Intelligence and Miscellaneous Articles. 463- 



the rapidity of vibration of a given sound may be determined. 

 This proceeding has recently been proposed anew by M. Savart. 

 Mr. Willis produced also an invention of Professor Robison, in 

 which a definite sound is emitted by a stop-cock through which a 

 stream of air passes, interrupted at regular small intervals. An 

 invention similar to this has been put in other forms by M. Cag- 

 niard de la Tour, one of which forms is the instrument which he 

 has called the Syren. A machine of Mr. Willis's invention was 

 exhibited (which he proposes to call a Lyophone) by means of which 

 is appeared that the sound in such cases is produced not by the 

 periodical interruption of the current of air, but by the close re- 

 currence of small noises ; it was likewise shown that by various dis- 

 positions of the holes through which the air passes, two or more 

 sounds may be brought out at the same time. Mr. Willis repeated 

 also some of M. Savart's experiments on embouchures, and showed, 

 contrary to the opinion expressed by that gentleman, that when air 

 passes through a narrow slit against an edge, the note is not affected 

 by the angle or material of the edge, or by the angle of the air ; 

 but only by the distance of the edge and its want of centrality ; the 

 effect of such embouchures when used in organ-pipes, and the 

 manner in which the note appears in these cases to be determined, 

 partly by the embouchure and partly by the pipe, was shown by 

 trial. There were exhibited, likewise, some experiments manifest- 

 ing the nature of the vibrations in the sounding-boards and bridges of 

 violins, the office and effect of the sound-post, and the form which 

 M. Savart, in virtue of his own views, is disposed to recommend for 

 this instrument. 



LXVII. Intelligence and Miscellaneous Articles. 



MR. GALBRAITH ON AN OMISSION IN HIS PAPER ON NORTH 

 POLAR DISTANCES. 



To the Editors of the Philosophical Magazine and Annals. 

 Gentlemen, 



IN my paper, published in the Philosophical Magazine for May 

 last, there has occurred an omission, which I request you to 

 supply as early as possible. 



The table was computed for the zenith distance, and therefore 

 cannot answer for the north polar distance without either forming 

 two tables, or using a constant with one table. The latter plan 

 1 preferred, by making the corrections for north polar distance to 

 the north of Greenwich negative, and applying the constant 

 fO"-53 throughout the whole table. The second part of the 

 table or zenith distance south gives still the correction in zenith 

 distance without the constant, and may be useful where that is re- 

 quired ; and thus both purposes are served : the particular I had 

 in view when I gave the table double arguments. From the time 

 I had drawn up the table till that when I wrote the explanation 

 and examples of application, this circumstance escaped me, which 



has 



