Inquiry into the Origin of Mud Rushes in De Beer's Mine. 65 



counteracting, to a certain extent, the maximum effect of the normal 

 decrease of pressure during the afternoon, and assisting or impeding 

 atmospheric depressions. A low temperature and a shallow depres- 

 sion might even reduce the pressures underground quite as much as 

 a deeper depression with a normal temperature. Moreover, since it 

 frequently happens that after a deep depression the temperature 

 gradient may be falling as rapidly as the pressure gradient is rising, 

 so it may happen that the maximum effect underground may not be 

 felt until some time after the passage of the centre of the depression. 

 I am not saying that it is so, but that the curves give colour to the 

 idea.' 1 ' 



The Kimberley Mine some time ago suffered with mud rushes 

 quite as dangerous as those now troubling the De Beer's Mine. I 

 have not been able to ascertain whether they also were sensitive to 

 atmospheric changes, for the simple reason that the last took place 

 shortly after my barometer record began. An attempt was made by 

 the management of the mines to cope with the Kimberley mud, by 

 driving a tunnel right round the mine near the junction of the black 

 shale and melaphyre (some 700 feet above the working places), with 

 the idea of catching the "surface water" which flowed into the 

 debris at that spot. Curiously enough there have been very few, if 

 any, mud rushes in the Kimberley Mine since this tunnel was made. 

 And it is therefore intended to make a tunnel at the same depth 

 round the De Beer's Mine. But it is to be noted that the 1,000 foot 

 level in the Kimberley Mine was well advanced, and the 1,200 foot 

 level opened, at the same time as the water tunnel was made, and 

 that both these levels tapped a quantity of water which, in all 

 probability, came straight from the quartzite. This by being led 

 away to the pumps could do nothing towards mud-making. If the 

 water above the melaphyre is responsible for the mud, there is no 

 apparent reason why mud rushes should not have taken place above 

 the quartzite level — which they did not. By one of those remark- 

 able coincidences, which will happen, after a systematic attack had 

 been made on the " surface water " in the De Beer's Mine sometime 

 during 1895, the number of mud rushes fell off considerably. And 

 the General Manager's report to the annual meeting of shareholders 



* It would be hazardous, at this early stage, to assert that the changes of 

 pressure act directly in bringing about a mud rush. The whole diminution of 

 power when surface pressure and temperature fall together would not at any 

 time be more than one-fiftieth of that keeping the mud in equilibrium. It is 

 quite possible that the pressure changes may act in some indirect way. Thus, 

 for example, to take a simple illustration, an engine driver is powerless of 

 himself to move his engine a single inch, but he can easily set free forces that 

 will move it miles. 



