46 Curiosities of Sound. 



The transmission of musical sounds through solids re- 

 ceived some beautiful illustrations in Professor TyndalFs 

 lectures. The following passage shows one of the magical 

 effects which he produced :— 



"In a room underneath this/' said the lecturer, "and 

 separated from it by two floors, is a piano. Through the two 

 floors passes a tin tube two and a half inches in diameter, and 

 along the axis of this tube passes a rod of deal, the end of 

 which emerges from the floor in front of the lecture table. 

 The rod is clasped by india-rubber bands, which entirely close 

 the tin tube. The lower rod rests upon the soundboard of the 

 piano, its upper end being exposed before you. An artist is 

 at this moment engaged at the instrument, but you hear no 

 sound. I place this violin upon the end of the rod; the 

 violin becomes instantly musical, not however, with the vibra- 

 tions of its own strings, but with those of the piano. I re- 

 move the violin, the sound ceases. I put in its place a guitar, 

 and the music revives. " 



A harp was rendered musical in the same way, and as 

 Professor Tyndall says, an uneducated person might well 

 believe that witchcraft was concerned in the production of 

 such music. 



The vibrations of columns of air of various lengths give 

 rise to the notes of organs and wind instruments, while pianos, 

 violins, etc., are an illustration of the operation of vibrating 

 strings, the sound of which would be feeble if it were not 

 reinforced by the elastic wood introduced into the structure of 

 such instruments. 



Long strings vibrate more slowly than short ones, and 

 thick ones than thin. If a whole string vibrates with a given 

 velocity, half of it will vibrate twice as quickly, a third three 

 times, and so on. 



Strings, or air columns may vibrate as wholes, or may 

 divide themselves into a number of equal parts, each one of 

 which vibrates as if it were a whole; but when strings vibrate 

 as ivholes, they vibrate more or less in subdivisions at the same 

 time, and hence arise harmonic notes, higher than the funda- 

 mental, or whole string, note. Different sorts of instruments 

 tuned to produce the same fundamental notes, will add to 

 them different harmonics, and thus be characterized by 

 distinct qualities of tone, timbres, as the French call them. 



The vibration of a string being compounded of whole 

 length vibrations, and of the harmonic, or part length vibrations, 

 just explained, there will be certain places at which the two 

 sets interfere and produce nodes, or points of comparative 

 (but not complete) rest ; and Dr. Thomas Young discovered 

 that when a string is plucked at any point, and caused to 



