Until men invented ways of staying unierwater for more than a few minutes, the wonders of the world below the sea were almost unknown.The main problem, of course, was air. How could air be supplied to swimmers below the surface of the sea? Pictures made about 2,900 years ago in Asia show men swimming under the surface with air bags tied to their bodies.A pipe from the bag carried air into the swimmer's mouth. But little progress was made in the invention of diving devices until about 1490, when a famous Italian painter, Leonardo da Vinci, besigned a complete diving suit.
In 1680 an Italian professor invented a large air bag with a glass window to be worn over the diver's head. To "clean" the air a breathing pipe went from the air bag, through another bag to remove moisture, and then again to the large air bag. The plan did not work, but it gave later inventors the idea of moving air around in diving de- vices.
In 1819 a German developed a way of forcing air into the head-covering by a machine operated above the water. Finally, in 1837 he invented the "hard-hat suit" which was to be used for almost a century.It had a metal covering for the head and an air pipe attached to a machine above water.It also had small openings to remove unwanted air.But there were two dangers to the diver inside the "hard-hat suit". One was a sudden rise to the surface, caus- ed by too great a supply of air. The other was the crushing of the body, caused by a sudden dive into deep water. The sudden rise to the surface could kill the diver; a sudden dive could force his body up into the head covering,which could also result in death.
Gradually the "hard-hat suit" was improved so thet the diver could be given a constant supply of breathable air. The diver could then move around under the ocean without worrying about his air supply.
During the 1940s diving underwater without a special suit became popular. Instead, divers used a breathing device and a small covering made of rubber and glass ovcr part of the face. To increase the swimmer's speed another new invention was used - a piece of rubber shaped like a giant foot,which was attached to each of the diver's own feet. The manufacture of rubber breathing pipes made it possible for divers to float on the surface of the water, observing the marine life beneath them. A special rubber suit made diving comfortable, even in icy waters. It was then passiblo to collect plant and vegetable life that had never been obtained before.
The most important advance, however, was the inven- tion of a self-contained underwater breathing apparatus, which is called a "scuba". The scuba consists of a mouth- piece joined to one or two tanks of compcessel air which are attached to the diver's back. The scuba makes it pos- sible for a diver-scientist to work 200 feet underwater - or even deeper - for several hours. As a result, scientists can now move around freely at great depths, learning about the wonders of the sea.
