408 Proceedings of the Royal Institution, 



responding sound ; the times of vibrations with the corresponding 

 notes, were illustrated by experiments and diagrams. The subdivi- 

 sions of rods were then referred to ; and the forms also of the curves 

 both of strings and rods touched upon, but it was stated that this part 

 of the subject was still very obscure. 



Having thus considered the different modes of vibrations, the 

 co-existence of these modes in the same string or rod was taken 

 up. Dr. Young's experiment upon the visible curve described by a 

 pianoforte string, was here referred to ; and his harmonic sliders 

 were also made use of, to illustrate the effect of two or more series 

 of undulations, and the form of the resulting curve, or wave. But 

 the principal illustrations of this part of the subject were derived from 

 the use of the kaleidophone, an instrument invented by Mr. Wheat- 

 stone, which at the same time that it allows the ordinary motion of 

 a rod to be combined with one or more of the modes of vibrations 

 producing sound, also renders the path of the end of the wire visible, 

 and so gives, as it were, a picture of the vibrations, rendering each 

 set visible and distinct from the others. As this instrument, with its 

 principles and effects, is fully described in this Journal, vol. i., p. 344, 

 we refer our readers to it on the present occasion. 



A mode of counting vibrations and other rapid motions by the 

 eye was referred to at the end of the evening, as promising some 

 new and interesting results. This subject is at present under inves- 



In the Library, amongst other interesting objects, was a portable 

 equatorial instrument, invented by Captain Kater, and laid upon the 

 table by Captain Grover, to whom it belonged. It is a small telescope, 

 only 71 inches long, with an aperture of l^^ inch, which with a 

 power of 80, shews very distinctly Saturn's ring, the eclips6s of 

 Jupiter's satellites, &c. The object glass is by Dollond. This is 

 mounted in a very ingenious manner, so that right ascensions and 

 declinations may be readily determined. There is also attached one 

 of Captain Kater's micrometers, for measuring vetf small angles; 

 The instrument was made by Mr. Robertson of Devonshire Street. 



[Conclusion of the Weekly Evening Meetings for this season.] 



