“How in the name of miracles!” I gasped. “Can you receive a wireless telegram under the sea?”
“By the Fessenden oscillator,” he replied, and added to the wireless man,
“Take this gentleman below and show him how it works.”
“Did you ever have another chap knock two stone together under water when you were taking a dive?” asked the operator. I nodded in vivid recollection.
“Then you have some idea how sounds are magnified under water. It is an old idea to put submarine bells down under lighthouses and fit ships with some kind of receiver so that the bells can be heard and warning given when it is too foggy to see the light. The advantage over the old-style bell-buoy lies in the fact that sound travels about four times as fast through water as through air,[16] and goes further and straighter because it isn’t deflected by winds or what the aviators call ‘air-pockets.’ The man who knows most about these things is Professor Fessenden, of the Submarine Signal Company of Boston, who first realized the possibility of telegraphing through water.[17]
Courtesy of the American Magazine.
Fessenden oscillator outside the hull of a ship. The “ear” of a modern vessel.
“Fastened outside the hull of this boat is one of the Fessenden oscillators: a steel disk eighteen inches in diameter, that can be vibrated very rapidly by electricity. These vibrations travel through the water, like wireless waves through the ether, till they strike the oscillator on another vessel and set it to vibrating in sympathy. To send a message, I start and stop the oscillator with this key so as to form the dots and dashes of the Morse code. To receive, I sit here with these receivers over my ears and ‘listen in,’ just like a wireless operator, till I pick up our call ‘X-4,’ ‘X-4.’”
“How far can you send a message under water?”