Sg6 , LECTUEE.XXXIir. 



scend from the key note by seven perfect fifths, which will complete the 

 scale. Any of these modes of temperament may be actually executed, either 

 by the estimation of a good ear, or, still more accurately, by counting the fre- 

 quency of the beats which the notes make with each other. 



For denoting precisely the absolute as well as the relative frequency of the 

 sounds of the different octaves, we employ the first seven letters of the 

 alphabet; A being the key note of the minor mode, in the scale of natural 

 notes, and C of the major. The peculiar characters used in music are gene- 

 rally disposed on five or more lines, with their intervening spaces, each im- 

 plying a separate step in the scale, setting out from any line at pleasure* 

 which is marked with an ill formed G, a C, or an F; a sharp or a flat im- 

 plying that all the notes written on the line, or in the space, to which it 

 belongs, are to be raised or depressed a semitone, and a natural restoring the 

 note to its original value. The actual frequency of the vibration of any note, 

 according to the pitch most usually employed, may be found, if we recollect 

 to call a noise, recurring every second, the first C, then the C denoted by the 

 mark of the tenor cliff will be the ninth, consisting of 256 vibrations in a 

 second. The fifth, consisting of sixteen vibrations, Avill be nearly the low- 

 est audible note, and the fourteenth the highest note used in music, but 

 the sixteenth, consisting of above 30 000 vibrations in a second, may perhaps 

 be an audible sound. The frequency of the vibrations of the other notes 

 may easily be calculated from the known relations which they bear to the 

 note thus determined. (Plate XXV. Fig. 355.) 



