524 NATURE'S TEACHINGS. 



number of drawings. I will, therefore, endeavour to explain 

 its principle in as brief terms as possible. 



The reader will observe that at the lower part of the instru- 

 ment there is a disc pierced with a number of holes, and that 

 above these are two dials. Below the perforated disc, and 

 therefore unseen, is a circular plate, also pierced with holes. 

 When a pipe is attached to the lower part of the instrument, 

 and air propelled through it, the disc begins to revolve, every 

 revolution being recorded by the dials, after the fashion of the 

 ordinary gas-meter. 



As the pressure is increased, the air, passing through the 

 holes, assumes a rhythmical beat, which soon becomes meta- 

 morphosed into musical notes. It is evident, therefore, that, 



HUMBLE-BEE. 



by means of this instrument, the number of vibrations which 

 produce a definite tone can be measured with absolute accuracy 

 by any one who has an ear capable of appreciating a musical 

 note. 



It is by means of the Siren that the much-disputed tonic of 

 C will be settled, the Continental and the English C being 

 greatly at variance, and even the English C having been 

 advanced almost a tone since the time of Handel. Much is it 

 to be wished that Italy, the home of song, and England, the 

 patron of song, could unite in their tonic, instead of having 

 systems so widely different that an Italian singer is at a loss 

 with the English pitch, as is an English singer with the Italian 

 pitch. 



The Siren is even brought into the service of entomologists, 

 enabling them to measure by the sound the rapidity with which 

 a flying insect moves its wings. By means of this instrument 



