small amounts required to build capacious condensation-chambers in connection with their works, and to erect such additional apparatus as may be necessary, in order to utilize the values contained in the matte. At the same time they ought to provide their works with complete chemical laboratories, which are, so far, I am sorry to say, nowhere to be found. It is only by subjecting raw materials, educts and products, to frequent analyses, that smelting processes can be conducted intelligently and economically. In the chapter in this report, on the smeltingworks of the Harz, will be found ample information in regard to a system which is peculiarly adapted for our western works. That this system may have to be modified in certain details, according to local circumstances, I need not add. To discern the necessity of such changes is the business of the trained metallurgist, and no other should ever be put in charge of a business in which so much depends upon the proper supervision of operations. The sooner the above suggestions are acted upon, the better will it be for the individual owners, and for the nation. It is high time, even in this rich Union, to put a stop to wanton waste of the precious and other metals, and to add, hereafter, to the wealth of the world, what has, so far, been only a source of useless expenditure.

CHAPTER XIX.

KÜSTEL'S ROASTING-FURNACE.

This apparatus is an improved reverberatory, and although I am not in possession of detailed working results from actual practice with it, the eminence of its inventor, Mr. Guido Küstel, of San Francisco, as a skillful and experienced metallurgist, entitles it to a place in this report. By the courtesy of Mr. Küstel, I am able to present drawings of the furnace, and the following description of it from his own pen:

Whoever has been engaged in roasting ores will admit that different classes of ore, for instance, gold sulphurets, (iron pyrites,) decomposed silver-ores, silver sulphurets, blendic-ores, &c., cannot be treated exactly in the same way, if the best roasting results are to be obtained. In this respect the old reverberatory was the proper furnace. The roaster had it in his power to modify the heat, the time of roasting, the amount of salt, lime, or sulphate of iron; the proper time of adding these ingredients, &c., till oxidation or expulsion of volatile base metals and chlorination of the silver was accomplished. But the expense was too high and the time of roasting too long. The introduction of the long reverberatory roasting-furnace diminished the expense and shortened the time of roasting, but the moving of ore from one end to the other through side doors was very tedious, and the roasting-time still too long, and the amount of labor required large.

All the disadvantages above mentioned are obviated by Küstel's improved furnace, of which Figs. 1 and 2 give a clear illustration: they are drawn to a scale of 6 feet to 1 inch. Fig. 1 is the horizontal and Fig. 2 the vertical section. There are in this furnace two very important improvements. The first consists in breaking the straight line of the long furnace. The working-doors g g are placed so that no lateral work is performed; only drawing and pushing on an inclined hearth is required. The ore is introduced through the hopper a, on the upper hearth a, spread equally, and after an hour's time drawn at g" and pushed from g' upon the second inclined hearth b, and from this upon the third, c, in the same way. No stirring is required unless very difficult ore is under treatment. The moving of the ore from one end of the furnace to the other is generally sufficient. The necessary heat is kept up by two or three fire-places, hh. The gases pass through the flue m above the roof into the dust-chamber d, and escape through the chimney e. The arrangement of having the working-doors at the end of the long sides enables the roaster to do a great deal more work than if tired out in the old way of moving the ore toward the fire-bridge.

The other improvement refers to the chloridizing chamber K, Fig. 2. The purpose of

this chamber is to shorten the time of roasting. It has been ascertained that the ore at rest in a red-hot condition continues to be chloridized when drawn out of the furnace. The ore falls through the opening, o, into the chamber, and remains there redhot for two or four hours, as may be required. Chlorine and volatile chloride metals, that are evolved, pass into the furnace and continue to chloridize the ore all along the furnace. In case there is no sulphur in the ore, sulphurous acid gas can be introduced through the pipe 1, simply by burning sulphur. The sulphurous gas is transformed into sulphuric acid and liberates the chlorine from the salt.

The inventor states that a furnace of this kind, by the aid of the chamber K, can put through from 15 to 20 tons of ore in twenty-four hours, employing two shifts of three men each, consuming less than one-fifth of a cord of wood per ton of ore. The roasting being perfectly under control, the highest percentage of chloride of silver is obtained.

Without interfering in the least with the advantages alluded to, these furnaces can be worked just as well by an approved mechanical arrangement, so that a continuous feeding direct from the battery is effected. Local circumstances will decide whether hand-work or machinery is preferred. The discharge of the ore from the chamber can be made at intervals or continuously by giving to the bottom a funnel shape and applying an endless-chain arrangement. A few small holes through the brick-work funnel may serve for the use of an iron rod in case choking occurs. The patent refers not only to the shape as represented by Figs. 1 and 2, but to any breaking of the straight line of a long furnace by which the lateral work is avoided.

CHAPTER XX.

BRÜCKNER'S CYLINDERS.

The Brückner cylinder, or revolving furnace, has been repeatedly described and alluded to in my reports, but I have never until now been able to present drawings illustrating its construction and use. Deeming it a highly successful apparatus, I give the accompanying illustrations of it, and quote the following paper, by Mr. C. M. Locke, civil engineer, of Cincinnati. I regret that exact and detailed working results are not yet at my disposal.

Brückner's revolving cylinders for roasting ores, &c., are now used at a number of the mills in Colorado and New Mexico, for the purpose of roasting and chloridizing silver-ores, with highly satisfactory results, even from those cylinders of small size, erected before the many improvements of recent date.

As examples of the larger improved cylinders, reference can be made to those erected at the Tennessee Reduction-Works, Silver City, Grant County, New Mexico, and those which were built, in 1871, at the celebrated Caribou Silver Mill and Mines, Colorado, a mining enterprise which has proved so satisfactory as to have been lately sold to a Holland company for an enormous amount.

Description of their construction.--These cylinders, as now constructed by Messrs Lane & Bodley, of Cincinnati, Ohio, are shown in the accompanying cuts, of which Fig. 1 is an elevation in perspective, Fig. 2 a longitudinal, and Fig. 3 a transverse section.

The exterior of the cylinder is a shell of boiler-iron, 12 feet long by 5 feet 6 inches in diameter. The ends are partially closed with similar material, leaving in the center a circular opening about 2 feet in diameter, bounded by a flange projecting several inches. Upon one side is placed an opening closed by a hinged door. Upon the outside of the cylinder are bolted three bands, as shown in Fig. I, in which the section of the first is square, and that of the third semicircular; the second, or middle band, is a strong spur gear. Passing through the cylinder are six pipes parallel to one another, in a plane at an angle of 15° to the axis of the cylinder; these pipes also lie in this plane at an angle of from 30° to 35° to the longitudinal axis of the plane, as shown in Fig. 2, where the internal arrangement of the cylinder is seen, a perforated diaphragm being formed through part of the cylinder by means of perforated plates placed between the above described pipes, the plates being held in place by longitudinal grooves upon these pipes.

The entire cylinder is lined with brick, (common building-brick have been found to answer the purpose very well,) the brick being placed in the following manner: The