23(> Intelligence and Miscellaneous Articles. 



TELOCITY OF SOUND IN MEMBRANOUS BODIES. 

 BY F. MELDE. 



The author gives the following extract from a longer memoir 

 which is shortly to appear. 



By membranous bodies he understands such bodies as are 

 capable of forming a membrane, which can be used for all pur- 

 poses for which membranes can be applied. To these belong, foi 

 instance, the various kinds of paper, linen and cotton materials, 

 caoutchouc, animal membranes, and so forth. The velocity ot 

 sound in such bodies differs greatly, but can be easily determined 

 by fixing narrow strips at both ends, rubbing them in the middle, 

 and determining the pitch of the fundamental note. If the 

 number of vibrations is n, and the length of the strip L, then 



L = 9 and 2 L = \ = the wave-length of the note in question ; so 



that the velocity is v = n\. In this way the following numbers 



were obtained for the velocity of sound. 



Metres. 



Paper soaked with wax 3040 



Stout red parchment-paper 2960 



Yellow silk paper 2046 



Drawing-paper 1955 



Smooth green paper 1952 



Yellow satin ribbon 1950 



Black paper 1923 



Peed paper 1852 



Hemp string . . 1720 



Cotton string 1280 



Coloured cross-ribbed silk ribbon .... 930 



Black wax cloth , 570 



Beiblatler cler Pltysik, vol. xv. p. 756. 



THE SOLITARY WAVE : CORRECTION OF A SIGN. 



To the Editors of the Philosophical Magazine and Journal. 



University College, Dundee, 

 Gentlemen, January 12, 1892. 



Tn my "Note supplementary to a Paper on the Solitary Wave,'" 

 which appeared in the December number of your Magazine, one 

 of the expressions is written with a wrong sign, and might there- 

 fore prove somewhat misleading. The series given in the second 

 line of page 555, the expansion of equation (5) of my paper "On 

 the Solitary Wave" (Phil. Mag. July 1891), for the case of x 

 negative, should be affected with the negative sign. Were this 

 not corrected it might appear to affect the argument, at least if 

 one were to attend only to the series as written, neglecting its 

 connexion with (5). 



I am, Gentlemen, 



Yours faithfully, 



John M c Cowan. 



