Joty—On the Volume Change of Rocks and Minerals attending Fusion. 508 
Meldometer observations show that this body softens at 865°C. The curious 
phenomenon was observed in the course of these experiments of the platinum 
subliming and growing in crystals on the surface of the highly heated bead. This 
indeed rendered the bead useless for further treatment, although conferring upon 
it a very beautiful appearance. A similar phenomenon was previously noticed 
attending the use of the meldometer. (Natwre, xuiv., 1891, p. 124.) 
Finally, a considerable number of experiments were made to determine the 
conditions under which bubbles were developed in basalt. Above a certain 
temperature, in most cases, the basalt of the Giant’s Causeway evolves minute 
bubbles. . Careful melting at a temperature short of this gave, generally, a bead 
free from vesicles. The bubbles developed at high temperatures could be driven 
off in the oxyhydrogen flame without any apparent change in the specimen and 
seemingly with but little loss. It is very certain that observations made on beads 
deprived of bubbles in this manner will more probably indicate volume 
changes occurring at considerable depths below the Earth’s surface than will 
beads in which the development of minute vesicles is permitted. Under 
conditions of high pressure the presence of volatile matter can hardly be supposed 
to seriously effect the volume-changes attending changes of temperature. 
NOTE ADDED IN THE PRESS. 
The Artificial Production of Diamond.—In the number of Nature (March 22, 
1894) in which I described the results obtained by the foregoing method as applied 
to the thermal expansion of diamond, I referred to the probability that, in the 
remarkable rapid thermal expansion, at high temperatures, of this substance, a clue 
to the requisite experimental conditions for its artificial production would be 
found. In short, that it was probable that the molecular operation, whereby the 
crystalline form of carbon changed to the amorphous form at the temperature of 
about 800° C., might, under suitable experimental conditions, be caused to take 
place in the reverse direction. If this surmise was correct, then high pressure 
applied while the amorphous carbon was maintained at a high temperature (some- 
where about 1000° C.) ought alone to suffice to bring about the artificial formation 
of diamond. These ideas, indeed, induced me at that time to undertake some 
experiments on these principles, but without definite success, principally owing to 
the yielding of the containing cylinders at the high temperatures. ‘The success 
of M. Moisson by the simultaneous application of high pressure, high temperature, 
and the solvent action of iron on carbon, occurred about this time, and I laid aside 
my experiments. At the same time I still ventured to question the necessity of 
TRANS. ROY. DUB. SOC., N.S. VOL. VI., PART XI. 8A 
