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In the last Example it is plain, that as the Difference of Latitude is more than the Latitude left, the Ship must have crossed the Equator, and consequently come into South Latitude.
Note. When one of the Places has no Latitude, or is on the
Equator, then the Lat. of the other Place is their Difference of La
Hence it follows, that in every Place the North Point of the Card shews the Position of the Meridian at that Place, and some one Rhumb or Point of the Card will coincide with, or be directed along : the Track that makes any given Angle with the Meridian; conseQuently, by the Help of the Card or Compass, a Ship may be kept in any proposed Track or Course.
A Rhumb Line, or Point, is a Right Line drawn from the Centre of the Compass to the Horizon, and is named from that Point of the Horizon it falls in with,
The Course is the Angle which any Rhumb Line makes with the Meridian, and is sometimes reckoned in Degrees, and sometimes in Points of the Compass; so that if a Ship sails upon the second Rhumb or N. N. E. the Course is 22 Degrees 30 Minutes: And so for any other, as in the following Table, which the Learner should be so well acquainted with, or the Compass, as to be able readily to tell how many Points any Course or Rhumb is distant from the Meridian, or from the Parallel,
LANE SAILING is the Art of Navigating a Ship upon Principles deduced from the Notion of the Earth's being an extended Plane ; and is no more than the Application of Plane Trigonometry to the Solution of the several Variations, or Cases; where the Hypothenuse, or lengest Side, is always the Rhumb that, the Ship sails upon. --- o The Perpendicular is the Difference of Latitude counted on the Meridian, and the Base the Departure: which is either Easting or Westing, counted from the Meridian. The Angle opposite the Base is the Course, or Angle, that the Ship makes with the Meridian ; and the Angle opposite the Perpendicular
is the Complement of the Course, which being taken together, make
always eight Points or Rhumbs, which is 90 Degrees. In constructing Figures relating to a Ship's ë. let the upper Part of the Paper, or what the Figure is drawn upon, always represent the North ; the lower Part will be the South; the Right Hand East ; and the Left West. Draw the North and South Line to represent the Meridian of the Place the Ship sails from ; then if the Ships Course is to the South
ward, mark the upper End of the Line for the Place failed from ; . but if the Course is Northward, mark the Lower End for that