WHEN it is considered that Witwatersrand as a goldfield dates back only to the year 1887, the development it has undergone in the intervening years must be granted to be quite unparalleled in the history of metalliferous mining. The reason for its sudden expansion are due partly to certain features which are more or less singular to itself, and partly to the fact that in its methods, has been incorporated all that modern science and the world's experience could teach. The features which are more or less peculiar to the Witwatersrand are:- 1. The particular nature of the gold occurrence. 2. The average width and grade of ore over very wide areas. 3. The permanence of the deposit to great depths. Owing to the proved persistence of the above mentioned factors of grade, width and continuity, a new departure in metalliferous mining was inaugurated. This lay in regarding the Rand banket area as a deposit similar for purposes or calculation to a coal basin. In an unprospected block of ground lying adjacent to other working properties, the average width and grade of the said working properties were regarded as affording a practical basis for the estimation of the same value in connection with the contiguous but unworked block named. Hence the practice arose of ordering enormous reducing plants, to be erected and ready for working at such time as it was estimated that from one-and-a-half to two years ore would be developed in readiness for mill supply.