THE KING OF METALS. 127 



strata. The ores occur in this way at Lake Superior. Such 

 masses of ore are almost always in crystalline inetaraorphic 

 rocks. They have been heated probably subjected to the 

 action of hot water. 



There is another species of iron ore very commonly asso- 

 ciated with these. It is magnetite. This is composed partly 

 of peroxide of iron and partly of protoxide of iron that is, 

 iron with only one proportion of oxygen combined with it. 

 Magnetite is richer, therefore, than hematite ton for ton of 

 ore it contains more iron. While powdered haematite is red, 

 and powdered limonite, brownish yellow, powdered magnetite 

 is black. Magnetite attracts the magnetic needle. "Lode- 

 stone" is magnetite so-called, probably, because it leads by 

 its attraction. Now, magnetite is often found in great im- 

 bedded masses, like haematite, and is regarded one of the 

 most desirable of ores. Often haematite and magnetite are 

 mingled together in the same bed; and the indication is, that 

 one is capable of conversion into the other. 



We often find, also, considerable formations in which 

 much iron ore exists in a disseminated state, imparting a 

 highly ferruginous character to the rock, but constituting 

 only a very "lean ore." It may be a haematitic quartzite or 

 a silicious haematite. We find all stages of transition from 

 pure ore masses to simple rock. The theory is often suggested 

 to me by the conditions under which these metamorphic ores ex- 

 ist, that they are simply accumulations of ores gathered together 

 from wide contiguous regions in the rock. It seems settled 

 that ores of lead, zinc, and silver are thus eliminated from the 

 country rock, as was explained in the last Talk. Hot, alka- 

 line waters are supposed to have had principal agency in the 

 work. But where the native metals occur, as gold, silver, or 

 copper, we must suppose that a dry fusing heat has been 

 present to reduce the ores previously formed, or drive together 

 metallic particles disseminated through the rock; or we must 

 suppose that an electro-chemical deposition has taken place 

 from a metalliferous solution, as in the electro-plating process. 

 In some way, at least, particles of a particular kind become 



