86 THE HON. SIR CHARLES ALGERNON PARSONS : EXPERIMENTS ON 



electrically heated at any pressure up to 4400 atmospheres, and in a few experiments 

 up to 6000 atmospheres. 



That at 15,000 atmospheres carbon and graphite electrically heated are either 

 directly transformed into soft graphite or are first vaporized and then condensed as 

 such. 



While the experiment of rapidly compressing a mixture of acetylene and oxygen 

 and the production of temperatures much in excess of that necessary to vaporize 

 carbon, accompanied by a momentary pressure of abouiTl5,000 atmospheres, confirms 

 the conclusion that the negative results obtained in the attempts to convert graphite 

 into diamond by electrical heating are not due to lack of temperature ; on the other 

 hand, the presence of minute crystals in the molten layer of the steel of the end of 

 the barrel subjected to high gaseous pressures of carbon monoxide, carbon dioxide, 

 and hydrogen appears to be connected with the other experiments bearing upon the 

 inclusion of gases in metal as a factor in the production of diamond. 



The experiment of firing a high velocity steel bullet with cupped nose through 

 vaporizing carbon into a hole in a block of steel has tested the effect of a momentary 

 pressure of about 300,000 atmospheres on carbon initially near its melting-point, and 

 probably raised by adiabatic compression by another 1000 C. 



The fact that only a very few minute crystals resembling diamond were produced 

 (probably from the iron) raises the question as to whether the duration of the 

 pressure is sufficient to start a transformation of graphite to diamond which can be 

 detected by analysis. We have distinct evidence that, with iron as the matrix, the 

 time is sufficient to form very small crystals which can be identified with some 

 certainty, so it therefore seems reasonable to conclude that there was no incipient 

 transformation in bulk, and that however long the pressure of 300,000 atmospheres 

 were applied, it is extremely doubtful if any change would occur. 



The pressure of 300,000 atmospheres is between one quarter to one half that 

 obtaining at the centre of the Earth, but vastly greater pressures exist at the centre 

 of the larger stars, and are produced by the collision of large bodies in space ; these 

 pressures are many thousands of times greater, and whether they would effect the 

 change it is impossible to predict. On the other hand, a heating effect on large 

 masses of iron might be produced by collisions, and owing to the heat generated by 

 adiabatic compression of the central portions, some of the mass would be melted 

 and subsequently cooled on release of the pressure, so that if heating and cooling 

 under pressure are alone necessary for the production of diamond large stones might 

 result. These considerations, though of interest as bearing upon the presence of 

 diamonds in meteorites and also indicating a possible origin of natural diamond, are 

 of no practical value to us because the pressures required are entirely beyond our 

 reach. There are, however, other considerations arising out of the experiments of 

 MARSDEN, MOISSAN, and CROOKES, as well as our own, which seem to give some hope 

 of solutions of the problem -at issue which lie within the means at our disposal. 



