68 WRITINGS OF JAMES SMITHSON. 



carbonate of soda at hand, I added a particle of nitre, whose 

 deflagration producing potash, lead was revived. 



A bit, which had been made white by ignition, being 

 wetted with nitrate of cobalt and again ignited, became 

 blue. 



Heated in a glass tube over a candle, it decrepitated, be- 

 came opaque and white, and water sublimed. 



Mr. Tennant mentioned to me a sort of explosion occa- 

 sioned by the sudden expulsion of the water, and character- 

 istic of this ore, which took place when it was heated at the 

 blow-pipe. With the very minute particles I have tried, no 

 effect of this sort was perceived. 



The above characters will prove sufficient, I apprehend^ 

 to make this substance known when met with. 



From Thomson's Annals of Philosophy, Vol. XVI, 1820, p. 100. 



Plomb Oomme. Mr. Smithson has given us some interesting details 

 respecting the history and properties of this mineral, which is a hydrous 

 aluminate 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 anal- 

 yzed it. The result of his analysis will be found in the Annals of Philoso- 

 phy, xiii. 881. (See Annals of Philosophy, xiv. 81.) 



OF A FIBROUS METALLIC COPPE1I. 



From Thomson's Annals of Philosophy, Vol. XVI, 1820, p. 46. 



PAEIS, March 17, 1820. 



SIR : There occur, in mineral collections, pieces of a cop- 

 per slag, having fibres of metallic copper in its cavities. I 

 have seen this fibrous copper erroneously placed among 

 native coppers. 



I possess samples of this kind from a foundery in the 

 Hartz. The metallic copper in the cavities, or air-holes, is 

 so delicately slender as to be a metallic wool. 



