399 



ing. I have little doubt but the Varna and Balaklava wire will be 

 the best yet made for the purpose. 



Without knowing exactly what the " retardation " may be in 

 terms of the element of time "a" of the diagrams, we may judge 

 what the retardation, if similarly estimated, would be found to be in 

 other cables of stated dimensions. Thus, if the retardation in 200 

 miles of submarine wire between Greenwich and Brussels be^th of 

 a second, the retardation in a cable of equal and similar transverse 

 section, extending half round the world (14,000 miles), would be 



[ ] x =490 seconds, or 84- minutes : 



\ 200 / 10 



and in the telegraphic cable (400 miles) between Varna and 

 Balaklava, of which the electro-statical capacity per unit of length 

 maybe about one-half greater than in the other, while the conduct- 

 ing power of the wire is probably the same, the retardation may be 



expected to be 



/400\2 3 I 3 , 



[ X-X = of a second. 



\200/ 2 10 5 



The rate at which distinct signals could be propagated to the 

 remote end would perhaps be one signal in about a quarter of an hour 

 in the former case, and nearly two signals in a second in the latter. 



IV. " Observations on the Human Voice." By MANUEL GARCIA, 

 Esq. Communicated by Dr. SHARPEY, Sec. R.S. Re- 

 ceived March 22, 1855. 



The pages which follow are intended to describe some observa- 

 tions made on the interior of the larynx during the act of singing. 

 The method which I have adopted is very simple. It consists in 

 placing a little mirror, fixed on a long handle suitably bent, in the 

 throat of the person experimented on against the soft palate and 

 uvula. The party ought to turn himself towards the sun, so that 

 the luminous rays falling on the little mirror, may be reflected on 

 the larynx. If the observer experiment on himself, he ought, by 

 means of a second mirror, to receive the rays of the sun, and direct 

 them on the mirror, which is placed against the uvula. We shall 



