric railways were vanishing, the first
pneumatic dispatch tubes were beginning to appear; I'll get
into that later.  But from that start, the pneumatic railway
idea began to return also.  At first these were designed for
freight.  Engineers J. Latimer Clark and T. W. Rammell formed
the Pneumatic Despatch Company, which built a demonstration tube
above ground in Battersea in 1861.  This line successfully carried
loads up to 3 tons... and even a few passengers, lying down in
the vehicles in the 30-inch pipe!  With the large pipe and small
vehicles, a much lower pressure could be used, no more than 0.025
atmosphere.  Vehicles ran on a 2-foot gauge track formed right
into the tube segments, and speeds up to 40 mph were reached.

When the Post Office became interested in the system, the company
built a tunnel from Euston station north about 1/2 mile to the PO's
North-West District Office, reusing the tube segments from the
Battersea demonstration.  This entered service in 1863 and was used
until the financial crisis of 1866.

A second line more than 2 miles long was built, south and east from
Euston to the General Post Office near St. Paul's.  This used a
tunnel 4 feet wide, containing track of gauge 3 feet 8.5 inches;
The end-to-end time was 9 minutes.

The Pneumatic Dispatch Railway, as it became known, operated until
1874, but at this point the Post Office decided that the time saving
wasn't worth the cost, not to mention the risk of a vehicle becoming
stuck in the tube.  The tunnel was later interrupted in places by
Underground construction, but the surviving segments saw some use as
utility conduits.  However, gas tended to leak into them; and one day
in 1928, a workman apparently used a match to see where to plug in a
fan to blow the gas out, and instead blew it *up*, over a half-mile
length of tunnel.

(In the 1920s, when electricity was available, London got a new
driverless train system with similar sized tunnels to the PDR's:
the "Post Office tube" Railway, later renamed MailRail.  Such
systems were also built in Switzerland, which was first, and
Germany.  MailRail operated until 2003, but was then closed for
cost reasons and because most mail sorting had moved to locations
it did not reach.)

Meanwhile, while these lines were moving the mail from the streets
of London to tunnels underneath, the first underground railways
were doing the same with passenger traffic.  The first section of
the Metropolitan Railway (from Farringdon, now Farringdon Street,
to Paddington station) opened in 1863.  It was promptly followed
by extensions, as well as competition in the form of the Metro-
politan District Railway, a subsidiary that got away.  (Their
routes in central London today form the London Underground's
Metropolitan, District, Circle, and Hammersmith & City Lines.)

Now there was no thought of operating the Metropolitan with
anything but steam locomotives, despite the line being mostly
in tunnel.  Sir John Fowler, who later co-designed the Forth Bridge,
did have the idea of a steam locomotive where the heat from the fire
would be retained in a cylinder of bricks, and therefore the fire
could be put out when traveling in the tunnels.  One example of
this design, later called Fowler's Ghost, was tried in 1862.
It was thermodynamically absurd: as C. Hamilton Ellis put it,
"the trouble was that her boiler not only refrained from producing
smoke, it produced very little steam either".

In the end both the Met and the District were worked with condensing
steam locomotives: these emitted smoke as usual, but their exhaust
steam, while running in tunnels, was directed back into the water
tanks and condensed.  The tanks were drained at the end of the run
and refilled with cold water.

So people were not only willing to travel in what amounted to an
opaque tube after all, but in one filled with smoke at that!  (The
smoke problem was bad enough on the Met that they arranged for ducts
to take air from the PDR's line where they crossed; later they built
"blowholes" from the tunnel into the street.  Neither helped much.)
But then why not a tube *without* smoke?  And so the pneumatic
railway was now tried; but it never got past the demonstration stage.

The longest line to carry passengers was opened at the Crystal
Palace in London in 1864.  It used a tunnel about 9 by 10 feet,
1800 feet long.  The driving fan was 22 feet across, generating
about 0.01 atmosphere of pressure -- the larger the tube, the
lower the pressure you need.  The vehicle was a full-size broad
gauge railway car ringed with bristles; it carried 35 passengers.
The trip took 50 seconds, thus averaging about 25 mph.  Another,
smaller demonstration line was built at a fair in the US in 1867
by Alfred Ely Beach, the publisher of Scientific American.

Beach then formed the Beach Pneumatic Transit Company, which
obtained permission to build a freight-carrying pneumatic line
under Broadway in New York.  But what he actually opened in 1870
was a passenger-carrying pneumatic subway, the only one to
actually operate under a city street.  It was only 312 feet long,
from Warren Street to Murray Street.  The tunnel was 9 feet in
diameter, and was worked by a single car with a capacity of
18 passengers.

Beach tried but failed to get permission to extend the line.
It closed after some months, and New York did not get a subway
again until 1904.

In London, a pneumatic underground line was started *with* permission,
but construction was never completed.  This was the Waterloo and
Whitehall Railway, which planned to connect Waterloo station to Great
Scotland Yard, 1/2 mile away, with a 12'9" diameter tunnel passing
under the Thames.  Considering that the Thames Tunnel project of
Sir Marc Brunel and Isambard Kingdom Brunel -- now now part of
the Underground's East London Line -- had faced massive technical
and financial difficulties before its long-delayed completion only
about 20 years previously, this was no mean undertaking.

The Waterloo & Whitehall was halted by the financial crisis of 1866;
and it was never revived.  The tunnel had been started from the
Great Scotland Yard end, and had just reached the river; work on
the underwater section was beginning.  There were other proposals
for passenger-carrying pneumatic lines, but none saw construction
in that form.  (At least one, under the Mersey at Liverpool, England,
was eventually opened as an ordinary railway.  Before electrification
it used condensing steam engines like the Metropolitan Railway's.)

The next type of underground line to open in London was the Tower
Subway, which also passed under the Thames.  It was a short route,
just under the river, worked by a small cable car.  It opened in
1870 and was short-lived.  (The tunnel served as a footway for a
while after that, then was taken over for utilities after the Tower
Bridge opened in 1894.  The Thames Tunnel, conversely, had been used
first as a footway, then converted to railway use.)

After this time, electric railways began to become practical.
The next underground line to open was the City & South London,
now part of the Underground's Northern Line.  Its first section
(from Stockwell to a now disused terminus at King William Street,
replaced by the present Bank station) opened in 1890.  It used
the new deep-level tube tunnels, with more limited ventilation
than on the Metropolitan Railway, so steam was out of the question
in any case.  The original plan was for cable haulage, but instead
the new electric locomotives were tried and the line has always
been operated electrically.  The line was first built with tunnels
as small as 10'2" diameter, forcing use of rather small cars.
(The cars also had only tiny windows, on the grounds that there
was nothing to see -- so they got the nickname of "padded cells".)

All of the later lines that went into the London Underground
system, opened from 1898 onwards, were built on the same general
pattern as the C&SL, with deep-level tubes and electric traction
-- usually by multiple-unit trains, and the two lines that used
electric locomotives were later converted.  The tube lines were
generally built with tunnels of 12 feet diameter or a little
smaller; the two lines that were under 11'8.25" diameter were
enlarged in the 1920s and 1930s to that minimum.  This is still
rather small compared to most other subways in the world, and gives
the tube trains their distinctive shape.

With the success of the electric lines, the Metropolitan and
District faced the loss of traffic, and they too were converted
to electricity -- at least for the underground sections in central
London -- in 1905.  The first line of the present New York subway
system opened in 1904 and this, too, has always used electricity.
(This was the original Interborough Rapid Transit route, from City
Hall station along the present Lexington Avenue, 42nd Street shuttle,
and 7th Avenue lines, initially as far as 145th Street).  Beach's
tunnel had been almost forgotten when the crews constructing a new
subway line there broke into it in 1912.

Meanwhile, the humble original concept of the pneumatic dispatch tube
continued to develop.  The first of them, 1.5 inches in diameter,
had been built in 1853 by J. Latimer Clark; it connected the
Electrical and [sic] International Telegraph Company's office in
Telegraph Street, London, with their branch 675 feet away at the
Stock Exchange.

The key invention was J. W. Willmott's double sluice valve of 1870,
which allowed rapid dispatching of successive capsules.  It was also
possible, as had been done on the pneumatic railways, to use both
positive pressure (on the order of 1 atmosphere) and vacuum, to
drive the capsules both ways from a single pumping station.  The
tubes became quite common; many miles were built in various European
and North American cities.  By 1886 London had over 34 miles of them
for the Post Office's telegraph service alone.  In 1893 Philadelphia
became the first of five US cities to connect its post offices with
pneumatic dispatch tubes; the New York system, which operated until
1953, eventually had east side and west side tubes running for most
of the length of Manhattan, and carried up to 55% of the city's letter
mail.  In Paris, one could pay a fee for a message, sometimes called
a pneumatogram, to be sent specifically by the tube.

Pneumatic dispatch tubes were also used within large buildings, or
between a main building and outbuilding, and some survive in such uses
to this day.  Since they can carry small packages, one important use
of them has been for transporting money, between a cashier and central
office.  Methods for automatic routing to different destinations were
developed; in one system, each capsule carried one of several different
reeds so that it made a musical note as it advanced through the pipe,
and a sound detector switched the pipe according to the note.

As well as the atmospheric and pneumatic railways and their cousin the
pneumatic dispatch tube, there was a fourth way that air pressure
was used to move people or freight.  In this design, rather than a
compressed-air or vacuum pipe running the length of the route, the
vehicles themselves carried a compressed-air reservoir.  Air from the
reservoir was simply used to drive cylinders in the same fashion as
the steam from the boiler of a regular locomotive.

Streetcar lines were operated on this system in several cities in
Europe and the US.  In the French city of Nantes, compressed-air
streetcars were used continuously from 1879 to 1917.  But their
greatest use was in Paris, where they served as many as 9 routes
simultaneously; 179 double-decker compressed-air cars were built and
operated there from 1894 until 1914.  The later models of these cars
were charged with 530 pounds (weight) of air compressed into about
95 cubic feet: 80 atmospheres of pressure.  The compressed-air storage
was under the floor, and the air had to be heated before use, to keep
the cylinders from freezing up.

But the major niche for this form of compressed-air power was in indus-
trial applications such as mines, where fire was a major hazard and
compressed air was already in use for other purposes but steam was not.
(Steam was more convenient, since you can get more of it at the same
pressure from the same size pressure vessel by filling it with boiling
hot water.)  Compressed-air locomotives for this purpose lasted so long
that I wouldn't be surprised to hear that a few are still in use today.

As mentioned above, in the late 20th century the atmospheric railway
reappeared.  In 1983 in Porto Alegre, Brazil, an aviation engineer
named Oskar Coester constructed a demonstration line with unmanned
vehicles.  In 1987 he joined the Sur Elevator company in a partnership
called Sur Coester; they market the system under the name Aeromovel.
And they have had a line in service at a fairground in Djakarta,
Indonesia, since December 1989.

This line is 2 miles long, elevated, on a concrete structure.  The cars
use steel wheels on steel rails.  The air pipe is rectangular, made of
concrete, and larger than those on the 19th century lines.  The longi-
tudinal valve is made of heavy cloth-reinforced rubber.  The vehicles
are controlled remotely by computer.

In January 1997, an educational program on the BBC called Local Heroes
showed the construction of a miniature atmospheric railway, powered by
a vacuum cleaner.  A simple 2-inch cardboard tube was used first as the
pipe, and this turned out to be flexible enough to seal itself, needing
no longitudinal valve at all.  When a 6-inch tube was tried, a line of
Post-It notes sufficed to form the valve.  Young viewers were invited to
try the experiments themselves.  Of course, these constructions did not
need to stand up to the weather.

Oh yes.

Pneumatic dispatch tubes were depicted in the 1985 movie "Brazil";
Beach's tunnel was depicted, in rather distorted form, in the 1989
movie "Ghostbusters II"; the modern form of the New York subway
has been depicted in many movies, notably the 1974 one "The Taking
of Pelham One Two Three"; but I don't believe the atmospheric or
pneumatic systems have ever been depicted at work in any movie.
Clearly this needs to be rectified! :-)

References and credits.

Almost all the information in this posting about the pneumatic and
atmospheric systems comes from one book...  "Atmospheric Railways:
A Victorian Venture in Silent Speed" by Charles Hadfield, 1967,
reprinted 1985 by Alan Sutton Publishing, Gloucester, England;
ISBN 0-86299-204-4.

The information on the Nantes and Paris compressed-air streetcars is from
the Musée des Transports Urbains at Paris.  The information about Aeromovel
comes from net postings by Andrew Waugh (citing the November 24, 1990,
issue of "New Scientist" magazine), Russell Day, and Jerry Schneider.
The BBC information was found on their web site.  The information on
the PDR is mostly from an article by Roger Cline in the September 1993
issue of Underground News (published by the London Underground Railway

For other topics, I principally consulted "The Pictorial Encyclopedia
of Railways", 1976 edition, by (C.) Hamilton Ellis, Hamlyn Publishing;
ISBN 0-600-37585-4.  Some details came from other books or my memory.
Mark Brader                     "Great things are not done by those                       who sit down and count the cost
SoftQuad Inc., Toronto           of every thought and act."  -- Daniel Gooch

This article is in the public domain.

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