(b) by increasing in the south, or (which causes a similar statical force) by decreasing in the north;
(c) by increasing in the north, or (which has the same effect) by decreasing in the south;
(d) by increasing in the west, or (which has the same effect) by decreasing in the east;
(e) by increasing in the east, or (which has the same effect) by decreasing in the west;
| Scale, 0 to 6. | Pressure in pounds per square foot. | Miles per hour. | Seaman’s Nomenclature. | Scale, 0 to 12. | Beaufort Scale. | ||
| 0·0 | 0·00 | 2 | Calm | 0 | |||
| 0·5 | 0·25 | 5 | Light Air | 1 | Just sufficient to make steerage way. | ||
| 1·0 | 1·00 | 10 | Light Breeze | 2 | With which a ship with all sail set would go in smooth water. | 1 to 2 knots. | |
| 1·5 | 2·25 | 15 | Gentle Breeze | 3 | 3 to 4 „ | ||
| 2·0 | 4·00 | 20 | Moderate Breeze | 4 | 5 to 6 „ | ||
| 2·5 | 6·25 | 27 | Fresh Breeze | 5 | In which she could just carry | Royals, &c. | |
| 3·0 | 9·00 | 35 | Strong Breeze | 6 | Single Reefs and T.G. Sails. | ||
| — | — | 42 | — | Double Reefs and Jib, &c. | |||
| 3·5 | — | 50 | Moderate Gale | 7 | Triple Reefs, &c. | ||
| 4·0 | 16·00 | 60 | Fresh Gale | 8 | |||
| 4·5 | 20·25 | — | Strong Gale | 9 | Close Reefs and Courses. | ||
| 5·0 | 25·00 | 70 | Whole Gale | 10 | In which she could just bear close-reefed Maintopsail and reefed Foresail. | ||
| 5·5 | 30·25 | 80 | Storm | 11 | Under Storm Staysails or Trysails. | ||
| 6·0 | 36·00 | 90 | Hurricane | 12 | Bare Poles. | ||
| With | (a) | similar wind and weather | will continue. |
| „ | (b) | winds will veer towards | west. |
| „ | (c) | „ „ | east. |
| „ | (d) | „ „ | north. |
| „ | (e) | „ „ | south. |
“The probable strength of wind will be in proportion to the rate of increase of statical force, or differences of barometrical readings. The position of least pressure must be carefully considered; as, in accordance with the law, the wind will blow around that locality. The same remark applies to areas of high pressure, which, however, very rarely occur in a well-defined manner over the British Isles.”
Referring to the table on page [76], the scale 0 to 6 was formerly used by meteorological observers at land stations, and it was intended to express, when the square of the grade was obtained, the pressure of the wind as given in the second column.
“The velocity is an approximation as near as can be obtained, from the values assigned by Neumayer, Stow, Laughton, Scott, Harris, James, &c.”[[15]]