[ 452 ] 



raeafures; therefore by any higher number of degrees above 2,2° 

 they gain ,0025 multiplied into that number. This is the firft or 

 fundamental produSl. 



ado. This produd multiplied into the logarithmic refult, ex- 

 preffed in fathoms, gives the fecond produd, whicli affords the 

 calorific refult or fupplemental height, and which I call the fup- 

 plemental produEl. For fince 1000 meafures of air gain by multi- 

 plication into the number of degrees expreffed in the fundamental 

 difference, the quantity indicated by the firft produd, it is plain 

 that the meafures indicated by the logarithmic refult would gain 

 by multiplication into that produd the quantity which refults from 

 that multiplication. This produd therefore added to the loga- 

 rithmic refult in temperatures above 32*', or fubftraded if below 

 32*^, gives the compleat meafure of the elevation. 



A FEW examples will render this procefs more intelligible to 

 many, f feled them chiefly from Sir George Schuckburg, becaufe 

 he had the rare advantage of having the cotemporaneous indica- 

 tions of his inftruments at one ftation noted by intelligent perfons, 

 while he himfelf obferved them at another ftation, namely, the 

 highcft. General Roy had fometimes the fame advantage, but I 

 fear not always, and hence probably the defedive meafure of 

 Mount Elio in Wales. 



Meafiirement 



1 



