2IO 



NATURE 



[July i, 1897 



resonators. No doubt the quality of the tones is best appre- 

 ciated by carrying the vibrations directly to the vicinity of the 

 dtum-head of the ear, as is usually done, by fine tubes ; but this 

 method is not always agreeable, and the pleasurable effect is 

 sadly marred by the friction noises. Still the fact that tones 

 are heard best in this way, as regards their (juality, proves to 

 my mind that the marks on the wax cylinder are accurate repre- 

 sentations of the varying intensities of the pressures caused by the 

 sound waves. Resonators, such as the large one you now 

 see, increase the volume of tone, and you will notice how 

 accurately the tones are reproduced. 



Now, let us see what we can make of the marks. I have 

 endeavoured to study the marks on the wax cylinder in three 

 different ways— by ca.sts, by photographs, and by mechanical 

 devices. 



As regards the first method — taking casts, which was also 

 attempted by Hermann and Boeke— the results were not satis- 

 factory. The most efficient method followed by me was to 

 paint in the cylinder, with a camel-hair brush, a layer of 

 celloidin dissolved in ether. This soon hardened, and the film 

 could then be peeled off. The thin film thus obtained was 

 then inverted on the stage of a microscope, and the marks were 

 seen in relief A photograph of the marks thus obtained is 

 now on the screen (Fig. i). 



The depressions are well seen, and their differences as regards 

 length are obvious. The method has the disadvantage of 

 flattening out the marks. 



I took numerous photographs, with the aid of the microscope 

 and camera, of portions of the surface of the cylinder on which 





tK^n^s^st^ 



Fig. I. — Celloidin cast (magnified) of marks on wax cylinder. Portion 

 of record of a military band. 



were records of many instruments and of the voice. I now 

 show you on the screen examples of such records (Fig. 2). 



Each figure, from above downwards, represents the ith of an 

 inch on the surface of the wax magnified fourteen diameters. 

 The grooves seen in each figure are, on the wax cylinder, j^^th 

 inch apart, and the length of the groove, from above down- 

 wards, represents in time the -i^th second — that is to say, when 

 each tracing was recorded, the sapphire point of the recorder 

 travelled over the distance represented in magnified proportions 

 in the ^yVth part of a second. By counting the number of in- 

 dentations or marks, which in a photograph have a curious 

 appearance of being in relief, one can at once determine approxi- 

 mately the pitch of the tone, the vibrations of which make the 

 impression. The tones highest in pitch were obtained from the 

 piccolo and the xylophone. Here the pitch was about 1920 

 vibrations per second. In Fig. A we have a picture of the 

 vibrations produced by the tones of the violin, and it will be 

 seen that they vary in character. Sometimes the marks are a 

 little apart, and at other times they blend into each other, the 

 mark widening out as the receding point cut into the wax and 

 then contracting as it receded. It is to be borne in mind that 

 even when the glass disc is not vibrating, the recorder ploughs 

 a groove on the cylinder, and when the glass disc vibrates each 

 vibration cuts deeper into the groove. The figure of the vibra- 

 tion of the tones of a flute (B) shows moniliform markings, 

 indicating that the disc may not, in some instances, return to 

 its position of rest for a short time. Sometimes the intensity of 

 the tone is so great as to cause, after each deeply ploughed 

 groove (as will be seen in the figure of the vibrations of the 

 tones of an organ, D), a rebound lifting the recorder up to the 

 surface of the cylinder, or even off the surface altogether. This 

 is the explanation of the smooth spaces between the ends of the 

 individual marks. 



To obtain a mechanical representation of the curves is a very 

 difficult matter. The difficulties were so far overcome by the 

 device of Jenkin and Ewing with the tinfoil phonograph. The 

 method followed by these observers, which was entirely 

 mechanical, was to cause the disc of the phonograph to record 



its movements on a drum moved at the same rate as that of the 

 cylinder. As I have already mentioned, Hermann photographed 

 the oscillations of a beam of light reflected from a small mirror 

 connected with the disc of the phonograph, the whole apparatus 

 moving slowly. My method consists in the adaptation of a light 

 lever to the phonograph itself, and so arranged that it (the point 

 of the marker) would travel over all the ups and downs of the 

 phonographic curve on the wax cylinder at an extremely slow 

 rate. The obvious objection to any method of directly recording 

 the ups and downs of the lever is that the inertia of the lever 



H 



NO. 1444. VOL. 56I 



Fig. 2. — From photographs of portions of the surface of the wax cylinder. 

 y^, violin. ^, flute. C, vowel ^. /), full organ. 



might cause extraneous vibrations, while, at the same time, the 

 smaller marks on the wax cylinder might be missed. These 

 objections, however, were removed by reducing the friction to 

 minimum, and by moving the phonograph cylinder so slowly as 

 to make the movement almost invisible to the naked eye. In 

 this way inertia ceases to give trouble. The first arrangement 

 gave curves of very small amplitude, a specimen of which I now 

 show you. 



Various mechanical arrangements were employed, some of 

 which I described to the Royal Society of Edinburgh in 

 February last. 



