$4 ee J. Lawrence Smith on Emery. 
relates*'to its composition and effective hardness ; the latter was 
ascertained in the way already described in speaking of the em- 
ery, and it has been found to vary with the composition of the 
mineral. The analyses were made in the same manner as those 
of the ——— and the results which I have obtained are as fol- 
lows: 
CORUNDUM. COMPOSITION. 
Eifective : | - 
TLocaliGiots Sanmire ae |Water. Alumina. | a — Lime.| Silica. gravel 
" . | 
* Seppe of Tri a ror | O751-|. reo || Os0. 
< aig Xe 90 Bgcag © oes 97°32 1:09 }——| 121 
ae ag Ty Pu wide hT | 3-8811-60 | 92:39 | 167 |1:12 | 2-05 | trace. 
Corundum of the island | 
Witatia, $440) sia. 65. | 3921 0:68 | 87°52 750 |0°82 | 2:01 |—— 
Corundum of Asia, 60 | 360; 166 | 86°62 821 10°70 | 3-85 |— 
Corundum of India | 3-89} 286 | 9312 91 j 1:02) 096 |—— 
Corundum of Asia,....] 57 | 380] 3°74 | 8732 | 812 [100 ) 261 
Corundum of India,....| 55 | 891] 310 | 8456 | 7:06 [1:20 | 400 | 0:25 
The most remarkable fact ascertained by these analyses, is the 
presence of water in variable quantity in all varieties of the co- 
rundum except the sapphire and ruby. ‘To me this fact hasa cer- 
tain value in proving that the corundum and the sapphire are 
formed under different circumstances and do not belong to the 
same geological formation. The different eee ne of these two 
species of corundum might make one suspect a difference in the 
condition of their formation ; and this is somewhat confirmed by 
the results of the beautiful openers of M. Ebelmen in ma- 
king artificial corundum by subjecting alumina and borax to the 
heat of a porcelain furnace for many hours; circumstances under 
which he always obtained crystals under some of the modifica- 
tions of hyaline corundum, and never as prismatic corundum. 
In addition to this, I remark that in my most thorough examina- 
tion of the localities of emery, not the slightest trace of sapphire 
or ruby was found. 
ft. The quantity of water found to exist in corundum, coming 
= from different localities, is variable, and it would appear that all 
other things equal, those containing the least water are the hard- 
est. I will not insist on the slight difference between the hard- 
ness of the sapphire and ruby, having made only one experiment 
upon each of these minerals. 
The two varieties of corundum are so evidently united by their 
system of erystallization, that I-would et undertake to separate 
them on account of the presence of water in one of them, and 
that in variable quantity ; nevertheless, fact is important as it 
». explains to a certain extent their differences in structure an 
I would remark that great pains was used to ascertain 
whether the water might not be due to the presence of Sees : 
