. Bulletin of the Geological Society of America. Geology. 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
. Bulletin of the Geological Society of America. Geology. 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 ;* 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. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Geological Society of America. [New York : The Society]
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