560 On the Refinage of understandai'd Silver. [June, 



to official assay ; and finding all materials, they receive for their labour 

 8 annas, or \ per 100 on the value of the metal. The cake of litharge 

 when cold is ground and sifted and yields granules of silver. The 

 sifted powder is made into a paste with cow-dung, and the lead recover- 

 ed in a furnace of particularly ingenious and effective construction — of 

 which the following is a sufficient description. 



A barrel-shaped clay cylinder is made, open at both ends, nine inches 

 diameter below by 12 to 15 above, and usually 24 inches high. A 

 bellows pipe of refractory clay 3 iuches in diameter enters at the side 

 about 4 inches from the top, and is led down the cylinder so that the 

 nozzle of the pipe is within six inches of the bottom. The cylinder 

 stands over a cup-shaped hollow made in the ground and sifted over 

 with a little wood ashes. To use this furnace it is first half filled with 

 charcoal and the fire kindled. The mixture of litharge and cow-dung 

 is then introduced in balls the size of an orange, with layers of charcoal 

 and the fire urged. The litharge is quickly reduced to the metallic 

 state, and the lead containing any silver present in solution, collects in 

 the cup-shaped hollow — 100 ibs of litharge can be thus worked off in 

 about 4 hours. This process is applied with remarkable success to the 

 treatment of sweepings and other rubbish containing not more than 

 1 per 100 to 2 per 100 of silver, but in this case a small and variable 

 quantity of borax is added to the mass of litharge, sweepings and cow- 

 dung. 



The basin below the cylinder is open at one side, but during the 

 process is kept partially closed by a heap of charcoal and a brick. This 

 being removed occasionally, the surface of the melted lead is raked 

 free from earthy slags by an iron rod, and the firing is continued till 

 the balls are all consumed. The cylinder is then removed, water 

 thrown on the lead — and this containing silver, is used for the next 

 cupellation refinage. 



The skill exhibited by the native refiners in conducting these processes 

 is beyond all praise, and for the scale on which they have to operate, 

 it would, I conceive, be scarcely practicable to effect any improvement 

 on their system. But it has serious inconveniences when we attempt 

 to follow it in large operations. Each operation is limited to about 2500 

 tola wt. and this may be repeated, so as to give 5000 as the day's work 

 of G men. The heat is almost intolerable, the lead fumes most dele- 



