256 MINING INDUSTEY. 



gated instead of a smooth surface on the inside of the tuh. This has been 

 found to assist greatly in the disintegration of the lumps of slime, which, 

 although consisting of the most minute particles, hold together, like clay, with 

 great tenacity when wet, and, in ordinary pans, frequently present a serious 

 obstacle to thorough amalgamation. According to late advices from Virginia 

 City, Mr. Parke has carried this improvement still further by making this 

 corrugated surface on a rim of cast iron. The corrugations may be on the 

 rim which is cast on the pan-bottom for the purpose of attaching the wooden 

 staves of the side, or the rim may be cast separately and placed in the pan. 

 The corrugated surface is 10 inches high and the rim is 3 inches thick. As 

 the wear of a pan-rim is Confined chiefly to within 10 inches of the bottom,, 

 the provision of this surface, which, like the shoes and dies, may be easily 

 renewed when worn down, without changing the pan, is deemed, a great 

 improvement. 



Roasting of Slimes. — Before the working of slimes raw, or without 

 roasting, had been brought to the degree of efficiency that it has in the hands 

 of the Messrs. Janin, some efforts were made to devise cheap methods of 

 roasting them with salt at a cost that would leave some margin of profit. 

 The usual means of roasting first-class ores is by reverberatory furnaces, 

 which involve a large expense, especially in labor, as the material to be 

 roasted must be constantly stirred and turned, in order to present every 

 particle to the oxidizing and chloridizing agencies. The cost of this method 

 is too great for slimes of ordinary value. 



For the purpose of eflfecting a cheaper roasting, a furnace was devised, 

 some time since, the chief object of which is to accomplish the operation with 

 the least possible amount of manual labor, using some mechanical contrivances 

 for stirring the pulp, and partly eflfecting, by the same means, the continuous 

 supply and discharge of the material. This invention, known as the O'Hara 

 and Thompson Roasting Furnace, sometimes as the Yerrington Furnace, 

 from the name of the proprieter of the patent, consists of a horizontal flue 4 

 feet wide and 11 inches high in the arch and 80 feet long, built of common 

 brick. At the two sides are three fireplaces, one near the middle on one 

 side, two near the ends on the opposite side. At one end of the furnace is a 

 chimney, but the main flue, just described, instead of opening directly into it, 



