grinds it like the effective action of the pestle in the mortar. There is no loss of power to obtain this motion, in fact, the friction being a rolling instead of a rubbing, it is reduced, and no one can fail to see its great advantage. I am rather surprised that the machine is not employed in Cornwall and other English mining districts. In America and Australia (and in stamping machinery the Americans are far in advance of us) they are almost universally adopted, and it is not uncommon to pass through as much as one ton per hour per four heads, of quartz stuff. Messrs. Harvey and Co., have constructed many of this type, and they have given the utmost satisfaction.

STONE BREAKERS.

All stamps should be fed by a stone breaker, such as "Blake's," which is so well known in every mining country that no details are necessary here. All the stone is fed to the stamps of one size, and a much better duty is obtained than if delivered as broken by sledges. Spalled stuff is very irregular in size, and the largest pieces are mostly the hardest and toughest. There is often a considerable tenacity exhibited in parting with the old system of working, but ere long no mine will be found without this valuable adjunct to profitable mining. It will be acknowledged by most engineers that rock can be broken much cheaper by this machine than by hand, and fed to any description of stamps. More stuff will be got through than if irregularly broken. In many cases some 30 per cent. to 40 per cent. more work has been done. It is also found in practice that the wear and tear of grates is much less in those stamps fed by machine broken rock. For copper ore dressing one medium size machine will keep two pair of rolls going easily, and there is a saving of 40 per cent. of dust and fine stuff over breaking the rock by hand.

The breakers should be set under the tram waggons, a large one to receive the stuff that comes from the shaft from which it passes into

a smaller one, and so on. The nature of the stuff to be broken, the cost of labour, the quantity and value of the ore, &c., must be carefully considered, as the spaller will select a quantity of ores from the lode, and so relieve the costs in cobbing in some instances, but it is mostly the practice to select the productive stuff and pass it all through. Lead ores are sometimes reduced small enough for jigging, revolving screens being used for the separation of the fine from the coarse; jigging, and all other machines, being placed in succession in order that the products of one machine may fall into the other and dispense with all hand labour. Blake's machine has been much improved recently by Mr. Marsden, and the steam engine applied direct to the crank and fly-wheel. It is said to do one-half more than the old machine. The machines are also supplied with revolving picking tables, revolving screens, elevators, &c., as may be required for different uses.

Whelpy and Storer, of Boston, have a stone breaker which may be termed a centrifugal crusher; it consists of a revolving horizontal concave disc 3 feet in diameter, and weighing about 10: cwt., which projects the rock from its centre to its sides with great force in consequence of the great rapidity at which it worksupwards of 1,025 times per minute-the box in which the disc works is 18 inches high, perforated with holes; it is fed from the centre, and the stuff thrown off successively until sufficiently fine to pass through the perforated sides. This machine is usually fed with stuff of about 4 inches diametar, and will reduce 200 tons per day of 24 hours to a size of coarse gravel or sand, which result will only be obtained at the high velocity of 1,025 revolutions per minute, and will require 10 horse-power, or about one horse-power per hour per ton of stuff.

Dodge's Crusher is combined with rolls, shaking table, and sieves. It is making some headway in America on account of its lightness, and consequently being a cheaper machine than

Blake's; it is a jaw crusher, the lever worked by an eccentric, and said to stand a large amount of work.

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Archer's new patent stone-breaker and crusher consists of a fluted or corrugated roller revolving in a jawed lever, having a reciprocating motion, which squeeze or crush the rock as brought under by the roller. This roller is fluted at right angles to the flutes or corrugations in the jaw or squeezer, and produces good cubical and uniform work without much dust. To vary the size a set of liners are supplied and inserted in the connecting bulks, so lowering or raising the end of lever. This machine may be

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used for grinding by replacing the roller with one of finer flutes, and the jaws or squeezer would be made smooth, and set as near the roller as possible. It is also supplied with elevators and screens, &c., for screening stuff, and loading carts as the stuff is broken.

Reedy's patent stone-breaker operates with three hammers on the tilt hammer principle, the anvil being a cutter, so the stone is cut, cleaved, or split by a sharp blow. It is said to produce little small, thereby making it efficient for breaking road metal.

Chamber's patent hydraulic stone-breaker consists of two rams working in water cylinders, and press alternately against a jaw or mouth-piece centred in the middle. Those rams are actuated by smaller plungers working in the cylinders, driven by a connecting rod from the shaft or engine, and have a stroke of 6 inches, which produce a stroke of inch in the rams and make 300 strokes per minute. The jaws are shoed with double chilled iron, and bite at each movement backward and forward. It will admit rock of about 9 inches at the top, and is reduced to size to drop to the bottom; it then receives another bite, and is reduced fine enough to pass through. This machine is much used at the Victoria Gold Mines, and will break 100 tons in 12 hours, requiring but little power. Such descriptions of machinery could be made mo re clear by the aid of sketches.

Rider's rock-breaker has not come into use much in Australia, although possessing some good points.

Goodman's was an infringment on Blake's patent, and was stopped by Mr. Marsden.

The German machines are also modifications of the same thing, and the Prussians requiring no patent, have so modified the jaw that when the bottom part of the chilled shoe is worn out it may be turned end for end.

There are numerous other machines patented for the same purpose, but I think the above the best selection, and Blake's is the best stone-breaker in use at present.

ROLLS.

Many patents have been brought before the public for crushing ores, and the Cornish Crusher has been remodelled and improved (?) from time to time, but, I think, among the many now in use, it may still be considered the best crusher for simplicity, strength, durability, and effectiveness. Some have tried rubber buffers, or springs, for keeping the rolls together, the advantage of which is the resistance increases as the rolls open, and occupies less space; but in the method mostly in use-weighted levers— the load is constant, the amount of pressure being regulated by weighted boxes carried on the levers, and its action is all that can be desired. Any unyielding substance happening to fall among the stuff, and carried unnoticed to the rolls, such as a steel gad, will pass through without fracture or injury to the rolls. The boxes only being weighted to overcome the material under operation will allow the rollers to slide between its guides, the unyielding stuff passing through. A certain amount of ore will pass through at the same time, and the same thing occurs also if the rolls are fed too fast, which has a tendency to choke and keep

them apart; therefore, regularity of feed, attention to size of stuff, and a proper adjustment of the weight boxes, must be observed to obtain the best results. There should be a series of rolls; the upper set crushing the larger stuff may be fluted, so as to get a finer grip on the stuff. To produce good jigger-work they should be 30 inches diameter by 18 inch face, and speed of periphery 50 feet per minute, provided with revolving screens or sizing trommels (say) 72 inches long by 24 diameter, and erected at an angle of 25° to that of the driving roller, working in water at a depth of two inches, which will effect a better separation, and prevent balling of the earthy matter. By using sizing trommels we send only such portions back to the crusher as cannot be jigged; this is not the case with the ordinary fine riddle and raff-wheel. This raff-wheel, or elevator, takes the stuff from the riddles, and lifts it again to the hopper, which may be large enough to contain one ton of ore, and is again passed through the rolls, and so on, continuously, until all is fine enough or has passed through the riddle. By using Blake's stone-breaker the fluted rolls may be dispensed with and the greater proportion of this re-crushing will be avoided, and, perhaps, 50 per cent. more stuff got through. This is effected by using a small size machine lastly, with jaws moving only one-eighth of an inch, and making 600 bites per minute.

Rolls have been manufactured of different materials, in order to obviate the necessity of frequent changing. They often become pitted, scored, and bulged; but the best material will be a hard, chilled, white iron mixture, such as I have seen turned out by Harvey and Co., which have an excessive amount of even wear. Those shells, shoes, or castings, when keyed on with lock nut taper wedges, form a compact mass with the spindle or axis, and are readily and easily removed when required to be changed. hand on the Continent,

Some of those machines are driven by but the best method of driving is the

mode universally employed in the West of England, viz., strong