(((Dan Howland remarks: The following essay, in true Victorian style, is more than a bit windy, but this very specific article could aid in exhuming many early pneumatic mail systems. Some paragraphs have been re- arranged for clarity.)))
"The transmission of matter through closed tubes by means of a current of air flowing therein is not by any means a novel idea, although its successful application to commercial purposes is of recent date. For the earliest suggestion of pneumatic transmission we must go back to the seventeenth century and search among the records of that venerable institution, the Royal Society of London.
"Here we find that Denis Papin presented to the society in the year 1667 a paper entitled the 'Double Pneumatic Pump.' He exhausted the air from a long metal tube, in which was a traveling piston which drew after it a carriage attached to it by means of a cord.
"At the close of the eighteenth century a certain M. Van Estin propelled a hollow ball containing a package through a tube several hundred feet long by means of a blast of air; the device, however, was regarded more as a toy than a useful invention.
"Of more practical value were the plans of Medhurst, a London engineer, who published pamphlets in 1810 and 1812 and again in 1832, when he proposed to connect a carriage running inside the tube with a passenger carriage running above it."
(((Jules Verne's recently unearthed 1863 novel, *Paris in the 20th Century* proposed a similar transit system, in which a train would be pulled by magnetic attraction to a metal object in a pneumatic tube.)))
"The distinction of being the first city to install a practical pneumatic tube system belongs to London, where in 1853 a 1 1/2 inch tube was laid between Founder's Court and the Stock Exchange, a distance of 220 yards. The Carrier was drawn through the tube by creating a vacuum, a steam pump being used for the purpose. The roughness of the interior of the iron tubes gave much trouble, and when subsequent extensions of the system were made in 1858 and later, 2 1/4 inch lead tubes were used, the carriers being made of gutta-percha with an outer lining of felt."
((("Gutta-percha" is a sort of early plastic made from the latex of Malaysian trees; it is not the punchline to a Chico Marx joke about fishing.)))
"The London system has grown steadily and now includes 42 stations and 34 miles of tubes. The latter are of cast iron and lined with lead. On the shorter lines, the inside diameter is 2 3/16 inches, and on the longer lines, 3 inches. The lines are laid out radially, air being compressed at one end and exhausted at the other. Similar systems are used in connection with the telegraph service in Liverpool, Manchester, Birmingham, Glasgow, Dublin and Newcastle.
"Mention should be made here of the underground pneumatic railways constructed in London, the first built in 1863, 1,800 feet in length and 2 feet 8 inches by 2 feet 8 inches in section; the latter tunnels built in 1872, running from Euston Station to the general post office, a distance of 2 3/4 miles. The latter was in duplicate and D-shaped in section, measuring 4 1/2 feet wide by 4 feet high, the straight portion being of cast iron and the bends of brick. It was operated by a fan which forced air into one tunnel and exhausted it from the other. The capacity of the line was about one ton per minute. It was not satisfactory and was ultimately abandoned."
Dan Howland (email@example.com)