1890.] XEW YORK ACADEMY OF SCIENCES. 147 



The most important exhibit was in the United Diamond Mines 

 Building, — in other words, the De Beers Mine, Limited, which 

 company controls twenty-nine-thirtieths of all diamonds mined 

 to-day — in which every process connected with the mining and 

 cutting of the diamond could be seen under one roof. 



First, the large sacks of earth, of which one thousand were 

 washed at the Exposition, were thrown on a screen which sifted 

 the material into a large washing-pan, or ''compound,^' as it is 

 called, about fifteen feet in diameter. In this compound all the 

 soft mud, light particles of shale, kimberlite, quartz, calcite, 

 and other minerals whose specific gravity is less than that of the 

 diamond, were floated out, and in the centre the diamond, gar- 

 net, pyroxene, and heavier minerals were concentrated. These 

 concentrates were then carefully sorted, the garnets and the dia- 

 monds being the only ones of value. 



In connection with this exhibit were shown models, or rather 

 reproductions, made of earth, and small models, exact dupli- 

 cates of the machinery and the tunnel systems used at the South 

 African Mines. In a large iron ••parrot-cage," similar to the 

 one in which the Kohinoor diamond was exhibited at the Lon- 

 don Exposition of 1851. the De Beers Consolidated Mines ex- 

 hibited 5,138 carats ef rough diamonds. Among these was a cut 

 diamond, the largest brilliant in the world, Aveighing 228^ carats, 

 which in the rough weighed over 400 carats, and one large octa- 

 hedral crystal weighing 30G carats, and a collection of 983 carats 

 of fancy-colored crystals of white, mauve, pink, orange, yellow, 

 brown, "and black ; also a large number of distorted and curious 

 crystals. The Bulfontein Mine exhibited 11,227 carats of rough 

 diamonds, and the Griqualand West Diamond Mining Company 

 a parcel of 45.003 carats. 



At the opening of the Exposition the diamonds were valued 

 iit 22 shillings a carat, and at its close at 38, so great has been 

 the advance in the price of rough diamonds. One thousand sacks 

 of diamond-earth were washed at the Exposition, and the average 

 amount of diamond found was 1^ carat to a load of earth. 



In connection with this exhibit was the cutting of diamonds, 

 carried on by M. Roulina, who reintroduced diamond-cutting in 

 France, and is one of the few men abroad who has utilized a 

 machine for the process. This machine, however, is very primi- 

 tive in comparison with the more perfect one invented fifteen 

 years ago in the L^nited States and in use here since. There 

 were also diamond-piercing machines in operation ; these re- 

 <:|uired from twenty to thirty days, of six hours each, to pierce 

 a diamond of about two millimetres in thickness, the piercing 

 jioint making 15,000 revolutions per minute. 



Xot without interest were the fragments of a diamond which 



