TO PLAY ON TWO WHISTLES AT ONCE
Double a length of gutta percha tubing, say two yards long, and cut a slit in the centre, where you insert one end of another piece of tubing, of the same or a greater length.
In the two end openings put whistles, and make the whole air-tight. Place the free end of the long piece around the nozzle of a bellows, and on forcing the air from which into this novel instrument a double succession of sounds can be produced. The whistles should be pitched differently, and more than two can be used.
ECHOES.
A good ear cannot distinguish one sound from another unless there is an interval of one-ninth of a second between the arrival of the two sounds. Sounds must, therefore, succeed each other at an interval of one-ninth of a second in order to be heard distinctly. Now, the velocity of sound being eleven hundred and twenty feet a second, in one-ninth of a second the sound would travel one hundred and twenty-four feet. Repeated echoes happen when two obstacles are placed opposite to one another, as parallel walls, for example, which reflect the sound successively.
Fig. 108.—Miss Echo.
A certain river has a bend in it, avoided by every one, as it was supposed to be haunted. At a certain hour in the evening, for many years, terrible curses were distinctly heard. Suddenly they ceased. Hearing an account of the strange phenomena, Mr. H. Panky determined to ascertain the cause, and carefully examined the river on each side for about a mile above and below the bend. He ascertained that at about the time the sounds ceased an old fisherman, who had lived on the opposite side of the river, full a mile from the spot where the curses where heard, had died. He was told that the fisherman was in the habit of crossing the river to a village, where he found a market for his fish, and where he spent his money for liquor; and that after drinking freely on his way home, while rowing across the river at night, he would swear terribly. This gentleman then persuaded a friend to go down the river to the place where the curses were formerly heard, while he remained in a boat on the river at the point at which the old man usually crossed. He then played on a bugle and sang several songs. His friend soon returned, and with eager delight exclaimed, “O, Hanky, such glorious music fills the air, just where the oaths used to be heard!” The neighbours came rushing down to hear it, and some fell on their knees, praying. They said, “The angels have driven the devil away.” Mr. Panky then asked what were the songs they heard. His friend described them correctly, and said he understood even the words, one of them being the famous Marseillaise, another a German song. The foreign words made the ignorant more sure that the sounds were supernatural. The magician then played on the bugle, and sang again the same songs, while his friend stood by; but his friend said the music was not equal to that he had heard below, where the sounds had really seemed heavenly.
The peculiar configuration of the river-banks had concentrated the sounds, and the distance and the water had softened them.