June 7.] THE NEW ZEALAND GAZETTE. 1489

(2) by figures on the dock-walls; (3) by bearings of a distant object.

55. Describe, in detail, how you would determine the deviation of your compass by the bearings of the sun; also by a star or planet.

56. Describe the uses to which the Napier’s diagram can be applied, and its special advantages.

57. Describe clearly how the Napier’s diagram is constructed.

58. For accuracy, what is the least number of points to which the ship’s head should be brought for constructing a complete curve of deviations, or a complete table of deviations?

59. Nearing land, and being anxious to check your deviations on a few courses you may probably require to steer, what is the least number of points it would be necessary to steady the ship’s head upon, if making use of a Napier’s diagram, in order to ascertain the deviation on each of the points, say, in a quadrant of the compass? and describe clearly how you would do this at sea.

60. Supposing you have no means of ascertaining the magnetic bearing of the distant object when swinging your ship for deviations, how could you find it, approximately, from bearings of the object taken with the ship’s head on equidistant compass points; and how far, as a rule, should the object be from the ship when swinging, or steaming round?

61. Example.—Having taken the following compass bearings of a distant object, find the object’s magnetic bearing, and thence the deviations:—

(a.) Magnetic Bearing required.

(b.) Construct a curve of deviations on a Napier’s diagram, with the deviations as above, and give the courses you would steer by the standard compass to make the following courses, magnetic:—

Magnetic courses: N.N.W., S.S.E., W.N.W., E.S.E.

Compass courses required:

(c.) Supposing you have steered the following courses by the standard compass, find the magnetic courses made from the above curve of deviations:—

Compass courses: N.N.E., E.N.E., S.S.W., W.S.W.

Magnetic courses required:

(d.) You have taken the following bearings of two distant objects by your standard compass as above: with the ship’s head at N.E. ½ E., find the bearings, magnetic:—

Compass bearings S.E. by S., and —N.N.W

Magnetic bearings required:

62. Assuming the deviations observed with ship’s head by compass to be as follows [or as in Question 61, whichever may be given], determine the value of the co-efficients A, B, C, D, and E, and from them construct a complete table of deviations (or for as many points as the Examiner may direct):—

Deviation at North [ ] South [ ]
N.E. [ ] S.W. [ ]
East [ ] West [ ]
S.E. [ ] N.W. [ ]

63. When swinging your ship, if it be required to construct deviation tables for two or more compasses situated in different parts of the vessel, describe the process, and how you would employ the Napier’s diagram for this purpose.

64. State your rule for determining whether deviation is easterly or westerly.

65. Is a knowledge of the value of the various coefficients of any advantage? If so, state why.

66. Describe (a) what is commonly known by the term “retentive” or “retained” magnetism, and how the ship acquires it when in port and at sea; (b) its effect on the compass-needle whilst ship’s head continues in the same direction; (c) the immediate consequence when the direction of the ship’s head is altered; and (d) the special precautions to be invariably observed at sea on the alteration of the ship’s course.

67. Describe a “dumb-card” or “pelorus,” and its use (a) in compensating a compass, (b) in determining the deviation.

68. If you determine the deviation by an azimuth or an amplitude of a heavenly body, it is then combined with variation, which together is sometimes called the correction for the compass. State when the deviation is the difference between the variation and the correction, and when the sum; and when it is of the same name as that of the correction, and when of the contrary name

69. In observing azimuths of heavenly bodies, the best method is by “time azimuths,” since these can be observed without an altitude when the ship is in port, or when the horizon cannot be defined from any cause. Give the sun’s declination, the hour of the day, and the latitude to find the true bearing of the sun.*

70. By night, if it be desirable to observe the correction of the compass: Give the day of the year, and time at ship, also the latitude of the place, to determine what stars will be in good position for this purpose.

71. If your correcting-magnets are so mounted that their positions can be altered, describe the process by which, on open sea, you can place the ship’s head magnetic N. (or S.), and magnetic E. (or W.), and can make the correction perfect.

72. Give the name of a star, the time, the place of ship, the variation of the compass, and the bearing of the star by compass: determine the deviation, and name it east or west.

73. Would you expect any change to be caused in the error of your compass by the ship heeling over either from the effect of the wind or the cargo?

74. Describe clearly the three principal causes of the heeling error on board an iron ship.

75. Towards which side of the ship would that part of magnetism induced in continuous transverse iron (which was horizontal while ship was upright) help to draw the north point of the needle when ship heels over (a) in the Northern Hemisphere, (b) in the Southern Hemisphere?

76. Supposing the compass were placed between the two parts of a divided beam or other athwartship iron, towards which side of the ship would iron so situated help to draw the north point of the needle when ship heels over (a) in the Northern Hemisphere, (b) in the Southern Hemisphere?

The process of finding time azimuths by the ordinary formula of spherical trigonometry is tedious, and, since on board an iron ship these observations should be often repeated, the candidate will be allowed to use any table or graphic or linear method that will solve the problem within a half of a degree, the altitude of the heavenly body not being given.