Inquiry into the Origin of Mud Hushes in De Beefs Mine. 59 



it could be forced at one swoop into the mine. Again, in the 

 three years dealt with by this paper, sixty-one inches of rain fell 

 (representing a volume of about five million cubic feet over the mine 

 area), into the open mine. Of this the greater portion would be 

 evaporated again almost immediately, particularly that falling in 

 small showers. Then again the top debris could absorb an enormous 

 quantity without being more than damped by the moisture. It 

 would be hard to show a probability that anything like a million 

 cubic feet of the five millions could eventually collect in dangerous 

 quantities into pockets in the vicinity of the deep working levels. 

 And yet there were fifty-three mud rushes in the same time, 

 averaging perhaps ten thousand to twenty thousand cubic feet 

 each in volume. 



Since the rainfall over the open mine is manifestly inadequate 

 to the task with which it has been burdened, the solid fact remains 

 that the water which makes the debris formidable must flow into the 

 mine from the sides. Now in sinking shafts and driving tunnels in 

 the solid rock outside the mine various feeders of water have been 

 struck, many of them quite sufficient for all the requirements of mud 

 rushes. In the rock tunnel, for example, on the 1,200 foot level 

 of the Kimberley Mine, is a feeder of water yielding perhaps five 

 thousand gallons per hour. On the 1,520 foot level of the same 

 mine is another (belonging doubtless to the same water system), 

 not so large, but still important. Physical observations upon these 

 during the last two years reveal little, if any, changes of tempera- 

 ture day after day. Their flow is constant whether the season be 

 wet or dry. Their temperatures agree pretty closely with Lord 

 Kelvin's theoretical estimate of increase according to depth within 

 the interior of the earth. In short, they are unaffected by current 

 meteorological conditions. These, then, indicate the water factor 

 of a mud rush. An underground spring with a flow of only one 

 hundred gallons per hour would, since it would penetrate the 

 debris at one spot, soon supply enough water for the greatest of 

 mud rushes, without any assistance from the local rainfall. The 

 two large springs in the Kimberley Mine, just referred to, and 

 indeed the largest springs in either that or the De Beer's Mine, 

 are in the quartzite. And here it may not be out of place to 

 mention that although the supply of top debris has always been 

 ample, mud rushes never occurred until the level of the quartzite 

 was reached. 



Without recognising the rainfall, then, we have at hand abundant 

 materials out of which the most highly finished mud rush may be 

 constructed. But to the miners, white and black, it is perhaps 



