Joty—On the Volume Change of Rocks and Minerals attending Fusion. 299 
1095° the finest dust was adhering to the platinum ribbon. At 1135° this stickiness 
had become more marked. At 1173° the basalt particles were running rapidly on 
the platinum ribbon ; 1153° was finally noted as a temperature at which small frag- 
ments slowly gather into rounded beads. This is of course a true liquid state, 
surface tension forces coming into operation. 
DIAMOND. 
The next determination made with this oven was the thermal expansion of 
diamond. As this determination marks another application of this method, and in 
its results serves to confirm its value, it is given here. 
The image on the screen scaled 4°70 inches, 0:07 inch placed in the position of 
the object, scaled 4:60 inches. The diameter of the diamond, from solid angle to 
At 850° begins to burn in Air. 
1000 
0° Temperature 500° 
Fic. 8. 
solid angle, was therefore 0°0715 inch. Also 0-001 inch, in the position of the 
object, measured 268 divisions of the micrometer beads. Hence 
L, -— I, NV x 0:001 
LT,  268~x 0:0715— 
Galv Temperature, Micrometer. Iz — Ty V2— Vi 
beet Centigrade. N. ia Vi 
Lala | 400° 22 0:00114 0°00342 
13°6 580 37 0:00193 0:00579 
15:1 686 ol 0:00265 000795 
16°2 750 65 0:00338 0:01014 
These are plotted in figure 8. At a temperature of 850 the diamond began to 
burn rapidly. Its surface soon became stepped in a manner characteristic of 
TRANS. ROY. DUB. SOC., N.S. VOL. VI., PART XII, WA 
