Diving helmet

The diving helmet emerged from a device designed for an entirely different purpose: rescuing people from burning buildings. The Deane brothers, John and Charles, had invented a smoke helmet for firefighters—a copper shell with a hose connected to a bellows pump that fed fresh air from outside the fire zone. Between 1823 and 1828, they realized that what protected lungs from smoke could also protect them from water. The first documented underwater test occurred in the River Thames near London in 1828.

The adjacent possible for practical diving required several technologies to converge. Air pumps capable of maintaining continuous pressure had been developed for industrial uses. Metalworking could produce the copper helmets and lead-weighted boots needed to counteract buoyancy. Canvas could be made waterproof. And crucially, there was economic demand: harbors needed maintenance, shipwrecks contained valuable cargo, and underwater construction was increasingly necessary.

The Deane brothers' early design was an open helmet—air continuously flowed in from a surface pump and escaped at the lower rim. This worked at shallow depths, but divers couldn't bend over without water rushing in. Augustus Siebe, a German-born engineer who had settled in London, manufactured the early prototypes for the Deanes. In the 1830s, expanding on improvements by another engineer named George Edwards, Siebe created the closed diving helmet—a design that would remain in use for over 150 years.

Siebe's innovation was simple but transformative: he sealed the helmet to a full-length watertight canvas suit and added an exhaust valve to regulate internal pressure. Divers could now work at any angle without drowning. The air supply from the surface pump maintained positive pressure inside the suit, preventing water from entering even if the diver inverted. Colonel Charles Pasley of the Royal Navy, who used Siebe's equipment to salvage the wreck of HMS Royal George, suggested making the helmet detachable from its metal collar, creating the standard diving dress that would dominate commercial and military diving until the late 20th century.

The technology enabled an era of underwater civil engineering. Divers could now inspect and repair harbor structures, lay telegraph cables on the ocean floor, and salvage ships that had previously been irretrievable. The Royal Navy adopted Siebe's equipment as standard issue. His company, Siebe Gorman, became synonymous with diving equipment—the design remained essentially unchanged from the 1830s until the Royal Navy finally retired it in 1989.

The path from smoke helmet to diving suit illustrates how technologies migrate between domains when the underlying physics is the same. Bellows pumping air through a hose to a sealed helmet solves both problems: keeping toxic gases out of lungs in a fire, keeping water out of lungs underwater. The Deane brothers saw the connection; Siebe perfected the execution. Modern scuba equipment would eventually make surface-supplied diving obsolete for many applications, but the fundamental insight—that humans could work underwater if continuously supplied with pressurized air—came from those first Thames River experiments in the 1820s.