Page:Small-boat sailing; an explanation of the management of small yachts, half-decked and open sailing-boats of various rigs; sailing on sea and on river; cruising, etc (IA smallboatsailing01knig).pdf/243

 true, we have no correction to make for variation. With our parallel rules we now work these bearings successively across the chart from the compass design to A and B, and from these points we draw two lines in the direction of the bearings. Where these lines cut each other, at C, is the exact position of our vessel at the time we took the bearings. We next measure the distance from the ship to either landmark or to our port, with the dividers, reading off the number of miles on the graduated meridian, or on the scale of miles printed on the chart.

When taking cross-bearings in this way, select such a position that the angle between them is as nearly as possible 90°; for the larger or the smaller than 90° the angle is, the greater will be the error in position caused by a slight error in taking a bearing.

An azimuth compass is a compass specially arranged for the observation of bearings. A moveable ring is fitted on the outside of the compass-bowl, having two sight-vanes exactly opposite each other. Each vane has a vertical slit in it, the slit in one being wider than that in the other, and having a horsehair stretched vertically across it. By turning the sight-vanes in the direction of the object and looking at it through both slits, a bearing can be taken with great accuracy. Azimuth compasses are not often carried on small yachts; but an ordinary steering compass can be made to serve for an azimuth by removing the cover from the binnacle