174 1 . — NATURAL VENTILATION . When we have two shafts of unequal depths to the same level underground , we have a circulation of air established , the character of which will be as follows : — … The consequence of this is , that we have a higher mean temperature and lighter column of air , length for length , in the shaft C D than in the shaft A B , at all times when the surface temperature is as low as , or lower than , the mean temperature of the locality . As the temperature of the…
Bergbautechnik
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