444 New Facts concerning the Diamond. [October, 



undergoing any change whatever. Another diamond, a 

 cut (rose) diamond, which was enclosed in a crucible as 

 before and heated for ten minutes in the furnace to a tem- 

 perature at which wrought-iron melts, retained its form and 

 the smoothness of its facets, but became quite black and 

 opaque and exhibited a strong metallic lustre. The black 

 portion formed a distinct layer of the thickness of a hair 

 covering the unaltered substance within. These results 

 confirm those of Schrotter, and appear to justify the view 

 that diamond, though it undergoes no change when exposed 

 to the greatest heat of a porcelain furnace or that at which 

 cast-iron melts, is slowly converted at the temperature of 

 molten wrought-iron into graphite. 



G. Rose states that some of the specimens of diamond 

 in the Berlin Collection appear quite black by reflected, 

 though translucent by transmitted, light, and that this black 

 substance lying in the little irregularities of the surface is 

 found by its behaviour in fused nitre to be graphite. The 

 relative ease with which graphite and diamond burn was 

 determined by exposing them to the same temperature for 

 the same time, when the following amounts of the three 

 specimens mentioned below were consumed : — 



Foliated graphite 27*45 per cent. 



Diamond 9776 ,, 



Granular massive graphite . . 100*00 ,, 



The method employed by M. von Baumhauer on 

 examining the action of heat upon the diamond was as 

 follows : — 



After previous weighing, the diamond was placed in a 

 small platinum crucible of an elongated and narrow form, 

 similar to those recommended by Mr. J. Lawrence Smith 

 for the decomposition of silicates by chloride of calcium. 

 To enable the operator to observe what took place in the 

 interior of the crucible, it was placed in an inclined position 

 and closed by a thin plate of mica ; an opening was pierced 

 in this plate, through which passed a small thin tube of 

 platinum, soldered at the other end to a glass tube connected 

 with an apparatus which supplied hydrogen dried over 

 sulphuric acid and chloride of calcium. By this means the 

 diamond is surrounded by an atmosphere of dry hydrogen 

 during the experiment. The crucible is heated to whiteness 

 over a gas flame, intensified by a current of air. It was 

 ascertained that the diamond, after exposure for fifteen 

 minutes to a temperature in which it became invisible (that 

 is, where the platinum and the diamond could no longer be 



