When we whistle we transform the lips into a reed and the mouth into a pipe. The tension of the lips and the shape of the mouth cavity decide the note. The lips are also used as a reed for blowing the flute, piccolo, and all the brass band instruments of the cornet order. In blowing a coach-horn the various harmonics of the fundamental note are brought out by altering the lip tension and the wind pressure. A cornet is practically a coach-horn rolled up into a convenient shape and furnished with three keys, the depression of which puts extra lengths of tubing in connection with the main tube--in fact, makes it longer. One key lowers the fundamental note of the horn half a tone; the second, a full tone; the third, a tone and a half. If the first and third are pressed down together, the note sinks two tones; if the second and third, two and a half tones; and simultaneous depression of all three gives a drop of three tones. The performer thus has seven possible fundamental notes, and several harmonics of each of these at his command; so that by a proper manipulation of the keys he can run up the chromatic scale. We should add that the cornet tube is an "open" pipe. So is that of the flute. The clarionet is a "stopped" pipe. [29] It is obvious that in Fig. 136, _2_, a pulse will pass from A to B and back in one-third the time required for it to pass from A to B and back in Fig. 136, _1_. [30] The science of hearing; from the Greek verb, [Greek: akouein], "to hear." [31] "Organs and Tuning," p. 245. Chapter XVI. TALKING-MACHINES. The phonograph--The recorder--The reproducer--The gramophone--The making of records--Cylinder records--Gramophone records. In the Patent Office Museum at South Kensington is a curious little piece of machinery--a metal cylinder mounted on a long axle, which has at one end a screw thread chased along it. The screw end rotates in a socket with a thread of equal pitch cut in it. To the other end is attached a handle. On an upright near the cylinder is mounted a sort of drum. The membrane of the drum carries a needle, which, when the membrane is agitated by the air-waves set up by human speech, digs into a sheet of tinfoil wrapped round the cylinder, pressing it into a helical groove turned on the cylinder from end to end. This construction is the first phonograph ever made. Thomas Edison, the "wizard of the West," devised it in 1876; and from this rude parent have descended the beautiful machines which record and reproduce human speech and musical sounds with startling accuracy. [Illustration: FIG. 146.--The "governor" of a phonograph.]