176 THE ORIGIN AND FORMATION OF THE DIAMOND. 



great heat, or some such agency- And it is very difficult to 

 see how diamond or graphite might be produced almost simul- 

 taneously by some slight change in the conditions, whereby, now 

 the one, and then the other, were formed ; so I am bound to 

 conclude that the graphite found in any particular diamond existed 

 before the latter was formed. As regards the theory that the 

 diamonds were formed from the graphite I was at one time 

 greatly enamoured of it, but I have reluctantly been obliged 

 to throw it aside. I have made miany scores of experiments 

 to settle that particular question alone, carried out for months 

 and years, because I returned to the idea again and again, but 

 I have entirely failed with it. Not only have I subjected graphite 

 to such treatment as I calculated it might have met with in the 

 mines, exposing it to a temperature ranging up to a red heat, 

 and in presence of water or water vapour, oxides or silicates of 

 iron, silicate of magnesium, powdered garnets, and so on : and 

 to a pressure extending up to well nigh 1,000 atmospheres, but 

 I have not only used ordinary graphite, but also graphite ob- 

 tained from cast iron, and graphite obtained from molten iron 

 cooled directly in cold water. Also, thinking the oxidised forms 

 of graphite more amenable, such as graphitic oxide, I have tried 

 them all, varying the conditions, of course, to suit, but in no case 

 has there been any approach to diamond. I, therefore, conclude 

 that the diamond in the South African Mines was not formed 

 from the graphite which we find associated with it. 



I have tried to imitate the production of graphite in nature by 

 subjecting various organic materials that might be supposed to be 

 present in fossils to such conditions as I thought would be in opera- 

 tion in cases of regional metamorphism, even to the extent of adding 

 fluorine, boracic acid, and so on, to the materials operated on, as 

 these substances are supposed to take part in metamorphic action, 

 but in most cases without result : and I conclude that one reason 

 for failure is that probably nature's operations took place very 

 slowly, extending, in the case of regional metamorphism, over 

 many years, or perhaps many centuries. And I fear that even 

 if we knew at this moment nature's method of making diamonds 

 the brief span of human life might compel us to modify it to 

 suit our limitations. I am persuaded, however, that the mode 

 of origin of the diamonds in the mines was not. in its general 

 character, very dissimilar to the production of graphite in regional 

 metamorphism, but that probably the pressure was greater. 

 and the parent carbonaceous material was in a more liquid con- 

 dition, the water, or steam, present in the mud volcanoes, 

 contributing to the mobility of the mass. 



Since there are so many gaps in our knowledge of the form- 

 ation of the diamond we are compelled to fall back to a certain 

 extent on theory. I have already alluded to the relationship 

 of the three forms of carbon. Thus, if charcoal is heated to the 

 temperature of the electric arc it is converted into graphite. 

 Diamond is also converted into graphite in the same way, and 

 on the other hand the graphite in cast iron can be converted 

 into microscopical diamonds. It is a chemical axiom that the 



