In 1925 Le Prieur saw a demonstration at the Industrial and Technical Exhibition in Paris of a diver using a breathing apparatus invented by Maurice Fernez. The Fernez breathing apparatus consisted of a simple T-shaped rubber mouthpiece. On one side this was connected to a long tube down which air was pumped from the surface. On the other side of the mouthpiece, excess and exhaled air escaped from a simple rubber "ducks bill" valve. The diver's nose was pinched by a pair of spring clamps ("pince nez") to prevent ingress of water, and his eyes were protected by small goggles with rubber surrounds.