TERRESTRIAL MAGNETISM, ETC. 257 



observation had shown an error (due, of course, to 

 the iron of the ship) of 25 W. in the compass 

 indication on the course on which they had been 

 steering. If the amount of the error had been 

 unaltered by the alteration of course, the change 

 would have been one point, and the ship would not 

 have gone ashore. Taking into account previous 

 observations made in the ship, Smith found (by an 

 application of the mathematical theory, which he 

 had set forth in the Admiralty Compass Manual}, 

 that the change of course actually made by the 

 captain would probably diminish the deviation from 

 25 to 18^, and showed that this change fully 

 accounted for the error in the course which caused 

 the loss of the ship. 



With reference to this old question the follow- 

 ing statement by Captain Creak, describing obser- 

 vations of unquestionable trustworthiness, is most 

 interesting, and of great practical importance. It 

 is extracted from his paper on the " Mariner's 

 Compass in Modern Vessels of War," communi- 

 cated to the Royal United Service Institution on 

 the 3 ist of May, 1889. 



VOL. III. S 



