130 . ON THE FOEMATIOX OF MOSS GOLD AIS^D SILTEE. 



tions of filamentous or moss-like coj)per, which are formed iu 

 cavities in pigs of certain kinds of regulus. Mr. Edward informs 

 me that, in making copper from Cornish ores, moss copper 

 seldom appears, but more of it is produced when these ores are 

 melted in admixture with a little Irish ore (copper pyrites mixed 

 with oniicli iron pyrites) : it occurs most abundantly when foreign 

 ores are much used. It is chiefly observed, and in the finest 

 state, uijpim^le metal, when all the cavities are filled with it, and 

 it is found protruding from the bottom of the pigs into the sand ^ 

 underneath ; sometimes a little of it, strong and ^'iry to the 

 to uch, appears on the upper surface' of the pigs. According to 

 Mr. Edward, it may be seen in the little prills or shots of metal 

 in the ore slag ; and the surface of the pigs of metal from the 

 calcined metal furnaces are covered with a coating of it, generally 

 of a dark colour, and as thick as the nap or pile on velvet. 



" In specimens in my collection the filaments of copper vaiy iu 

 size from the finest thread to fibres -tq of an inch in diameter, and 

 from one of three specimens obtained from a fine-metal furnace 

 bottom I have taken separate filaments perfectly continuous, and 

 exceeding 5 inches in length. 



" Under the microscope the filaments present numerous minute 

 parallel and longitudinal lines or grooves, as though they consisted 

 of bundles of extremely delicate fibres. * * * * * * * 



"The mode in which these fibres are produced is an interesting 

 subject of inquiry. Each fibre seems to have been pushed, as it 

 were, through a draw-plate, and at a temperature when the metal 

 was soft, but certainly not exceeding that of well-melted copper, 

 for otherwise the fibres immediately after their protrusion would 

 have been remelted into globules." Then he goes on to mention 

 that " filaments of silver, which, examined under the microscope, 

 appear to possess identically the same structure as those of moss 

 copper, may be formed by heating finely-divided sidphide of 

 silver in a current of hydrogen at a temperature sufficient to 

 agglutinate the sulphide, but below the actual melting point of 

 silver: This beautiful experiment may be made in a glass tube, 

 through which a current of the gas is passed. Long delicate 

 fibres of silver may be seen protruding from minute rounded 

 masses of the sidphide ; and as they are produced while these 

 masses are in a soft state, and lying free in the tube, the idea 

 that they residt from the application of external mechanical 

 pressure in a similar mamier to maccaroni, can hardly be enter- 

 tained. 



" There seems to be a force in operation at the base of each 

 filament, wliich causes the particles of silver at the moment of 

 liberation successively to arrange themselves in one continuous 

 fibre or series of fibres ; or, in other words, each filament grows, 

 as it were, from a root imbedded in sulphide of silver." 



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