I. From the following Table find the correct magnetic bearing of the distant object, and thence the deviation :

Answer, Magnetic bearing, S. 52° 58′ E.

II. From the above Table construct a Napier's curve, and give the courses you would steer by standard compass to make the following courses correct magnetic :

(a) W. by S. 3 S. (6) N. 1 E. (c) E. & N. (d) SE. S.

Answer, (a) S. 86° W.
(c) N. 661° E.

(b) N. 1° E.

(d) S. 45° E.

III. Suppose you steer the following courses

by standard compass, find the correct magnetic courses from the curve drawn :

(a) E. by S. S. (b) SSW. W. (c) NE. E. (d) North.

Answer, (a) S. 621° E.

(c) N. 65° E.

(b) S. 183 W.

(d) N. 4° E. IV. You have taken the following bearings of distant objects by your standard compass as above; with the ship's head as given, find the correct magnetic bearings:

S. 30° 50' E.

Answer, N. 68° 4' E.

S. 54° 11′ W. S. 2° 30' E.

87. Deviation of two or more compasses.-It is sometimes required to determine the deviation of two or more compasses on board the same ship. In such cases it is most convenient to bring the ship's head, correct magnetic, to as many points as may be necessary; and the bearing of the ship's head by each compass should be simultaneously recorded, whilst the deviation is calculated only for the standard compass. Then, having obtained this, the deviations for the other compasses on the positions of the ship's head noticed may be obtained by comparison; and the deviations thus obtained must be laid down on Napier's diagrams, using one for each compass. In all these cases, as the ship's head is taken correct magnetic, the deviations must be laid off on the plain lines instead of the dotted ones, and the table for each compass can be constructed as before.

L

EXAMINATIONS

OF

MASTERS AND MATES.

Notice of Alteration in Examination Papers.

AFTER the 1st day of March, 1872, all candidates presenting themselves for examination for Masters' Certificates will be required to give answers to as many questions as may be marked with a cross by the Examiner. These questions are, at the same time, intended to test the candidate's handwriting and spelling, to both of which special attention should be paid by him.

For the Table of Deviations,' which heretofore formed part of Form Exn. 7, the questions contained in the following list have been substituted. Candidates for Certificates of Competency as Masters Ordinary will be required to answer at least eight of such of these questions as may be marked with a cross by the Examiner. Candidates for First Class Certificates (Masters Extra) will be required to answer the whole of these questions. THOMAS GRAY.

DEVIATION OF THE COMPASS.

[N.B.-The candidate is to answer correctly at least eight of such of the following questions as are marked with a cross by the Examiner. The Examiner will not mark less than twelve.]

1. What do you mean by deviation of the compass ?

Deviation is a compass error caused by iron in a ship's build or her cargo; or, by compasses being placed too near each other; or, it is the difference between the magnetic and compass bearings of any distant object.-ART. 43.

2. How do you determine the deviation (a) when in port, and (b) when at sea?

(a) In Port.-Select a distant object not less than from six to eight miles distant, and after having made a table of the points of the compass, swing the ship so as to bring her head to every point, and mark the bearings of the distant object opposite the position of the ship's head. Then take the mean of the bearings on the eight principal points of the ship's head-this will be the correct magnetic bearing of the distant object. The difference between the correct and the other bearings gives the deviation for each point.

(b) At Sea. Find the compass error by one of the following methods:

I. An amplitude.

II. An azimuth.

III. The sun at noon.

IV. A star crossing the meridian.

V. Or, approximately, by the North Pole star in north latitude.

Then with the ship's known latitude and longitude

take the variation as marked on the Admiralty chart; the difference between the compass error and the variation gives the deviation.-ARTS. 46, 47, 48, 49.

3. Having determined the deviation with the ship's head on the various points of the compass, how do you know when it is easterly and when westerly?

(a) In Port.-The deviation is easterly if the correct magnetic bearing be to the right, but westerly if it be to the left of the compass bearing.

(b) At Sea. It is easterly if the compass error be to the right, and westerly if the compass error be to the left of the variation reckoning from the north.-ARTS. 46, 47, 48, 49.

4. Why is it necessary, in order to ascertain the deviations, to bring the ship's head in more than one direction?

Because the deviation changes with the direction of the ship's head.-ART. 44.

5. For accuracy, what is the least number of points to which the ship's head should be brought?

Eight equidistant points are the fewest that can be used with accuracy, although, if the deviation be known on the four intercardinal points, an approximate table can be calculated.—ARTS. 49, 83.

6. How would you find the deviation when sailing along a well-known coast ?

I would first determine the magnetic bearing of some landmark or lighthouse. Then bring the vessel's head to rest on each point of the compass, and note down the bearings of the object opposite to the position of the ship's head. What the bearings by compass differ from the magnetic bearing is the deviation.