722 



THE POPULAR SCIENCE MONTHLY. 



the end of the longer arm of this lever is a pointed slip of thin copper- 

 foil, which just touched the vertical surface of a smoked-glass plate. 

 The point on the short arm of the lever rested in the furrow in which 

 are the depressions and elevations made in the foil on the cylinder. 

 Rotating the cylinder with a slow and uniform motion, while the plate 

 of glass was slid along, the point of copper-foil scraped the lampblack 

 off the smoked-glass plate and traced on it the magnified profile of 

 the depressions and elevations in the foil on the cylinder. I say ex- 

 pressly elevations as well as depressions in the foil, because, when the 

 plate vibrates outward, the furrow in the foil often entirely disap. 

 pears, and is always lessened in its depth by this outward motion of 

 the point. One who has never made a special investigation of the 

 character of the impressions on the phonograph, and forms his opinion 

 from their appearance to his eye, might state that they are simply 

 dots and dashes, like the marks on the filet of a Morse instrument. 



Another method of obtaining the profile of the impressions on the 

 foil is to back it with an easily-fusible substance, and then, cutting 

 through the middle of the furrows, we obtain a section, in which the 

 edge of the foil presents to us the form of the elevations and depres- 

 sions. 



The instrument has been so short a time in my possession, that I 

 have not had the leisure to make on it the careful and extended series 

 of experiments which it deserves. I have, however, obtained several 

 traces, and I have especially studied the characters of the trace of the 

 sound of bat. As far as the few experiments warrant an expression 

 of opinion, it seems that the profile of the impressions made on the 

 phonograph and the contours of the flames of Kunig, when vibrated 

 by the same compound sound, bear a close resemblance. 



In Fig. 3 we give on line A the appearance to the eye of the im- 



3J> 



Fig. 3. 



pressions on the foil, when the sound of a in bat is sung against the 

 iron plate of the phonograph. B is the magnified profile of these im- 

 pressions on the smoked glass obtained as described above. C gives 

 the appearance of Konig's flame when the same sound is sung quite 

 close to its membrane. I say expressly quite close to its membrane, 

 for the form of the trace obtained from a point attached to a mem- 

 brane vibrating under the influence of a compound sound depends on 



