Mr. J. R Napiek on Ships^ Compasses. 



873 



been laid off to a scale of 1 inch, equal to 120°. As in the former case, 

 two sets of small circles denote actual observations, and are placed 

 exactly over those places in the sheer plan at which the observations 

 were taken in the vessel ; further, where the curves lie above this axis 

 the south end of the needle was attracted towards the 

 side of the vessel, when under the north, was the at- 

 tracted end ; a second set of dotted circles represent a 

 second set of observations made on the vessel after 

 her launch, and when lying at Lancefield Quay, with 

 her head pointing south-east, show a great change in 

 the deviations. 



While on this subject, I may mention a method suggested to me some 

 time ago by Mr. Archibald Smith for finding the deviation of a steamer's 

 compass. Its simplicity and the speed with which it can be executed 

 are favourable to its adoption, and there can, I believe, be little or no 

 oblique retained magnetism to interfere with the results, as the shaking 

 of the vessel from the motion of the machinery must tend to bring it to 

 its natural position. 



The steamer is supposed to be in sight of a prominent object as far off 

 as possible, and the bearings of this object taken ; while the vessel steams 

 steadily on each of the 32, 16, 8, or even 4 points of the compass by 

 which the bearings are taken. The mean of these bearings measured all 

 in one direction will give very nearly the true magnetic bearing of the 

 distant object, and of course the difference of each bearing from the 

 mean, is the error or deviation of the compass, which has to be properly 

 allowed for. 



As an example, I have taken the bearings from the deviation curve of 

 the iron brig " Haiti" (vide diagram), for 4 and for 8 points. 



Ship's Head by Standard Compass. 



N + 15 



N.E —15 



E —28 



S.E —24 



S —10 



S.W + 10 



W + 31 



N.W + 36 



Vol. III.— No. 6. 



Let the bearings of the distant object be N. 

 when the ship's lead by her standard com- 

 pass is N.W. The other bearings will be as 

 follows : — 



Bearings of Dist Object 



Ship's Head. 



N.W N. 



N N. 21°W. 



N.E N. 51 W. 



E N. 64 W. 



S.E N. 60 W. 



S N. 46 W. 



S.W N. 26 W. 



W N. 5 W. 



8)273 



Correct magnetic. 



N. 34125W. 

 .N. 36 W. 



