TERRESTRIAL MAGNETISM, ETC. 313 



34 degrees growing up in the voyage from England 

 to Algoa Bay, and disappearing on her return to 

 England, has been corrected by a Flinders bar 

 attached to the front side of the binnacle, and the 

 ship now goes and comes through that long voyage 

 with no greater changes of compass error than 

 might be experienced in the same time in a ship 

 plying across the Irish Channel. 



The Flinders bar supplied with the compass is a 

 round bar of soft iron, 3 inches in diameter, and of 

 whatever length of from 6 inches to 24 inches is 

 found to be proper for the actual position of the 

 compass in any particular ship. To make up the 

 proper length it is supplied in pieces of 12 inches, 

 6 inches, 3 inches, i^ inches, and two pieces of f 

 of an inch. In making up the proper length the 

 longest piece should be uppermost and the others 

 below it in order of their lengths. The weight of 

 the bar is supported on a wooden column or bar 

 resting on a pedestal fixed to the binnacle near its 

 foot, this w r ooden bar being cut to such a length, or 

 so made up of pieces, as to give the proper height 

 to the upper end of the iron bar. The compound 



