Latitude of northermost ex tremity of Grenada - - 12° 14' N.
Distance 38' =218 M.
2. When the given places are under the same parallel.
Rule.—If that parallel is the equator, the difference, or sum of their longitudes is the distance between them. If not, take half the interval between the given places, lay it off on the Meridian on each side of the given parallel, and the inter cepted degrees will be the distance be tween the places. If the given parallel is near the north or south extremity of the chart, the following method may be used. Take an extent of a few degrees from that part of the meridian where the given parallel is the middle of the extent ; then the number of extents, and parts of an extent, contained between the given places, being multiplied by the length of an extent, will give the required distance.
Example.—Required the distance be tween Cape Canton and Funchal, both lying nearly in the same parallel. By proceeding as directed above, the dis tance will be found to be 6° 44', or 404 3. When the given places differ both in latitude and longitude.
Rule.—Find the difference of latitude between the given places, and take it from the equator or graduated parallel ; then lay the edge of a scale over the given places, and move or slide one point of the compass along the edge of the scale, until the other point just touches a parallel. Now, the distance between
the place where the point of the compass rested, and the point of intersection of the edge of the scale and parallel being applied to the equator, or divided paral lel, will give the distance between the places in degrees and parts of a degree ; which, multiplied by 60, will give the dis tance in miles.
Example.—Required the distance be tween Cape Finisterre and Porto Santo.
Take the difference of latitude be tween the given places, viz. 9° 54', from the graduated parallel, and move one point of the compass along the edge of the scale, laid previously over these places, until the other point just touches a parallel: now the interval between the place where the point of the compass rested, and the point of intersection of the scale, and parallel, being applied to the divided parallel, will measure 11° 24', or 684 miles.