Although best known for his proof that comets follow regular orbits around the sun, Edmond Halley was also an inventor. Halley invented and tested one of the world’s first submersible.  In this diving bell as many as four men could descend beneath the surface of water and spend hours observing life on the bottom or performing salvage operations.

Halley described his new craft in a paper he wrote in 1716 for the Royal Society entitled, The Art of Living under Water.  He began this work with an explanation of the problem. Stated simply, humans required a continuous supply of fresh air if they were to survive underwater. Halley explained that he was not certain why this was the case but there could be little doubt that it was true.  “By experiment it is found that a gallon of air, included in a bladder, and by a pipe reciprocally inspired and expired by the lungs of a man, will become unfit for any further respiration, in little more than one minute of time.”

Halley then goes on to describe a diving bell he had created. Constructed in the shape of a “truncate cone” — a cone with a flattened point — the bell had a window on its top surface to admit light, as well as a stopcock to vent stale air. The bottom of the bell was open to the water, and a bench ran around the inner circumference, about one foot from the bottom. Constructed of wood, the bell measured three feet wide at the top, and five feet at the bottom. The lower edge of the bell was weighted with lead so that the bell had a negative buoyancy and would sink even when the interior was full of air.

The diving bell was suspended by a sturdy hawser that descended from one of the spars of a British navy ship. The sailors slowly lowered the aquanauts into the watery depths, stopping at twelve-foot intervals to replenish the air supply. Halley rigged a series barrels on a rope and pulley system to carry fresh air below to the divers. As each barrel arrived, the aquanauts opened its stopcock and replenished the air in their craft.

Halley noted that with every thirty feet of descent, the water pressure compressed the air in his craft to half of its original volume. Consequently, it was necessary to stop at regular intervals to add new air to drive the water back down. The other nasty effect was that mounting pressure pressed painfully on the divers’ eardrums. “On the first descent of the bell, a pressure begins to be felt on each ear, which by degrees grows painful, like as if a quill were forcibly thrust into the hole of the ear.”  Halley noted, with increasing pressure, the ear eventually clears itself: “the force overcoming the obstacle, that constringes these pores, yields to the pressure, and letting some condensed air slip in, present ease ensues.” Halley and his men discovered that equalization happened more quickly and less painfully if the divers placed drops of warm olive oil in their ear canals before descending.

The other negative aspect of the mounting pressure was that it concentrated the air into a small space. This air quickly heated from the men’s exhalations and became “unfit for respiration.” When the air grew unpalatable, the divers vented some of it out of the stopcock in the top of the bell, and replenished it by drawing down fresh barrels of air from the surface.

The diving bell was a spectacular success. Halley reported that he and four companions had spent more than ninety minutes at a time below the water, achieving depths of sixty feet with absolutely no ill effect. Moreover, he had rigged up a watertight helmet that allowed a diver to walk outside of the bell at depth. The diver was connected to the bell by twin leather hoses — one carried fresh air to the helmet, while the other returned the diver’s exhalations to the bell. Because the air in the diving bell was pressurized by the water outside the bell, the diver had no difficulty breathing and was able to move with complete freedom.

Halley, in announcing his invention to the Royal Society, noted that the bell could be used for fishing, pearl diving, or salvage operations on sunken ships. He also anticipated that it would be useful for constructing underwater moles to serve as the foundation of bridges and other structures. And, finally, his invention opened a brand-new frontier for human exploration. The vast, underwater domain was thrown open, and awaited a brave new band of explorers.

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