44 ECONOMIC GEOLOGY. 



of description, and mention the contrivances employed by Mr. Paddock 

 to reduce the bulk of the copper ores while increasing their value. It is 

 of no use to send to market lean ores, because of the expense of trans- 

 porting worthless rock. Hence various methods are in use to concen- 

 trate them. The oldest method is to pick out the best pieces and throw 

 away the poorer ones. In this way these ores may be easily brought to 

 8 or lo per cent, valuation. When the metal is very abundant, another 

 process reduces the ores in a furnace by smelting to a matt of 40 or 60 

 per cent, copper, and thus saves a great deal in transportation. Another 

 method, well adapted to the New Hampshire ore, is to remove the copper 

 by a wet process of extraction. This will be mentioned soon in detail. 

 Still another plan has been adopted by Mr. Paddock. The ore is pulver- 

 ized, and the copper ore separated from the lighter worthless rock by 

 virtue of its greater weight. Wet and dry jigs are used for this pur- 

 pose, and the results appear to be satisfactory. The ores are concen- 

 trated to 1 5 or 20 per cent, in this way, very cheaply, and are in excellent 

 condition for smelting. 



To carry on this business a mill is required, estimated to cost, with all 

 the apparatus, if set up new, about ^17,000. There must be an engine, 

 a crusher, apparatus for elevating the crushed rock to an upper chamber 

 where sieves may classify the material into several sizes, and the dry 

 and wet jigs. I will briefly describe the process as it is being carried 

 on at the mill in Lyman. An engine is at work driving a rock-crusher, 

 elevating the powdered rock, shaking both jigs, drying the wet products, 

 and for other purposes. It requires the services of one person to keep 

 the engine in order, and a second to furnish rock for the crusher. In the 

 upper chamber are sieves separating the pulverized rock into five parts ; 

 first, the coarser pieces, which are made automatically to descend to the 

 wet jig in the basement; second, three grades of coarseness, suitable for 

 the Chubb concentrator, or dry jig; lastly, the slums or dust, which is 

 too fine to be separated by either of the jigs. No attendance is required 

 to separate these different grades and carry them to their proper places ; 

 the business is attended to by machinery. The Chubb separator is a 

 patented contrivance, making use of intermittent air puffs to classify the 

 material into three parts ; first, the ore concentrated to its utmost extent; 

 second, the worthless material fit only to be thrown away ; and third, 



