APPENDIX IX	331
	rich deposit is a wash from another source, and that the diamonds con­tained therein are due to the concentrating action of ages and may have no connection whatever with the underlying rock. It does not follow that rich alluvial diamond diggings betoken rich diamond-bearing pipes. It has been shown that the top layer of clayey red earth in the (Trans­vaal) Premier Mine is rich in diamonds, that the yellow earth below it is comparatively poor, and that the yield of the blue ground is either unknown, or if known to those interested, has not been made public. The yield of the Premier Mine is said to be phenomenal, but a study of the published figures will show that the method adopted for calculating the yield of the ground is unique in South African diamond mining. At Kimberley practically all the top ground from De Beers Premier Mine was sent to the washing machines and the total yield of diamonds was divided by the total number of loads sent to the machines. In the Pre­toria District, it is authentically reported that the ground is first sorted in the mine before being loaded and a very considerable portion of the ground is rejected. This is quite the proper course to pursue, for it would be useless to wash stones and waste. The good ground is then loaded into trucks and sent to the washing machines. The ground which passes through the one and a half inch mesh of the cylinder screens goes into the pans ; the remaining portion, consisting of coarse lumps and clay, is rejected. The yield of the ground is based upon the results of the fine ground onlv. By this means of calculating, the yield per load of original ground is doubled or trebled. Mention is made of this so that the reader may see how results of yield are obtained in different localities.