Table II.
Correction due to Mean Temperature of the Air.
| Mean Temp. | Factor. | Mean Temp. | Factor. | Mean Temp. | Factor. |
| 10° | 0·955 | 35° | 1·006 | 60° | 1·057 |
| 11 | ·957 | 36 | 1·008 | 61 | 1·059 |
| 12 | ·959 | 37 | 1·010 | 62 | 1·061 |
| 13 | ·961 | 38 | 1·012 | 63 | 1·063 |
| 14 | ·963 | 39 | 1·014 | 64 | 1·065 |
| 15 | ·965 | 40 | 1·016 | 65 | 1·067 |
| 16 | ·967 | 41 | 1·018 | 66 | 1·069 |
| 17 | ·969 | 42 | 1·020 | 67 | 1·071 |
| 18 | ·971 | 43 | 1·022 | 68 | 1·073 |
| 19 | ·974 | 44 | 1·024 | 69 | 1·075 |
| 20 | ·976 | 45 | 1·026 | 70 | 1·077 |
| 21 | ·978 | 46 | 1·029 | 71 | 1·079 |
| 22 | ·980 | 47 | 1·031 | 72 | 1·081 |
| 23 | ·982 | 48 | 1·033 | 73 | 1·083 |
| 24 | ·984 | 49 | 1·035 | 74 | 1·086 |
| 25 | ·986 | 50 | 1·037 | 75 | 1·088 |
| 26 | ·988 | 51 | 1·039 | 76 | 1·090 |
| 27 | ·990 | 52 | 1·041 | 77 | 1·092 |
| 28 | ·992 | 53 | 1·043 | 78 | 1·094 |
| 29 | ·994 | 54 | 1·045 | 79 | 1·096 |
| 30 | ·996 | 55 | 1·047 | 80 | 1·098 |
| 31 | 0·998 | 56 | 1·049 | 81 | 1·100 |
| 32 | 1·000 | 57 | 1·051 | 82 | 1·102 |
| 33 | 1·002 | 58 | 1·053 | 83 | 1·104 |
| 34 | 1·004 | 59 | 1·055 | 84 | 1·106 |
Table III.
| Latitude. | Factor. | Latitude. | Factor. | Latitude. | Factor. |
| 80° | 0·99751 | 50 | 0·99954 | 20 | 1·00203 |
| 75 | 0·99770 | 45 | 1·00000 | 15 | 1·00230 |
| 70 | 0·99797 | 40 | 1·00046 | 10 | 1·00249 |
| 65 | 0·99830 | 35 | 1·00090 | 5 | 1·00261 |
| 60 | 0·99868 | 30 | 1·00132 | 0 | 1·00265 |
| 55 | 0·99910 | 25 | 1·00170 |
Table IV.
| Height in Thousand Feet. | Correction Additive. | Height in Thousand Feet. | Correction Additive. |
| 1 | 3 | 14 | 44 |
| 2 | 5 | 15 | 48 |
| 3 | 8 | 16 | 52 |
| 4 | 11 | 17 | 56 |
| 5 | 14 | 18 | 60 |
| 6 | 17 | 19 | 65 |
| 7 | 20 | 20 | 69 |
| 8 | 23 | 21 | 74 |
| 9 | 26 | 22 | 78 |
| 10 | 30 | 23 | 83 |
| 11 | 33 | 24 | 88 |
| 12 | 37 | 25 | 93 |
| 13 | 41 | 26 | 98 |
Example 1. On October 21st, 1852, when Mr. Welsh ascended in a balloon, at 3h. 30m. p.m., the barometer, corrected and reduced, was 18·85, the air temperature 27°, while at Greenwich, 159 feet above the sea, the barometer at the same time was 29·97 inches, air temperature 49°, the balloon not being more than 5 miles S.W. from over Greenwich; required its elevation.
| Feet. | |||||||
| Barometer | in Balloon | 18·85, | Table I. | = | 13007 | ||
| " | at Greenwich | 29·97 | " | 883 | |||
| 12124 | |||||||
| Mean Temperature, 38°, Table II. Factor | 1·012 | ||||||
| 12269· | |||||||
| Latitude 51½°, Factor from Table III. | ·99941 | ||||||
| 12262 | |||||||
| Correction from Table IV. | 38 | ||||||
| 12300 | |||||||
| Elevation of Greenwich | 159 | ||||||
| "Balloon | 12459 | feet. | |||||