102 DRESSING OF OUES 



lino of curvature necessary for the cam is obtained by taking (1) a circular piece of 

 board having a radius equal to the horizontal distance from the centre of the cam axle to 

 the centre of the lifter ; (2) a piece of thread with a pencil-point attached to the end ; (3) 

 measuring the desired lift of the head on the thread from such pencil-point, then attaching 

 the end of the thread to the periphery of the circular piece of wood ; (4) winding the 

 thread on the periphery of the wood, laying the wood on a smooth board, unwinding the 

 thread whilst being stretched to its utmost limit and at the same time tracing with the 

 pencil-point the required curve. As it is desirable that the cam may be in contact with 

 the tappet at the least practicable distance from the axle the curve is modified by giv- 

 ing to the cam a greater curvature near each of its ends. The cam point is also as 

 near to the lifter as is practicable, without coming into actual contact. The axle is 

 of round iron, from 4 to 6 inches diameter, turned, with two key- ways cut, for the pur- 

 pose of securing the cams in their places. In some instances the shaft extends the 

 entire length of the various batteries, but a separate light shaft for each battery of 

 four or five stamps is preferred. 



In such case each axle receives its motion from a counter shaft, the two shafts being 

 connected together by means of belts and riggers. The order in which the heads fall 

 varies in different mills, but the condition of having an uniform load on the engine at 

 one and the same time, as well as a free and effective fall, should be observed. In a 

 five-stamp battery the order of fall is commonly : (1.) Middle head; (2.) End right 

 hand head; (3.) Second head on left ; (4.) Second head on right ; and (5.) End stamp 

 head on left. The key- ways in the cams are cut so that when the latter are fixed, the 

 heads are lifted in the order above stated. Occasionally quartz is crushed dry, but 

 much more frequently water is admitted to the boxes by means of gas-pipes fitted with 

 regulating cocks. When it is necessary to hang one or more of the heads a workman 

 lays a smooth piece of board l inch thick on the face of the cam as it is rising 

 to the tappet, and holds the board whilst the head is lifting. When high enough a 

 stud, articulated on a small shaft extending the length of the battery is put under the 

 tappet, when the cam will freely revolve. To set the head in motion the board is 

 again introduced and the stud withdrawn. The power required for each head of 

 average weight, including friction, is about 1| horse. The belts are manu- 

 factured out of a combination of canvas and India-rubber, and from the first motion to 

 the intermediate shaft are sometimes as much as 2 feet wide. The belts from the 

 second motion to the cam shaft are made of thinner material and are from 12 to 14 

 inches wide. The shafts are frequently provided with cast-iron driving riggers. In 

 some cases, however, the riggers are constructed of either kiln-dried wood, with arms 

 inserted in a cast-iron boss and then turned off in place, or they are built solid of well 

 seasoned planks, on bored bosses and concentrically turned, after being keyed to the 

 shaft. 



In Colorado the stamp heads, are often, however, run more slowly, and have a 

 greater fall than the heads employed in the Californian and Nevada mills. The 

 average weight of head is from 500 to 600 Ibs., minimum beats 15, maximum 40, 

 average 30 per minute, with a fall of from 12 to 18 inches. The heads generally re- 

 volve and fall in an iron mortar, 4 or 5 feet long, 12 or 14 inches wide, the bottom being 

 sometimes 9 or 10 inches thick. This casting is commonly laid on a block of timber, 

 which rests on cross timbers. The mortar, is recessed for dies, having an octagonal 

 base and a wearing cylindrical head of iron, commonly 8 inches in diameter. The 

 battery box is entirely of wood and arranged so as to be readily removed. The ' grates' 

 are of sheet iron, with very fine slot holes, about ^ of an inch long, and an equal distance 

 apart. 



The grate is usually from 9 to 10 inches wide, and the length of the box. It is 

 fitted in a frame which is kept in position either by moans of wedges or set screws. 

 The lifter stem has usually a screw thread for adjusting the tappet, the latter being 

 lightened by means of a key, driven in ways, cut in the tappet and stem. When tho 

 driving power is a steam-engine, power is frequently transmitted to a counter shaft 

 by means of a belt and to tho stamps axle by spur wheels. This axle, as in Cornwall, 

 usually extends tho length of tho whole of the batteries. Water is introduced into 

 each battery box, tho quantity being sufficient to carry out the stuff as soon as it is 

 reduced to the necessary degree of fineness. For the milling of gold ores, the ends of 

 the battery box are lined with amalgamated copper plates, a third plate 10 or 12 

 inches wide, the length of tho battery fixed in a frame, is secured in an inclined posi- 

 tion behind tho stamps, whilst a fourth but a narrower plate is placed on tho front 

 side of the box. The average weight of stuff stamped per day is believed to be less 

 than a ton per head ; tho volume of water is, say 2,500 gallons per ton of rock. The 

 tendency of improvements is in tho direction of employing lighter heads, a lower fall, 

 and an increased number of beats per minute. 

 Australian Stamps, At tho Port Phillip Company's Works, Cluncs, Victoria, tho 



