I. 2. 3. EXAMPLES FOR PRACTICE. 1885.-January 10th, in Longitude 10° W. The observed meridian altitude of the sun's lower limb was 51° 3′ 15′′ bearing North. Index Error, 3' 15" to subtract. Height of eye 17 feet. Required the Latitude. The observed meridian bearing South. Index Required the Latitude. The observed meridian bearing North. Index Required the Latitude. The observed meridian bearing North. Index Required the Latitude. 1885.-February 1st, in Longitude 135° E. altitude of the sun's lower limb was 49° o' o" Error 1' 10" to add. Height of eye 18 feet. 1885. March 20th, in Longitude 91° 10′ E. altitude of the sun's lower limb was 61° 30′ 0′′ Error 6' to subtract. Height of eye 19 feet. 4. 1885.-April 30th, in Longitude 71° 30′ W. altitude of the sun's lower limb was 81° o' o" Error 4' 10" to add. Height of eye 19 feet. 5. 1885.-May 17th, in Longitude o° 40′ W. The observed meridian altitude of the sun's lower limb was 21° 9' 10" bearing North. Index Error 3' 15" to subtract. Height of eye 20 feet. Required the Latitude. 6. 1885.-June 21st, in Longitude 15° E. The observed meridian altitude of the sun's lower limb was 11° 19′ 30′′ bearing North. Index Error 2' 10" to subtract. Height of eye 21 feet. Required the Latitude. 7. 1885.-July 18th, in Longitude 150° W. The observed meridian altitude of the sun's lower limb was 52° 15' 0", bearing South. Index Error 1' 40" to add. Height of eye 23 feet. Required the Latitude. 8. 1885.-August 31st, in Longitude o°. The observed meridian altitude of the sun's lower limb was 46° o' 10", bearing South. Index Error o' 10" to add. Height of eye 22 feet. Required the Latitude. 9. 1885.-September 22nd, in Longitude 170° 10′ W. The observed meridian altitude of the sun's lower limb was 60° 7′ 20′′, bearing North. Index Error 3' 10" to subtract. Height of eye 24 feet. Required the Latitude. 10. 1885.-October 1st, in Longitude 125° 6' E. The observed meridian altitude of the sun's lower limb was 72° 6' 10", bearing South. Index Error 5' 20" to subtract. Height of eye 17 feet. Required the Latitude. II. 1885.-November 30th, in Longitude 178° E. The observed meridian altitude of the sun's lower limb was 24° 59′ o", bearing South. Index Error 4' 30" to subtract. Height of eye 18 feet. Required the Latitude. 12, 1885. December 29th, in Longitude 2° W. The observed meridian altitude of the sun's lower limb was 35° 58 40′′, bearing South. Index Error 2′ 40′′ to add. Height of eye 19 feet. Required the Latitude. D PARALLEL SAILING. RULE. To the log. secant of the Lat. add the log. of the Departure, rejecting 10 from the index, gives the log. of the Difference of Longitude. EXAMPLE:-In Latitude 16° 29′ S. the departure made good was 91.5 miles. Required the D. Long. by parallel sailing. Latitude 16° 29 secant Dep. 91.5 D. Long. 95.42 .... 10.018226 1.961421 1.979647 In each of the following examples the Diff. Long. is TO FIND THE DIFFERENCE OF LATITUDE. The Latitudes of the same name, subtract; TO FIND THE MERIDIONAL DIFFERENCE OF LATITUDE. From Table III. take out the Mer. parts for the two Latitudes; subtract; The Latitudes of the same name, The result is the M. d. Lat. TO FIND THe differenCE OF LONGitude. The Longitudes of the same name, subtract; The Longitudes of different names, add; Bring the result into miles, and name it D. Long. Note. If the Longitudes have been added and their sum exceeds 180° subtract the sum from 360°, and bring the remainder into miles. TO FIND THE COURSE. From the Log. of D. Long (index increased by 10) subtract Log. of M. d. Lat. The result is Log Tangent. of the Course. TO FIND THE DISTANCE. To Log. Secant of the Course add Log. of D. Lat. The result, subtracting 10 from index is the Log. of the Distance. Latitudes Longitudes TO NAME THE COURSE.-If the ship sails : From North to more North the course is North. From South to more South the course is South. From East to more East, the course is East. Note.-The True Course may be named by the following method:-Draw a line East and West to represent the Equator; lay off the two Latitudes ; you can then see at a glance whether the ship sails North or South. Then -draw another line North and South to represent the Meridian of Greenwich; lay off the two Longitudes, and you can see at once if the ship sails East or West. Answer: Course S. 50° 9′ W. Distance 3463 miles. EXAMPLE. Required the Course and Distance from A to B on Mercator's principle. Lat. of A 12° 3' N. M. p..... 728 Long. of A 76° 3′ W. 169 40 E. Answer: Course N. 75° 9′ W. Distance 6313 miles. 6. Lat. A 7° 14′ N. Lat. B 51 7 N. 7.-Lat. A 21° 19′ N. Lat. B 47 50 S. 8.-Lat. A 41° 10′ S. Lat. B 53 19 N. 9.-Lat. A 81° 15′ N. Lat. B O O 10.-Lat. A 60° 4' N. Lat. B 49 5 N. 11. Lat. A 75° 12′ S. Lat. B 70 15 S. 12.—Lat. A 21° 45′ N. Lat. B 16 59 S. |