The angle ADN will be the course, the line AC the departure, and the line AE the difference of longitude. Its comp. 34 06 or the angle of course. With the distance 250, and nearest difference of latitude 2073, is found course 34°, and departure 139.8. And with the comiddle latitude 62° as course, and departure 1395, is found distance 158, which is the difference of longitude. Solution by Mercator's Sailing. Construct the triangle DAC, as B before. Find the meridional difference of latitude, and set it off northward from D to E. Draw EB to the westward of E, and parallel to CA. Continue DA till it intersect EB in B. EB will be the difference of longitude. Computation. The course and departure are found by plane sailing, as Course and departure being found, as before, the meridional difference of latitude 234, taken as difference of latitude under the same course, gives departure or difference of longitude 158.3. 7. From a port in latitude 53° 7′ N. a ship sails ESE. till her departure becomes 112 miles. It is required to determine the distance sailed, and the difference of longitude made. Solution by Middle Latitude Sailing. Construction. Draw the meridian NS, and from a point D in the same draw DA on a SSE. course. Draw the parallel of latitude Da to the eastward 112 miles, the departure. Draw likewise the line aA parallel to NS, and intersecting DA in A. Through A draw the parallel AC intersecting NS in C. DC will be the difference of latitude, and DA the distance. Find the latitude, to which she is come, and thence the middle latitude. From A draw the line AE, making the angle CAE= the middle latitude, and the said line will be the difference of longitude. Computation. To find the difference of latitude by plane sailing. Cosine middle latitude 37° 17 ar. co. 0°21779 : Tangent course 67 30 10.38277 :: Difference of latitude 46'4 I'66645 : Difference of longitude 184'9 2.26692 By By the Traverse Table. With course 6 points, and distance 112 miles, is found difference of latitude 46'3, and distance 121. And with comiddle latitude 37 as course, and the same departure, is found 186 the difference of longitude in the column of distance. Solution by Mercator's Sailing. Construction. Construct the triangle DAC, as before, and find the present latitude. D From the two latitudes and their corresponding meridional parts find the meridional difference of latitude, which E set off to the southward from D to E. 1 C Draw EB to the eastward from E, and parallel to CA. Continue DA till it intersect EB in B. EB will be the difference of longitude. Computation. The distance and difference of latitude are found by plane sailing, as has already been done; and thence the two latitudes. Lat. from which she sailed 53° 07′ N. Mer. parts 3775 |