THE SOUTH-AFRICAN DIAMOND-MIXES. 471 



by surface drainage after heavy rains, and sometimes covers fifty or 

 sixty acres, when good boating and wild-duck shooting may be had 

 upon it, but in times of drought it is entirely dry. The water of the 

 pan, and of another body, Blankenberg's Vley, is leased by the diggers 

 for mining purposes. Except that it is semicircular instead of being 

 circular or oval, the description of the Dutoitspan is very similar to 

 that of the other mines. 



The gems were extracted from the earth, at the beginning, when 

 everything was crude and done in haste, and when water was scarce, 

 by the method of " dry-sorting," which consisted in sifting the ex- 

 cavated ground through hand-sieves, and then passing the finer por- 

 tions over a sorting-table. By this method as many diamonds were 

 missed as were found, and frequently the yield from the rewashing 

 of the earth over which the process had been performed gave better 

 returns than were gained in the first instance. A modification of the 

 " cradle " was then introduced, but it eventually gave way to the " Ro- 

 tary Washing-Machine," which is still generally employed. It consists 

 of an annular-shaped pan, from eight to fourteen feet in diameter, 

 which is closed by an outer and an inner rim, of which the inner rim is 

 about four feet in diameter, and is not so high as the outer rim. A ver- 

 tical shaft rotates in the center of the open space, carrying ten arms ra- 

 diating around it, each of which has half a dozen vertical knives, or 

 teeth, set within half an inch of scraping the bottom of the pan. The 

 diamondiferous ground, mixed with water, enters through an orifice in 

 the outer rim of the pan, and is stirred up into a ripple by the revolving 

 knives, whereby the lighter stuff comes to the surface and continually 

 floats away through an orifice in the inner rim, while the heavier gravel 

 falls to the bottom of the pan. The mud, or " tailings," which flows to 

 waste over the inner rim, is led by a shoot to a pit, whence it is lifted 

 by a chain and bucket elevator some twenty or thirty feet high. At 

 the top of the elevator the buckets deliver the tailings onto suitable 

 screens, over which the solid mud runs to waste, while the muddy 

 water is led back by an overhead shoot to the machine to assist in 

 forming a puddle of sufficient consistency to float the lighter stones in 

 the pan, and allow only the heaviest ground to accumulate at the bot- 

 tom. For the better mixing of this puddle, an inclined cylindrical 

 screen is fixed above the level of the pan. The dry ground from the 

 mine is tipped into the upper end of the screen, where it is met by the 

 muddy water from the elevator and a certain amount of clear water. 

 The large stones, of a size unlikely to include diamonds, roll out at 

 the lower end of the cylinder, but the puddle, carrying all the smaller 

 stones with it, passes through the wire netting of the screen and down 

 a shoot into the pan, as above described. At the end of the day's 

 work the machine is stopped, and the contents of the pan, after they 

 have undergone an intermediate cleaning in a cradle, or in a small 

 gravitating machine, called a "pulsator," are emptied upon the sort- 



