[14] Electric current.
[15] From an article by Admiral Selfridge in the “Outlook.”
[16] The velocity of sound in dry air at a temperature of 32 degrees Fahrenheit is about 1087 feet a second, in water at 44 degrees, about 4708 feet a second.
[17] The sound of the first gun of the salute fired by the Russian fleet in Cronstadt harbor to celebrate the coronation of Alexander II in 1855 was the signal for the crew of the submerged submarine Le Diable Marin to begin singing the National Anthem. Their voices, accompanied by a band of four pieces, were distinctly heard above the surface. This novel concert had been planned by Wilhelm Bauer, the designer of the submarine and one of the earliest students of under-water acoustics. He succeeded in signaling from one side of the harbor to another by striking a submerged piece of sheet-iron with a hammer.
[18] “Scientific American,” January 28, 1911, page 87.
[19] “Scientific American,” November 23, 1912.
[20] Titherington’s History of the Spanish-American War, p. 139.
[21] Ibid., page 202.
[22] He had done notable work with mines himself, during the Russo-Turkish War of 1878.
[23] This was a very popular type with the Confederate Torpedo Service in the Civil War.