[ "3 ] 



From the preceding obfervations and tables are deduced the 

 following rules to determine the adual differences of the heights 

 of the places of obfervation. 



R U L E I. 



ReOUce the temperature of the mercury in each barometer 

 to the mean temperature at each flation. 



R U L E II. 



Reduce the obferved temperatures of the atmofphere at the 

 dlflferent ftations to the imaginary uniform temperature. 



RULE III. 



Seek the common logarithms of each obferved height, cor- 

 reaed by rule I. in inches and tenths, and rejed: the index. 



Gut off the fitft four figures with a comma, and place the 

 logarithms one under the other. The differences of the parts 

 of thefe logarithms, preceding the comma, fhew the adual 

 differences of the heights of the ftations in Englifh fathoms ; 

 and the differences to the right df the comma in decimals of a 

 fathom, provided the mean temperature of the atmofphere 



VOI..V. P .^'^^' 



