46 Mr. Smithson OH a fihrons Metallic Copper. [July, 



by precipitating a solution of nickel with an alkaline carbonate. 

 When a bicarbir>nate is employed to precipitate the nickel, the 

 precipitate is much paler, and appears to be a sesquicarbonate ; 

 for Berthier found it composed of 



Carbonic acid 21-0 



Protoxide of nickel 48-3 



Water 30-7 



100-0 

 (Ann. de Chim. et de Phys. xiii. 67.) 



{To be continued.) 



Article II. 

 On a fibrous Metallic Copper. By James Smithson, Esq. F.R.S, 



(To Dr. Thomson.^ 



SIR, Paris, March 17, 1820. 



There occur, in mineral collections, pieces of a copper slac^, 

 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. 



From several considerations, it appeared to me to be beyond 

 all doubt that the opinion of these fibres having been produced 

 by crystallization was perfectly inadmissible ; and I was for a 

 very long time totally unable to come to any conjecture with 

 respect to the mode in which they had originated. 



Looking on one of these specimens this morning, an idea 

 struck me which is, I am convinced, the solution of this knotty 

 problem. 



It occurred to me that these fibres had been generated at the 

 instant of consolidation of the fused slag. That by its shrinking 

 at that moment, it had compressed drops of copper, still in a 

 fluid state, dispersed in its substance, and squeezed a portion 

 of it through the minute spaces between its particles, under this 

 fibrous form, into its cavities, or air-holes. 



For this operation to take place, the concurrence of several 

 conditions is required. The slag must be so thick and pasty as 

 to retain metallic copper scattered through it. It must have 

 developed bubbles of some gas which have occasioned vacuities 

 in it. It must be less fusible than the copper, but in so very 

 small a degree that the copper consolidates as the fibres of it are 

 formed. 



It is evident that on this supposition these fibres of copper 

 are produced by a process entirely the same as that employed 



