. Precious stones, a popular account of their characters, occurrence and applications, with an introduction to their determination, for mineralogists, lapidaries, jewellers, etc. With an appendix on pearls and coral. Precious stones; Pearls; Corals. 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
. Precious stones, a popular account of their characters, occurrence and applications, with an introduction to their determination, for mineralogists, lapidaries, jewellers, etc. With an appendix on pearls and coral. Precious stones; Pearls; Corals. 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
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