l8o THE ORIGIN AND FORMATION OF THE DIAMOND. 



containing liquid carbon dioxide in their cavities at the orchnary 

 temperature, we can say that, if they had been formed at a 

 very moderate red heat, the pressure must have reached some 

 300 atmospheres at that temperature, and was possibly much 

 more. Sir William Crookes has shown that the residue remaining 

 after the explosion of cordite in closed vessels, where the tem- 

 perature was calculated to exceed 3,000° C, and the pressure 

 to equal 50 tons on the square inch, contained minute diamonds. 

 Had the experiment been carried out at the ordinar}- pressiae 

 the carbon in the ash would have remained as graphite only. 



Fifth — As regards the carbonaceous source from which dia- 

 monds were derived, one can only speculate as to its character, 

 with little else to guide one. I have mentioned carbon dioxide 

 and carbonates, but a very lengthy series of experiments, carried 

 out on carbon dioxide both in the liquid condition, in the condition 

 of a gas, and dissolved in water, as well as in the condition of 

 various carbonates, has failed to give me any assurance that it 

 was a possible source of the diamond. Carbonaceous sub- 

 stances, soluble and insoluble in water, hydrocarbons belonging 

 both to the paraffin and aromatic series, and a very large number 

 of other substances containing carbon, have all been subjected to 

 experiment and all so far with negative results. It is possible, 

 of course, that in some of those experiments the conditions may 

 have been at fault, or that they were not continued long enough 

 to give any positive results ; and also, perhaps, that any very 

 minute diamonds that may have been formed may have been 

 overlooked. As regards the use of very high temperatures such 

 as are obtained in the electric furnace, many experimenters 

 evidently think that success lies in that direction, although in 

 face of the facts I have mentioned it cannot be allowed that 

 nature has made use of such high temperatures in forming the 

 diamond. In experiments at such high temperatures the great 

 difficulty lies in apphdng sufficient pressure, because, while the 

 temperature of the electric furnace will convert all forms of 

 carbon into graphite, pressure, probably very considerable, will 

 be needed to convert the graphite into diamonds. I have 

 spoken of the formation of graphite in certain exi)eriments. 

 even at the ordinary temperature, and, certainly, nature did 

 not make use of very high temperatures in the formation of 

 graphite from fossil remains in case of regional metamorphism : 

 I have alluded to the use of endothermic compounds in the 

 various experiments ; I have also expressed the opinion that 

 if we had a convenient method of making graphite we have simply 

 to modify the physical conditions to obtain diamond insteacl. 

 The use of suitable endothermic compounds to accomplish this 

 object would, to all intents and purposes, be practically adopting 

 the principle of the electric furnace, only instead of applying 

 a high temperature as in the case of the furnace we shoulcl 

 use compounds that would confer a very high temperature 

 on the atoms of carbon at the moment they are set free, whilst 

 the temperature of the general mass would remain at a moderate 

 amount only. 



