552 MINING INDFSTEY. 



the heavier and better portions of the ore and the escaping amalgam. Usually 

 there is a long wooden sluice or canal, the bottom of which is covered with 

 copper in the same manner as the tables just described, or with coarse 

 blankets which catch the pyrites and some amalgam, which being washed off 

 from the blankets and collected, may be treated in grinding pans or sold to 

 other parties for treatment by methods to be noticed further on. The amal- 

 gam formed in the batteries and on the tables is cleaned up at intervals vary- 

 ing in length according to the richness of the ore. In some mills the out- 

 side plates or those on the inclined tables are cleaned daily, while the bat- 

 teries are allowed to run three or four days without cleaning. The outside 

 plates are cleaned by carefully scraping oif the adhering amalgam, first gently 

 with a knife and finally with a thick piece of hard gum or rubber, which 

 scrapes the surface closely without cutting or scratching it. The plate is then 

 washed with water and prepared for use again by sprinkling quicksilver over 

 it, spreading the same evenly by means of a cloth, thus forming a freshly amal- 

 gamated or quicksilver-coated surface. 



The plates that are fitted into each battery, or mortar, are cleaned in 

 like manner, and the mortars themselves, the stamps being hung up and the 

 housings sufficiently removed, undergo a similar operation, the shoes, dies, 

 and interior iron-work being carefully scraped with a knife, in order to re- 

 move the adhering amalgam. The amalgam, thus collected, contains some 

 impurities, in the form of pyrites, iron, and dirt, which must be removed 

 before retorting. It is usually put into a wedgewood mortar, or other suit- 

 able vessel, and stirred or agitated with water, by which means the dirt or 

 lighter portions rise to the surface, and may be floated or washed oif into a 

 cistern or other vessel, and collected there for future treatment. The amal- 

 gam may then be rendered fluid by the addition of more quicksilver, the im- 

 purities brought to the surface by agitation, and skimmed or cleaned by a 

 piece of coarse blanket, to which the particles of dirt and other foreign sub- 

 stances adhere. By repeated operations the amalgam may be obtained in a 

 very clean condition, the skimmings being subsequently cleaned in similar 

 manner. "When thus prepared the amalgam is strained through a piece of 

 cloth and forcibly pressed so as to squeeze out as much as possible of the 

 surplus quicksilver. The remainder is then retorted. In most mills small 



