(((Dan Howland remarks: here followed a description of a pneumatic subway system capable of carrying ten people.)))
"Less well known but equally meritorious was the system of pneumatic postal tubes designed by Mr. Beach at about the same period. (...)
"In 1870, also, he built an 8 inch iron tube a thousand feet long, whose interior was glazed to form a smooth surface. This lead to a large receiving box, from which a second pipe led to an exhausting engine. A letter dropped into the pipe at any point was swept along by suction due to the exhaustion of the air from the box, from which it was easily removed."
(((Illustrations show a car about the size of a backyard steam train. Above it, postal workers sort letters and drop them into slots. To maintain the difference in air pressure, at the end of each slot is a tiny revolving door, laid sideways like a paddlewheel. As the car approached, slots and tabs in the top of the car tripped the appropriate paddlewheel, dropping letters into the correct compartments of the car.)))
Dan Howland (firstname.lastname@example.org)