134 ON THE FORMATIO^^ OF MOSS GOLD AND SILYEE. 



Professor Liversidge is now carrying on shows us how crystals 

 are formed on the earth, it will he one step forward in the 

 investigation into the mysteries of nature. 



Mr. Dixox, F.C.S., asked whether the silver was melted during 

 the reduction. Did not the air raise the temperature of 

 portion by the combustion of the sulphur ; and would not that 

 be sufficient to melt the silver ? 



Professor Liversidge said that the silver presented no trace 

 of fusion. The temperature was ascertained by placing a piece 

 of zinc and tin or cadmium close to the spot on which the sulphide 

 of silver was; so that the two were kept at the same temperature. 

 He did not think the increasing growth of the metal was due to 

 the combustion of the combined sulphur. The crystals increased 

 at a much greater rate in length* and breadth than in thickness. 

 The sulphide was reduced to a metallic state at a heat just 

 about that of melting tin. The reduction did not take place 

 regularly. These silver gi'owths started out from particular 

 points, and increased in size. It was not a case of mere reduction. 

 If it were, they would get the whole surface of sulphide of silver 

 equally reduced. The reduction seems to take place capriciously, 

 as if the point were determined by some nucleus ; fibres of 

 silver stood out from the unreduced surface of the sulphide. 

 One could almost see the fibres grow. There was a great change 

 in a minute. It was generally supposed that the deposits of 

 native metal' could only have been formed by electric current or 

 by the agency of great heat, perhaps assisted by the vapour of 

 water. By these experiments it was shown that they could get 

 metals in forms not distinguishable from the natural ones. He 

 had in his hand a specimen of quartz containing filiform threads 

 of gold. In most cases the contorted crystals occur in little 

 cavities, not in the solid quartz. With regard to volcanic rocks 

 only drying the vegetation under them, in the district of Etna 

 people depended for their store of ice on the snow covered and 

 protected by ashes overlaid by lava. 



Mr. W. J. Stephens, M.A., remarked that when lava was run- 

 ning the part next the ground was tolerably cool, while what 

 came over it was red hot. 



Professor Liyersidge, in answer to a question, said it did 

 not follow from his experiments that the crystals obtained were 

 pure gold. Moss copper is specially pure. Certain metals might 

 perhaps be purified by this process. 



He also stated that he was not at present prepared to put 

 forth any very definite and final theory to account for the forma- 

 tion of the moss metals ; the above communication was intended 

 merely as a preliminary notice of certain results already obtained 

 from a large series of intended experiments now in hand. 



