in the interval, Height of Eye 21 feet. Required the line of position when the first Altitude was taken; also the bearing of the Sun, and the position of the ship by Sumner's Method when the second Altitude was observed, the ship being supposed to be between the parallels of 47° o' N. and 47° 20' N. II. If at sea on August 8th, 1885, A.M., and uncertain of my position, when the Chronometer showed 7d 22h 55m 36 Greenwich Mean Time, the observed Altitude of the Sun's L. L. was 54° 35′ o", and again P.M. the same day, when the Chronometer showed 842h 14m8s Greenwich Mean Time, the observed Altitude of the Sun's L. L. was 46° 46′ 25′′, the ship having made 22 miles on a true S.W. S. course in the interval, Height of Eye 18 feet. Required the line of position when the first Altitude was taken; also the bearing of the Sun, and the position of the ship by Sumner's Method when the second Altitude was observed, the ship being supposed to be between the parallels of 48° 35′ N. and 49° 5' N. 12. If at sea on September 29th, 1885, A.M., and uncertain of my position, when the Chronometer showed 28d 11h 952 Greenwich Mean Time, the observed Altitude of the Sun's L. L. was 22° 2′ o", and again A.M. the same day, when the Chronometer showed 28d 13h 5740 Greenwich Mean Time, the observed Altitude of the Sun's L. L. was 39° 1′ 32′′, the ship having made 20 miles on a true E. by N. course in the interval, Height of Eye 21 feet. Required the line of position when the first Altitude was taken; also the bearing of the Sun, and the position of the ship by Sumner's Method when the second Altitude was observed, the ship being supposed to be between the parallels of 47° 30' N. and 48° o' N. PRACTICAL EXAMINATION ON THE FOR ONLY MATES, FIRST MATES AND MASTERS. The Deviation Table given below is to be used in all the questions on the use of the chart. It should be particularly noticed that this Table contains the Deviation of the Compass for all directions of the ship's head by that compass, whereas in the Examination we have to find the deviation of the compass for a given direction of the ship's head by a correct magnetic compass. This may easily be found by Napier's diagram (if allowed); if not allowed, it may be found by allowing the deviations from the Table on the courses opposite which they stand, the results will be the Correct Magnetic Courses corresponding to the Compass courses or Ship's Head by Compass. We then have a second table of deviations for directions of ship's head correct magnetic. TABLE OF DEVIATIONS. Example.-Suppose the true course to be W. by N., the variation to be 260 W., and the compass course is required. [The Canditate will be required to work out the following questions either on a true or " magnetic chart, whichever may be handed to him by the Examiner; and also determine whether the Chart is a "true "magnetic" one, and whether it is for the northern or southern, and eastern or western hemisphere.] or The Chart to accompany these Examples, price 6d., may be had of J. Newton, Sailors' Home, London, by post, 7d. 1. Using Deviation Card No.-find the Course to be Steered by Compass from A to B, also the Distance. (Var. 26° W.) Directions.-Lay a pair of parallel rulers over the points indicated by A and B, and join these points by a straight line. Then, taking care to preserve their direction, move the rulers to the centre of the Compass, when the True or the Magnetic Course is found, depending upon the Compass on the Chart as to whether it is a True or Magnetic Compass. If the Compass is a Magnetic Compass, you proceed to apply the deviation to obtain the Compass Course; but, if the Compass on the Chart is a True Compass, you must seek on the Chart the Variation nearest the position of the ship. Note. In the following Examples the Variation is assumed to be 26° W., and the Compass on the Chart is considered as a True Compass. This being so, the True Course from A to B is found to be N.W. by N. We then proceed as follows: True Course N.W. by N.....or N. 33° 45' W. Variation.. 26° o' W. to the Right. The distance from A to B is found in the usual way on the Graduated Meridian, and in this instance is 72 miles. ANSWER-Compass Course, N 1° W. Variation, 26° W. Deviation, 6° 50′ W. II. With the ship's head on the above Compass Course F bore by Compass N 61° E., and G bore by Compass N 29° W., give the ship's position. Directions.-The Compass on the Chart being a True Compass, it is necessary to turn these two Compass Bearings into True Bearings by applying the deviation and variation. Now place the parallel rulers on N.N.E. E. on the Chart Compass, and being careful to preserve their direction, move them to the point F, from which point draw a line towards the ship, see small Chart p. 84. Next lay off from G its True Bearing N.W. by W. ↓ W., and where these two bearings cross each other is the position of the ship, the Latitude and Longitude of which are found in the usual way to be— ANSWER.-Latitude 47° 25' N. Note.-If the degrees of Longitude are not printed on the Chart on which the Candidate has to do the above work, they will be marked in pencil or ink by the Examiner, either along the top or bottom, or the Candidate must mark them himself. The Longitude is West if the degrees increase to the left hand, but East if they increase to the right hand. III. With the ship's head on the above Compass Course C bore N 79° W. by Compass, and after continuing on the same course 11 miles it bore S. 661° W., find the position of the ship, and her distance from C at second Bearing. Directions. First turn the two Compass Bearings into True Bearings. Thus : 1st Compass Bearing N. 79° 30' W. 2nd Compass Bearing Deviation.. 6° 50' W. Deviation ......N. 112° 20′ W. True bearing.... or W. S. W. S. 67° 40' W. S. 66° 30′ W. 6° 50' W. S. 59° 40' W. 26° o' W. S. 33° 40′ W. or S.W. by S. |