420 On Metallic JMinerals. 



NOTE 14. 



In several places along the northern shore of the St. 

 Lawrence, below Mai Bay, veins of magnetic iron are 

 found in the rocks, and they are said in consequence, to 

 exert an influence upon the ship's compass, in passing up 

 and down the river. Captain Bayfield, however, never 

 noticed any thing of the sort, but attributes the observed 

 difference in the compasses of vessels from the bearings 

 laid down in correct charts, to the local attraction of the 

 vessels themselves. This local attraction, which varies in 

 different vessels according to the quantity and distribution 

 of iron in the construction, equipment, and cargo of the 

 vessel, and also according to the situation in which the 

 compass is placed with respect to the focus of attraction, is 

 called the deviation. The deviation has but lately been 

 taken into account, and allowed for in His Majesty's ships, 

 and is in general entirely overlooked in merchant vessels. 

 The error, from this cause, in those latitudes frequently 

 exceeds a point of the compass. 



NOTE 15. 



A Mr. Mason appears to have examined the country in 

 the neighbourhood of Charlotteville with a view to ascer- 

 tain the quantity of bog ore in it. He says — " The bog 

 ore is scattered over the whole of the country ; but I do 

 not know any one bed of ore that will exceed one hundred 

 and twenty-six tons. 1 spent three months in examining 

 the country for ore, and I calculate that it will take all the 

 ore 1 found within twenty miles of this place, to suj)ply a 

 small furnace for seven years; but 1 believe considerable 



