6'11 PHILOSOPHICAL TRANSACTIONS. [ANNO 1800. 



tube was as much at liberty as possible, all the harmonics corresponding to the 

 numbers from 1 to 13, were distinctly observed; several of them at the same time, 

 and others by means of different blows. This result seems to differ from the cal- 

 culations of Euler and Riccati, confirmed as they are by the repeated experiments 

 of Chladni; it is not therefore brought forward as sufficiently controverting those 

 calculations, but as showing the necessity of a revision of the experiments. 

 Scarcely any note could ever be heard when a rod was loosely held at its extre- 

 mity ; nor when it was held in the middle, and struck f of the length from one 

 end. The very ingenious method of Chladni, of observing the vibrations of plates 

 by strewing fine sand over them, and discovering the quiescent Jines by the figures 

 into which it is thrown, has hitherto been little known in this country: his treatise 

 on the phenomena is so complete, that no other experiments of the kind were 

 thought necessary. Glass vessels of various descriptions, whether made to sound 

 by percussion or friction, were found to be almost entirely free from harmonic 

 notes; and this observation coincides with the experiments of Chladni. 



15. Of the Human Foice. — The human voice, which was the object originally pro- 

 posed to be illustrated by these researches, is of so complicated a nature, and so 

 imperfectly understood, that it can be on this occasion but superficially considered. 

 No person, unless we except M. Ferrein, has published any thing very important 

 on the subject of the formation of the voice, before or since Dodart ; his reasoning 

 has fully shown the analogy between the voice and the voix humaine and regal 

 organ-pipes: but his comparison with the whistle is unfortunate; nor is he more 

 happy in his account of the falsetto. A kind of experimental analysis of the voice 

 may be thus exhibited. By drawing in the breath, and at the same time properly 

 contracting the larynx, a slow vibration of the ligaments of the glottis may be 

 produced, making a distinct clicking sound ; on increasing the tension, and the 

 velocity of the breath, this clicking is lost, and the sound becomes continuous, but 

 of an extremely grave pitch : it may, by a good ear, be distinguished 2 octaves be- 

 low the lowest a of a common bass voice, consisting in that case of about 2(5 vibra- 

 tions in a second. The same sound may be raised nearly to the pitch of the com- 

 mon voice ; but it is never smooth and clear, except perhaps in some of those per- 

 sons called ventriloquists. When the pitch is raised still higher, the upper orifice 

 of the larynx, formed by the summits of the arytaenoid cartilages and the epiglottis, 

 seems to succeed to the office of the ligaments of the glottis, and to produce a re- 

 trograde falsetto, which is capable of a very great degree of acuteness. The same 

 difference probably takes place between the natural voice and the common falsetto : 

 the rimula glottidis being too long to admit of a sufficient degree of tension for xery 

 acute sounds, the upper orifice of the larynx supplies its place ; hence, taking a 

 note within the compass of either voice, it may be held, with the same expanse of 

 air, 2 or 3 times as long in a falsetto as in a natural voice ; hence too, the difficulty 

 of passing smoothly from the one voice to the other. It has been remarked, that 

 the larynx is always elevated when the sound is acute : but this elevation is only 



