1865.] on the Magnetism of Ships. 303 



adjustment have been practised, each of which lias its advantages and 

 disadvantages. 



" i . The system recommended by a Committee of Men of Science and 

 Naval Officers appointed by the Admiralty in 1837, and which has been 

 uniformly followed in the Royal Navy from that time. In this system 

 each ship has a ' Standard Compass,' distinct from the Steering-Compass, 

 fixed in a position selected, not for the convenience of the steersman, but 

 for the moderate and uniform amount of the deviation at and around it. 

 The ship is navigated solely by that compass. The deviation of that 

 compass on each course is ascertained by the process of ' swinging' the 

 ship ; a table of deviation is formed, and the deviations given by the 

 tables are applied as corrections to the courses steered. 



" 2. The system proposed by the Astronomer Royal in 1839, and which 

 is understood to be generally followed in the mercantile marine. In this 

 system the deviations of the compass are compensated by magnets (and 

 occasionally soft iron). The ship is navigated by the compass so cor- 

 rected generally the steering-compass, and generally without any tabular 

 correction. 



" It would not be right, considering the weight of authority on each 

 side, to pronounce any decided opinion against either of those modes of 

 correction when properly used. The first system has proved in the Royal 

 Navy to be one which can be used without danger. The same cannot be 

 said of the second method as regards the mercantile marine ; but the prin- 

 cipal danger of the method arises from what is in truth an abuse of the 

 method : it is that, in reliance on the power of correcting any amount of 

 original deviation, however great, the navigating-compass is placed in a 

 position in which the original deviations are excessive and vary rapidly, and 

 in which no navigating-compass should be placed. 



" In merchant ships the most convenient place for the steering-compass 

 is generally near the upper part of the stern-post, the rudder-head, the 

 tiller, and the iron spindle of the steering-wheel all, from their shape and 

 position, powerfully magnetic. The constructor and owner, for the sake of 

 economy, desire that the steering-compass should be the navigating-com- 

 pass. The compass-adjuster fears that any objection on his part would be 

 considered a confession of incompetence, and that some less scrupulous 

 adjuster would not hesitate to undertake the correction. The correction 

 can only be made by powerful magnets. The compass is then held, as it 

 were, in equilibrium by powerful antagonistic force ; and when the changes 

 take place, which it is known do take place in all new iron ships, or when 

 any changes take place in the magnets, large errors are introduced, which 

 are the more fatal because the shipmaster is taught to believe that his 

 compass is correct. 



" This abuse of the method is one the temptation to which is unfortu- 

 nately so strong, that it is believed it can only be effectually prevented by 

 prohibiting the use of the steering-compass as the navigating-compass, or 



