MECHANICS AND USEFUL ARTS. 49 



most of the gold ores of Colorado, California, etc. ; and the loss 

 of silver in working many of the copper and lead ores. Besides 

 these are many ores that cannot be worked by any of the present 

 methods ; or, at least, only where labor and fuel cost but little. 

 Of these are the low-grade copper ores, with which our country 

 abounds ; the mixed ores of galena and blende ; of nickel, copper, 

 and cobalt ; and of galena and silver. 



To work an ore properly, every useful element should, if pos- 

 sible, be converted into a saleable commodity ; and the expense 

 of working the ore should be paid by the sale of those parts that 

 are now rejected as refuse. 



The first step in our system is to reduce the ore to an impal- 

 pable powder. 



For this purpose we have designed the breaker or whirling- 

 table, for splintering the ores by jiercussion, and the pulverizer 

 for reducing them to dust. 



It will not be questioned that an ore in the state of powder is 

 in the best condition to be acted upon by chemical reagents. 

 Having, then, accomplished this first step, the next is the use of 

 the water furnace, which consists of a hollow tower or upright 

 flue of masonry, in the form of a truncated cone, and a horizontal 

 flue starting from its base. The bottom of the tower and flue is 

 formed by a water-trough, in which is a horizontal shaft, furnished 

 with paddles, which is made to revolve to keep the burned ore in 

 motion, that it may be thoroughly lixiviated. Around the head 

 of the tower are four fire-boxes, together forming a cross with a 

 voided circular centre. 



Their tops are arched so as to form a flue inclining downward, 

 to approach the tower-head. Resting upon the tops of these 

 arches is a dome, which has a central opening, through which the 

 ores and reagents are fed into the furnace. At the extreme end 

 of the horizontal flue is a draft and spray-wheel revolving in a 

 chamber. A wooden flue or conductor leads from this to a second 

 wheel of the same character. We fill the trough with water, 

 kindle the fires, and set the draft and spray-wheels in motion. 

 The action of the wheels draws the converging flames from the 

 fire-boxes down the tower. These flames extend down but a 

 short distance, depending upon the kind of fuel used, and but 

 slowl}' heat the tower ; resort is therefore had to the use of pul- 

 verized fuel, in order to obtain the desired heat. There are two 

 fan-blowers ; one to supply air, the other to force powders of any 

 kind into the head of the furnace. 



These blowers are now put in motion, the second one forcing 

 pulverized tan bark, or coal of any kind, into the flames jjro- 

 eeeding from the fire-boxes. 



The minute particles of pulverized fuel, each surrounded by 

 its atmosphere of oxygen, ignite with intense combustion. Both 

 equivalents of heat are ajiplied at the point of work. By this 

 method, in the furnace we have now in operation, fifty pounds of 

 charcoal will create an intensely hot flame twenty feet long and 

 three feet in diameter, and lasting an hour. 



The walls of the tower now radiate an intense heat inwardly, 

 6 



