Page:Popular Science Monthly Volume 16.djvu/199

Force of wind, nautical scale.	Nautical designation.		Sail that a full-rigged ship may carry, close-hauled by the wind; also her probable speed.	Sail that a full-rigged ship may carry, wind on quarter; also her probable speed.	Force of wind in pounds per square foot.	Velocity of wind in miles per hour.
0	Calm.		All sail.	All sail.	0	0
1	Light airs.		All plain sail and stay-sails; smooth sea; 0·5 to 1 knot per hour.	All plain sail and stud­ding sails; smooth sea; 1 to 1·5 knot per hour.	0·064 to 0·019	1 to 2
2	Light breezes.		All plain sail and stay-sails; smooth sea; about 2 knots.	All plain sail and stud­ding-sails; smooth sea; 2 to 3·5 knots.	0·08	4
3	Gentle beeezes.		All plain sail and stay-sails; smooth sea; 3 to 4 knots.	All plain sail and stud­ding-sails; smooth sea; 4 to 5 knots.	0·36	9
4	Moderate breezes.		All plain sail and stay-sails; smooth sea; 5 to 6 knots.	All plain sail and stud­ding-sails; smooth sea; 6 to 7 knots.	1·0	14
5	Stiff breezes.		Courses, top-sails; to’­gallant sails, and stay-sails; mod. sea; 6 to 7 kts.	All plain sail and stud­ding-sails; moderate sea; 8 to 9 knots.	1·5	17
6	Fresh breezes.		Courses, single-reefed top-sails, to’­gallant sails; moderate sea; 7 to 9 knots.	Courses, top-sails, to’­gallant sails, lower and top­mast stud­ding-sails; mod. sea; 10 to 12 kts.	2	20
7	Very fresh breezes.		Courses, double-reefed top-sails, fore top­mast stay-sail; moderate sea; about 7 knots.	Courses, single-reefed top-sails, to’­gallant sails; moderate sea; 12 to 14 knots.	3	24
8	Moderate gale.		Single-reefed courses, treble-reefed fore and main top-sails, close-reefed, mizzen, fore top-mast stay-sail; rough sea; 4 to 5 knots.	Single-reefed courses, double-reefed fore and main top-sails, close-reefed mizzen; rough sea; about 10 knots.	5	30
9	Strong gale.		Close-reefed courses, close-reefed fore and main top-sails, storm stay-sail; rough sea.	Close-reefed courses, close-reefed fore and main top-sails, storm stay-sails; rough sea.	8	40
10	Very strong gale.		Close-reefed fore sail, close-reefed main top-sail, fore storm stay-sail; very rough sea.	Close-reefed fore-sail, close-reefed main top-sail, fore storm stay-sail; very rough sea.	23	67
11	Violent gale.		Storm-sails, or close-reefed main top-sail and fore storm stay-sail; very rough sea.	Close-reefed fore-sail, close-reefed main top-sail, fore storm stay-sail.	32	80
12	$\scriptstyle {\left\{{\begin{matrix}\ \\\\\ \ \end{matrix}}\right.}$	Hurricane, Typhoon, Cyclone.	None: lying to; drif­ting bodily to leeward.	Scudding under bare poles.	50 and upward	100 and upward

The above sail and speed, corresponding to various forces of the wind, are but approximations to what really takes place according to particular circumstances, such as model of ship, course steered with reference to the wind, condition of the sea, etc.

The customary designations of the clouds are employed, and the portion of clear sky is denoted by figures—10 representing a wholly clear sky, 0 an entirely cloudy one, and intermediate numbers a sky partly clear and partly cloudy.

In the column descriptive of the weather, the following symbols are used, and by means of them, all the possible variations of