100 Historical Sketch of Improvements in [Aug. 



10. — The green variety of fluor spar discovered lately in the 

 lead mine of Middlehope Shields, near the village of Westgate, 

 in the county of Durham, has been described by Dr. Clarke 

 {Annals of Philosoplij/, xiv. 34). I have received several speci- 

 mens of it, and can attest its great beauty. 



11. Ore of Tellurium. — I have not yet had an opportunity of 

 seeing any specimens of the ore of tellurium said to have been 

 discovered in Connecticut, at New Stratford, and cannot, there- 

 fore, add any thing to the account which I transcribed from the 

 American Journal. (See Annals of Philosophy, xiv. 66.) 



12. Compound of Sulphuret oj Lead and Arsenic. — This is a 

 new mineral species discovered by Mr. Smithson, and described 

 by him in the Annals of Philosophy, xiv. 96. It was found in 

 a magnesian lime rock in the Upper Valais. It has a metallic 

 aspect, a grey colour, and a fracture in some directions vitreous, 

 in others foliated. When triturated, yields a red powder. Mr. 

 Smithson, by a set of very minute but satisfactory experiments, 

 demonstrated that its constituents were sulphur, arsenic, and 

 lead. 



13. Plomb Gomme. — Mr. Smithson has given us some inte- 

 resting details respecting the history and properties of this 

 mineral, which is a hydrous aluminatc of lead. It has a yellow 

 colour, and is exceedingly similar in appearance to Mullen glass. 

 When heated, it decrepitates violently ; and if it be heated by 

 the blow-pipe, in contact with an alkali, lead is reduced. Its 

 nature was first ascertained by Mr. Tennant. Berzelius has 

 lately analyzed it. The result of his analysis will be found in the 

 Annals of Philosophy, xiii. 381. (See Annals of Philosophy, 

 xiv. 31.) 



14. Octahedral Iron Ore. — M. Robiquet has shown that this 

 ore usually contains titanium. (Ibid. p. 384.) 



15. Arsenical ISickel {Cupfer Nickel). — This mineral from 

 Allemont has been lately subjected to an elaborate analysis by 

 M. Berthier, who found it composed of 



Nickel 39-94 



Cobalt 00-16 



Arsenic 48-80 



Antimony 8-00 



Sulphur 2-00 



Iron and manganese Trace 



98-90 

 Or its constituents may be thus stated : 



Arseniuret of nickel 88-55 



Arseniuret of cobalt 0*35 



iSulphate of antimony 10-00 



98-90 

 (Ann. de Chim. et de Phys.xiii. 52.) 



