Deviation ()f't?ie Compass. 37 



met with and sometimes exceeded, and let the points of change 

 be north and south, such a vessel, on coming from the Baltic, 

 and steering S. 67° W., or W. S W. nearly, will have 4^° wes- 

 terly deviation, — that is, by the attraction of the vessel, the 

 north point of the compass will be drawn towards the west 4J°. 

 By this deviation, therefore, if no allowance be made for it, she 

 will be carried, within the limits of the proposed distance, twenty- 

 six miles to the south-eastward of her reckoning. Now it is very 

 evident, from a simple inspection of the chart of the German 

 Ocean and English Channel, that had there been an allowance of 

 twenty-six miles made on the courses of the vessels already men- 

 tioned as having been lost on the Haak Sand, an allowance 

 which the wind at the time would have amply admitted^ they 

 would have all gone considerably to the westward of every dan- 

 ger, and the two men-of-war, the Hero and Minotaur, and 

 four transports, together with above 1000 men, would have been 

 saved. 



As to the other case (the St George and Defiance), I am not 

 sufficiently acquainted with all the circumstances to speak de- 

 cidedly of the influence of the local attraction. But I think it 

 exceedingly probable, that had their commanders been fully 

 aware of the deceptive influence of this, then httle understood 

 phenomenon, they would at all events have steered a course so 

 much more westerly as might, by possibility, have preserved 

 them from the catastrophe which ensued. 



Various methods have been devised for the discovery and cor- 

 rection of this insidious influence, some of which it may be pro- 

 per, in conclusion of this article, briefly to describe. 



The first regular process employed for the determination of 

 the " deviation" was to take the bearing of a distant object by a 

 compass in the binnacle, whilst the ship was laid at anchor or at 

 moorings, and successively to observe the relative bearings when * 

 the ship's head was put on each point of the compass in succes- 

 sion, as she was gradually " swung" round. In this case, the 

 bearings which were found to accord with the correct magnetic 

 meridian determined the points of change, or those positions of 

 the ship's head in which the compass gave correct indications ; 

 and the diff'erences of the bearings in all other positions of the 



