482 Mr. William CrooJces [June 11, 



crumble. At this stage the treatment of the diamonds assumes more 

 the nature of farming than mining. To assist pulverisation by ex- 

 posing the larger pieces to atmospheric influences, the ground is 

 frequently harrowed and occasionally watered. The length of time 

 necessary for crumbling the ground preparatory to washing, depends 

 on the season of the year and the amount of rain. The longer the 

 ground remains exposed the better it is for washing. When the 

 process is complete the softened friable blue clay is again loaded into 

 trucks and taken to the washing machinery, where it is agitated with 

 water and forced tlirough a series of revolving cylinders j^erforated 

 with holes about an inch in diameter ; incorrigible lumps that will 

 not pass the cylinders are again subjected either to the weathering 

 process or passed between crushing rollers. 



The fine ground which has passed through the holes in the 

 cylinder, together with a plentiful current of water, flows into the 

 washing pans (Fig. 11). These pans are of iron, 14 feet in diameter, 

 furnished with ten arras each having six or seven teeth. The teeth 

 are set to form a spiral, so that when the arms revolve the teeth carry 

 the heavy deposit to the outer rim of the pan, while the lighter 

 material passes towards the centre and is carried from the pan by the 

 flow of water. The heavy deposit contains the diamonds. It remains 

 on the bottom of the pan and near its outer rim. This deposit is 

 drawn off every twelve hours by means of a broad slot in the bottom 

 of the pan. The average quantity of blue ground passed through each 

 pan is from 400 to 450 loads in ten hours. The deposit left in each 

 pan after putting through the above number of loads amounts to 

 three or four loads, which go to the pulsator for further concentra- 

 tion. 



The pulsator (Fig. 12) is an ingeniously designed, somewhat com- 

 plicated machine for dealing with the diamantiferous gravel already 

 reduced one hundred times from the blue ground ; the pulsator still 

 further concentrating it till the stones can be picked out by hand. 

 The value of the diamonds in a load of original blue ground is about 

 30,s., the gravel sent to the pulsator from the pans, reduced a hundred- 

 fold, is worth 1601. a load. 



The sorting room in the pulsator house is long, narrow and well 

 lighted. Here the rich gravel is brought in wet, a sieveful at a 

 time, and is dumped in a heap on tables covered with iron plates. 

 The tables at one end take the coarsest lumps, next comes the gravel 

 which passed the |-inch holes, then the next in order, and so on. 

 The first sorting, where the danger of robbery is greatest, is done 

 by thoroughly trustworthy white men. Sweeping the heap of gravel 

 to the right, the sorter scrapes a little of it to the centre of the table 

 by means of a flat piece of sheet zinc (Fig. 13). With this tool he 

 rapidly surveys the grains, seizes the diamonds, and puts them into 

 a little tin box in front of him. The stuff is then swept off to the left, 

 and another lot taken, and so on, till the sieveful of gravel is ex- 

 hausted and another brought in. 



