324 



either exclusively in the length or in the tension of the vocal chords, 

 or in the size of the aperture of the glottis, or in the velocity or the 

 temperature imparted to the air in its transit through these passages. 

 He regards the organs of the voice as combining the properties of wind 

 and of stringed musical instruments ; and shows, first, that for the pro- 

 duction of any musical tone it is necessary that the vocal chords should 

 previously be made mutually to approximate 3 and, secondly, that the 

 muscular forces acting on the arytenoid cartilages and vocal chords 

 are adequate not only to resist the pressure of the column of air issu- 

 ing from the lungs, but also to render either the whole or certain 

 portions of the vocal chords susceptible of vibration when traversed 

 by the current of respired air. In proportion as these parts of the 

 vocal chords, thus rendered vibratory, increase in length, the number 

 of their vibrations, performed in a given time, diminishes, and the 

 tone of the sound emitted becomes, in consequence, more grave ; 

 and, conversely, the tone is more acute as the vibrating portions of 

 the chord are shorter : these phsenomena being precisely analogous 

 to those which take place in stringed musical instruments. 



The author concludes his paper with some observations on the 

 comparative physiology of the voice; and on the extensive range and 

 superior excellence of this faculty in man. 



The following letter was read j 



British Museum, February 26th, 1835. 



My Dear Sir, 



I am commanded by His Royal Highness the President of the 

 Royal Society to request that you will state from the Chair, at the 

 close of this evening's meeting, how sincerely His Royal Highness re- 

 grets that, in consequence of the opinion of Dr. Maton and his 

 other medical advisers, he is obliged, for the present, to forego the 

 pleasure, so truly gratifying to himself, of holding the usual Soirees 

 at Kensington Palace. His Royal Highness, however, hopes that, by 

 the blessing of Providence, he may yet have the satisfaction of receiv- 

 ing the Fellows as heretofore, before the termination of the present 

 Session. 



I am ever, my dear Sir, faithfully yours, 



John George Children, Sec. R. S. 



John William Lubbock, Esq. 

 V. P. and Treas. R. S. 



March 5, 1835. 



Sir BENJAMIN COLLINS BRODIE, Bart., Vice-President, in 



the Chair. 



A paper was read, entitled, u A new Method of discovering the 

 Equations of Caustics." By G. H. S. Johnson, M.A., Tutor of Queen's 

 College, Oxford. Communicated by the Rev. Baden Powell, M.A., 

 F.R.S. 



Peculiar difficulty has hitherto attended the determination of the 



