200 



SYSTEMATIC DESCRIPTION OF PRECIOUS STONES 



by horse-power, and finally by steam, the delay in the adoption of the latter being caused 

 bv the cost of importing machinery and coal. In spite of this difficulty, there were in J 880 

 no less than 150 steam-engines employed at the Kimberley mines, and in 1882 this number 

 had been increased to 386 with a total horse-power of 4000, and this was further supple- 

 mented by the use of 1500 horses and mules. 



The continual increase in depth of the claims was attended by increasing difficulty in 

 excavating the tuff and by frequent accidents, due to falls of loosened material. These 

 difficulties were still further complicated by the fact that falls of reef also began to take 

 place. Often masses of rock would fall sufficient to bury, wholly or in part, many of the 

 surrounding claims; and in such claims no further excavation of "blue ground" was 

 possible until the overlying mass of reef had been removed. In September of 1882, in the 



S. -Shafts 



D 'JHabas^ c^es 



Fig. 40. Section through the Kimberley mine. (Scale, 1 : 4800.) 



Kimberley mine, there was a fall of reef, estimated at about 350,000 tons, which buried no 

 less than 64 claims ; in 1878 one-quarter of the total area of the mine was strewn with 

 fragments of reef. In 1879 and 1880, ^300,000 was expended in removing this fallen 

 material, and in 1882, dP500,000 more was spent for the same purpose, and even then this 

 obstacle to progress was not entirely removed. From the Kimberley mine alone a total of 

 about four million cubic yards of reef have been removed, at a cost of d£'2,000,000. To 

 what an extent the difficulties occasioned by a fall of reef influence the production of stones 

 can be seen from the fact that the yield of the Kimberley mine, during the 18 months 

 which preceded the catastrophe mentioned above, was 1,429,728 carats, but in the following 

 18 months only 850,396 carats. The frequent falls of masses of reef and the removal of 

 other masses which threatened to fall, resulted in a great increase in the surface area of the 

 mine. Thus in the middle of the eighties, the Kimberley mine, a representation of which 

 is shown in the lower figure of Plate VIII., was a crater-like pit 385 yards long, 330 wide 

 and 400 feet deep. 



