Corundum Stone from Asia. 417 
tion : whereas the octoedral ruby was from 3,571 to 3,625, and 
inferior in hardness, not only to the diamond, but to the Co- 
rundum; the specific gravity of which, in its different appear- 
ance of form and colour, I found to vary from 3^7^ to 4,166; 
and I suppose it to be subject to a variation from 3,300 to 
4,300: after which, the jargon will come, with a specific gra- 
vity of 4,600 ; easily distinguished also, by its crystallization, 
from the abovementioned gems. The above specific gravities, 
Mr. Hatchett very obligingly assisted me in taking, with his 
accurate scales, in the temperature of 6 o°. It will not be un- 
derstood that I depend entirely on the specific gravity ; on the 
contrary, I connect this quality with crystallization : hardness 
is the next criterion ; and analysis must separate the component 
parts, and demonstrate the analogy or identity of substances, 
or of compounds. The improvements of Mr. Klaproth s pro- 
cess are evident, by the comparison of his first analysis, and 
his last analysis, of Corundum. 
In the first it consisted of 
Corundum earth - 68 o 
Siliceous earth - 31 5° 
Iron and nickel - o 50 
100 
By the last analysis of Mr. Klaproth, the Corundum of 
the Peninsula of India consisted of 
Argillaceous earth 
- s 9 
50 
Siliceous earth 
5 
5P 
Oxide of iron 
1 
25 
Loss 
3 
75 
- - ; • 
100 
MDCCXCVIIJ. 3 H 
