NATURAL PHILOSOPHY. 183 



pen rest on the sui'face of a blackened cylinder which can be 

 caused to rotate. Among other results, Mr. Donders found that, 

 when a simple note was sounded, a simple sinuosity was traced 

 on the rotating cylinder. The form of tfie curve varies with the 

 pitch of the voice. 



A treble voice gives for the same note and the same vowel a 

 simpler curve than a bass voice. The thi'ce "sounding" conso- 

 nants produced almost as simple curves as the vowels, ditfering 

 slightly, however, from them. Many consonants, which preceded 

 or followed a vowel, produced a characteristic modilication at the 

 beginning or at the end of the curve given by the vowel. M. 

 Koenig has also been able to obtain writings of the human voice 

 with his phonautograph, and has traced with correct difi'erences 

 the four notes, ut, mi, sol, ut ; finally, M. Koenig has succeeded 

 in recording an air, composed on eight notes of the gamut. 



After this there is a most elegant apparatus for comparing the 

 vibrations of two sounding columns of air by means of gas flames. 

 This does for organ-pipes what Lissajous' experiments did for 

 tuning-forks; the composition of vibrations in both cases are now 

 rendered visible. Two jets of gas, placed over each otlier, are 

 made to communicate by branch tubes with the nodal points of 

 two organ-pipes. In front is a turning mirror in which the gas- 

 jets can be viewed. When the two organ-pipes are in perfect 

 unison, the flames appear in the rotating mirror no longer as two 

 parallel series vertically superposed, but are seen to alternate 

 with each other. If the pijaes are arranged so as to give beats, 

 the images of the two series will be sometimes superposed and 

 sometimes alternating. If two jjipes be taken which sound utg 

 and S0I3, in the mirror two images of one series are seen to cor- 

 respond with three of the other. By simple arrangements the 

 eftects can be varied in a most instructive manner. 



In another apparatus, somewhat similar in principle, the quality 

 of a sound can be visibly sejjarated into its elementary notes by 

 means of gas flames. Ten resonant sjiheres are fixed one over 

 the other, in a series gradually diminishing in size. Each com- 

 municates by a tube with a box, which forms a jiressure case, and 

 from which spring ten jets of gas, also placed in a line one over 

 the other. A revolving mirror parallel to this line shows Avhich 

 flames are put in vibration by the resonant globes ; the flames in 

 communication with the spheres in which there is no resonance 

 appearing simply as a line of light. 



An apparatus for the study of the simple and composite vibra- 

 toi-y movement in cords was suggested by M. Melde, in "Pog- 

 gendorft'^s Annalen." This, as made by M. Koenig, is as follows : 

 A cord is stretched between two tuning-forks, which are fixed 

 upon an upright sujjport. When the forks are caused to vibrate, 

 the cord will be observed to show the co-existence of the harmon- 

 ics with the fundamental note, or the co-existence of two harmon- 

 ics. The beats can also be shown, either with the fundamenal 

 note or with one of its harmonics. By simply varying the tension 

 of the cord, and using ditt'erent tuning-forks, an immense number 

 of vibratory forms can be produced at pleasure. With this inter- 



