the Corundum Stone, and Us Varieties, &c. 237 
Mr. Werner, following the system his genius had just then 
formed in mineralogy, was conducted to exactly the same 
results. 
The very small number of perfectly defined crystals of this 
stone which existed in the cabinets of Europe, (they being 
much more rich in cut and polished specimens,) did not permit 
either of the above-mentioned mineralogists to obtain a clear 
idea of the whole of its characters, so as to enable him to 
give a proper description of it. Rome' de Lisle, indeed, may 
be said to have made a step backwards, by excluding from the 
number of its crystalline forms, the rhomboid, w r hich, in the first 
edition of his Crystallography, he had assigned to it, on account 
of a crystal of that form, which was among the stones preserved 
in the Garde Meuble of the King of France. This stone, 
which was of a blue colour inclining to purple, and of a very 
considerable size, (since it weighed no less than 132 carats,) had 
been polished ; a circumstance which had necessarily altered its 
form in some measure, although there is reason to believe that 
it had been polished only upon its natural surfaces. ' Rome' de 
Lisle, however, who had, merely for the above reason, excluded 
the rhomboid from the forms of the sapphire, being induced 
afterwards to recur to his former opinion, made another mistake, 
by assigning to this substance, the rhomboid of sulphate of iron 
or martial vitriol, (the measures of which are very nearly from 
82° to 98", ) as that which properly belonged to it. 
Our mineralogical knowledge with respect to corundum, was 
therefore very little advanced, when we became acquainted with 
that which was sent from India. Mr. Greville, in the Paper to 
which I have already referred, has given a very interesting and 
instructive account, not only respecting the introduction of this 
mdcccii. I i 
