The result is two noon positions, the first without considering the current, which in the other is taken into account. The current could be considered on each course, but such a degree of precision is seldom necessary. The ship's position differs slightly from that found by the preceding method, but is quite near enough to meet the demands of practice. — 123° 00'.1 W. 125 08.6 W. 2 08.5 W. 128'.5 Lat. Far. L. — 37° 41'.8 N. Long. Far. L. 40 44.3 N. Long. ship Dif. 182.5 = 3 02.5 N. Dif. = Co. N. 29° W. dist. 209' } The last course and distance has been found by Mercator sailing, using logarithms; but while by middle latitude sailing a result nearly the same is obtained, the former method should be favored when the distance is great or near the limits of Table 2. DAY’S WORK Example 4.—A ship had Progreso light bearing S. by E. distant 6'.5. Ship's head S. by E. 12 E. Deviation as per table on page 16. Throughout the 24 hours a current set W. by S. (magnetic) 78 of a mile per hour. Variation 6° 45' E. The ship was sailed as follows: Find the course and distance made good and the ship's position. From that position find the course and distance to Heald Bank lightship. PROGRESO LIGHT HEALD BANK LIGHTSHIP 29° 06' 05" N. 1'.6 E. 25.6 9.8 21.4 15.7 N. by W. N. by E.Y2E. N. E. AN. N. W.YN. N. N. W. N. W. N. N. W. W. by S. 6° E. 10°00' W. 6.5 N. 14° 30' W. 6.'3 N. W. 14 pt. 45 E 8 15 W, 27.4 N 21 00 46.7 N.18 34 W. 44:3 Ꮃ . 44.6 45 53.5 21.0 S.85 30 W. 14.8 Lat. Pro. It. 21° 17'00" N. + 25 02 00 N. 2) 46 19 00 The traverse table is not used in the practice of navigation, but its use must be learned that more practical means may be used to keep account of a ship's track. Usually the following method is not wanted at an examination, but should be used in practice. The former is quite satisfactory so far as the final result is concerned, which is not known until the end of the day. By this the ship's position may be known at any moment. In other words, by one the ship takes the man and by the other the man takes the ship. + dif. 23.1 E. 27.7 N. Lat. Pro. L. 21° 17'. N. Long. Pro. L. 89° 39'.5 W. + 6.3 N. = 21° dep. 1'.6= dif. + 1.7 W. 21 23.3 N. Long. noon 89 41 .2.W. 25.6 N. 10.6 E. 22 dep. 9.8= 21 48.9 N. Long. 4 P.M. 89 30.6 W. + 24.6 N. dif. 22 13.5 N. 22 dep. 2I 4= Long. 8 P.M. 89 07.5 W. + dif. + 20.2 W. 22 dep. I8.7= 22 41 .2 N. Long. Mdt. 89 27.7 W. + dif. + 16.1 W. 23 dep. I4 8= 23 25.5 N. Long. 4 A.M. 89 43.8 W. + 44.6 N. dif. + 30.5 W. 24 10.1 N. 24 dep. 27.98 Long. 8 A.M. 90 14.3 W. +_53.5 N. dif. + 19.8W. 90 34.1 W. dif. (current) + 23 .I W. 25 02 . N. 25 dep. 20.95 Long. noon 90 57.2 W. 44.3 N. |