Pneumatic messaging blows cylindrical carriers in tubes, carrying messages and small items in closed systems, which were pioneered and developed in London in the 1850’s, ironically to support a new electric communications technology, the telegraph.
Britain’s first telegraph line went from Paddington to Slough and made headlines in 1844 when it transmitted the news of the birth at Windsor of Queen Victoria’s second son, Prince Alfred, to London. But it was several years before this technology would catch on outside the railways (which used them to pass train running information along the line). After being exhibited in the Great Exhibition of 1851, telegraph use took off in Britain, providing London with near-instant communication with other cities. Once the first telegraph submarine cable linked England and France and other parts of Europe in 1852, London was connected near-instantly with its neighbouring countries. Telegraphy exploded following the similar exponential network growth curve that steam railways had just experienced. As about half of the telegrams were for stock and commodity prices, and a further third being business related (the remainder were to do with personal or family matters, telegraphy was rapidly changing the nature of society. It was the internet of the Victorian age.
Telegraph Bandwidth Limitations
As the popularity and volume of telegraph messages increased, many telegraphy companies established branch offices around central London to assist in collecting and distributing telegram communications. But telegraph offices in London were becoming inundated by telegrams during the day, causing backlogs. And whilst telegram messages travelled at great speed between cities, forwarding them a few hundred yards in the heavily crowded streets of London via messenger boys could take hours and sometimes over a day. Hiring more of the expensive telegraph operators to retransmit telegrams locally was not seen as cost effective at all, as they were often idle at branch offices.
Non-Electric but Pneumatic Solution
Surprisingly, it was a non-electric pneumatic tube, designed and constructed by engineer J Latimer Clark, which sent telegrams more cheaply and quickly within cities themselves. Clark built the world’s first practical pneumatic tube that carried messages in carriers in 1853, between the Electric and International Telegraph Company headquarters (called the Central Telegraph Station) on Telegraph Street in Lothbury and their offices at the Stock Exchange on Threadneedle Street. Half of all telegrams in London were being sent between these two offices.
The tube used was 1½inch in diameter, with messages conveyed in felt bags pulled by the air vacuum generated by a 6 horse power (hp) steam engine. Telegrams were sent from the Stock Exchange 675 ft. to the Central Telegraph Station, with the carriers being returned by hand.
All manner of carrier construction and material was tried – leather, felt, vulcanised fibre, celluloid, aluminium and brass. By much experimentation it was determined that carriers made of gutta-percha (an early kind of plastic made from the latex of Far East trees) with an outer lining of felt or leather for less friction were the most durable. The diameter of the cylinder was slightly smaller than that of the tube to enable it to traverse bends, and had a felt skirt to provide the air seal. Being the pioneering installation, there were problems with carriers getting stuck, especially in curves, but these issues were progressively worked through. The engine pulled the carrier with up to six telegrams the distance in 30 seconds, half the time it took to send an average telegram.
Latimer Clark was later one of the principal drivers behind the London Pneumatic Despatch Company, the pneumatic tube mail railway that opened in 1863, a topic to which we will return in a later article over on our sister site, London Reconnections.
Pneumatic Message Advantages
Pneumatic tubes (or telegraph tubes as they were also known) saved cost because they did not require skilled, well-paid telegraph operators, and they eliminated mistakes that often occurred in re-transmission. Pushing a carrier into a pipe requires much less skill. There was also no error in transcription, which was a frequent occurrence, and cash, documents and other small objects could be conveyed securely. As telegrams could be sent in a pneumatic tube carrier faster than post and cheaper than telegrams, as well as being faster and cheaper than a messenger, it is perhaps no surprise they soon became a popular method of communication.
The next tube, the Electric and International Telegraph Company built, in 1858, was over ten times longer at 3,120 ft. Powered by a much bigger 20hp engine and using a larger 2¼ inch diameter tube for greater message capacity, it linked up another office in Mincing Lane, just west of Fenchurch Street station.
In 1860 the Electric and International Telegraph Company systems linked their new, larger Lothbury central office with a station at Cornhill near the Bank of England. Many other pneumatic tube lines were soon installed radiating out from this office, laid in pairs, one up and one down.
The former headquarters of the Electric & International Telegraph Company (known as the ‘Electric’) near the GPO was used until the Central Telegraph Office moved there in 1874, (The English & Irish Magnetic Telegraph Company being known as the ‘Magnetic’).
Longer and busier lines were built with 3 inch diameter tubing, such as the Messrs. Siemens Bros. line installed for the Post Office under the streets between the Central Telegraph Station and the General Post Office (GPO). It was completed in 1870, and soon extended to Fleet Street and Charing Cross.
Nationalisation of the Telegraph Network
Several private telegraph companies handled telegraphy, but given the importance that telegraphy communications was starting to have, the government in 1868 passed the Telegraphs Act to nationalise inland telegraph companies and incorporate these communications within the Post Office. This is a rare case of the laissez faire economic policies of the era being set aside for national interests, and demonstrates the key role that the government viewed for the new communication medium.
State acquisition was made in combination with a standard one shilling for 20 words inland rate telegram, and introduction of telegram services to Post Office branches throughout the country. This greatly increased the reach of telegraph communications, and required a number of new pneumatic tubes to be installed in London.
Central Telegraph Office – It’s Quicker by Tube!
Indeed the success and growth of telegraphy meant that the Electric’s Telegraph Street office had become grossly overcrowded by the time of nationalisation, and so the new Post Office begain construction of a new building to act as their new Central Telegraph Office (CTO). This was completed in 1874, with the Post Office persuading the City to rename Bell Alley, on which the CTO was sited, to “Telegraph Street.” The CTO was designed to be the hub of both the British telegraph network and the London pneumatic tube network. The latter simplified work at branch offices, as well as expediting communications at GPO West itself, the official (albeit rarely used) name for the CTO.
In fact it is fair to say that the CTO could not function without the extensive in house tube system, which initially comprised 12 tubes. Even telegrams transferred on the same floor went via the tubes for more efficiency, which avoided the confusion of messengers gathering around the message-sorting and routing desks.
Telegraph operators formed an exclusive but unofficial community closed to themselves, forming the world’s first online community. They observed a strict hierarchy, as befitting the British class structure, that developed from the fact that the fastest and best operators worked in London at the busiest offices, with slower less accurate ones working progressively further out. Furthermore, operators had their own lingo and secrets. This caused concern for the businesses using telegraphs over the privacy of the messages.
Given that half the messages were sent by businesses, and many of those concerned stock and commodity prices, pneumatic messages were faster, more secure and more reliable than telegrams within cities. Telegrams were often forwarded on from station to station numerous times to reach their destination, and thus were seen by many eyes. Hence business and government readily took to the more secure pneumatic tubes as this reduced the number of individuals who read their messages.
Eventually, nearly all branch telegraph offices were connected directly to the CTO via pneumatic tubes but with only a few intermediate stations. The Post Office Engineer-in-Chief calculated that trunk 3 inch tubes, with cylinders carrying up to 55 telegrams that could be sent every 10 to 30 seconds (depending on the distance), was the equivalent of seven telegraph wires and 14 operators working at peak efficiency.
Furthermore, most carriers were not sent full, so the tubes handled message surges much better than the serial telegraphy system. This was demonstrated during the run-up to, and events of, the Franco-Prussian War which broke out in July 1870. This threatened to (and actually did) destabilise the European balance of power, which had lasted since 1815. So pneumatic tubes were a critical part of London’s, the country’s, and the Empire’s economic and government communications network.
By 1875 the CTO had 450 telegraphic instruments on three floors, linked by 68 pneumatic house tubes in a highly integrated system. The longest internal tube transit time was only 10 seconds. The London system grew steadily and the Post Office had at one point 11 miles of house tubes and 74 miles of street tubes, connecting cable companies, branch offices, two railway termini, a bank, and three newspapers on Fleet Street. By 1891 over 32 million telegrams a year were being sent world-wide. Half of which were sent in the United Kingdom, with half of those passing through the CTO in London.
Indeed such was the continued growth of communications that a fourth storey was added to the CTO only 10 years after its construction, enlarged twice in 1901 and 1902, then a fifth storey added in 1930. At its busiest it had a staff of 5,000 working around the clock, connecting all corners of the Empire as part of what became known as the “All Red Line.”
This was the informal name for the network of telegraph lines that connected London with the Empire, so named because on many political maps, the British Empire was coloured red. The government felt the All Red system should land only on British controlled soil for security purposes, and the network was designed with so many redundancies that 49 cuts would be needed to isolate the United Kingdom. The 1911 Committee on Imperial Defence report stated that the Imperial Wireless Chain should only be a reserve to the All Red Line, because enemies could interrupt or intercept radio messages. Despite its great cost (2 million at the time) the telegraph network succeeded – British communications remained uninterrupted during World War I, whilst Britain quickly succeeded in cutting Germany’s worldwide network.
Technology Spreads to Other Cities
After London’s pioneering development, similar systems were installed in the provinces, starting in 1864 in Liverpool. This system was also the first in which messages could be sent in both directions: carriers were propelled by compressed air in one direction, and a vacuum in the other. This technique became common for use on systems with lower volumes.
London’s successful pneumatic tubes soon spawned similar systems in Berlin (1865), Paris (1866), and Vienna (1867), followed by most major European and US cities. By the 1870’s similar systems were operating in every modern major city of the world.
Pneumatic communications were seen as being the next big technology, following steam traction and the electric telegraph. Jules Verne’s “Paris in the Twentieth Century” of 1863 included pneumatic tube trains that stretched across oceans, and his later “The Day of an American Journalist in 2889” depicted submarine pneumatic tubes carrying people faster than aeroplanes, due to the vacuum providing less friction.
Eventually, paris developed a more intensive pneumatic network that operated more like an express post, allowing the bleu envelopes to be mailed from mail boxes, post offices, and even from boxes mounted on the rear of trams, to be unloaded at the end of the line.
Refining the Technology
By 1874 an extensive system of telegram tubes was in place, linking the Central Telegraph Office on St. Martin’s le Grand with London’s district post offices, distributing around 4.5 million messages annually. By 1886 London had 94 telegram tubes totalling 34½ miles, powered by four 50 hp. engines, connected to 70 Post Office branches. Several tubes remained privately-owned at that time and were leased by the GPO. Businesses and individuals could simplify addressing of telegrams by purchasing and renewing a unique one word telegraphic address, that would enable the sender to omit (or forget) the full postal address. An example is SCOPO, for a patent law firm near Chancery Lane. As such telegraphic addresses can be seen as forerunners of today’s internet domains and email addresses – a simple way to find and contact a company or individual.
Pneumatic Tube Types
Three types of pneumatic tube systems were eventually implemented: street, house and ticket tubes, as well as related but simpler voice tubes.
Street tubes were made of lead, laid within iron ducts for protection one to two feet under the street between branch post offices to the CTO (from whence they were telegraphed). Remarkably, many of these tubes are still intact, today often housing telecoms cables. Most tubes were 2½ inches in diameter, with 3 inch diameter tubes being used for heavily trafficked lines. There were a few light 1½ inch tubes which carried 5 telegrams per carrier, whilst the 2½ inch carriers could hold 30 messages, and the largest held up to 55. The carriers reached an average speed of 30 feet per second or 20mph and could be dispatched every few seconds in short tubes or every 30 or 40 seconds in long tubes. Street tubes required pressures of up to 12 lb. per sq. inch above ambient. By the 1930’s, two electric compressors replaced steam engines to power all of the street tubes in London.
House pneumatic tubes sent message carriers between different parts of the same or adjoining buildings. Usually 1.5 inch diameter, they were installed and used in a great number of private and government offices. In Post Office branch offices, house tubes were also used to pass telegrams from the public counter to the instrument room. House tubes ran in loops, to allow external messages to both be sent and received, as well as handling internal communications.
As mentioned above, house tubes were soon installed in telegraph offices themselves to pass messages more quickly and efficiently between the hundreds of workers. In 1875 the CTO had 450 telegraph instruments on three floors, grouped by Metropolitan, Provincial and International lines, all interconnected by 68 house tubes for transferring messages and tracking charges. House tubes were also later installed in some telephone exchanges for sending fault dockets from test desks and switchrooms to apparatus rooms.
Shorter house tubes were powered by hand pump (when the tubes were short and the traffic light), necessitating physically fit men, vetted before hiring by the company doctor. Later some house tubes were supplanted by electric power.
It was estimated that over one hundred house tubes were in use in London, in post offices, telegraph and telephone exchanges, as well as later on in department and large stores for secure cash handling.
Pneumatic tube systems were also built into larger Royal Navy ships such as battleships and aircraft carriers, connecting the wireless telegraphy (as it was called in the Navy), the bridge, the engine room and other parts of the ship, as one of numerous communications systems for redundancy.
Telephone systems as we know today were introduced in the early 1880’s, and although capable of much greater bandwidth than telegraph, the two forms co-existed, and were still supplemented by pneumatic communication. Specifically, pneumatic ticket tubes were installed in telephone exchanges to book and forward telephone calls.
The first Post Office ticket tube installation was in the London Trunk Exchange in GPO South, Carter Lane, EC1 in 1911. The tubes were of a slim rectangular design, 2 5/8″ x 3/8″, and dispensed with the carrier altogether, using instead hard paper dockets that were written on, bent up to form a sail, then blown through to set up and route calls. Once the call was placed, the docket was then sent with the time and duration of the call to the accounting office to record the call’s charge. Ticket tubes also conveyed fault dockets between switchboards and the apparatus rooms. Several dockets could be sent in quick succession, typically 12 per minute but more was possible at a higher risk of blockage. The average number sent in a day was 15,000. The Post Office estimated that this system saved five operators.
In the 1930’s with the rapid growth of the telephone network, hundreds more ticket tubes were installed in GPO South.
Voice Pipes and Speaking Tubes
Steam powered ships were much noisier and larger than their sail powered predecessors,which meant that traditional shouting of navigational commands no longer worked. Scientific American of May 1897 wrote:
A form of speaking tube for use of steamers has recently been introduced in England. The peculiarity of it lies in the fact that the pipe is insulated from the body of the ship by a covering of waterproof textile material. This latter, being a very bad conductor of sound, enables long lengths of tube to be used without rendering the speech transmitted inaudible at the far end. The distance from the bridge to the engine room on the steamer India is over 300 feet, yet even with the engines running it is possible to hear clearly in the engine room, through the tube there fitted, orders given on the bridge. An electric call is fitted, as the ordinary whistle cannot be used for so long a length of pipe.
Shipboard electric telephones were still a couple decades in the future, so a simple version of tubes were developed as voicepipes in the 1890s (again by the British) to provide shipboard communications.
The maritime term was voicepipe whilst those on land were called speaking-tubes. Systems typically had a removable whistle plugged into each end, to be blown from the other end to announce impending communication, hence the expression “I’ll get him on the blower”. Some longer voicepipes had an electric buzzer and wire installed alongside to signal the desire to communicate.
Shipborne voicepipes had to compete with the noise of machinery and weather, which is why they had a larger diameter than speaking tubes. Acoustic losses in a tube are due to viscous friction between the vibrating air and the walls of the tube. On doubling the tube diameter, the wall area for a given length is also doubled, but the mass of air in that length is quadrupled, thus a bigger tube has lower sound loss. Increasing the diameter of the pipes, however, would decrease the intelligibility of human speech, due to the relationship between the frequencies of typical speech and the frequencies of sound attenuated within the larger tube. The attenuated affect of the voicepipe tube on the voice can be heard on the Beatles’ song ‘Yellow Submarine’.
Early open cockpit aeroplanes, where wind and engine noise made normal speech between pilot and observer/gunner impossible, also had voicepipes.
Terrestrial speaking tubes in contrast were short pipe runs in a relatively quiet environment, so had smaller 1-2 inch diameter tubing than the sea-going version, which was also easier to conceal in walls and under floors, and didn’t require acoustic insulation. They were used in offices to contact different departments, in affluent houses to contact servants and in expensive cars to speak with the chauffeur.
Wire Pulley and Conveyor Complementary House Systems
Wire carriers with baskets, cash balls, miniature cash railways, multiple-wire and band conveyors were also installed within and between rooms of larger telegraph offices for transferring messages for onward transmission. Wire carrier and cash ball systems were installed in stores for the delivery of cash, bills, and small merchandise items.
The result was Victorian engineering deluxe and a modern retro-Victorian steampunk’s delight of telegraphs, pneumatic tubes, telephone tubes and overhead wire baskets shuttling messages overhead, underfloor, and through walls hither and thither to expedite messages as part of a well-engineered information and message processing and routing centre.
Pneumatic Tubes into the Twentieth Century
The CTO, with its pneumatic tubes still working but its telegraphs augmented by the telephone system, was still considered the communications hub of the country and empire in the mid-twentieth century. So important was it still to the British economy that it was deliberately and successfully targeted by the Luftwaffe, badly damaging it in December 1940, which affected the pneumatic tube network as well. Fortunately seven of the street tubes were transferred to the reserve King Edward Post Office building nearby within the year. The full tube network was restored after the war along with the reconstructed CTO.
Government Pneumatic Tubes
Up to 1859, the British Foreign Office had to send telegrams to the telegraph office like any other individual or company. In 1878 London’s longest street tube section of four 3″ tubes was completed, connecting the House of Commons and the CTO, with an intermediate station at West Strand, a distance of 2 miles 353 yards. Two tubes went via the Strand and two via the Bazelgette Embankment. At the same time, the Post Office took advantage of the street excavation to lay revenue earning pneumatic tubes for newspaper companies along Fleet Street.
By 1870 telegraph lines were installed at the Foreign and Colonial Offices, and submarine cables were starting to reach most continents. This effectively centralised power and decision making in London. No longer were commanders and governors in the field required to take the initiative to make decisions, being weeks or months away from London. Event reports and decisions could be sent around the world in near real time.
A self-contained government-only pneumatic tube network connecting offices all along Whitehall, with its hub in the basement of the War Office, was started between the House of Commons and the Press Bureau in Whitehall with the Press Bureau terminal, to connect to the Central Telegraph Office in 1918. By World War II the government tubes sub-system had been expanded connect 10 Downing Street, the Cabinet War Office, the Admiralty and the Home Office, to the Foreign Office, the Colonial Office, the India Office, the Treasury, and several branch telegraph offices. A separate 13″ by 5″ rectangular tube system for document box files was built between the War Office, the Montagu underground bunker, Quarter Master General House and Metropole which transported 50,000 documents a day. The total cost of the government sub-centre network was about £60,000, but was deemed to save thousands of pounds a year in communication costs, with unknown thousands more in the more expeditious handling of events.
The Goodge Street North deep shelter in its role as Supreme Allied Command Headquarters was also connected by a Lamson street pneumatic tube system to Churchill’s Cabinet War Rooms under Whitehall (Lamson being the premiere British pneumatic tube company starting around 1900). The tube terminals can still be seen by the public in the Cabinet War Rooms.
Telephone cable tunnels had also been dug between various government buildings by 1940, but despite this the pneumatic tubes were still intensively used for sending documents, plans, and maps.
It is not known how long these government tubes were used after the war, but some may still be in service today, as they are secure, unjammable, and not susceptible to electronic eavesdropping or electro-magnetic interference.
The book ‘The Official History of Britain and the European Community’ writes of a pneumatic tube system which ran between 10 Downing St and the Foreign Office as recently as 2003. Peter Stothard’s “Thirty Days: An Inside Account of Tony Blair at War” describes the underground Foreign Office in operation:
A young team of shift-workers, operating both encrypted computers and antique compressed-air communication tubes, gathers intelligence, turns it into memoranda and tries to make sure that the right people read it.
There was also a house tube system in the House of Commons, which may still be operational.
The Post-War Post Office Tube Network
In 1957 the CTO street tube network was still quite large, even though it carried only 10,000 telegrams a day versus the 50,000 a day in 1909, and connected:
- 40 Post Office district and branch offices
- 2 Postal Sorting Offices
- 2 Railway station post offices
- 3 Post Office service departments
- 1 Post Office accountants department
- 3 Newspapers
- 1 Bank
- 3 Cable companies
- War Office sub-centre of 6 offices including the House of Commons
Pneumatic Tubes Today – Pneumatic Age to the Space Age
By the later half of the twentieth century the popular image of pneumatic tubes had changed from seeing them as a technological marvel of the nineteenth century, to them being a symbol of bureaucracy, as they were primarily used by governments and large businesses. George Orwell’s “Nineteen Eighty-Four” character Winston (like his namesake in the Cabinet War Rooms) used pneumatic tube communications, in the novel to rewrite history based on newspapers delivered by tube.
Despite this the London street tube system remained in use till 1962, when it was shut down, having been superseded by telephone networks, telexes and teleprinters. Some of the pneumatic tubes were later used to house telecommunications cables, but most were abandoned and forgotten. Many of the house and ticket tubes likely continued in use for longer, but few records were made of their fate.
In the end the Post Office pneumatic tubes had worked reliably, effectively and economically for a century but telephones and modern communication methods have all but rendered them obsolete. Today your chances of finding a pneumatic tube system in operation are small, although search around and you will find them – mainly for niche applications of speed and/or security for items that cannot be sent electronically.
Pneumatic tubes are still being built into new hospitals for example. They are used to rush samples, medications, x-rays, and reports between labs, operating rooms and nursing stations far faster than a person could do on foot (which can be life critical) and less laboriously. Some banks also still use them to transport documents and money, whilst large stores do so to send receipts and cash securely to safes. Even some large libraries still use them to send request slips. Finally, small tubes send very short half life radioactive isotopes very quickly in nuclear reactors, and even Nasa’s original Mission Control Centre in Florida (until the mid 1960’s) had pneumatic tubes to connect controller consoles with support rooms.
The London pneumatic tube network may be gone and forgotten, but little outposts of the technology that once powered it still remain.
I would like to thank David Holt and Graham F for their excellent contributions and assistance in the writing of these articles.