New Tables for Finding Heights by the Barometer. 77 



Small Corrections, depending on Decrease of Gravity at the Upper Station, 

 Height of the Barometer at the Loioer Station, and the Latitude. 



A. — n (F' — F)-|- small corrections. 



Rule. — Take out the values of F corresponding to the heights of the baro- 

 meter at the upper and lower stations ; take their difference, Mhich in case 

 one of them is negative will be their numerical sum, multiply the difference 

 by the vaUie of n corresponding to the sum of the temperatures of the air at 

 each station ; the product A will be very nearly the height in feet of one 

 station above the other. To this value, apply the small corrections for a 

 final result. If the barometer be a mercurial one, a further correction of 

 2 J feet will have to be subtracted for each degree of excess of the temperature 

 of the mercury at the lower station over that of the upper. 



Example. — On May 8, 1889, an aneroid barometer, at the meteorological 

 station near the summit of Mount Macedon, indicated 27 '03 in., the tempera- 

 ture of the air being 59° ; the same barometer, a few hours after, read at 

 the Melbourne Railway Station 30-23 in., the temperature of the air being 

 62*. Find the difference of height : — 



27-03 in. F= 2987-8 

 30-23 in. =-119-6 



Diff. 



3107-4 

 100-1 = n for 121° 



3107-4 

 3 1 



3110-5 

 Small corrections + 8-2 



Difference of height . . 3118-7 



