that part of its force which is directed against the hull and rigging, together with a considerable portion of its action upon the sails, tends to drive her immediately from the direction of the wind, or what is called to LEE-WARD. But since the bow of a ship exposes less surface to the water than her side, the resistance will be less in the first case than in the second, consequently, the velocity in the direction of her head, will in most cases be greater than in the direction of her side, and her real course will be between those two directions.

The quantity of lee-way to be allowed will depend upon a variety of circumstances, as the trim of the ship, the quantity of sail she is under, her velocity through the water, &c., no accurate rule can be laid down for determining at all times the quantity of lee-way that ought to be allowed.

The lee-way which the ship makes may be very accurately determined as follows,—provided the ship be kept steady to the wind during the operation,-describe a semi-circle on the taffrail, with its diameter at right angles to the ship's keel, and divide its circumference into points and quarters, and having a low crutch or swivel in the centre; after heaving the log, the line must be passed into the crutch, just before it is drawn in, and the points and parts of a point, contained between the direction of the log line and the fore and aft line of the semi-circle, will be the lee-way.

Lee-way is always to be allowed from the wind, that is, to the right of the course steered, when the ship is on the PORT TACK, to the left when on the STARBOARD TACK, the observer looking from the centre of the compass towards the point the ship is sailing upon; for example, a ship sailing S. with the wind S.S.W. has her starboard tacks on board, and lee-way must be allowed to the left.

VARIATION.

The needle of the mariner's compass seldom points to the true north of the horizon, and its direction from that point is called the Variation of the Compass.

It is called east or west variation according as the north point of the compass needle is drawn to the east or west points of the true north point of the horizon. Thus, if the north end of the needle points N.N.W. the variation is said to be two points westerly, and the N.N.E. point of the compass will coincide with the meridian. If the north point of the needle be directed to N.E.byN. the compass is then said to have three points easterly variation. The variation is different in different parts of the world, and constantly on the change, and some places have no variation at all; a look at a magnetic chart will shew the extraordinary curves made by the magnetic meridians.

In correcting the compass courses for the variation, observe the two following rules.

With the true course and variation given to find the

compass course.

Rule 1. If the variation be easterly allow it to the left of the course, but if westerly to the right, thus; if the true course of a ship should be S.W.byW. and the variation 2 points W. her compass course would be W.byS.W.

With the course steered by compass, and the variation

given, find the true course.

Rule 2. Now, if the variation be easterly allow it to the right but if westerly allow it to the left of the compass course, thus; if a ship's course by compass be N.E.byE.E. and the variation 14W. her true course will be N.E.E.

In working through the following day's works, the first of which is given at page 27, with the courses fully corrected for lee-way and variation, the pupil will have an opportunity of familiarizing himself with these rules, and their application.