THE IRON SERIES, CONTINUED. 



115 



is irregular and of lower grade and runs from 6 to 10 feet thick. 

 The Pilot Knob mines in this solid ore are now substantially 

 exhausted. 



Recent drill holes ou the northerly slope and below the out- 

 cropping face of ore have shown that under the Cambrian strata of 



FIG. 23. View of open cut at Pilot Knob, Mo., shoiving the bedded char- 

 acter of the iron ore. From a photograph by J. F. Kemp, 1888. 



the valley there is a great bed of ore boulders or breccia in clay, 

 much as is the case at Iron Mountain, later described. Analyses 

 of cores were not, however, sufficiently encouraging for develop- 

 ment during the present low prices for iron. Doubtless the bed 

 will afford important reserves. 



2.02.33. Near Pilot Knob are two other hills of porphyry, 



