METALS. 95 



The lustre by which they are distinguished, 

 called the metallic lustre, is not easily described, but 

 may be exemplified in that of silver, steel, lead, tin, 

 &c., as distinguished from that of glass, diamond, 

 &c. Mica has a lustre which approaches that 

 called the metallic, but it loses this on being 

 scratched, while the metals do not ; on the con- 

 trary, they are more brilliant when fresh cut. This 

 property of the metals renders them highly useful 

 for ornamental purposes, and for reflecting light, 

 as in mirrors. 



Metals are the best conductors of heat, and also 

 of electricity. 



Some of the metals are capable of being extended 

 under the blows of a hammer, which property 

 is called malleability, and is peculiar to metals. 

 Others, again, are brittle, on which account they 

 were formerly called semi-metals. The malleable 

 metals are, gold, platina, silver, palladium, potas- 

 sium, sodium, mercury in its frozen state, copper, 

 iron, lead, tin, zinc, and nickel. These differ 

 much in their degrees of malleability. Gold may 

 be beat into the thinnest leaves, and zinc is very 

 little malleable, except when heated. The malle- 

 able metals are also ductile, or may be drawn out 

 into wire. Gold and platina may be drawn into 

 the finest wire. 



One of the metals, iron, is capable of being 

 made very elastic, which renders it fit for making 

 springs. 



Most of the metals are very fusible, or capable of 

 being rendered fluid by the application of heat; 

 on this account they may be cast into moulds, and 

 formed into various utensils: some of the metals 

 are volatile at a high degree of heat. 



None of them are very hard naturally ; but some 



