DETERMINATION OE HEIGHTS. 
215 
Part I. gives the altitude, subject to correction, for the temperature of 
the air, and for the other influences which are the subjects of Parts II., 
III., IV., and Y. 
Method of Computation. —(1) Take from Part I. the two numbers cor 
responding to the two barometric heights; (2) from their difference sub¬ 
tract the correction found in Part II., with the difference between the 
thermometers that are attached to the barometers ( Mem .: this correction 
is not wanted for aneroids, for their works are mechanically compensated 
for temperature); (3) for the temperature of the intermediate air between 
the two stations, multiply the nine-hundredth part of the value already 
obtained by the difference between the sum of the temperatures at the 
two stations and 64°. This correction is additive when the sum of the 
temperatures exceeds 64°, otherwise it is subtractive; or, what comes 
to the same thing, use the multiplier already given in Table II., p. 213. 
(4) For further precision take corrections from Parts III. and IV., also 
from Part V., when the lower station is so high as to bring the case 
within the range of that table:— 
(Example i.) 
Upper Station. 
o 
Lower Station 
by Sea. 
o 
Thermometer in open air . 
't hermometer in barometer 
Barometer 
Latitude 2i Q . 
p. l4 T _ ( for 30*046 inches 
laitl. gives ( for inchea 
70 3 
70*3 
Inches. 
23*66 
77*5 
77*5 
Inches. 
30*046 
27649*7 
21406*9 
Difference . 6242*8 
Part II. gives for 77°*5 — 70°*3 (= 7°*2) . —16*9 
Approximate altitude . 6225*9 
6225^9 x (77-- 5 + 70°*3 - 64°) = 6*918 X 83*8 . — + 579 * 7 * 
900 - 
Nearly correct altitude . 6805*6 
Part III. gives for above altitude and latitude 2i°. +13*3 
Part IV. gives for above altitude. + 19*3 
Part V. is not used in this case. o*o 
Correct height above sea. 6838*2 feet. 
* If Table II., p. 213, had been used, we should have written— 
.T° J =74° nearly. 
2 
The corresponding multiplier is 1*0933 
1*0933 X 6225*9 = 6806*8, 
