7. In the following table give the correct magnetic bearing of the distant object, and thence the

In this example we first add together the eight given bearings of the distant object, making 575° 20', and divide the sum by eight, giving as the result S. 71° 55′ W. This is the correct magnetic bearing of the distant object. We next take the difference between the magnetic bearing thus obtained and the bearings as given in the table: thus, for the ship's head north the bearing is S. 73° W., and the difference between this and the magnetic bearing S. 71° 55′ W. is 1° 5', and because the magnetic is to the left hand of the compass bearing the deviation is marked 1° 5' W. Again, take S.E., the compass bearing is S. 59° 40′ W., and the difference between this and the magnetic bearing S. 71° 55′ W. is 12° 15', but now the magnetic is to the right hand of the compass bearing, hence the deviation is entered opposite to ship's head S.E., 12° 15′ E.—ARTS. 47, 84.

8. With the deviation as before, give the courses you would steer by the standard compass to make the following courses, correct magnetic:(1) NE. (2) West. (3) South. (4) WSW.

Answer.-(1) N. 35° 20′ E. (2) N. 72° 50′ W. (3) S. 1° 30′ E. (4) S. 84° 30′ W.-ARTS. 50, 86.

9. Supposing you have steered the following courses by the standard compass, find the correct magnetic courses made from the above deviation

table.
(1) SE.

(2) SW.

Answer. (1) (3) S. 72° 50' E.

(3) East. (4) WNW. S. 32° 30′ E. (2) S. 33° 30′ W. (4) N. 83° 30′ W.—ARTS. 50, 86. 10. You have taken the following bearings of two distant objects by your standard compass as above; with the ship's head at ENE., find the bearings, correct magnetic.

Compass bearing 1st object N.W. & N. Correct magnetic Ñ. 23° 30′ W.

Compass bearing 2nd object S. 29° 40′ E. Correct magnetic S. 13° 50′E.—ART. 50.

11. Name some suitable objects by which you could readily obtain the deviation of the compass when sailing along the coasts of the English Channel.

(1) At South Foreland, two bright fixed lights in one at W. by N.

(2) At Hurst beach, two bright fixed lights in one at NE. by E. E., visible at nine miles. (3) At Portland, two bright fixed lights by night, and two white towers in one, NNW. W.

(4) Eddystone in one with Plymouth Breakwater light, NE. and SW.

(5) Lizard, two brilliant fixed lights and two towers in one, W. 2 N. and E. ₫ S.

12. Do you expect the deviation to change? if so, state under what circumstances.

Yes (a) With the heeling of the ship.

With a change in the direction of the ship's head.

(c) With a change in geographical position.

(d) With a heavy blow, as being struck by a heavy sea.

(e) With a change or shifting of a cargo. (f) With the appearance of the Aurora. (g) With the ship (if of wood) being struck by lightning.-ART. 44.

13. How often is it advisable to test the accuracy of your table of deviations ?

No opportunity for verification should be neglected, and every day the compasses should be attended to.-ART. 44.

14. State briefly what you have chiefly to guard against in selecting a position for the compass.

The compasses should be placed out of the influence of individual masses of iron, and as near as possible in the fore and aft midship line of the vessel. Near the iron rudder-head, iron axle or upright of the steering-wheel, near the foot of an iron mast, the funnel or davits, &c., should be avoided.-ART. 43.

15. The compasses of iron ships are more or less affected by what is termed the heeling error; on what courses does this error vanish, and on what courses is it the greatest ?

The heeling error is found only in iron or composite ships. It vanishes when the vessel is being steered E. or W., and is greatest when the vessel is being steered N. or S. by the affected compass. -ART. 71.

16. State to which side of the ship, in the majority of cases, is the north point of the compass drawn in the Northern Hemisphere; and what effect has it on the assumed position of the ship when she is steering on northerly and also on southerly courses ?

When heeling in N. latitude, the north point of the needle is, as a rule, drawn to the higher side of the vessel; thus if a vessel be in N. latitude, she will if steered on one northerly course go to that side which is most elevated, if the compass be above upper deck; and to the other side on southerly courses.-ART. 74.

the

17. The effect being as you state, on what courses would you keep away, and on what courses would you keep closer to the wind, in order to make good a given compass course?

If a vessel be steered steadily for a fixed point on the horizon, she will then appear to fall off as she heels on northerly courses, and to come up on southerly ones. Hence, in steering by compass, we must keep away by compass on either tack, as the ship heels when on northerly courses; and keep closer to the wind by compass, on either tack, when on southerly courses.-ART. 74.

18. Does the same rule hold good in both hemispheres with regard to the heeling error?

The reverse of the rules above given hold good with regard to the heeling error in the Southern Hemisphere.-Art. 74.

19. Your steering compass having a large error, how would you proceed to correct that compass, by compensating magnets and soft iron, in order to reduce the error within manageable limits?

TO COMPENSATE FOR SEMI-CIRCULAR DEVIATION. -I would make two chalk lines, meeting directly under the centre of the compass, one running fore and aft, the other athwartships, and bring the ship's head correct magnetic E. or W., and place a magnet with its centre on the athwartships chalk line and parallel to the fore and aft one, being care

ful that the right end is forward according to the deviation. Then move it towards or from the compass until the latter points out the correct magnetic position of the ship's head. Sometimes twɔ magnets, one on each side, are required.

Next bring the ship's head magnetic N. or S., and place another magnet athwartships with its centre in the fore and aft chalk line, and proceed in the same way. This deviation changes with a change in the geographical position of the ship, hence it is necessary to move the magnets as circumstances may require.

TO COMPENSATE FOR QUADRANTAL DEVIATION.— I would bring the ship's head to the N.E., S.E., S.W., or N.W. correct magnetic, and place the soft iron correctors one to port, the other to starboard, and move them to or from the compass until it shows the correct magnetic position of the ship's head. This compensation remains the same in all geographical positions.-ART. 79-80.