INDUSTRIAL MINERALS DIAGRAM 19 229 



Loadstone is a kind of iron ore which, possesses the property of 

 attracting iron to it. When bars of soft iron are rubbed with it, 

 they acquire the same property, and are then called magnets. 

 Loadstone is not, however, the only body which thus attracts 

 others. It is enough to rub a stick of sealing wax on cloth, and 

 put it near the down of a feather or a very small piece of paper, 

 to see these very light bodies attracted as is iron by the magnet. 

 This, however, is produced by electricity, and not by mag- 

 netism. 



"When a piece of soft iron has thus been rendered magnetic, 

 we find that one end attracts and the other repels iron. If the 

 magnet is then suspended so that it can move freely, we shall 

 find that it will move round until the attracting or positive pole 

 points to the north, and the repelling or negative pole to the 

 south. The mariner'' s compass, by which ships are guided across 

 the sea, is formed of a needle which has thus been rendered mag- 

 netic, and always points north and south. 



Copper ore. Copper, like iron, is rarely met with in a pure 

 state, but is nearly always mixed with sulphur. The treatment 

 of copper ore is rather tedious. When it has been washed and 

 crushed, it is roasted several times to burn the sulphur. It is 

 then melted, and the copper separates. Copper is of a red 

 colour, and is used to make boilers, saucepans, and a variety of 

 utensils, but they ought always to be kept very clean, as other- 

 wise verdigris forms in them, which is a violent poison. To avoid 

 this inconvenience, the inside of copper vessels which are not re- 

 quired to be exposed to a great heat, are tinned, but they are use- 

 less if too much heated, as the tinning melts. 



When copper and tin are mixed together in proper propor- 

 tions, we obtain bronze, which is more durable than copper, and 

 much less easily tarnished in the air. Bronze is used to make 

 statues, cannons, and a great many objects which are very little 

 injured by time. 



When we add a certain quantity of zinc to copper, instead of 

 tin, we obtain brass. These mixtures of two metals are gener- 

 ally called alloys. 



