3H POPULAR LECTURES AND ADDRESSES. 



column of iron and wood is kept in position and 

 protected from rain and spray by a brass tube 

 with upper end closed, going down over it. 



The main object of the Flinders bar is to 

 counterbalance the component of the ship's 

 horizontal force on the compass, which is due to 

 magnetism induced by the vertical component of 

 the terrestrial magnetic force. Hence, in all 

 ordinary cases, the ship's iron being symmetrical 

 on the two sides of the fore-and-aft midship 

 vertical plane, and the compass being placed in 

 this plane, the Flinders bar must be placed in it 

 also, and therefore must be exactly in the middle 

 of the front side, or of the after side, of the 

 binnacle. The Flinders bar essentially corrects, 

 wholly and permanently, the constituent of the 

 heeling error, which has its maximum values on 

 the east and west courses. A subordinate object 

 of the Flinders bar, as supplied to my compass, is 

 to partially correct the constituent of the heeling 

 error, which has equal maximum values on the 

 north and south courses, by partially counter- 

 balancing the component force on the compass, 



