The first underwater breathing regulator was invented in 1860 by the French engineer Benoît Rouquayrol, to provide assistance in escaping from flooded mines. In 1864 Rouquayrol met the naval lieutenant Auguste Denayrouze, and together they adapted Rouquayrol's regulator for use in diving. This apparatus went into mass production in 1865, and the first sets were ordered by the French Navy.
During the Second World War, Emile Gagnan – an engineer working at the French industrial gas supplier Air Liquide – miniaturised and adapted a Denayrouze–Rouquayrol regulator to be used in gas generators, in response to a fuel shortage resulting from German requisitioning. Gagnan's boss, Henri Melchior, happened to be the father–in–law of another naval lieutenant, Jacques–Yves Cousteau, and he knew that Cousteau was looking for an automatic demand regulator to increase the useful period of the underwater breathing apparatus invented by Commander Yves le Prieur. Melchior introduced Cousteau to Gagnan in December 1942. On Cousteau's initiative, Gagnan's regulator was adapted to diving, and the new Cousteau–Gagnan patent was registered some weeks later, in 1943.
In 1946, Gagnan and Cousteau founded La Spirotechnique ('breathing technology'), as a division of Air Liquide, in order to mass–produce and sell their invention. They had a new 1945 patent, and the apparatus was known as CG45 (C for Cousteau, G for Gagnan and 45 for the year 1945). In France it was marketed as the scaphandre autonome ('scuba set'), scaphandre Cousteau–Gagnan ('Cousteau–Gagnan scuba set'), or simply the CG45; but for the English–speaking market Cousteau needed a more appealing name, and so he coined the trade name 'Aqua–Lung'.
If ever you're asked in a quiz, "Who invented the aqualung?", the answer required is invariably "Jacques Cousteau".
© Haydn Thompson 2018