The New Yorker: “The walls of the Central Intelligence Agency’s original headquarters, in Langley, Virginia, contain more than thirty miles of four-inch steel tubing. The tubes were installed in the early nineteen-sixties, as part of an elaborate, vacuum-powered intra-office mail system. Messages, sealed in fibreglass containers, rocketed at thirty feet a second among approximately a hundred and fifty stations spread over eight floors. Senders specified each capsule’s destination by manipulating brass rings at its base; electro-mechanical widgets in the tubes read those settings and routed each capsule toward its destination. At its peak, the system delivered seventy-five hundred messages each day.

According to oral histories maintained by the C.I.A., employees were saddened when, in the late nineteen-eighties, during an expansion of the headquarters, this steampunk mail system was shut down. Some of them reminisced about the comforting thunk, thunk of the capsules arriving at a station; others worried that internal office communication would become unacceptably slow, or that runners would wear themselves out delivering messages on foot. The agency’s archives contain a photograph of a pin that reads “Save the Tubes.”

The C.I.A.’s tube system is a defining example of one of the major technological movements of the twentieth century: the push to create what communication specialists call “asynchronous messaging” in the workplace. An interaction is said to be synchronous when all parties participate at the same time, while standing in the same room, perhaps, or by telephone. Asynchronous communication, by contrast, doesn’t require the receiver to be present when a message is sent. I can send a message to you whenever I want; you answer it at your leisure…”