. Transactions of the Institution of Mining Engineers . k10 feet deep, the ends of the holes being closed by means of an irondoor about J inch thick, with a pad (made from old canvas-belting)forming an airtight joint between the door and the rock-face around thehole, which is cemented smooth for this purpose. These curves showclearly the give and take of heat between the rock and the ventilating 336 TRANSACTIONS INSTITUTION OF MINING ENGINEERS. [VOL. LXII. current in accordance with the seasonal changes of temperature of theoutside air. Another interesting point which they bring out is thetime
. Transactions of the Institution of Mining Engineers . k10 feet deep, the ends of the holes being closed by means of an irondoor about J inch thick, with a pad (made from old canvas-belting)forming an airtight joint between the door and the rock-face around thehole, which is cemented smooth for this purpose. These curves showclearly the give and take of heat between the rock and the ventilating 336 TRANSACTIONS INSTITUTION OF MINING ENGINEERS. [VOL. LXII. current in accordance with the seasonal changes of temperature of theoutside air. Another interesting point which they bring out is thetime-lag effect; the peaks and valleys of Curve B seem to occur on theaverage about 40 days behind those of Curve A, while Curve C similarlyappears to lag about 43 days (average) behind Curve B. Curves C andD, however, keep fairly well in step with each other. Mr. J. P. Rees (Birmingham University) wrote: Mr Davies hasremarked on an interesting feature shown by several of the charts, ofwhich no explanation is given in my paper. This feature is the fall in. ^ . > o ^ uJ O O UJ -< u < Q. <-) u. s oD ul O O uJ•z^ot^->o<a,- z -1 < UJ < £1. < D 3T u. S 1918 Fig. 2.—Surface Air- akd Underground Rock-temperatures at the Morro Velho Mine, Brazil. absolute moisture-content of the ingoing air immediately after leavingthe bottom of the downcast shaft. The explanation of this is that thewalls and dust in the intake airways act, within limits, as anautomatic regulator of the moisture-content of the air. When theabsolute moisture-content rises, the walls adsorb moisture from the airand tend to keep it dry; and, on the other hand, when the moisture-content of the air falls, the walls give off moisture to the air, tendingto keep it wet. Generally, during the night the moisture-content of theair falls and the walls become drier; during the day the moisture-content of the ingoing air rises and the walls adso
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Keywords: ., bo, bookcentury1800, bookdecade1890, booksubjectmineralindustries
