MR CONNELL ON SULPHURET OF CADMIUM. g23 



ring continues to be formed to the last, whilst, with zinc-blende and soda, a white 

 ring is formed ; and in those zinc-blendes which contain a little cadmium, the red 

 ring, according to Berzelius, is formed at fii-st only, and is succeeded by the 

 white sublimate of zinc. With borax, the sulphuret of cadmium gives a trans- 

 parent yeUow glass. 



I was extremely happy to find, that the idea had occurred to Professor 

 Jameson, which was early suggested to myself, that the mineralogical name of 

 this substance should be derived from that of the distinguished nobleman who 

 first observed it ; and it is satisfactory to think, that the beauty of this mineral, 

 and its interesting natm'e and properties, render it not altogether imworthy of 

 being associated with Lord Greenock's name. I cordially concur in the name of 

 Greenockite, which has been already proposed for it by Professor Jameson. 



It is already known that the artificial sulphuret of cadmium may be used as 

 a pigment. This will also apply to the native, if it could be got in sufficient 

 quantity. I have had some experiments made on a minute scale with this view, 

 with the finely ground powder of the mineral, used as a water colour. Its tint is 

 an orange-yeUow, differing from that of any of the ordinary yellow pigments. 

 Mixed with blue it gives a green. 



Since the above paper was read, Mr Nicol has informed me that he has sa- 

 tisfied himself that Greenockite possesses the property of depolarizing light. 

 Professor Forbes has also obtained distinct proof of the same fact ; and has far- 

 ther observed a curious effect of dichroism by polarized light, which does not 

 take place with common. These observations lead to the same conclusion which 

 its apparent crystalline form suggested, that the mineral does not belong to the 

 tessular system. But farther investigation is probably necessary to determine 

 whether the form belongs to the rhombohedral system, as the fine crystal already 

 referred to would seem to indicate, or to the prismatic, as the observations of Mr 

 Brooke, published by Professor Jameson (Ed. Phil. Joum.) since this paper was 

 read, would appear to suggest. 



VOL. XIV. PART II. 5 Y 



