This strange apparatus hanging at the Cité de la Mer museum in Cherbourg, France, looks like some kind of a medieval torture device, but is actually the world’s first diving machine. And a very successful one at that.

Its inventor, John Lethbridge, was a wool merchant of Newton Abbot, a market town of Devon, England. Not much is known of his childhood or what inspired him to create a diving machine. A BBC article simply notes that John Lethbridge had a lot of mouths to feed—he had 17 children—which necessitated him to come up with an ingenious method of making money.

Before his invention, diving was conducted with the help of a diving bell which is essentially an inverted cup, or a bell without the clapper, that is lowered into the water with the person inside breathing the air that is trapped inside the chamber. The diver could come out of the open bottom, do whatever work he was sent to do, and then go back inside the bell. John Lethbridge was the first person to design a working diving suit, which he called a “diving machine”.

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The machine looked like a wooden barrel about six feet long, inside which the diver lay on his stomach. It had a round window to look outside and two holes to stick the arms out. Oiled leather cuffs around the upper arms formed an almost water proof seal. The diving machine had no air supply other than the air trapped inside before the chamber was closed. While that doesn’t sound like much, it was enough air for Lethbridge to stay underwater for thirty minutes at a time. The chamber had two air valves at the top through which fresh air could be pumped inside using bellows whenever the diver surfaced. The device was raised and lowered with the means of a cable, but Lethbridge also provided the diver with weights that he could discard and rise to the surface without assistance.

Lethbridge hoped to reach great depth but when he tested his machine he found that beyond fifty feet the water pressure caused leaks around the armholes, window and entrance hatch. Lethbridge found he could easily dive to 18 meters and up to 22 meters with some difficulty.

Despite its limits, Lethbridge made good use of his diving machine in the waters of the British Isles and elsewhere in the Atlantic salvaging valuable cargoes from underwater shipwrecks. He soon came to the notice of many London-based shipping companies such as the British East India Company and the Dutch East India Company, who employed him for salvaging work.

In 1794, the Dutch East India Company ship Slotter Hooge was en route to Java from Holland when it sank during a gale near Porto Santo on Madeira island. Of the 254 on board, only 33 survived. In the flooded hold 60 feet below were three tons of silver ingots and three massive chest of coins. Lethbridge was hired at 10 pound sterling a month, plus his expenses and bonuses. In his first attempt, Lethbridge recovered 349 ingots and more than 9,000 coins, as well as two guns. Throughout that summer he made several trips to the wreck and recovered nearly half of the lost treasure.

Over the next thirty years Lethbridge dived on a number of wrecks and made a great deal of money. From an unsuccessful wool merchant struggling to support his family, Lethbridge rose to became a man of wealth, owning the estate of Odicknoll in Kingskerswell.

Lethbridge’s original diving machine didn’t survive, but his drawings did, from which several replicas have been built and exhibited at various maritime museums across the world, including one at his hometown at the Newton Abbot.