170 Mr. Herapath on the Velocity of Sound and 



The difference may, therefore, be easily computed : <« Take a 

 ■jljjth of the altitude in yards ; subtract a ^th of this from 

 itself; and then add -f^ths of the part so subtracted." Thus, 

 if the altitude was 7600 yards — 



76 ^maoU. ^i> . 'i 



- 7.6 



+ 1.52 



69^92 

 And in centigrade degrees — '* To a ^^-J-^th of the alt. in fathoms 

 add twice a yji^th of itself, and then a-^s^th of this corrrection." 

 For example, in the preceding instance : — 



38 

 .76 

 .076 



38°.836 

 Applying this rule to the cases extracted by Mr. Ivory from 

 Ramond's collection of observations, we shall find it agree with 

 the observations much better than the observations, probably 

 by different individuals, at the same place, agree with one ano- 

 ther^ as the following table shews : — 



