Aug. 2.] THE NEW ZEALAND GAZETTE. 3101

when building, or when her head is at right angles to that direction, and in what direction of the ship’s head would you expect to find the least disturbance?

33. Describe quadrantal deviation, and state what coefficients represent it; also on what points of the ship’s head, by compass, each of these coefficients gives the greatest amount of deviation, and why it is called quadrantal deviation.

34. On what points of the compass will each of the coefficients, D and E, + and —, give easterly, and on what points westerly, deviation?

35. What conditions of the iron of a ship will produce + D, and what — D?

36. State clearly which end of horizontal iron running athwartship (such as beams, &c.), and of horizontal iron running fore and aft of a ship, acquires red and which blue polarity, by induction, when ship’s head is at N.E., S.E., S.W., and N.W. respectively.

37. Describe the nature of the deviation represented by coefficients + A and — A, and describe the errors in the construction of the compass, and other causes, that frequently produce it.

38. What is the object of compensating the compass by magnets, &c., and what are the general advantages of a compensated compass over an uncompensated one?

39. Before adjusting the compass of an iron ship, what is it desirable to do with the view of eliminating as far as possible what may be termed the unstable part of the magnetism of the ship?

40. Describe clearly the tentative method of compass-adjustment—that is, the compensation of coefficients B, C, and D, with ship upright—as generally practised by compass-adjusters in ships of the mercantile marine.

41. State at what distance, as a general rule, the magnets and soft-iron correctors should be placed from the compass-needles, and what will be the consequence if they are placed too near the needles?

42. Is it necessary that the magnets used for compensating coefficients B and C should be placed on the deck? If not, state where they may also be placed, and the rules to be observed in placing them into position.

43. Does the B found on board ship usually arise altogether from subpermanent magnetism, or does part of it usually arise from some other cause or causes?

44. If the part of B due to induced magnetism in vertical soft iron, as well as the part due to subpermanent magnetism, are corrected by a magnet alone, as is generally the case, what is frequently the consequence of the ship changing her magnetic latitude and hemisphere?

45. How should each of these two parts of B, strictly speaking, be compensated?

46. Assuming, for the sake of clearness, that your steering-compass is unavoidably placed very near to the head of the stern-post (and other vertical iron at the stern), thereby causing a very large — B from induced magnetism, describe briefly any method by which the approximate position for the compensating vertical iron bar (Flinder’s or Rundell’s) could be estimated in order to reduce the error; describe also how you would proceed, in order to improve, if not to perfect, its position after observations have been made on the magnetic equator.

47. State if standard compasses, as well as steering-compasses, are generally subject to this disturbance from induced magnetism in vertical iron; also whether the attraction in all cases found is to be towards the stern; and, if not, state the conditions under which it might be towards the bow, and how the compensating soft iron bar should then be placed.

48. Generally speaking, does the magnetism induced in vertical iron usually have any effect in producing the coefficient C (ship upright) or is it generally produced by subpermanent magnetism alone? State also your reasons for saying so.

49. Provided the needles of your compass are not so long and powerful, and so near, as to cause the soft-iron correctors to become magnetized by induction, would the coefficient D, if properly compensated as you have described (Ans. 40), be likely to remain so in all latitudes and both hemispheres? If so, state the reason why.

50. Under what circumstances does the character of A and E so change as to render it desirable that these coefficients should be disregarded or modified?

51. Supposing your compasses were allowed to remain uncompensated, explain clearly what would be the probable changes (ship upright) in the deviations produced, separately, by (1) the subpermanent magnetism of the ship alone, (2) by the induced magnetism in vertical soft iron; (a) on reaching the Equator; (b) in the Southern Hemisphere.

52. Assuming you were able to arrive at the proper proportions to be corrected, and were then to exactly compensate the subpermanent magnetism of the ship by means of a permanent magnet, and the induced magnetism in vertical iron by a soft-iron bar, would you expect any deviation to take place in your compass as the ship changed her latitude and hemisphere? And state your reasons for saying so.

53. Supposing the coefficient D from horizontal soft iron were allowed to remain uncompensated, would you, or would you not, expect the D to differ in name or amount on the ship changing her magnetic latitude and hemisphere? And state the reason.

54. Describe how you would determine the deviation of your compass—(1) by reciprocal bearings; (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 deviation:—

(a.) Magnetic Bearing required.

(b.) Construct a curve of deviations on a Napier’s diagram, with the deviations as above, and give the