[ 473 ] 



&c and the upper 24,1. Now in the table the oppofite number 

 to 28,1 is 3386, which added to 421 1 gives 7597, the neareft ta- 

 bular number is 7605, which denotes the mercurial height 23, 9,- 

 the error then is only 0,2 of an inch. 



3tio. The barometrical height below being given, to find on 

 what elevation the barometer above fhould ftand at a given num- 

 ber ot inches, temperature 32**. This is in effe£t to feek the ap- 

 proximate height of that elevation, and therefore the elevation is 

 found in the fame manner. Thus the barometer below being at 

 28,4, the eleva;tion at which it would fland at 25,7 is 2603 feet- 



Note. — The table commencing at 30, Ihavelaferted becaufe wfc 

 generally reckon upwards from the level of the fea, at which the 

 mean meicurial height,, temperature 32*, is 30 inches. The inter^ 

 mediate tenths muft be found by fubftradion from logarithm 30. 

 Thus the height of mercury 29,1 denotes an elevation of 793 

 feet. 



CHAP. 



