bse rved in some Metalliferous Veins. 281 



spoken of the conversion of copper-pyrites into purple copper- 

 ore; now this conversion is certainly not analogous to deposition. 

 I have, however, a series of experiments in progress, which, I 

 think, will shew that no change takes place in the pyrites, the 

 appearances being occasioned by a PRECIPITATION OF PURPLE 

 COPPER THEREON. This (if confirmed by more extended expe- 

 rience) will at once reduce the fact to a mere repetition of M. 

 BecquerePs experiments; with such modifications only as render 

 it less like the simplicity of nature. 



I regard these currents as merely local, originating probably 

 in inequalities of temperature prevailing among different ores, 

 in various rocks, at different depths ; possibly also in voltaic 

 combinations of various metallic substances. These may be 

 adequate to the induction of chemical changes within certain li- 

 mits ; but that they perform any more important function in the 

 economy of nature I do not believe. I have the honour to re- 

 main, Sir, your very faithful humble servant, 



W. J. KENWOOD. 

 To WILLIAM STURGEON, Esq. 



P. S. It is still an object to be determined by experiment, 

 whether these currents have any decomposing or heating power, 

 or whether they will yield a spark. I have long contemplated 

 making the examination, but have been hitherto prevented by 

 more pressing occupations. 



4. CLARENCE STREET, PENZAKCE, 

 December 6. 1836. 



Analysis of Fossil Scales from the Old Red Sandstone, Claxh- 

 bennie, Perthshire. By A. CONNELL, Esq. F. R. S. E. 

 Communicated by the Author. 



THE following analysis may be added to those of fossil scales 

 from other formations, formerly published.* For the scales 

 now examined, I have to thank Mr Robison, Secretary of the 

 Royal Society, who found them at the above-mentioned place, 

 and sent them to me for analysis. 



They presented quite a different appearance from all those 



* New Edin. Phil. Journal, October 1835. 



