444 
Mr. Greville on the 
in Oriental rubies and sapphires. It was by this appearance, Mr. 
Greville was led to try the effect of cutting the foremen- 
tioned stones en cabochon; whereby a similar effect of triple 
reflection, which formed stars of six rays from a common 
centre, was produced in the Oriental ruby, in the sapphire, and 
in the Corundum. 
It is to be lamented that Mr. Werner did not send, with 
his models, the specific gravity of each of the rubies, and the 
measures of their angles : we should then have had data to de - 
cide, whether the rubies sent by IVfx- Werner were, as I sup- 
pose them to be, Oriental rubies, or sapphires ; and, with equal 
certainty, whether the parallelopi pedal rhomboid corresponds 
precisely with that of the Corundum; by this, the perfect iden- 
tity, or analogy, between the Corundum and the sapphire, would 
have been no longer doubtful. 
