100 THE ORIGIN OP CREATION. 



on raising them six feet and over, they showed differently. He 

 thus discovered that the tin cans had caused the deviation, as 

 they were merely sheet iron covered with tin \ so during the 

 remainder of the voyage he steered with a conjpass fixed half 

 way up the mizen mast. He stated that if he had sailed from 

 Boston, in thick weather, instead of from New York, it was 

 highly probable he should have lost his vessel on Cape Cod. 

 But it would not require a full cargo of tin cans to make such 

 difference in the compass, as only one tin can, if sufficiently 

 near, would affect it. Before iron ships came into use, we heard 

 an account of a difficulty from compasses on board one of H. 

 M. Ships, the officers finding an error in her position after every 

 night's sailing. An investigation showed it to be caused by 

 the officer of the night watch, carelessly placing his speaking 

 trumpet in the binnacle, alongside of the compass, when he 

 came on deck. 



The influences to which compasses in iron shipa, or steamers, 

 are subject, are more numerous. 



The first great cause of deviation, is from the iron sides and 

 projections of the vessel, all iron projections, such as stanchions, 

 davits, etc., acting as separate poles to the ship's magnetism. 



The uppermost sides of the ship and the projections, will 

 always in northern latitudes attract the " north " point of 

 the compass. Thus if the ship rolls heavily from side to side, the 

 compasses will move from side to side with every roll. But if 

 the ship sails with a steady list to one side, the north point of 

 the compass will keep inclining to the uppermost side as long 

 as it is so. A vessel from this cause is apt to go a long way out 

 of her course; and instead of attributing the trouble to the 

 deviation of the compass, currents are stated to have caused it 



