[' 3^9 ] 



Thus in the firft hundred feet it becomes 54° — ^408 = 53°,592. 

 And at 200 feet it becomes 54° — ,40b x 2, &c. 



2do, The rafe of diminution being known, fuppofe ,408 to 

 find its amount at a given height, fuppofe 1364 feet? By the 

 fecond formula we have 0,408 X 13,64 =:5*',5. 



3io. The diminution of heat being known, fuppofe 5°, 5, and 

 alfo its rate, fuppofe 0,408, to find the height at which this 

 diminution takes place ? By the third formula we have 



of the truth 



——z =13,48 which X 100 = 134S feet, which wants but i c feef 

 0,408 



Hence we fee that heights may often be meafured by thermo- 

 metors only with tolerable accuracy. 



-40. The heat aliove, fuppofe 48^,5, and its diminution, fuppofe 

 5*^,5 being given, to find the heat below} By the fourth formula 



48^5+5°,5-54^ 



5°. So alfo the heat below, and the diminution above, being; 

 known, the heat above may be found by the fifth formula as is . 

 evident. Thus 54*^ (in the laft example) — 5,5 = 48,5. 



, 6°. The ; 



