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Show Great l!t In Deeo Mines. Tho latett ritermln.- m of rise In temporaturo In descending underground under-ground gives 2t3 feet for ovqry degree centigrade or 135 feet for a Use of ono degiee Fahrenheit. Tho dlfferenco In temperature of different rock substances sub-stances Is almost Inappreciable. Experiments mndo in deep mines to prove that tho heat of tho rocks does not precludo mining operations at even 1.000 feet, because If tho recognized recog-nized formn'i of 125 degiees Fahrenheit Fahren-heit at 3,r.O feet, demonstrated that such a tcrtij rature Is not reached. The as&i'iMnn sometimes made that r mining ml- extend to as great a depth as 1 ) feet If ullage could bo accomp'Mbed Is im'-nable. Tho difficulties mltl not bo In haulaga, but, first, li ' of breathing under the enormous n" ospherlc piossure, and, secondly, Increase of temperature. A mass of air In a down-cast shaft of CO degrees Fab enhclt nt the surface at a depth of lO.OOO feet would attain a temperatuie of !0 degrees by Its own weight. Ileiijihfnl mining would bo Impossible. |