This potential money-losing delay prompted J. Latimer Clark's 1853 installation of a 220-yard pneumatic tube between the London Stock Exchange in Threadneedle Street and the Electric Telegraph Company's Central Station in Lothbury. By 1866, there were similar installations in Berlin and Paris. Numerous other major cities followed in their footsteps, and soon the pneumatic tubes carried individual letters and letters in bulk in addition to telegrams.
Carrying letters in bulk required larger tubes than single letters or telegrams did, and sometimes you'd see pneumatic tubes at a width of 3 inches in order to carry bulk letters. The tubes themselves worked via a pressure differential -- pressure dropped in front of the pneumatic canister, which propelled it along the tube at speeds approaching 25 miles per hour. The letters and telegrams were (and still are) always creased when they arrive, as they have to be rolled to fit in a tube.
The Parisian network, which is the subject of this post, had its first tube line put into place in 1866, between the telegraph offices at the Grand Hotel and the place de la Bourse. In 1867, this was extended into a one-way hexagon between the telegraph offices of place de la Bourse, rue Jean-Jacques Rousseau, rue de Rivoli, rue des Saints-Peres, the Central Telegraph Office (rue de Grenelle), rue Boissy d'Anglas, and back to Grand Hotel.
A map of the Parisian network of pneumatic tubes from 1971..
During the decade between 1867 and 1877, a two-day tube was laid between Central and Bourse and several additional polygonal systems were hooked into the system. The system was opened to the public in 1879, and by 1881 it was decided to connect the whole of Paris to the network. The tubes that ran through the Paris sewers mainly consisted of 65-mm diameter tubing, but from 1888 on, there were more 80-mm tubes put in. The one-way tubes within the system were also swiftly replaced with two-way tubes. As of 1974, about one-third of the pneumatic post system used the larger-diameter tubes.
Sadly, the Parisian network of pneumatic tubes -- the Poste Pneumatique -- was only in operation until 1984. At its height in 1953, the network spanned 450 kilometers underground and carried 11 million pieces of mail per year.
Imagine seeing this system at its height. This huge system of pneumatic tubes zipping mail to and fro around a massive metropolis while the telegraph clicks away in the next office over. The frenetic activity as your Steampunk hero goes into the pneumatic post office to send a telegram zooming to the halls of power. Kind of cool isn't it?