676 



MATURE 



\Oct. 24, 1878 



Mr. Edison, in his telephone and phonograph experi- 

 ments, discovered that the vibrations of the vocal chords 

 were capable of producing considerable mechanical effect. 

 Acting on this hint, he began experiments on a phono- 

 meter, or instrument for measuring the mechanical force of 

 sound-waves produced by the human voice. In the course 

 of these experiments he constructed the machine shown 

 in Fig. 3, which exhibits the dynamic force of the voice. 

 The machine has a diaphragm and mouth-piece similar 

 to a phonograph. A spring which is secured to the bed 

 piece rests on a piece of rubber tubing placed against the 

 diaphragm. This spring carries a pawl that acts on a 

 ratchet or roughened wheel on the fly-wheel shaft. A 

 sound made in the mouth-piece creates vibrations in the 

 diaphragm, which are sufficient to propel the fly-wheel 

 with considerable velocity. It requires a surprising 

 amount of pressure on the fly-wheel shaft to stop the 

 machine while a continuous sound is made in the mouth- 

 piece. 



The speaking trumpet, which, for two centuries at 

 least, has been employed to direct sound so that it may 



be heard over a long distance, is much used at sea, and 

 is often employed on land to direct vocal sounds so that 

 they may be heard above other sounds. It is tolerably 

 certain that the speaking trumpet is of modern origin, 

 and that it is the invention of Samuel Moreland, 

 1670. 



Kiroher, in his " Ars Magna et Umbra" and in his 

 " Phonurgia," mentions a kind of gigantic speakmg- 

 trumpet, described as the horn of Alexander. According 

 to Kircher, this horn enabled Alexander the Great to call 

 his soldiers from a distance of ten miles. The diameter 

 of the ring must have been eight feet, and Kircher con- 

 jectures that it was mounted on three poles. 



Late in the last century Prof. Huth, a German, made a 

 model of the horn, and found that it served as a powerful 

 speaking-trumpet, but we are considerably in doubt as to 

 the distance through which sounds can be projected 

 through such an instrument. 



The ear-trumpet, which is the counterpart of the 

 speaking-trumpet, has been made in various forms during 

 the last two centuries, but no form yet devised has any 





Fig. 4. — Plan of Megaphone. 



advantage over a plain conical tube with a bell-shaped or 

 flaring mouth. 



Mr. Edison, in his researches on sound, has made many 

 curious experiments, one of the most interesting of which 

 is that of conversing through a distance of i^ to 2 miles 

 with no other apparatus than a few paper funnels. These 

 funnels constitute the megaphone, an instrument wonder- 

 ful both for its simplicity and effectiveness. In the plan. 

 Fig. 4, the details of construction are clearly shown, and 

 Fig. 5 represents the instrument as it stands on the 

 balcony of Mr. Edison's laboratory. A mile and a half 

 distant there is another instrument exactly like the one in 



Fig. 5. 



The two larger funnels are 6 feet 8 inches long and 27J 

 inches in diameter at the larger end. These funnels are 

 each provided with a flexible ear- tube, the end of which 

 is placed in the ear. The speaking-trumpet in the middle 

 does not differ materially from the ordinary ones. It is 

 a little longer and has a larger bell mouth. With this 

 instrument conversation can be readily carried on through 

 a distance of i J to 2 miles. A low whisper, uttered with- 



FlG. 5. — Edison's Megaph ine. 



out using the speaking-trumpet, is distinctly audible at a 

 thousand feet, and walking through grass and weeds may 

 be heard at a much greater distance. 



These statements, it must be understood, are given on the 

 authority of the Scietitijic American, but some experi- 

 ments lately made with a paper megaphone by Prof. 

 Barrett lend them strong support 



COLOUR BLINDNESS IN RELATION TO THE 

 HOMERIC EXPRESSIONS FOR COLOUR 



IN an article on " The Colour Sense " in the number of 

 the Nineteenth Century for October last, Mr. Glad- 

 stone points out certain peculiarities, very remarkable 

 and very difficult to account for, in the expressions for 

 colour used by Homer. "Although," he says, "this 

 writer has used light in its various forms for his pur- 

 poses with perhaps greater splendour and effect than any 

 other poet, yet the colour adjectives and colour descrip- 

 tions of the poems are not only imperfect but highly 



