464 Transactions of the South African Philosophical Society. 



3000 B.C., resemble those of Brazil, the diamonds being found 

 in gravels or conglomerates. 



The deposits of Borneo and Australia are of least importance. 



The concluding chapter on the mode of origin of the Cape 

 diamonds deals mainly with the light thrown on the question 

 by Moissan's experiments and the inferences which may be 

 drawn from the occurrence of diamonds in meteorites, in native 

 iron and in steel, as well as in the basic serpentine breccia of 

 Kimberley. The author holds that the diamonds have not been 

 formed in the breccia, but, with many of the other fragments, 

 have been brought up from great depths where probably they 

 originated in much the same way as the artificial diamonds of 

 M. Moissan, namely, from the crystallisation of carbon fused in 

 molten iron. 



G. S. C. 



Crookes, William, F.E.S., M.E.I. " Diamonds." A lecture given 

 at the Eoyal Institution of Great Britain on June 11, 1897. 



The lecture begins with a description of the five chief diamond 

 mines near Kimberley, and an account of the process now 

 adopted for extracting the diamonds from the blue ground. 

 The chief chemical and physical properties of the diamond are 

 next dealt with, reference being made to the " exploding " of 

 diamonds and their fluorescent and phosphorescent properties. 



The artificial production of diamonds by M. Moissan's method 

 serves the author as an introduction to the mode of origin of 

 the mineral in nature, and according to Prof. Sir Wm. Crookes, 

 " the diamond has not been formed in situ in the blue ground. 

 The diamond genesis must have taken place at great depths 

 under enormous pressure." The pipes in which the diamonds 

 are now found were filled from below and the diamonds erupted 

 with a mud volcano. The ferric origin of the diamond is 

 corroborated by the ferruginous character of the country around 

 the pipes, and the ferric hypothesis in Prof. Crookes' opinion 

 also explains the volcanic pipes, and in this connection reference 

 is made to the value of a careful magnetic survey. 



The lecture concludes with mention of the occurrence of 

 diamonds in meteorites. Meydenbauer's theory that diamonds 

 are of cosmic origin, and the parallelism of the occurrence of 

 the diamond in the Kimberley blue and in meteorites is brought 

 under notice. 



G. S. C. 



