horns and trumpets of crystal, flutes of porcelain, fiddles of faience, Alpine horns, a bassoon of such extraordinary adjustment that it is a day's work to dismount it; and many other most curious contrivances for producing melodies and accompaniments.
One of the most simple whistles, most closely approaching the theoretical form, is the American, or secret whistle (Fig. 2), which is composed of a strip of metal bent over, one end of which. A, is cut beveled, and is placed opposite the opening of 
Fig. 2.—Secret Whistle. Outer View and Section. the hollow box o o'. Apply the mouth and blow at—no sound is produced; and in this lies the secret of the instrument. But on closing the open ring T with the thumb and forefinger, a vigorous whistling sound is obtained, the intensity of which may be modified by raising or lowering the bevel. A, so as to bring it nearer to or farther away from the box o o'.
A pen and pencil-case whistle, with which dealers in holiday toys have had considerable success, deserves to be mentioned here. It is an ordinary whistle at the end of a tube, in which a solid cylinder is moved so as to modify at the will of the performer the length of the column of vibrating air. Persons skilled in using it are able to play a considerable variety of simple tunes upon it. Among the whistles that give out several notes, we
Fig. 3.—Commandant's Whistle.
also cite the commandant's whistle (Fig. 3), which, besides its mouth, has two openings that are controlled by the fore and middle fingers. With both holes closed, it gives the note sol; with hole No. 1 open, do; and with both holes open, mi.
