4 MODERN SCIENCE READER 



on coming to the surface shows extreme tension. More 

 diamonds are found in fragments and splinters than in 

 perfect crystals; and it is noteworthy that, although these 

 splinters and fragments must be derived from the breaking 

 up of a large crystal, yet in only one instance have pieces 

 been found which could be fitted together; and these 

 occurred at different levels. Does not this fact point to 

 the conclusion that the blue ground is not their true matrix ? 

 Nature does not make fragments of crystals. As the edges 

 of the crystals are still sharp and unabraded, the locus of 

 formation cannot have been very distant from the present 

 sites. There were probably many sites of crystallization 

 differing in place and time, or we should not see such dis- 

 tinctive characters in the gems from different mines, nor 

 indeed in diamonds from different parts of the same mine. 



Although my experiments are chiefly connected with the 

 physical and chemical properties of diamonds, and with 

 researches on the perplexities of their probable formation, 

 it will be a kind of compensation for some of my theories 

 if I bring before the reader the general character of the 

 South African diamond mines and their surroundings. 



The most famous diamond mines in the world are Kim- 

 berley, De Beers, Dutoitspan, Bulfontein and Wesselton. 

 Kimberley is practically in the center of the present 

 diamond-producing area. The five diamond mines are all 

 contained in a precious circle three and one half miles in 

 diameter. They are irregular-shaped round or oval pipes, 

 extending vertically downward to unknown depths and 

 becoming narrower as the depth increases. They are con- 

 sidered to be volcanic necks filled from below with a hetero- 

 geneous mixture of fragments of surrounding rocks, and of 

 older rocks, such as granite, mingled and cemented with a 

 bluish-colored hard mass, in which famous "blue ground " 

 the imbedded diamonds are hidden. 



How the great pipes were originally formed it is hard to 

 say. They were certainly not burst through in the ordinary 

 manner of volcanic eruption, since the surrounding and 



