December 26, 1901] 



NA TURE 



185 



The amplitudes of the tracings thus obtained from the tones of 

 the voice were o"', 025 (l inch), while those of the mirror were 

 only o™'", 125 (i/200th inch). 



Fig. S. — The sound b t 



RigoUot and Chavanon,' in 1883, constructed a mirror-appar- 

 atus shown in Fig. 20, and Hermann,- in 18S9, used a somewhat 

 similar arrangement, the tracings of which are given in Fig. 21. 



for recording movements of j 



mbrane. 



An ideal method for recording vibrations was devised by 

 Rops in 1893, ideal inasmuch as it does not use any vibrating 

 membrane or lever, or anything having inertia. A diagram is 

 given in Fig. 22. 



l^ltv/»Vvav^.VVlv*U/'l-'M^lL/WvlVn^Rv'Hv'Mv'>lvA di. 



)/\AAAAAAAAAAA/V\ 



\ vowels and of the 1 

 apparatus of Schneebeli. 



It is based on the principle of photographing the effects of 

 interferences of light waves. Rays from a luminous source A 



NO. 1678, VOL. 65] 



pass through the lenses (/ q so as to become parallel. They 

 then pass through a slit d and a hole in a diaphragm b, and 

 they are focussed by a lens /{of 15 centimetres focal length) so 

 as to fall on a glass plate Sj. The ray divides into two, a^ and a^, 

 and they run parallel, the ray a, passing through the air while o, 

 passes along a lube g {\'^ centimetres in length), the ends of 

 which are closed by the glass plates /; and h^. A few centimetres 

 from the tube there is a resonator, i, into which the vowels are 

 sung, thus causing condensations and rarefactions of the air, 



-Apparatus of He 

 :l.-iss kept in its plat 



d^ Wooden prism ; 

 I screw damp, e ; a. 



"iG. 12. — The recording portion of the Sprachzeichner of Hensen. 

 y; ;', frame having a joint, z\ b, woodtn point ; ^, smoked glass. 



3. — Writing portion of Hensen's apparatus, m, n, weights supporting 

 ' '- ' carrying marker /, with a point r; ^,a disc communicating 

 ■rker / the movements of the membrane ; s, smoked glass 



to th 

 plate. 



disturbing the ray /; //,, while the ray passing through'jthe tube 

 g is unaffected. The two rays are again united by s, ; they then 

 pass through an objective c and a lens s to a slit in a screen 

 so as to fall on sensitive paper on the drum T. A diaphragm b 

 cuts off secondary reflections. Thus beautiful images are 

 formed corresponding to the vowels spoken or chanted into the 

 resonator. 



The invention of the tinfoil phonograph by Edison in 1877, 

 and the improvement of the instrument by the labours of Edison, 



