t88 



T. C. HOPKINS — CAMBRO-SILURIAN LIMONITE ORES 



8 c 



Some of the ore pits are 

 shallow, striking the lime- 

 stone in situ at a depth of 8 

 or 10 feet. Many of them 

 range in depth from 50 to 90 

 feet, hut the ore frequently 

 extends to a much greater 

 depth. The expense of ele- 

 vating the materials and of 

 keeping out the water gener- 

 ally causes a cessation of 

 work at about 90 feet below 

 the surface. The actual 

 depth of the ore deposit in a 

 few places is surprisingly 

 great. At the Lehman mine, 

 in Cumberland county, a 

 hole was drilled 435 feet be- 

 low the bottom of the ore pit. 

 The report of the boring gave 

 340 feet of ore (presumably 

 ore and clay), 40 feet of blue 

 clay, 30 feet of white clay, 

 and 25 feet of " mountain 

 clay."* A record of a well- 

 boring at Lambourne, in the 

 Nittany valley, gives 300 feet 

 of ore and clay, 450 feet of 

 white sand, 16 feet of lime- 

 stone, a total depth of 766 

 feet, or 750 feet to the solid 

 limestone rock, yet lime- 

 stone may be seen outcrop- 

 ping on all sides of this well 

 less than half a mile distant. 

 It is difficult to account for 

 the excessive deep disinte- 

 gration of the rocks at this 

 point. 



Prime and Lesley empha- 

 size the statement that the' 

 ore occurs in regular belts 



* Second Geol. Survey of Pennsylvania, An. Rept., L886, pt. iv, p. L462. 



