The Undersea World of Edmond Halley
The famous astronomer also designed the world’s first diving bell
Although best known for his proof that comets — and in particular Halley’s Comet — followed regular orbits around the sun, Edmond Halley was a scientific prodigy. In addition to applying Newtonian mathematics to comets, he charted the stars of the southern skies, searched for a method to allow sailors to calculate longitude, and attempted to calculate the age of the earth by studying the rising levels of salt in the seas. He translated Greek and Latin scientific texts into English, and when he became interested in the writings of Apollonius, taught himself Arabic to translate those treatises. Halley was an active and adventurous thinker, a largely uncredited leader of the scientific revolution, and a prodigious polymath.
He was also an inventor. In fact, Halley invented and tested one of the world’s first successful diving bells. With his submersible, 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’s Philosophical Transactions, entitled, The Art of Living under Water: Or, a Discourse concerning the Means of furnishing Air at the Bottom of the Sea, in any ordinary Depths. 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—an explanation awaited the investigation of an anatomist — 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 rehearsed some of the established methods of supplying air to a diver. Natives that he had seen in Bermuda soaked a sponge in oil, trapping air in the sponge’s vesicles. Halley deemed this impractical: a sponge was limited in the amount of air it could hold. Moreover, as the diver descended, the increasing pressure forced air out of the sponge.
Another method, he wrote, was to “contrive double flexible pipes, to circulate air down into a cavity enclosing the diver as with armor, to bear off this pressure of the water.” This would allow the diver to draw a breath. It was necessary, however, to pressurize the air at the surface with a bellows pump, otherwise the diver would not be able to breathe underwater.
Although a diver could stay below longer than a sponge diver, the system was still limited. It really didn’t work at depths much greater than fifteen feet. The water pressure made it difficult to breathe, and the diving suit, stitched together of leather or skins, was prone to leaking. If the suit tore, “water will rush in with such violence, as to endanger the life of the man below, who may be drowned before he can be drawn up.”
Clearly a better solution was required if humans were to begin exploring the seafloor.
Halley’s Diving Bell
In the second half of his paper, Edmond Halley described the 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 of thirty-six gallon 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.”
The first submariners did not know the scuba diver’s trick of clearing the ears, but, as 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 it opened a new range of underwater activities. 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. Though widely recognized for his pioneering work with comets and other astronomical phenomenon, Edmond Halley also paved the path for future undersea exploration.
Source: Edmond Halley, “The Art of Living Under Water.” Philosophical Transactions, 29 (1714–1716): 492–4992 (English modernized by this author).