320 POPULAR LECTURES AND ADDRESSES. 



force, whether she crosses the magnetic equator or 

 not, the rule in respect of the fore-and-aft correction 

 is as follows : 



Correct the deviations found by observation on the 

 east or west courses by the fore-and-aft magnets when 

 the ship is going to places of weaker, and by the 

 Flinders bar when she is going to places of stronger, 

 vertical force, wJiether in the southern or northern 

 Jiemisphere. 



After a few voyages the proper proportion of 

 correction by Flinders bar to correction by bar- 

 magnets will be practically realized. 



For a ship with a compass permanently relieved 

 of quadrantal error, and with a binnacle provided 

 with these appliances for adjustment, the regular 

 management of the compass at sea becomes very 

 simple. Whenever an error exceeding two or three 

 degrees is ascertained on any course, it may be 

 corrected by a slight readjustment of the correcting 

 magnets, performed in such a manner as not to 

 disturb the direction which the needle would show 

 if the ship were steered on a course at right angles 

 to that on which the error is found. Occasionally, 



