MAGNETISM. 99 



prop, rfy on tho North Aim-rimi! coast and other shores of 

 lute, h is. through this and other causes, been lamentable. 



. itlistan.ling the long time that the mariner's compass 

 has bfi'ii iisril, scientific, as well as practical men, seem to be 

 .rant as over of the influences to which the needle is 

 subject, and to have learned absolutely nothing in this respect, 

 to efficiently protect their vessels from danger. Since the in- 

 troduction of iron vessels also, accidents have become more 

 numerous, even as high, compared with wooden vessels, as 8 to 

 I, and yet the only invention brought into use to prevent the 

 deviations, is one of the most stupid, not to say dangerous, that 

 could have been thought of, viz. : the placing of fixed magnets 

 on the deck of a vessel under tho compass. For the one 

 thing absolutely required in the use of a compass, is perfect 

 freedom from all magnetic influence, except that of the earth's 

 polarity, and yet fixed magnets are placed in such a manner, 

 that if the ship alters its position, or its course, by storm or 

 otherwise, the true marking of the compass is lost altogether. 



In wooden vessels there is not so much danger of deviation 

 as in an iron vessel, and the only care necessary, is that no irtm 

 of any description be placed near the compass. Any metal 

 required for the fitting up of the ship should be of composition. 

 Care also should be taken with the description of cargo, stowed 

 under or near tho compass. 



We re-id lately of a Captain who sailed from New York for 

 Japan, with a cargo of petroleum in tin cases, and after being 

 out a day, found he had been going more southwardly than he 

 expected. On making an examination of the compasses, and 

 trying them in different parts of his ship, he found that any- 

 where within three feet of the main deck they were alike, but 



