222 MINING INDUSTEY, 



of tlie pan, at the surface, downward toward tlie center, producing the sur- 

 face of a hollow cone, through the aperture at the base of the driver and out- 

 ward through the channels and between the surfaces of the shoes and dies, 

 to the circumference, where it rises to repeat the process. The legs or stand- 

 ards of the driver, connecting it with the muller-plate, promote this circula- 

 tion by forcing the pulp to the center and downward between the shoes and 

 dies. The pan is said to require about four horse-power. 



Vaeney's Pan. — This is one of the older flat-bottomed pans, that has 

 long been in great favor with many mill-men. The points of difference be- 

 tween it and Wheeler's are not of very great importance. It has about the 

 same dimensions and capacity. It has no steam-chamber, but a pipe intro- 

 duces steam directly into the ore, above the muUer. 



The dies, on the pan-bottoms, are arranged nearly like those of the 

 Wheeler. In this pan, and sometimes in others, the radial slots in, and the 

 spaces between, the dies are filled with pieces of hard wood, of which the 

 fiber is fixed vertically. The wooden surface wears slightly in advance of 

 the die, afibrding a passage for the pulp, and, according to some, increasing 

 the grinding capacity of the pan. 



The shoes, of which there are twelve, are fastened by bolts to the mul- 

 ler. The circular plate of the muUer is separate from the hub or driver, on 

 which it rests, and which has two projections at the base by which motion is 

 imparted to the muILer. The hub or driver is keyed to the vertical shaft or 

 spindle, by which means it is set in revolution. 



Hepburn and Peteeson's Pan. — Fig. 3, on Plate XXI, presents a view 

 of Hepburn and Peterson's pan. The bottom of this pan has the form of an 

 inverted cone, inclining toward the center, as may be readily seen in the fig- 

 ure. The bottom is covered by four dies of corresponding form, which are 

 secured in a manner similar to that employed in the other pans already 

 described. There is no steam-chamber in the bottom, steam being intro- 

 duced directly. In the center of the pan a hoUow pillar rises, through which 

 the driving shaft passes. The form of the muUer corresponds with that of 

 the bottom, and at the center has an upright hollow cone, by means of which 

 it is connected with the hub or driver. The under side of the muUer is fur- 



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