gis Count de Bournon’s Description of 
appear to be situated between the laminae of felspar ; at least, if 
a piece of it be broken off, and put into nitric acid, a slight effer- 
vescence is produced, which however is but momentary. These 
particles are most numerous, at those parts where the felspar 
and the metallic substance already described come into contact 
with each other. 
I have placed a specimen of each of these stones in Mr, 
Greville’s collection. 
Notwithstanding there is a considerable difference in the na- 
ture of the matter which may be considered as the basis of these 
two pieces, yet the particular nature of the substances contained 
in them, which are perfectly similar to each other, seems to 
render it highly probable that the place of their origin was the 
same. But it also appears probable, from every circumstance 
respecting these stones, that they must have come, not from a 
mass of rock of the same nature as themselves, but from some 
veins, to the destruction of which may also very likely be owing 
the great quantity of spinelles contained in the sands of certain 
rivers of Ceylon. Would it be hazarding too much, to suppose 
that the crystals of perfect corundum which are found in this 
sand have also the same origin; and that (being much more 
rarely met with, and in much less quantity,) they have only 
a partial existence, or one that is confined to certain parts of 
the veins already spoken of. The small portions of felspar, and 
also of calcareous spar, which are sometimes, although very 
rarely, found in this sand, (perhaps because the sand has been 
already freed from such substances,) tends to support the sup- 
position I have just made, namely, that these two substances 
are a mong those which compose the real matrix of the stones 
here treated of. 
