88 



JVA TURE 



[November i8, 1909 



was tested in regard to its porosity, and this was found 

 to be considerable — a remarkable result, having in view 

 the conditions under which it had been formed. 



Another point of interest was that where the soft 

 graphite had been driven into the Acheson graphite plug 

 at the bottom of the apparatus it became extremely hard, 

 so much so that a hard steel file made little or no 

 impression upon it. 



The main difference in treatment of this part of the 

 graphite as compared with the remainder is that it was 

 cooled much more quickly, thanks to the high heat con- 

 ductivity of the Acheson graphite plug. The cause of 

 hardening has hitherto not met with any satisfactory 

 explanation. 



No appreciable quantity of carbide of magnesia was 

 formed in the experiments. The magnesia close to the 

 graphite core contained traces of carbides, but as there 

 were always traces of iron left from the drilling-out 

 process, this may be plausibly accounted for by the forma- 

 tion of carbide of iron. 



The graphite was finally systematically searched for 

 microscopic diamonds by Staudenmaier's modification of 

 Brodie's method of conversion of graphite into graphitic 

 acid,' or else by Moissan's modification of the same 

 method.^ A convenient means of distinguishing diamond 

 in fine powder from most or all of the substances which 

 are not separated by a liquid of density 3.34 at 4° C. is 

 to heat the powder in a silver spoon to a dull red heat 

 in fused potassium hydroxide. Check experiments showed 

 that diamond dust easily passing a sieve with 100 threads 

 to the inch would withstand the action of molten caustic 

 potash at a temperature at which the edges of the silver 

 spoon began to melt for five or ten minutes. Crystals of 

 alumina or of carborundum are entirely destroyed by this 

 fusion, but the diamond particles seemed to have under- 

 gone no change. In fact, the individual fragments could 

 be recognised under the microscope after passing through 

 the ordeal. 



I am ted to consider that my experiments indicate that 

 no wholesale transformation of amorphous carbon or 

 graphite into diamond can be brought about by tempera- 

 tures of the order of 2000° C. and pressures of more than 

 50 and less than 100 tons per square inch. There is some 

 uncertainty, as already mentioned, in regard to the actual 

 pressures operative during the trials. Prof. Tammann has, 

 however, obligingly directed my attention to the fact that 

 the equilibrium curve graphite-diamond may nevertheless 

 have been crossed, but that no diamond was formed 

 because time for crystallisation was not allowed under the 

 conditions of the experiment. I confess my idea in 

 making the trials was that the amorphous carbon or 

 graphite might be forced to melt, and then that the con- 

 ditions would require it to re-crystallise as diamond — not, 

 of course, in the form of large clear crystals, but rather 

 in the form of bort or black diamond. 



The experiments described have only been rendered 

 possible by the invention of high-speed steel, which keeps 

 its hardness up to nearly, or quite, a red heat, and any 

 further advance — mainly in the direction of the allow- 

 ance of more time — must wait for improvements in that 

 material. It may very well be, however, that the limits 

 of temperature within which crystallisation in diamond 

 form can take place are really very narrow at any 

 pressure ; and in this case it will be a matter of very 

 great difficulty to make an apparatus in which the con- 

 ditions could be kept constant for a sufficient length of 

 time, and the difficulty would be greater the higher the 

 temperature. 



It is noteworthy from this point of view that in 

 Moissan's artificial production of diamond very much lower 

 pressures and temperatures were used than those just 

 described. I have shown ' that, using iron as a solvent, 

 it is highly improbable that Moissan attained a pressure of 

 more than 20 tons/sq. inch, and when silver was employed 

 the pressure must have been much lower. .'\ similar 

 criticism places the effective temperature of formation of 

 diamond in iron or silver spheroids at something of the 

 order of 1500° C. Comparing the experiments of Moissan 

 with those described above, it looks as if Roozeboom's 



1 Tier , iSq8, xxx!., 1485. 2 Electric Furnace, 49, translation. 



■' Journ. Chem. Soc, xciii., igoS, itsi. 



NO. 2090, VOL. 82] 



opinion is at present the most probable, viz. that solvents 

 are necessary in order to depress the crystallisation point 

 of diamond to a temperature at which the transformation 

 to graphite is slow enough for rapid cooling to interrupt 

 it. In this case the next step would be to repeat the 

 experiments I have described at the highest possible 

 pressure in the presence of iron, though Mr. Parsons ' 

 has already made some trials in this direction with 

 negative results. We have, however, many metals which 

 have never been tried in this connection, and one or other 

 of them may turn out to have the requisite properties. 



UNIVERSITY AND EDUCATIONAL 

 INTELLIGENCE. 



Cambridge. — The board of anthropological studies has 

 elected Mr. A. R. Brown, fellow of Trinity College, to 

 the Anthony Wilkin studentship in ethnology and 

 archeology. The John Winbolt prize has been awarded 

 to Mr. E. T. Busk, of King's College. 



A university lectureship in zoology, recently held by 

 Prof. Gardiner, is now vacant. The general beard of 

 studies will shortly proceed to appoint a lecturer to hold 

 office from January i, 1910, until September 30, 1914. 

 The annual stipend is 50/. Candidates are requested to 

 send their applications, with testimonials if they think 

 fit, to the Vice-Chancellor on or before Saturday, 

 November 27. 



The Vice-Chancellor gives notice, on behalf of the board 

 of geographical studies, that the Rev. T. G. Bonney, 

 F.R.S., has consented to deliver a lecture in Cambridge on 

 Thursday, November 25, at J p.m., on " A Desert Phase 

 in the Development of Britain." By permission of Prof. 

 Hughes the lecture, which will be illustrated by lantern- 

 slides, will be given in the large lecture-room of the 

 Sedgwick Museum of Geology. 



The professor of botany also gives notice that Dr. 

 H. H. W. Pearson, of Gonville and Caius College (pro- 

 fessor of botany in the South African College, Cape Town), 

 has consented to deliver a lecture at the Botany School 

 on Friday, November ig, at 5 p.m., on " A Botanical 

 Journey in South-west Africa." 



The general board of studies has approved Dr. C. S. 

 Myers, of Gonville and Caius College, and A. E. Western, 

 of Trinity College, for the degree of Doctor in Science. 



Liverpool. — Mr. W. S. .'\bell, instructor in naval 

 architecture at the Royal Naval College, Greenwich, has 

 been appointed to the chair of naval architecture endowed 

 by Mr. Alexander Elder. 



Oxford. — Mr. Balfour will deliver the Romanes lecture 

 in the Sheldonian Theatre on Wednesday, November 24. 

 Lord Curzon of Kedleston, Chancellor of the University, 

 will preside. 



SOCIETIES AND ACADEMIES. 



LO.NDON. 

 Royal Society, November 11. — Sir Archibald Geikie, 

 K.C.B., president, in the chair. — H. C. Ross: The 

 vacuolation of the blood-platelets : an experimental proof 

 of their cellular nature. — H. G. Plimmer and Captain 

 W. B. Fry : Further results of the experimental treatment 

 of trypanosomiasis, being a progress report to a com- 

 mittee of the Royal Society. — G. S. West and B. M. 

 Griffiths : HilUiousia mirabilis, a giant sulphur bacterium. 

 — Dr. H. B. Fantham and Miss .Annie Porter : The 

 modes of division of Spirochaeta recurrcntis and S. 

 duttoni as observed in the living organisms. The observa- 

 tions recorded were made on living Spirochsetes. The 

 examination of living material is imperative, as results 

 based only on stained preparations are not always trust- 

 worthy. Both longitudinal and transverse division occur 

 in Spirochastes, as seen in S. recuryeiitis, S. duttoni, S. 

 anodontae, and S. balbianii. There is a periodicity in 

 the direction of division exhibited by S. recurtentis and 

 5. duttoni. At the onset of infection longitudinal division 

 occurs. This is followed by transverse division of the 

 ' Lac. cit 



