264 Mr. Vivian on the Process of Amalgamation [April, 



are constantly kept in the barrels, fresh pieces being added as 

 the metal becomes dissolved. 



In charging the barrels, the water is first admitted, then the 

 ore, and with these the barrels are put in motion, and so conti- 

 nued for about an hour and a half. At the expiration of this 

 time, if the ore and water are found to be well mixed, and of a 

 proper consistency, the barrel being somewhat more than two- 

 thirds full, the mercury is added, after which the barrels are 

 made to revolve at the rate of 16 or 18 times in a minute, for 

 about 18 hours. The contents of the barrels are then examined, 

 and if the process be found to have gone on satisfactorily, they 

 are filled with water, and turned slowly for a few minutes. The 

 small aperture in the centre of the bung before mentioned, is 

 then opened, and a wooden pipe fitted into it. This pipe has 

 attached to it at right angles a leather pi])e, which is furnished 

 with a cock and a mouth-piece of metal, and may be made to 

 communicate by means of a wooden pipe, with arange of gutters 

 laid under the floor of the room. The apparatus being thus 

 arranged, the bung of the barrel is turned downward, the cock 

 is opened on the silver-holding mercury, which, from its great 

 specific gravity, had collected at the bottom of the mixture, flows 

 through the pipe into the gutters, which lead to a filtering sack, 

 suspended over a stone trough, in an apartment on the ground 

 floor of the fourth division of the building. 



The mercury which has not combined with the silver is here 

 separated as it passes through the filter, either by its specific 

 gravity, or by a slight pressure of the hand on the sack whilst 

 the ama'fgam remains within it. The latter is composed of six 

 parts of mercury and one of silver, and is of such a consistency 

 as to retain an impression made by the finger. When it is found 

 that the greater part of the silver-liolding mercury has passed 

 out of the barrel, the cock is turned; the apparatus removed ; 

 and the remaining contents of the barrels discharged through 

 the large bung-hole into the gutters, which empty into large tubs 

 in the floor below. Whilst this operation is performing, care is 

 taken not to allow the pieces of iron contained in the barrels to 

 pass through the bung hole. These gutters are then washed 

 with water froui a pipe connected with a cistern near the water 

 wheel, and the amalgamation process begins again. The time 

 occupied in filling and emptying the barrels is about six hours, 

 making the whole time of the process twenty- four hours. 



i shall now offer some practical remarks on the most import- 

 ant points to be attended to in concluding this operation. And 

 fir>t with respect to the consistency of the mixture in the barrels. 

 This, which may appear ai first a trifling object in itself, is of the 

 utmost consequence ; for if the mass be in too fluid a state, the 

 mercury will remain at the bottom of the barrel, without being 

 brought into contact with the ore ; whilst, on the other hand, if 

 the mass be loo thick, the particles of metal will not move freely 



