- ing compass is in position, the Lubber's Line (a
vertical mark on the compass-bowl) must be pointing directly towards the ship's head. Consequently, the point on the compass-card which is in line with the lubber's line shows the direction by compass of the ship's head. What is known as the liquid compass is the best for a small yacht—that is, one in which the bowl is filled with spirit or glycerine, so as to retard the motion of the compass-card; for the violent jumping of a little boat in a sea-way is apt to make the ordinary compass-card swing and spin round so that it becomes impossible to steer by it. Even when a liquid compass is used the card is often very unsteady; in that case watch the points on the card as they swing past the lubber's line. The mean between the extreme points reached will be the direction of the vessel's head.
Before one sets out on a cruise the vessel should be 'swung' to ascertain if there be any deviation of the compass—that is, error due to the local attraction of the ballast or other iron on board. The yacht should be swung when she is at her moorings. In the first place, the correct compass-bearings of some distant object should be ascertained. This can be done by means of a compass raised to such a height above the deck as to be beyond all local attraction; or, if the exact position of the vessel is known, the bearings of some known object (a lighthouse, for example) can be found by reference to a
