120 
DETERMINATION OF ALTITUDES BY BAROMETER. 
The following example is introduced to illustrate the method of computation above described : 
EXAMPLE. 
Data for determining the altitude of Camp 22, near upper end of upper canon of Pit river. 
Date. 
Hour. 
No. of 
barometer. 
Reading of 
barometer. 
Attached 
thermometer. 
Detached 
thermometer. 
1855. 
Inches. 
o 
o 
August 7 
6 p. m. 
1060 
25. 990 
77. 0 
75. 0 
6 p. m. 
1089 
25. 957 
77. 0 
75. 0 
9 p. HI. 
1060 
25. 990 
63. 5 
65. 0 
9 p. m. 
1089 
25. 953 
63. 5 
65. 0 
August 8 
6 a. m. 
1060 
26.025 
48. 0 
47. 0 
6 a. m. 
1089 
25. 981 
47.5 
47. 0 
Corrections applied before computation. 
6 p. m., August 7. 
9 p. m., August 7. 
6 a. m,, August 8. 
Bar. 1060. 
Bar. 1089. 
Bar. 1060. 
Bar. 1089. 
Bar. 1060. 
Bar. 1089. 
Inches. 
Inches. 
Inches. 
Jnches. 
Inches. 
Inches. 
Barometric reading_ 
25. 990 
25. 957 
25 i 990 
25. 953 
26. 025 
25. 981 
Correction for temperature of mercury.. 
—. 112 
— 112 
—. 081 
—. 081 
—. 045 
—. 044 
Correction for instrumental errors ... 
. 000 
+. 044 
. 000 
+. 044 
. 000 
+. 044 
Correction for horary oscillation-- 
+. 020 
+. 020 
—. 004 
—. 004 
O 
O 
f 
—.040 
Correction for abnormal oscillation_ 
+. 075 
+. 075 
+. 075 
+.075 
+. 040 
+. 040 
Corrected readings__ 
25. 973 
25. 984 
25. 980 
25. 987 
25. 980 
25. 981 
Mean of corrected readings, 25.981 inches. 
Mean daily air temperature, about 67° Fahrenheit. 
Computation by Loomis’ tables. 
H = 30. 057 H' == 25. 981 
i= 64° t' — 07° 
Part I gives for 
H = 30. 057 
H' = 25. 981 
27659. 2 
23851. 8 
Approximate altitude a _ 
a , , 3807.4 
— (t 4- t‘ —64) 
900 v ~ ' 
900 
X 67 
3807.4 
283.4 
Second approximate altitude A..... 4090.8 
Part III gives for A = 4090. 8 and L = 41° 50'_ 1.8 
Part IV gives for A = 4090. 8_____ 11. 1 
Altitude of station in feet 
4103. 7 
