AND AGRICULTURE. 



23 



which means that it can be drawn out very fine ; 

 and it is malleable, that is, it can be rolled or 

 hammered out very thin. (See Appendix, 10.) 



OXIDE OF IRON. If iron is exposed to 

 the atmosphere, it becomes, after a while, cov- 

 ered with a reddish-brown powder, or rust ; this 

 rust is oxide of iron ; the iron has attracted a 

 portion of oxygen from the atmosphere, and 

 combined with it. Metals will not oxidize in a 

 dry place, or protected from moisture. (See 

 Appendix, 11.) 



Sometimes the oxide of manganese, a sub- 

 stance very much like the oxide of iron, is found 



Fig. 8. 



Questions. What is the rust of iron ? Will metals ox- 

 idize in a dry air ? What oxide, much like iron, is some- 

 times found in soils and plants ? 



