io6 SCIENTIFIC APPARATUS. 



2. The reciprocal influence of instruments on apparatus no 

 better instance of which can be found than the discovery of 

 Tartini's " Terzo Suono," or third sound ; originally taught by the 

 great violinist to his pupils as a means of accurate tuning, but 

 involving a new and important acoustical principle. 



3. In many cases instruments of music actually stand in the 

 place of apparatus. Strictly considered, a musical note is of itself 

 a mathematical fact ; quite independent of its power of exciting 

 emotion and pleasure by its artistic production. On the other 

 hand, tuning and intonation, originally left entirely to the accurate 

 and cultivated ear of a skilled performer, have become a branch of 

 science, with definite laws and practical rules ; insomuch that the 

 instinctive departures from a fixed tuning, which the older violinists 

 made by a kind of instinct, are now explained, and even the dis- 

 position of various instruments with differing qualities in an 

 orchestra is shown to be correct, or the contrary, according as 

 the harmonics of each peculiar tone are consonant or dissonant. 



