1880.] Artificial Formation of the Diamond. 189 



inclosing vessel strong enough to withstand the enormous pressure 

 and high temperature, tubes constructed on the gun- barrel principle 

 (with a wrought iron coil), of only half an inch bore and four inches 

 external diameter, being torn open in nine cases out of ten. 



The carbon obtained in the successful experiments is as hard as 

 natural diamond, scratching all other crystals, and it does not affect 

 polarised light. T have obtained crystals with curved faces belonging 

 to the octahedral form, and diamond is the only substance crystal- 

 lising in this manner. The crystals burn easily on thin platinum-foil 

 over a good blowpipe, and leave no residue, and after two days' 

 immersion in hydrofluoric acid they show no sign of dissolving, even 

 when boiled. On heating a splinter in the electric arc, it turned 

 black — a very characteristic reaction of diamond. 



Lastly, a little apparatus was constructed for effecting a combustion 

 of the crystals and determining their composition. The ordinary 

 organic analysis method was used, but the diamond crystals were laid 

 on a thin piece of platinum-foil, and this was ignited by an electric 

 current, and the combustion conducted in pure oxygen. The result 

 obtained was, that the sample (14 mgrms.) contained 97*85 per cento 

 of carbon, a very close approximation, considering the small quantity 

 at my disposal. The apparatus and all analyses will be fully described 

 in a future paper. 



Eeceived February 25, 1880. 



Extract from a letter from Mr. Hannay, dated 23rd February : — 

 "I forgot, in the preliminary notice, to mention that the specific 

 gravity of the diamond I have obtained ranges as high as 3*5 ; this 

 being determined by flotation, using a mixture of bromide and fluoride 

 of arsenic." 



Presents, February 5, 1880. 



Transactions. 



Haarlem : — Societe Hollandaise des Sciences. Archives Neer- 

 landaises. Tome XIV. Livr. 3-5. 8vo. Harlem 1879. 



The Society. 



Helsingfors :— Finska Vetenskapssocietet. Helsningsskrift af Otto 

 E. A. Hjelt, 8vo. Helsingfors 1877. The Society. 



Innsbruck : — JNaturwissenschaftlich-medizinischer Vereim Berichte. 

 Jahrg. IX. 8vo. Innsbruck 1879. The Union. 



