3100
THE NEW ZEALAND GAZETTE.
[No. 74

45. Can the compensation of the heeling error be depended upon when the ship changes her latitude? If not, state the reason.

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APPENDIX K.

SYLLABUS OF EXAMINATION IN THE LAWS OF THE DEVIATION OF THE COMPASSES OF AN IRON SHIP, AND IN THE MEANS OF COMPENSATING OR CORRECTING IT.

Candidates for the voluntary examination in compass-deviation and for extra master’s certificate will be required to give written answers to twenty-two of the questions; these will be marked by a cross by the Examiner.

They will also be required to show, by means of Beall’s deviascope, a sound practical knowledge of the tentative method of compass-adjustment, and be able to demonstrate experimentally the effect of any given disturbing force upon the compass, showing under what conditions (if any) it may vary and what steps should be taken to compensate it. Viva voce questions by the Examiner upon the practical application of any of the questions in the compass syllabus must be answered clearly and concisely, and practically demonstrated on the deviascope where possible. Questions 31, 61, 62, 69, 70, 72, and 92 will be marked by the Examiner in all cases, the other questions being constantly varied.

1. Describe an artificial magnet, and how a steel bar or needle is usually magnetized.

2. Which end of the compass-needle, or a magnet, is commonly termed the red, and which the blue pole?

3. Which is the red magnetic pole of the earth, and which the blue? and give their geographical positions.

4. What effect has the pole of one magnet of either name on the pole of the same name of another magnet, and what would be the consequence of the pole of one magnet of either name being brought near enough to affect the pole of contrary name, if in these cases both magnets were freely suspended?

5. By applying this law to all magnets, natural as well as artificial, describe what would be the result on a magnetic bar or needle, freely suspended but constrained by weight or by the nature of its mounting to preserve a horizontal position; and what would be the result, if so mounted, but free to move in every direction, the earth being regarded as a natural magnet?

6. What is the cause of the variation of the compass?

7. What is meant by the deviation of the compass?

8. What is meant by the term “local attraction”; under what circumstances have ship’s compasses, from recent careful investigation, been found to be affected by it? and name some of the localities in different parts of the world where this disturbance is to be found, and, consequently, where increased vigilance is necessary.

9. What do you understand by the term “soft” iron; and what are its properties as regards acquiring and retaining magnetism?

10. What do you understand by the term “hard” iron; and what are its properties as regards acquiring and retaining magnetism?

11. Describe the meaning of the term “horizontal force” of the earth. Where is the greatest, and where the least; and what effect has it in respect to the increase or decrease of the directive force of the compass-needle?

12. Does the magnetic equator coincide with the geographical equator? If not, state clearly how it is situated.

13. Where can the values of the magnetic dip, the earth’s horizontal force, and the variation be found?

14. State in what parts of the globe lying in the usual tracks of navigation the variation changes very rapidly, and what special precautions should be observed when navigating these localities; also why a “variation” chart is then very useful.

15. Why is a knowledge of the magnetic dip and the earth’s horizontal force important in dealing with compass-deviations?

16. Describe the meaning of the term “vertical force” of the earth. Where is the greatest, and where the least?

17. Would you expect a compass to be more seriously affected by any given disturbing force when near the magnetic equator, or near the poles? and state the reason.

18. State briefly, (a) the essentials of an efficient compass; and (b) what you would consider a good arrangement of the needles—that is, whether long or short, single or double, &c.—with a view to good compensation.

19. In stowing away spare compass-cards or magnets, how would you place them with regard to each other, or what might be the probable consequence?

20. State briefly the chief points to be considered when selecting a position for your compass on board ship, and what would be particularly guarded against.

21. What is meant by “transient induced magnetism”?

22. Which is the red and which the blue pole of a mass of soft vertical iron (or of any soft iron not in a horizontal position) by induction, and what effect would the upper and lower ends of it have on a compass-needle in the Northern Hemisphere?

23. Which is the red and which the blue pole of a mass of soft vertical iron by induction, and what effect would the upper and lower ends of it have on the compass-needle in the Southern Hemisphere?

24. What effect would a bar of soft vertical iron have on the compass-needle on the magnetic equator?

25. Describe what is usually termed the subpermanent* magnetism of an iron ship, and state when and how it is acquired, and which is the subpermanent red and which is the blue pole, and why it is called subpermanent magnetism.

26. What is meant by “the composition of forces” and “the parallelogram of forces”? and show how the knowledge of these is valuable in ascertaining and compensating the subpermanent magnetism of an iron ship.

27. Describe the nature of the coefficient B and C plus (+), and minus (−), and the different magnetic forces they represent; also why they are said to produce semicircular deviations.

28. Can semicircular deviations be produced by any other force than the subpermanent magnetism of the ship? If so, by what?

29. On what points, by compass-bearings of the ship’s head, does + B give westerly deviation, and on what point does it give easterly; also on what points does − B give westerly, and on what points easterly?

30. On what points does + C give westerly deviation, and on what points easterly; also on what points does − C give westerly, and on what points easterly, deviation?

31. The value of either coefficient B or C being given, also the magnetic direction of the ship’s head while she was being built, determine by the traverse tables the approximate value of the other coefficient C or B; and, the value of both these coefficients being given, determine approximately the direction by compass of the ship’s head whilst being built, assuming, of course, that these coefficients resulted altogether from subpermanent magnetism.

32. Would you expect the greatest disturbance of the needle from the effects of subpermanent magnetism alone to take place when ship’s head is in same direction as

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The term “subpermanent” magnetism in the syllabus is used in the sense proposed by the late Sir G. B. Airy, to denote the character of the permanent magnetism of an iron ship as distinguished from the permanent magnetism of a magnetized steel bar. The terms “subpermanent” and “permanent” throughout the syllabus may therefore be considered as synonymous.