OCR Text |
Show IEJT AT DEPTH EUSTIS IBS Rock Temperature Rises Four Degrees to 1000 Feet in Noted Rand Mine. Al a recent meeting cf tl:t: Midland (British) Institute of Mining Unginfcera an interesting communication from .U. If. Clifford v as read, describing1 conditions pro vale i-.t. in tlio City IX ep mine, one uf tho largest and deepest of tho Hand. At tho present tima tlio workings, which are confined to the uijerniost pur-tion pur-tion of t!;e ntine, extend over an area of approximately 10. Out) feet along- tho strike by ;;:00 fot on thu dip, and the greatest vertical depth at. present is 400u feet. On tho Vv'itwatersrand tho temperature temper-ature of tho rocks increases at tho rate of 4 decrees for every lOoO feet In depth, and the rock temperature at 4 Tj 0 0 feet is Si decrree;. This would not bo at all serious were it Put for- tlio fact that -the air. shortly after leaving: tiie? ma in intakes, in-takes, very soon becomes saturated in consequence of regulations stipulating that all rock surfaces should be kept w,et lit order to prevent tho dissemination dissemina-tion of dust. A saturated air at a temperature of S-i degrees Fahrenheit in scarcely suppout-able suppout-able unless the air Ttas in aetivo motion, and this latter conditiuu could not be maintained at every point, particularly in development ends. They had therefore reached tho limit on the City Deep, and had yet an additional addi-tional 2000 feet to go when the new shaft is cotnplet ed, and wore laced with tlio necessity of reducing the air temperature from between 9a and luO degrees Fahren-lmiL Fahren-lmiL w hich it would bo at 7000 feet to about 75 degrees Fahrenheit. The principle prin-ciple that aa being relied upon was the heat-absorbing- capacity of the ventilating ventilat-ing current of air duo to evaporation and to Ha specific heat. Local cooling- near tlio bottom of dovt ncast shafts v as. of ; course, taking piaco everywhere, but it! generally remained local euoiing. |