128 WALKS AND TALKS. 



aggregated in "veins," in "lodes," in "segregations;" and thus 

 the huge lenticular masses of haematite may have been formed. 



Perhaps this theory is sustained by the relations of iron ores 

 to the stratification. Often all stratification is obscure or 

 wanting; often the stratification of the country rock can be 

 traced through the ore-body ; not unfrequently the ore-mass is 

 a vast stratified formation. Pilot Knob, in Missouri, is a 

 great iron-schist a schistose formation in which the once dis- 

 seminated iron particles appear to have been driven by some 

 agency, into a particular part of the formation. In this case, 

 the richest part of the formation is at the pinnacle of the 

 knob, and the schist decreases in richness as we descend to 

 the base. 



Now, there are two suggestions in reference to the way in 

 which iron ore particles have been accumulated first, fossili- 

 zation of ancient iron-bogs ; second, segregation. If the great 

 masses found in metamorphic strata seem rather to be the results 

 of segregation, some of the younger iron deposits appear to be 

 of the nature of fossilized swamps. Probably, too, some rich 

 stratified ores, like those back of Milwaukee, and those near 

 Rochester, New York, were precipitated in shallow seas the 

 iron brought in by springs. This is a third suggestion. 



There is still another way in which iron combinations ap- 

 pear to accumulate. It is a modification of the segregation 

 process. You have seen, sometimes, in a yellowish or reddish 

 sandstone that is, a ferruginous sandstone some concentric 

 bands of a deeper color bands formed by an increased 

 amount of oxide of iron. Now observe that the lines of 

 stratification of the rock pass quite through these spheroidal 

 forms. It is manifest, therefore, that the spheroidal aggrega- 

 tions took place after the sediments were laid down after 

 the rock was formed. If so, then the iron material must have 

 /moved through the consolidated rock. How did it move? 

 Could solid particles of iron-oxide travel from all directions 

 toward a common center, and all halt at a common distance 

 from that center? Evidently not, only pure water or clcnr 

 solutions could thus move. We may, therefore, conclude th:it 



