TUNGSTEN 225 



cools it contracts, and so draws the plates firmly against 

 the frame. 



The whole ship is thus put together by rivets, so that in 

 a large vessel there are many millions of them, and the holes 

 through which they pass have all been drilled or cut by tung- 

 sten steel tools. 



In battle-ships the armour-plates are made of a very hard 

 tungsten alloy, and, indeed, the need for specially hard steel 

 in all engines of war is vital. 



MOLYBDENUM, which occurs in a mineral called molyb- 

 denite, also like tungsten hardens steel, and is sometimes 

 employed instead of tungsten. 



SOURCES OF SUPPLY of tungsten and molybdenum : 



In Cornwall wolfram ore is found, but generally in associa- 

 tion with tin ore, from which it has to be separated before 

 the tungsten can be obtained from it. 



Burma. The principal wolfram mines are at Tavoy, on the 

 coast of Tenasserim, and the output of these mines is about 

 one-third of the world's total production. There are deposits 

 in other parts of Burma, but these are not so extensively 

 worked, on account of difficulties of transport. 



Australia. From Port Cairns, on the Queensland coast, 

 a railway runs inland to Georgetown. There is a branch 

 southwards to Herberton and one northwards to Chillagoe. 

 The wolfram-bearing country in this part of Queensland is 

 estimated to extend over an area of three thousand five 

 hundred square miles, and it is stated that these Chillagoe 

 and Herberton mineral fields alone ' can supply the world's 

 demands and have a good deal to spare afterwards '. Besides 

 wolfram, molybdenite is extensively mined. 



In New South Wales wolfram occurs in many places, but 

 the chief mining centre at present is at Torrington to the 

 north of Emmaville, on the New England tableland. 



Victoria has deposits of wolfram, molybdenite, and schulite, 

 and Tasmania of wolfram, and there are deposits of schulite 

 in New Zealand. 



2203 p 



