126 WALKS AND TALKS. 



water saturates. Here is black muck a fine peaty material 

 but it is colored and charged with this ocherous deposit. 

 After some years, the peaty matter decays, and disappears, to 

 some extent. Then we see the iron compound aggregated 

 and compacted in irregular masses. It has now become bog 

 iron ore. It is a kind of limonite, so-called. It can now be 

 smelted in a furnace and the pure iron extracted. 



If this swamp should be sunken below sea-level, and heavy 

 layers of marine sediments spread over it, the bog ore would 

 be compressed into a compact stratum. Then if all these for- 

 mations should be converted to solid rock, our bed of bog ore 

 would be exactly such a bed 'of limonite as we actually find 

 in some situations deep in the rocks. It would be an old fossil 

 swamp. But suppose some thousands of feet of sediments should 

 be piled over it. Then the heat of the earth's interior would 

 come up and bake the ore-bed. Very likely the water would 

 be expelled from our limonite, and it would become simply a 

 peroxide it would assume a red color it would be hematite, 

 which means blood-red ore. Now such beds of hiematite form 

 many of our most valuable deposits of iron ore. Much of the 

 ore in the Lake Superior region is of this kind also in North- 

 ern New York and in other regions. But if this old hsema- 

 tite is left exposed to water for some years if the bed be- 

 comes soaked with water, it changes back to limonite; it 

 becomes yellow and somewhat soft. The miners sometimes 

 call it "soft hematite." It is easily quarried and easily 

 smelted, and every body likes it though ton for ton of ore, 

 it contains less iron than hard or true haematite. 



I do not assert that all limonite and haematite have come 

 into existence in this way. But I am sure this theory is highly 

 plausible for some beds of iron ore. But now, I have noticed iron 

 ores in such situations that perhaps a different explanation is 

 more reasonable. I have seen great masses of iron ores inclosed 

 in the midst of great stratified formations. The ore-masses are 

 huge lenticular accumulations sometimes of great purity, 

 sometimes mixed with rocky matter, sometimes bounded ab- 

 ruptly, and sometimes blending gradually with the contiguous 



