130 - Transactions. 



acknowledging. In tliis vessel the co-efficients are very small, A= —1° 17', 

 B- -0° 31', C= +3° 31', D= +6° 50', E- +0° 25', and, assuming that 

 any change is due only to the influence of hard iron, I find that the greatest 

 difference in deviation due to change of magnetic latitude between Auckland 

 and the Bluff amounts to only 2° 32', or a fourth of a point nearly ; this 

 occurs on the N.W. point, and in a run of five miles would place the vessel 

 about one-fifth of a mile to westward of its true position. It must, 

 however, be thoroughly understood that no soft iron should be so placed as to 

 influence the compass of the steel vessel. The changes due to difference of 

 magnetic latitude, and also to heeling error, have brought a great feeling of 

 distrust as to the compensation of compass errors by magnets into the 

 m.er chant navy. This arises partly from no warning as to the existence of 

 such changes being certain to take place having been given to shipmasters, 

 and partly from their not having been cautioned that compensation by 

 magnets is not intended to eliminate all compass errors, but only to bring 

 them within such limits as may render navigation more easy. Something 

 may also be due to erroneous compensation, and thus it has happened that 

 after a vessel had got some distance upon her voyage the courses steered did 

 not produce the desired effect, and the magnets have been considered the 

 prime cause of the ship not being in the place to which the courses steered 

 should have carried her. Compasses are, in the merchant navy, frequently 

 placed with the most utter indifference as to the position and amount of the 

 adjacent iron, and this will be found to be the case in both wood and iron- 

 built ships ', compensation in such cases is useless, as from the influence of soft 

 iron the deviations are continually changing in value. It is with a view to 

 the correction of this indifference that the Board of Trade now require every 

 candidate for examination as Master to answer certain questions as to the 

 effect of iron on the compass-needle, with the hope that the result will be in 

 time that masters of vessels will attend to the placing of the compasses in 

 more effective positions, and I hope that in a few years the important 

 effects due to deviation, heeling error, and change of magnetic latitude, will be 

 so well understood that it will be a matter of some difficulty to obtain 

 a captain for any vessel which has not at least one compass placed with due 

 regard to the magnetic character of the ship. In small vessels it is a matter 

 of great difficulty to place the compasses properly, but there can be very little 

 in placing them so that they may be much more reliable than is often the case 

 at present. 



