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NOTICE OF EXAMINATIONS.

COMPASS DEVIATION.

IN December 1869 the attention of the Board of Trade was called by Mr. Laurie, a shipbuilder of Glasgow, to a course of lectures, originated by himself, which was then about to be given at the University of Glasgow, on the Theory and Practice of Compass Deviation; and Mr. Laurie, at the same time, pointed out the advantage which would result to the seafaring community if shipmasters were encouraged to attend the course in question, and obtain the College Certificate that they possessed a competent knowledge of the subject. The Board of Trade, always desirous that knowledge on the subject of compass deviation should be possessed by masters of iron ships, at once approved of Mr. Laurie's suggestion, and expressed their willingness to make a suitable endorsement on the certificate of competency of any master or mate who may hereafter pass the examination at the Glasgow University to which Mr. Laurie had called attention.

The Board of Trade also propose to extend examinations in compass deviation, as occasion may offer, to the various ports at which examinations of masters and mates are held.

The scientific reputation and special qualifications of Mr. J. T. Towson, Examiner in Navigation at Liverpool, seemed to point to that place as the most suitable for the first essays; and after communication with the Liverpool Local Marine Board, who fully concurred in the importance of the proposed step, Mr. Towson was specially appointed at Liverpool as Examiner in Compass Deviation.

By this Board's desire, Mr. Towson has drawn the following syllabus of examination for use at that port.

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In this labour he has had the advantage of the suggestions of the Astronomer Royal, and of Capt. Frederick J. Evans, R.N., Superintendent of the Magnetic Department of the Admiralty. This syllabus will be altered from time to time as the necessity for alteration becomes apparent.

The fee for examination will be two pounds, which should be paid to the Superintendent of the Mercantile Marine Office in the usual manner, and will be brought to account by him as a separate item in his account current. If the candidate passes the examination successfully, an endorsement to that effect will be duly made in the Office of the Board of Trade upon the master's or mate's certificate held by him. If he fails to pass successfully, the fee will not be returned.

The Board of Trade lay stress upon the fact that this examination is purely voluntary and honorary. They trust, however, that, in the present days of iron shipbuilding, the importance of a special knowledge of compass deviation and correction will be fully recognised by masters and mates as well as by owners and underwriters. They also trust that holders of certificates of com

petency will gladly take all steps in their power to earn the special distinction conferred by the certificate of examination.

THOMAS GRAY.

SYLLABUS OF EXAMINATION OF MASTERS IN THE LAWS OF THE DEVIATION OF THE COMPASSES OF AN IRON SHIP, AND IN THE MEANS OF COMPENSATING or

CORRECTING IT.

1. Describe an artificial magnet, and how a steel bar or needle is usually magnetised.-ARTS. 1, 29, 30, 31, 33.

2. [For the sake of simplicity it is desirable to adopt the nomenclature of the Astronomer Royal, and call that pole of the compass needle that points to the magnetic north the red, and the other the blue pole.] 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 ?-ART. 4.

3. By applying this law to all magnets, natural as well as artificial, show what would be the result on a magnetic bar or needle freely suspended, but by weight or by the nature of its mounting constrained to preserve a horizontal position; and what result, if so mounted, but free to move in every direction, the earth being regarded as a natural magnet ?—ART. 11.

4. Which is the red magnetic pole of the earth, and which the blue ?-ART. 6.

5. What is the cause of the variation of the compass ?-ART. 42.

6. What is meant by the deviation of the compass ?-ART. 43.

7. Describe the sub-permanent magnetism of an iron ship, and state when and how it is acquired, and which is the sub-permanent red and which is the blue pole, and why it is called sub-permanent magnetism.-Art. 53.

8. 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 sub-permanent magnetism of an iron ship ?-ART. 51.

9. Describe the co-efficients B and C, plus (+), and minus (-), and why they are said to produce semicircular deviations ?-Arts. 53, 56.

10. On what points, by compass bearing of the ship's head, does + B give westerly deviation, and on what does it give easterly; also on what points does B give westerly, and on what points easterly ?-ART. 56.

11. On what points does + C give westerly, and on what points easterly; also on what points does -C give westerly, and on what points easterly deviation ?-ART. 56.

12. How would you compensate the co-efficient C?-ART. 79.

13. How would you compensate the co-efficient B ?-ART. 79.

14. If the value either of co-efficient B or C be given, also the magnetic direction of the ship's head while she was being built, how by the traverse tables would you determine the approximate value of the other co-efficient C or B; and if the

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value of both these co-efficients be given, how would you determine approximately the direction, by compass, of the ship's head whilst being built ?

-ART. 56.

15. What is meant by transient induced magnetism ?-ART. 7.

16. Under what circumstances does induced magnetism give semicircular deviation ?-ARTS. 51, 53.

17. How would you compensate B resulting from induced magnetism, and why for this purpose would you adopt a different mode of compensation to that employed in correcting - B produced by sub-permanent magnetism ?-ART. 79.

18. Describe quadrantal deviation, and state what co-efficients represent it; also on what points of the ship's head, by compass, each of these coefficients gives the greatest amount of deviation?— ART. 57.

19. On what points of the compass will each of these co-efficients, D and E + and -, give easterly, and on what points westerly deviation ?-ART. 57.

20. Generally + D gives the greatest amount of quadrantal deviation; how should it be compensated ?--ART. 80.

21. If D be compensated in the manner you have described, will it remain so in every latitude? If so, state the reason why.-Art. 80.

22. What conditions of the iron of a ship will produce + D and what - D?-ART. 57.

23. Describe the nature of the deviation resulting from + A and A, and describe the error in the construction of the compass that frequently produces them.—ART. 57.

24. Under what circumstances does the character of A and E so change as to render it desir