AN ATOLL IN THIS PACIFIC OCEAN.
[CHAPTER XX.]
LIGHT UNDER WATER.—PEARL-FISHING AND TURTLE-HUNTING.
Frank was curious to know how it was possible to see under water. He thought it would be dark at great depths, and, if so, it would be impossible to do anything there on account of the darkness. Lamps could not be made to burn under water, and until this was done the explorers of the sea could not make much progress.
Captain Johnson replied that Frank's theory was correct. As the diver goes down the light becomes more and more dim, but the dimness or the absence of it depends upon the clearness of the water where he is at work. If the water is clear and the sunlight good, there is no trouble about seeing at any depth to which a diver may safely descend. In a stream like the Mississippi or the Missouri river it will be darker at ten feet deep than in the Mediterranean at a hundred.
"But science has come to our aid," he continued, "by giving us the electric light. There is one form of it that can burn in a vacuum—in fact, it needs a vacuum for its proper working. Now all you have to do is to insulate the wires leading to the glass globe that holds the light, and you can carry it under the water without the least trouble.