THE KING OF METALS. 127 



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

 masses of ore are almost always in crystalline metaraorphic / 

 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 hseuiatite ton for ton of 

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

 and powdered limouite, 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 hsematite, and is regarded one of the 

 most desirable of ores. Often hsematite 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 hsematitic quartzite or 

 a silicious hsematite. 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 i 

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

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

 line waters are supposed to have had principal agency in th 

 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 



