224 NICKEL, TUNGSTEN 



is the fact that it tarnishes but slightly in damp air. For this 

 reason it is used to coat or plate other metals, thus rendering 

 them brighter and safe from rust. Rifle bullets are sheathed 

 with it. 



SOURCES OF SUPPLY. Sudbury in Ontario produces two-thirds 

 of all the nickel in the world. The nickel- ore district covers 

 an area of 800 square miles, and ' there is no doubt that 

 Canada is able to furnish all the nickel ore required for use 

 in the empire '. 



There are also deposits in Tasmania, Newfoundland, South 

 Africa, and Egypt. 



Tungsten is not found alone in nature, but always in com- 

 bination with some of the other metals. It occurs principally 

 in wolfram and schulite. 



Wolfram (FcWO 4 ) is a dark- brown mineral consisting of 

 iron and tungsten combined with oxygen, and the tungsten 

 (generally in the form of a powder) has to be extracted from 

 it by a complicated process. 



.In schulite (CaWO 4 ) calcium takes the place of iron. The 

 importance of tungsten lies in the fact that a small proportion 

 of it added to steel increases the hardness of the latter in the 

 most wonderful manner, and not only its hardness, but its 

 6 temper ', for it can be made red-hot without changing its 

 quality. 



Thus, all sorts of cutting tools are made of tungsten steel, for 

 these need special hardness, as they have to cut hard substances 

 such as iron and steel. 



To take one instance. A modern ship is built of steel. 

 After the keel has been laid down, and the ribs securely fastened 

 into place, the whole is covered with large plates of steel. 

 These plates are fastened on to the framework of the ship 

 with rivets. In each plate holes are bored or punched out, 

 and these are placed over corresponding holes in the frame- 

 work. Then a white-hot rivet about two inches long is put 

 through each hole and hammered flat at each end, so 

 that it becomes in shape like a double-headed nail. As it 



