The next figure shows the construction of a battery and its fram for a wet-crushing silver mill. The ore, after passing through a Blake rock-breaker, is received in the feeding box mounted upon rollers From this it drops into the mortar. This mortar is made with grates upon each side. The stamped ore, after settling in vats, is worked by charges in pans. The framework of this battery is different from the preceding, but the arrangements for feeding, hanging up stamps, &c., are similar.

Wet-crushing Silver Battery.

HOWLAND'S ROTARY BATTERY.

This is a compact and portable form of battery, designed and patented by W. H. Howland. It was introduced to the notice of the mill-men of California and Nevada several years ago, and was at first used to a considerable extent, but was gradually replaced in nearly all the mills by the ordinary straight battery. These batteries were early adopted by Mr. A. B. Paul, in the mills erected by him below Gold Hill, and he has recently given his opinion of their merits as follows: "No act of mine in mining has been more criticised than the adopting of these batteries in my Washoe operations. Their adoption was no blind work, as I had used them for three successive years previous, and in no test with other mills was I beat in returns. I had then, and have now, great faith in

their principle. It certainly is in the right direction. They will, in time, I am confident, become popular, especially when introduced with the later improvements, on account of their simplicity, efficient working. and cheapness."

Howland's Rotary Battery.

It is claimed by the inventor that very great improvements in the construction have recently been made, based upon the experience of y seven years of constant working of the old style of the rotary iron battery. It is now offered by the Miners' Foundry to miners as a "new and highly improved rotary quartz mill," of less cost than the straight batteries, and requiring less power.

The construction is shown by the figure, page 666. The whole battery is of iron; the stamps are set in a circle around a central vertical shaft carrying the cams. Motion is imparted to this shaft by means of bevel-gearing. The cams are thus carried round horizontally, and lift each stamp in succession. These rotary batteries are cast in three sectious. The first section has the mortar or base, screen frames and feed openings in one piece; the second section contains the lower guide boxes, (which are of wood,) driving gears, and cam-wheel; the upper section contains the upper guide-boxes. These three sections are bolted together, with thin pieces of wood-packing between each. The stems, tappets, stamps, shoes, and dies are the same as in the ordinary cast straight batteries.

The openings for delivery through screens of the ordinary construction are seen at the base. The stamped stuff collects in the annular trough, cast in one piece with the mortar, so that there is no leakage, and is discharged by a chute at one side. It is claimed as one of the advantages of this improved form that there is more metal in the mortar or base than in the old form of rotary battery, and that the leakage at the base of the column, the jar and loosening of bolts, and the wear of guide-boxes, formerly complained of, are now entirely obviated.

Its compactness and lightness as compared with the ordinary straight battery, and its being complete in itself, not requiring timber framing and supports, commend it specially to those who wish to work their ores in districts remote from supplies of timber. Mr. W. D. Gray, the superintendent of the mill of the Imperial Company, at Gold Hill, Nevada, writes to Mr. Howland, February, 1869, as follows respecting the rotary battery:

Yours of 10th instant is at hand, in which you speak of having just finished and shipped for White Pine an 8-stamp rotary battery, made from a new and improved set of patterns. For a new country, where lumber is scarce and labor necessarily high, there is no battery now in use that will equal yours. The little time required to set it up ready to run is an important consideration. The greatest objection urged against the rotary battery has been the cost of keeping them in repair, compared with the straight battery. But my experience for the last eight years proves this a mistake. The annual report of the Imperial Silver Mining Company shows quite a percentage in favor of the Gold Hill mill (five 8-stamp rotary batteries) over the Rock Point mill, both in cost of repairs, expense of running, and yield per ton of ore worked-the first of which I have had charge of for the last five years. The Rock Point mill, run by water, has straight batteries. I think this comparison can be fully substantiated, as far as expense of repairs is concerned; also as compared with any other mill run in Storey County for the last five years.

The mill above referred to was designed for the Grant District, and weighed, when complete, less than six tons. The stamps weighed 600 pounds each, and were designed to make 100 drops per minute. When working up to its full capacity it will crush from twelve to sixteen tons, dry, in twenty-four hours. The total height of the machine is about eight feet, and the weight of the mortar is 3,000 pounds.

WILSON'S STEAM STAMPS.

One of the most successful of the attempts to apply steam direct to the stems of stamps has been made by Mr. T. R. Wilson, of Philadel

phia, Pennsylvania, whose mills have been in practical operation at sereral of our western mines. The general appearance and arrangement of the battery is shown by the figure. Steam is taken directly by a twoinch pipe to a short cylinder around the stem of each stamp above the frame and by suitable valves is made to act under or above a piston upon the prolongation of the stem. so as to either raise or throw down the stanp at will. The force of the steam can thus be added to the weight and momentum of the stamp in falling, in order to increase the rapidity and force of the blows, and thus to give an increased product of stamped ore in a given time. Two stamps are placed in each bat tery. The mortar is made in the usual form for double grates, one on each side, but is heavier than those intended for ordinary stamps. The two stamps are intended to strike about 400 blows per minute, For 200 blows to each stamp; and it is claimed by the manufacturers that they will stamp fine one ton For more of hard rock in one hour.

Wilson's Steam Stamps.

It is automatic in its action, cams being adjusted upon the upper ends of the stems and operating the valves as the stems move up and down. The following data will show the force with which the stamps may be made to strike:

Diameter of cylinder, 5 inches, area in square inches......
Diameter of upper piston rod 2 inches, area in square inches....
Total area of piston for down pressure of steam....

Multiply by pressure of steam in the boiler, (70 pounds)....
Add weight of stamp and stem...

This shows a force of about one ton, and it is so considered by the inventor. The steam-pressure at the battery is usually less than stated, say 65 pounds. The length of the cylinders is 74 inches, and the thick ness of the piston is 3 inches; there is therefore room for an extreme stroke of 14 inches, but an allowance must be made for the wear of shoes and dies. In setting up the machine an allowance of five inches is made for this, a space being left of this length under the piston, when the shoes and dies are new. This leaves a space of 94 inches for the movement of the piston; but in practice it is not run over 6 inches,