SINGING FLAMES are produced by burning hydrogen in a tube; a musical note is thus produced in the same way as the air causes a note in an organ pipe. Faraday attributed the sound to rapid vibration caused by successive explosions of the burning gas. The Gas Harmonicon has been made on this principle. The air, being heated in the glass tube, ascends, and the flame is thus permitted to come up more forcibly in the tube; so violent agitation results when the air tries to get into the opening above. The size of the flame and its position in the tube will give a certain note which will be the same note as the air would emit if in a pipe, for the vibrations give the sound. Sir Charles Wheatstone has shown by experiment how sound can be transmitted by placing a rod on a musical-box, and carrying the rod through the ceiling. When a guitar or violin was placed upon the rod, the sounds of the musical-box were distinctly heard in the upper room. A _Phantom Band_ can be made by connecting certain instruments with others being played on under the stage. Every one will then appear to play by itself. CHAPTER XVIII ELECTRICITY. DERIVATION OF ELECTRICITY—SEALING-WAX EXPERIMENT—THE ELECTROPHORUS—LEYDEN JAR—POSITIVE AND NEGATIVE—THE ELECTROSCOPE—ELECTRIC MACHINES. We have now briefly and of course imperfectly reviewed the phenomena of Vibration, as exemplified in what we term Heat, Light, and Sound. We now come to a most mysterious servant of mankind, as mysterious as any Djinn of romance; viz., ELECTRICITY. The term Electricity is derived from the Greek word _electron_, meaning “amber”; because from amber the properties of what we call “Electricity” were first discovered. Six hundred years before the Christian Era, Thales wrote concerning the attraction which amber, when rubbed, possessed for light and dry bodies. But it is to an Englishman named Gilbert that we owe the word “Electricity,” which he derived from the Greek, and in his works (about 1600 A.D.) he discusses the force of the so-called “fluid.” Otto von Guerike, of “air-pump” celebrity, and many other philosophers after him, continued the investigation of the subject. At the beginning of the last century great attention was paid to the Electric Machine. The Leyden Jar was, as its name denotes, discovered by Muschenbrock, of Leyden, (though the honour was disputed). Franklin made the first lightning conductor in 1760. Volta and Galvani, to whose invention we owe “Voltaic Electricity” and “Galvanism,” and Faraday in more modern times gave a great impetus to electrical science. The great part that electricity has been playing in the domestic history of the world since Faraday’s lamented death, is probably known to the youngest of our readers. What the future of this agent may be we can only guess, but even now we may regard electricity as only in its infancy.