Working Underwater: The Story of the Commercial Diving Industry

A replica of John Lethbridge’s diving
engine at La Cité de la Mer in
Cherbourg, France.
feet in diameter at the top, 5 feet in diameter at
the bottom and 5 feet high. With a volume of 64
cubic feet, it needed nearly 4,000 pounds of
lead sheathing to overcome its buoyancy.
Rather than using a pump to supply air to
his bell, he sent air down in weighted 36-
gallon barrels through which fresh air could
be taken in via a hose. Stale air, which he
referred to as “warm” air, was released
through a valve at the top of the bell.
“This I take to be an invention applicable to
various uses,” he wrote, “such as fishing for
pearls, diving for coral or sponges and the like,
in far greater depths than has hitherto been
thought possible; also for the fitting and
placing of the foundations of moles, bridges,
&c., in rocky bottoms, and for cleaning and
scrubbing of ships’ bottoms when foul, in
calm weather at sea.”
Halley was not interested in becoming a
professional diver, but he did personally test
his invention. He went down 60 feet and
remained submerged for more than an hour
and a half.
“…I found that I could do anything that
required to be done just under us,” Halley
wrote in describing his descent, “and that I
could, for a space as wide as the circuit of the
bell, lay the bottom of the sea so far dry, as not
to be over shoes thereon. And, by the glass
window, so much light was transmitted, that
when the sea was clear, and especially when
the sun shone, I could see perfectly well to
write or read….
However, the scientist observed that being
that deep hurt his ears “as if a quill had been
thrust into them.” Clearly, there were
additional factors in diving to be considered
other than the availability of oxygen.
While knights and nobles did the scientific
work, in 1715 an English commoner named
John Lethbridge (1678-1759) sought to
convert theory to money. As an alternative to
the diving bell, the Devonshire man had a
cooper build him a leather-sealed, wooden
cylinder with watertight portals through
which arms could protrude, making the
person inside look something like a walking
fat cigar. He called his lead-weighted
apparatus a diving engine. It was six feet long,
with a diameter of two and a half feet at the
top, 18 inches at the bottom. That gave it a
volume of about 30 gallons. Once inside,
while peering through a glass window, a diver
could descend to 60 feet (and to 72 feet “with
great difficulty”) and stay down using the air
trapped inside for about 30 minutes. Before
the diver ran out of air, the “engine” would be
pulled to the surface and the air inside
replenished with a bellows. In the advent of
an emergency, the device had detachable
weights so that it would pop to the surface if
they were released.
Though his “engine” was not an engine in the
modern sense of the word, it certainly proved to
be an economic engine. Using the wooden
submersible he invented, Lethbridge and his son
spent the next three decades doing salvage work
on shipwrecks. His contract to salvage the
sunken Slotter Hooge for the Dutch East India
Company provided that he would be paid 10
pounds sterling a month, plus expenses. Any
bonuses would be up to the “generosity of the
company directors.” While profit had for
centuries been the primary motive for risking
one’s life underwater, Lethbridge was arguably
the first commercial diver.
Sixty years after Lethbridge had his “diving
engine” built, in 1775 Edinburgh confectioner
Charles Spalding enhanced Halley’s diving bell
design, and the astronomer’s air supply
technique by developing a weight mechanism to
make it easier to lower and raise the container.
WORKING UNDERWATER: The Story of the Commercial Diving Industry
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