214 MINING INDUSTEY. 



curvature near each of its ends, in order that the cam, in its revolution, may 

 come in contact w^ith the tappet at the least practicable distance from the 

 cam-shaft, where the concussion is less than at a greater distance, and to 

 diminish the friction between the extreme end of the cam and the face of the 

 tappet. The face of the cam is 2 or 2 J inches wide. Its extreme end is 

 fashioned so as to correspond to the outer edge of the tappet, which is circu- 

 lar. The cam is placed as near the stamp-stem as practicable, without com- 

 ing in contact with it. The cams are caused to revolve by means of the cam- 

 shaft, to which they are secured by one or, sometimes, two keys or wedges. 



The cam-shaft is a round shaft of iron, which is smoothly turned and 

 finished, having one or two key-seats or grooves, cut in it lengthwise, for the 

 purpose of securing the cams in their places. The shaft rests in boxes, which 

 are usually supported by shoulders cut on the upright posts of the battery 

 frame. Cam-shafts vary in diameter from 4 to 6 or 7 inches, according to 

 the number of cams to be fixed upon them and the weight of the stamps to be 

 raised. In some mills a single cam-shaft is made long enough to carry all the 

 cams for as many batteries as there may be. In Nevada and California, how- 

 ever, short cam-shafts are in general use, a separate shaft being employed for 

 each battery, or, in many cases, one shaft for two batteries. Separate cam- 

 shafts are preferred, on account of the independence of each battery, so that 

 if one be stopped by any accident to the cams or the stamps, or for repairs of 

 any kind, the operation of the others is uninterrupted. Each shaft, in such 

 case, is driven by its proper pulley, which receives its motion, by means of 

 belting, from a countershaft. In the figures on Plate XIX the pulleys and 

 belting are shown. The cam-shaft is set in motion by applying the tighten- 

 ing pulley to the belt. 



The number of stamps in each battery is commonly four or five. The 

 latter number seems to be preferred. The order in which they are allowed 

 to drop is not always arranged in the same manner in different mills, but the 

 desired conditions are that the weight of the stamps to be raised may be uni- 

 formly distributed on the cam-shaft, so that the weight of metal lifted may 

 be, as nearly as possible, the same at any moment of the revolution, and that 

 each stamp may fall effectively upon the material to be crushed, and, by the 

 force of its blow, aid in the proper distribution of the stuff among its neigh- 



