300 Joty—On the Volume Change of Rocks and Minerals attending Fusion. 
certain crystals, and as Professor Judd has recently (Trans. Roy. Soe. vol. 187 a, 
p. 222) shown, often exhibited in the case of the Burmese rubies. Once com- 
menced, the combustion continued till the oven was cooled down to about 712°. 
The peculiar appearance of this diamond after removal from the oven is shown in 
Plate xvu., which is from a photograph. The enlargement is 65 diameters. In 
these experiments on diamond the little vertical forceps seen in figure 1 was called 
into requisition. The oven is inverted, the slit being downwards. The diamond 
was held in a cradle of platinum wire clipped in the forceps, and so that it occupied 
the centre of the oven. 
It is not in place to consider these experiments here. It may be pointed out, 
however, that they appear to meet tangentially those of Fizeau, but the latter 
experiments are confined to a remotely placed range of temperature. 
AUGITE. 
The following observations on augite are referable to the thermometric curve 
used in the preceding. The bead was prepared in the oxyhydrogen flame, and 
was probably free from bubbles. Diameter of bead 0-064 inch. 
Galy. Temperate, Mierometer. nah no 
17-5 820° 107 0:00592 ‘01676 
18-0 850 112 0-00620 ‘01860 
18-9 890 123 0:00681 "02043 
ie 440 52 000288 00864 
16-0 740 96 0:00531 ‘01593 
17-6 830 168 0:00598 “01794 
19:05 900 123 0-00681 “02043 
20°5 970 141 0-00781 02343 
9°75 335 33 0:00183 00549 
22°6 1068 151 0:00836 "02508 
23-0 1085 174 0-00963 02889 
21°9 1040 161 0:00892 02676 
23-5 1110 19 0:01052 ‘03156 
23°8 1120 195 0-01080 03240 
At a temperature of 1120° a photograph of this bead was taken, and again after 
it had been cooled to air temperature. These have been previously referred to, 
and are reproduced, in outline, as far as possible, accurately in figure 7. 
It will be noticed in making these observations that the temperature was not 
steadily altered in one direction, but observations were made at various tempera- 
