Corundum Stone from Asia. 427 
character, after they shall have been fully verified, may be very 
simple and general. It will not require perfect crystals ; for, 
when crystals separate into laminas, which subdivide into frag- 
ments, and shew the form or arrangement of their molecules, 
it is easy, from such fragments, to connect them with their pri- 
mitive crystal, and consequently with their class'. It will be 
a great step, to obtain one regular and permanent external cha- 
racter. Attention to other characters will be necessary, to as- 
certain the nature of the substance ; and other external charac- 
ters, such as irregular fracture, colour, &c. must be resorted to, 
where no permanent characters exist ; but from their nature 
they are fallible, and in fact are seldom conclusive. 
The progress of crystallography appearing to me of conse- 
quence to the progress of mineralogy, induced me to desire the 
Count de Bournon, abovementioned, one of the honourable 
victims to his allegiance to his King, to describe such crystals. 
In my collection, as shewed the different known modifications 
of Corundum; which will develop the theory of crystalliza- 
tion, so far as is consistent with the avowed object of this 
Paper. The subject, I believe, has not hitherto been submit- 
ted to the consideration of this Society. The translation of the 
Count de Bournon’s description has been carefully made to 
preserve its clearness, and I hope it will be favourably received 
by the Society, and make some amends for my tedious intro- 
duction. 
After it, I have added a table, connecting in one view the spe- 
cific gravities of Corundum, & c. herein mentioned, with those 
given by other authors. 
