by means of the Temperature at which Water Boils. 35 

 the altitude in feet, to be generally conformable to the expression 



h 



300+ 35o' 



we may represent the difference of temperature by 



653 (T-T') 

 375 + T-T" 



or, as nearly as the nature of the case admits, 



T=/'+g(2ir-T'). 



Example. — Professor Forbes found the boiling-point on the 

 Col d'Erin, between Evolena and Zermatt, to be 191°-93, and 

 the air 34° F. ; whilst the barometer at Geneva was 28*73 in./ 

 and the temperature 72°, to determine the height. Here, 



by Table I. . . A' = 10834 feet. 

 by Table III. . h == = 1134 „ 



Difference . . 9700 „ 



T== i(34+ 72) =53, multiplier in Table II. 1-04555 ; 



.\ height above Geneva 10142 feet, 



and above the sea . . . 10142 + 1343 = 11485 „ 



By Logarithms. 

 Log 28-73 in. . 1*45834 

 Table I. log B' . 1-29765 

 Difference . . 0*16069 log . 9*20599 

 t=53°F. . . Table II., log A. 4-80016 

 H'-H = 10142 ft. as before, log . 4*00615 

 And if we take the upper observation only into account, 



T=34°+^(212 -191 -93) = 34° + 17 = 51 o , 



and h'= 10834; hence by Table II., 



H'=10834x 1-04145 = 11283 feet 



above the point where water boils at 212°, differing from the 

 determination above, from both observations, by about 200 feet, 

 or j'g-th of the height ; but the observation at Geneva gives its 

 height above this point as only 1235 feet instead of 1343 feet, 

 indicating that the pressure of 30 inches at the time of the obser- 

 vation occurred about 108 feet above the sea-level. 

 Colaba, Bombay, October 1862. J. Burgess. 



D2 



