[ 3^^ ] 



The height of this line in any 'atitude, divided by 100, gives 

 the number of terms in the arithmetical progreflion, each confifl- 

 ing of 100 feet; and the difference of the heat below, and 32°, 

 gives a dividend, which, divided by the number of terms, lefs one, 

 gives the common difference of the progreflion*; and the common 

 difference, multiplied by the number of terms in the height of a 



mountain, 



* It is commonly a decimal fraflion, of which the three firft fignificative figures 

 are generally fuilicient, but it is fafer to take four in fome cafes. 



