Metals. 225 



medy this, the metals are generally heated red- 

 hot, and cooled again slowly ; in this case their 

 malleability will be increased; and this is called 

 annealing them : but this is not done in beating- 

 out gold leaf; it may therefore be very probably 

 broken in several places, and have minute flaws 

 which transmit the light. Krammer says, if the 

 gold is annealed, the leaf will be quite opake. 



3. Metals are likewise distinguished by their 

 properties with regard to electricity, which rank 

 them among the most powerful of conductors, 

 and render them more easily affected by light- 

 ning than any other matter. 



4. Another property of metals is fusion by 

 heat. In this state they always retain their 

 opacity ; and there is always a sort of repulsion 

 between them and any vessels into which they 

 can be poured, except metallic ones. Their 

 particles, when melted, have an attraction for 

 one another, in consequence of which they form 

 into spheres. This is evident in quicksilver when 

 thrown upon a table, the globules reflect all the 

 objects round. In general, melted metals have 

 a repulsion for other fluids; hence they cannot 

 be mixed with oils, melted salts, or earths; but 

 some of the combustible bodies unite with them 

 in their melted state. 



5. The most common and best known metals 

 possess malleability ; and metals are the only 

 bodies in which this property is found. 



As to the effects of heat upon metals, they be- 



L 5 



