I have even heard that some years ago the extradition of a rogue was the signal for disorderly scenes and an expostulatory address, because he had not been convicted of theft since his arrival at Johannesburg. He had made a considerable sum of money there, and was accompanied to the station by a number of friends.
No sketch of Johannesburg would be complete without a few words about the gold-mines.
I am no authority on the subject, but I will describe what was told me and what I saw; and as the engineer who was good enough to give me some information knew me to be ignorant, my precis will be a little 'Manual on Mining' for the use of novices.
In the first place, there is an essential difference between the manner in which gold is found in Witwatersrand and in other districts, such as Klondyke, Senegal, or the Soudan. In the latter, the gold is in grains, either embedded between the frozen stones, or rolling in the beds of rivers. The auriferous mud is taken up and washed, and the gold is retained. Nothing could be simpler.
In the Rand, however, the working of the mines is purely scientific. The mineral is found in blocks of quartz and silicious clay containing pyrites of auriferous copper and gold.
After calculating the direction of the reef, one must dig down to a greater or less depth to find it. Dynamite is then used to detach the gold-bearing quartz, which is brought to the surface. It has the appearance of very hard white stone, slightly veined with blue. It is carried off to the batteries in Decauville trucks, and there a crushing-mill, which looks like a gigantic coffee-mill, and sledge-hammers combined into groups of five, reduce it to a very fine powder. A current of air spreads this powder over copper-plates covered with mercury.
A large proportion of the gold, about 60 per cent., amalgamates with the mercury, and once a fortnight the amalgam is scraped off. After fusion the mercury in the amalgam volatilizes, leaving a deposit of almost pure gold.
The residuum of the first process is afterwards poured into huge vats of from 10 to 12 metres in diameter, in which cyanide of potassium has been placed. A solution of cyanide of gold is thus obtained, and this is put into cases lined with strips of zinc, on which the gold is precipitated. The 40 per cent. lost in the first process is thus recovered.