TUESDAY, JANUARY 11th, 



There was a Lecture on " Sound "Waves," by Alfred B. Harding, 

 Esq., F.P.S., F.S.Sc. 



The Lecturer gave a brief account of Wave Motion, as 

 «xp]aining the phenomena of light and heat, and probably of 

 electricity and magnetism, and explained that sound was also due 

 to the impact, in this case, upon the organs of hearing, of undula- 

 tions set up in the atmosphere by the vibrations of sonorous bodies. 

 The physical difference between a musical note and what we call 

 noise is merely this : — a musical note is caused by a succession of 

 sounds, however produced, following each other at regular intervals, 

 and so rapidly as to blend together into one effect ; a succession of 

 irregular, confused sounds, is called noise. He showed that 

 musical notes may be produced by very various and often unex- 

 pected means. For instance, by holding a card against the teeth 

 of a rotating wheel he obtained a series of taps, linking themselves 

 into a note, whose pitch rose as the Avheel increased in speed. The 

 vibrations of tuning-forks were explained and illustrated, and it 

 was shown that in all cases the pitch of the resultant note was 

 dependent on the number of vibrations in a given time, while the 

 loudness or intensity was regulated by the amplitude of the 

 movement. A gas flame was made to produce notes of varying 

 character by placing tubes of different lengths over it, thus causing 

 a rapid series of explosions. 



The ear fails to pick out separate sounds which follow each 

 •other at the rate of sixteen or more per second, while beyond 

 30,000 per second most ears are unable to perceive any effect. 

 The practical range of musical vibrations lies between forty and 

 4,000 per second, embracing about seven octaves. 



The most perfect musical instrument in the world is the 

 human voice, which is caused by the vibration of the "vocal cords" 

 due to the outrush of air from the lungs through the glottis. 

 •Sweetness and smoothness of voice mainly depend upon the 

 perfect closure at regular intervals of the opening in the glottis. 



When vibrations are set up in an elastic medium there is 



