[ 45^ ] 



Here the error of my method is 13,21 feet. Schuckburg's er- 

 ror is 11,5 feet, and' Roy's — 2 feet. But in calculating the height 

 from the obfervations taken the next day, July the 12th, Roy's 

 error was . . 29,5 feet, Schuckburg's . . 19,7 feet, and mine . . 20,6 

 feet. Phil. Tranf. 1778, p. 685. 



Here it is evident, that thefe errors arofe from a faulty deter- 

 mination of the temperature of the atmofphere, for the approxi- 

 mate height found by. General Roy, July nth, was lower than 

 that found July 12th. On the nth it was 3142 feet, and on the 

 1 2th it was 3145 feet, and yet the compleat height was more de- 

 fedive. By my calculation it was higher the fecond day than on 

 the firft, and yet the error was jninus, though plus on the firfl 

 day. 



I SHALL here add farther, that th6error in calculating the height 

 of Snowden, from the obfervations of Auguft 7th, two hours 

 P. M. is by Schuckburg's method 8,1 feet, by mine 9,7, by Roy's 

 3,7 ; but by the mean of nine obfervations on diiFerent days, Roy's 

 error is 6,1 ; ihe calculation that gave the beft refult was made on 

 obfervations at nine o'clock A. M. and the worft were made on ob- 

 fervations during a haze or fog, whether above or below; which 

 fhews that the errors of thefe calculations proceed chiefly from the 

 diforderly progreflion of heat into the atmofphere. Hence the 

 winter feafon is not well fuited to them.' 



tsf?'.\ Having 



