§ 5. One atmosphere = 14·7 lb. per sq. in. = 2116 lb. per sq. ft. = 760 millimetres of mercury.
A column of water 2·3 ft. high corresponds to a pressure of 1 lb. per sq. in.
1 H.P. = 33,000 ft.-lb. per min. = 746 watts.
Volts × amperes = watts.
π = 3·1416. g = 32·182 ft. per sec. at London.
§ 6. Table of Equivalent Inclinations.
| Rise. | Angle in Degs. | ||||
| 1 | in | 30 | 1·91 | ||
| 1 | " | 25 | 2·29 | ||
| 1 | " | 20 | 2·87 | ||
| 1 | " | 18 | 3·18 | ||
| 1 | " | 16 | 3·58 | ||
| 1 | " | 14 | 4·09 | ||
| 1 | " | 12 | 4·78 | ||
| 1 | " | 10 | 5·73 | ||
| 1 | " | 9 | 6·38 | ||
| 1 | " | 8 | 7·18 | ||
| 1 | " | 7 | 8·22 | ||
| 1 | " | 6 | 9·6 | ||
| 1 | " | 5 | 11·53 | ||
| 1 | " | 4 | 14·48 | ||
| 1 | " | 3 | 19·45 | ||
| 1 | " | 2 | 30·00 | ||
| 1 | " | √2 | 45·00 | ||
§ 7. Table of Skin Friction.
Per sq. ft. for various speeds and surface lengths.
| Velocity of Wind | 1 ft. Plane | 2 ft. Plane | 4 ft. Plane | 8 ft. Plane |
| 10 | ·00112 | ·00105 | ·00101 | ·000967 |
| 15 | ·00237 | ·00226 | ·00215 | ·00205 |
| 20 | ·00402 | ·00384 | ·00365 | ·00349 |
| 25 | ·00606 | ·00579 | ·00551 | ·00527 |
| 30 | ·00850 | ·00810 | ·00772 | ·00736 |
| 35 | ·01130 | ·0108 | ·0103 | ·0098 |