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taking in or discharging an iron cargo; after collision or violent concussion ; after steering on

one course for a considerable time. 13. As often as possible. 14. Against placing the compass near elongated pieces of

iron, especially when in a vertical position, such as stanchions, davits, capstan spindle, funnels, ventilating shafts, &c., and not near tranverse iron bulk

heads. 15. The error vanishes when the ship's head is at or

near E. or W. by the disturbed compass, and

greatest when her head is at or near N. or S. 16. The North end of the needle is drawn to the highest

side of the ship or to windward in the Northern hemisphere, consequently the ship will be found to windward of her supposed position on Northerly

courses, and to leeward on Southerly courses, 17. Keep away on either tack when steering Northerly

courses, and keep closer to the wind when on

Southerly courses. 18. No; generally the reverse rule holds good in the

Southern hemisphere. 19. Draw two chalk lines on the deck, one fore and aft,

the other athwart ship, crossing each other exactly below the centre of the compass. Place the ship's head correct magnetic N. or S. Then place the centre of a magnet on the fore and aft line, at right angles to it, either before or abaft the compass, taking care to have the N. or Red end of the magnet to port, or to starboard, according as the N. or Red end of the compass needle is drawn to port or to starboard. Move the magnet to or from the compass until the ship's head is N. or S. by the compass. Now bring the ship's head E, or w. correct magnetic. Place the centre of another magnet on the athwart ship line and at right angles to it, having the N. or Red end of the magnet

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forward, or aft, according as the N. or Red end of the compass needle is drawn forward or aft. Move the magnet to or from the compass until the ship’s head is E. or W. by the compass. Lastly, place the ship's head at one of the quadrantal points, say N.E. correct magnetic, place soft iron correctors, one on the port side, and the other on the starboard side of the compass, and in the same horizontal plane with the compass card. Move these correctors to or from the compass until the ship's head is N.E. by compass. This last compensation remains unaltered by change of

ship’s geographical position. Note.-Candidates for Masters Certificates are now required to draw diagrams

similar to those which follow, showing the positions in which the bar magnets and soft iron correctors are placed, as described in answer to No. 19 Question; also to show the position of the bar magnet which compensates the heeling error alluded to in No. 17 Question. He must also write a short description of the diagrams. It must be observed that the North ends of the bar magnets are RED; the North ends of the Compass Needles being marked in the same manner,

DESCRIPTION AND EXPLANATION OF DIAGRAMS. Fig. I and Fig. 2 are diagrams intended to show the method of compensating for semicircular deviation caused by sub-permanent magnetism.

In Fig. 1 the ship's head is placed correct magnetic North. The North or red end of the compass needle is supposed to be drawn to starboard, as at n. The centre of magnet A is placed on the fore and aft line, the red or North end towards the starboard side, and is moved to or from the compass until the North or red end of the magnet A repels, and the other or South end attracts the North or red end of the compass needle back to N. The magnet A is then fixed to the deck.

In Fig 2 the ship's head is placed correct magnetic East. The North or red end of the compass needle is drawn

towards the bow. The centre of another magnet, B, is placed on the 'thwart-ship line, with the red or North end towards the bow, and is moved to or from the compass until the North or red end of the magnet B repels, and the other or South end attracts the North or red end of the compass needle back to N. The magnet B is then fixed to the deck.

Fig. 3 is a diagram intended to show the method of compensating for quadrantal deviation arising from induced magnetism in horizontal soft iron. The ship's head is placed at one of the quadrantal points, in this diagram it is placed at N.E. correct magnetic.

C and D, in Fig. 3, are soft-iron correctors on each side of the compass, and on the same horizontal plane with it. These correctors are moved to or from the compass until the N.E. point of the compass points to the ship's head.

The heeling error arises from the transverse iron (such as beams) becoming magnetic when the ship heels. To ascertain if there is any heeling error, place the ship's head N. by standard compass, and keeping her head in that position give the ship a heel to port or starboard about 10 degrees; then, if there is any error, it will be found, in the majority of cases, that in the Northern hemisphere the North end of the compass needle will be drawn to the highest side of the ship; while in the Southern hemisphere the South end of the compass needle is drawn to the highest side.

To compensate for this error, place a magnet in a vertical position (see Figs. 4 and 5) below the centre of the compass, and in a socket or other contrivance so that it can be raised or lowered as required, taking care to have the N. or S. end uppermost, according as the N. or S. end of the compass needle is drawn to the highest side of the ship. Then raise or lower the magnet until the ship's head is N. by compass. Fig. 4 shows the effect upon the compass when the ship

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