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 since the vehicle would be large
enough to require tracks, this became known as a pneumatic railway.</p>
<p>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. <enttype='PERSON'>Medhurst</ent>
did try to raise capital to implement this system, but failed.</p>
<p>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 1830's and 1840's that the steam
railway was shown to be practical in both engineering and financial
senses.</p>
<p>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.)</p>
<p>The success of the 1830's railways gave rise to the <enttype='ORG'>Railway</ent> Mania
of the 1840's, 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:</p>
<p> * The <enttype='GPE'>Dublin</ent>&<enttype='GPE'>Kingstown</ent>, from <enttype='GPE'>Kingstown</ent> to <enttype='GPE'>Dalkey</ent> in <enttype='GPE'>Ireland</ent>,
1.5 miles long; operated 1844-54.
* The <enttype='GPE'>London</ent>&<enttype='GPE'>Croydon</ent>, from <enttype='GPE'>Croydon</ent> to <enttype='ORG'>Forest Hill</ent> in <enttype='GPE'>London</ent>,
<enttype='GPE'>England</ent>, 5 miles, then extended to <enttype='ORG'>New Cross</ent> for a total
of 7.5 miles; operated 1846-47.
* The <enttype='GPE'>Paris</ent> a St-Germain, from Bois de Vezinet to St-Germain
in <enttype='GPE'>Paris</ent>, <enttype='GPE'>France</ent>, 1.4 miles long; operated 1847-60.
* The <enttype='GPE'>South Devon</ent>, from <enttype='GPE'>Exeter</ent> to <enttype='GPE'>Teignmouth</ent> in <enttype='GPE'>Devonshire</ent>,
<enttype='GPE'>England</ent>, 15 miles, then extended to <enttype='ORG'>Newton</ent> (now <enttype='ORG'>Newton</ent> Abbot),
20 miles altogether; operated 1847-48.</p>
<p>I note in passing that while I (as a fan of his) might like <enttype='GPE'>Isambard</ent>
Kingdom <enttype='ORG'>Brunel</ent> to have invented the atmospheric system used on the
<enttype='GPE'>South Devon</ent>, it is wrong to say that he did so. He did choose it
and actively promoted it (well, "actively" is redundant with <enttype='ORG'>Brunel</ent>).
It was actually developed by <enttype='PERSON'>Samuel Clegg</ent> and <enttype='PERSON'>Joseph</ent> and <enttype='PERSON'>Jacob Samuda</ent>.</p>
<p>Both of the longer, if shorter-lived, English lines used atmospheric
propulsion in both directions of travel, whereas the <enttype='NORP'>French</ent> and <enttype='NORP'>Irish</ent>
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).</p>
<p>All four lines were converted to ordinary steam railways in the end,
and for the next 130 years the atmospheric system appeared dead.
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!</p>
<p>(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.)</p>
<p>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.)</p>
<p>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.</p>
<p>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. The next atmospheric railway
to open actually appeared in 1990!</p>
<p>While the 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
by extensions, as well as competition in the form of the <enttype='GPE'>Metropolitan</ent> District <enttype='ORG'>Railway</ent>, a subsidiary that got away. (Their
routes in central <enttype='GPE'>London</ent> today form the <enttype='GPE'>London</ent> Underground's
<enttype='GPE'>Metropolitan</ent>, District, Circle, and <enttype='GPE'>Hammersmith</ent>& City Lines.)</p>
<p>Now there was no thought of operating the <enttype='GPE'>Metropolitan</ent> with
anything but steam locomotives, despite the line being mostly
in tunnel. Sir <enttype='PERSON'>John Fowler</ent>, 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
Encyclopedia of <enttype='ORG'>Railway</ent>s", 1976 edition, by (C.) <enttype='PERSON'>Hamilton Ellis</ent>,
<enttype='ORG'>Hamlyn Publishing</ent>; ISBN 0-600-37585-4; some details came from other
books or my memory.</p>
<p>The information about the <enttype='GPE'>Djakarta</ent> line comes from two postings in
rec.railroad, one last November by <enttype='PERSON'>Andrew Waugh</ent> quoting the November 24
issue of "<enttype='ORG'>New Scientist</ent>" magazine, and the recent one by <enttype='PERSON'>Russell Day</ent>
citing "Towards 2000".</p>
<p>--
<enttype='PERSON'>Mark Brader</ent>"Great things are not done by those
SoftQuad Inc., <enttype='GPE'>Toronto</ent> who sit down and count the cost
<enttype='ORG'>utzoo</ent>!sq!<enttype='ORG'>msb</ent>, <enttype='ORG'>msb</ent>@sq.com of every thought and act." -- <enttype='PERSON'>Daniel</ent> Gooch</p>
