object the utilization of the electric current in metallurgical operations, and there is no doubt that in the near future many minerals now smelted with fuel will be reduced to metals by electrical processes. The electric current possesses the great advantage of allowing a most efficient utilization of the heat; and also complete control of the exposure of the molten metals to air or gases.

XXII. BRIQUETTING.

At many blast-furnace plants "fines" are made into briquettes with the ordinary die-and-plunger machines; but if free acid or copper sulphate be present, the surfaces of both dies and plungers are rapidly corroded, which obviously increases the diameter of the dies and diminishes that of the plungers. As this solvent action continues, a point is soon reached when the plunger no longer fills the die-opening, and pressure forces the material through the space between them, instead of consolidating the mass.

When a sufficient amount of plastic material, such as slimes, can be obtained to mix with fine ore and flue-dust, so as to give the mass the property of "flowage" under pressure, it may be briquetted in machines similar to those used in making building-brick by the "stiff-tempered" process. Solvents do not interfere with the operation of these machines, and by constructing the working-parts of steel and phosphor-bronze, it is possible to make briquettes dry enough to pass directly into a blastfurnace at the rate of 600 to 800 tons per day for each machine employed, at a cost of less than half that of the die-and-plunger system.

XXIII. CHLORINATION.

Chlorination is confined almost entirely to sulphide gold-ores carrying so little silver that its loss may be disregarded, and which require a preliminary roasting before treatment. The early methods of tank-leaching have all been superseded by barrel-chlorination, and in some of the latest plants chlorine is produced by electrolysis instead of by the decomposition of bleaching-powder with sulphuric acid.

The largest plants operating under this system treat custom ores, and the stress of competition, together with the necessity of handling constantly increasing tonnages, has brought about great improvements in both machinery and methods.

The most desirable features of this process of gold-extraction are the high percentage recoverable, and the rapidity with which clean-ups can be made, rendering it easy at all times to know exactly what results are being obtained.

The largest plants operating under this system are situated in Colorado City, Colo., where two mills owned by one concern have an aggregate capacity of 800 tons per day.

XXIV. CYANIDATION.

While the first patent for extracting gold from its ores by cyanide solutions was issued in 1867, it was not until McArthur and Forest took it up in 1889 that practical results of any value were obtained. Since that time the use of the process has increased by leaps and bounds in all of the principal gold-producing countries, and to-day it is the principal factor in the world's steadily increasing gold-production. Cyaniding seems to work with equal facility on raw ore, roasted ore, and tailings, and with the steady improvement in the mechanics as well as the chemistry of the process, it bids fair to do even greater things in the future than it has done in the past. Nor is its use confined entirely to the extraction of gold. In many districts it is operating with great success on mixed gold- and silver-ores. At Millers, Nev., two plants with an aggregate capacity of 700 tons per day are operating on Tonopah ores, in which the average ratio of silver to gold is 80 to 1.

The largest and perhaps the most complex cyanide-plant in the United States is the Golden Cycle mill, at Colorado City, Colo., which has a daily capacity of 1,000 tons, and treats exclusively Cripple Creek ore, all of which requires careful roasting and very fine crushing. The Homestake cyanide-mill handles a larger tonnage, but treats only tailings.

Next to this plant in point of size and importance, and handling ore of much higher grade, is the new mill of the Goldfield Consolidated Co., Nevada, which has a capacity of 600 tons per day, and contains the very latest improvements, culled from American, African, Australian, and Mexican practice.

XXV. FUME-RECOVERY.

No department of metallurgy has made slower progress than this most important division, but now, through an unholy alli

ance between the unscrupulous contingent-fee attorney and the greedy land-owner, the success of "smoke-farming" is compelling the smelting companies to do for self-preservation something which they should long ago have undertaken for profit. Out of the almost numberless devices which have been tried for fume-recovery, the bag-house affords the best solution of the problem yet devised. Bags were used for the recovery of both zinc oxide and lampblack more than 50 years ago, but were not used for fume-recovery until 1878, when Bartlett set up a small plant at Portland, Me. The first large successful installation of this kind was erected by the Globe Smelting Co., in 1885, and has been in continuous operation ever since. While the bag-house has been eminently successful in the recovery of blast-furnace fume, it cannot be used on fumes from reverberatory roasting- or smelting-furnaces, owing to the fact that a portion of the sulphur dioxide formed by the oxidation of the sulphur is raised to sulphur trioxide by contact with incandescent ferric oxide. At the United States Smelting Works, in Utah, provision for protecting the bag-house from sulphur trioxide is made by blowing into the flues zinc oxide, which immediately absorbs the sulphur trioxide present to such an extent that it has been found quite possible to use cotton bags. The bag-house has proved very efficient in recovering fume from lead-refineries and all lead-smelting operations excepting roasting. In large copper-smelting plants, where large volumes of gas are produced carrying a sufficient amount of sulphur trioxide to destroy woven fabrics, three systems are in usenamely: radiation, decreased velocity, and friction—and in many cases two or more of these methods are combined. At the Washoe plant, in Anaconda, long steel-covered flues of enormous cross-section have been installed for a number of years, and, while this system does not effect a complete recovery of the fumes, it is as nearly perfect as it is possible to make a plant to-day. At Great Falls, Mont., the Boston & Montana Co. is installing the friction system at a cost exceeding $1,000,000, which includes the construction of a stack 506 ft. high and 50 ft. in diameter and a dust-chamber in the flue-system, of such width that the furnace-gases will pass through it at a velocity considerably less than 500 ft. per minute. From the roof of this flue-chamber more than a million steel wires will

be suspended, an arrangement which experiment has shown to increase greatly the settling-efficiency of the dust-chamber. This installation is practically completed, but it will be some time before the results obtained can be accurately determined.

I need not add that where (as in some Eastern works) metallurgical and commercial conditions permit the manufacture of suphuric acid from the fumes, this method offers special advantages.

XXVI. CONCLUSION.

The subjects already alluded to occupy but a small portion of the field covered by our 4,000 widely-scattered members, but I hope that enough have been mentioned to serve as topics for discussion at this meeting. The ever-widening range of operations, the constantly expanding magnitude of mining undertakings, and the continually increasing complexity of both machinery and methods are daily creating new openings for mining engineers. To meet this demand our technical schools and colleges are yearly sending out an increasing number of graduates, whose opportunities and responsibilities will be even greater than those of the engineers controlling the activities of to-day. Even now, one change very much to be desired is beginning to become apparent. Heretofore it has too often been considered that an engineer's accountability ended when he discharged his full duty to his employer. To-day we are beginning to realize that the public forms a third party, vitally concerned in the results of the work in which mining engineers are engaged. As large investments are usually held by divided ownership and stocks are often scattered far and wide, so that the owners of small holdings have little or no opportunity to become conversant with the exact conditions of the properties the stocks represent, an engineer's duty should be to see that no word or act of his can be construed so as to give one man an opportunity to take advantage of, or mislead, another. Every one, no matter what his station, has a duty to society and his fellow-men which can never be either ignored or neglected. The employer, whether an individual or a corporation, is entitled to all of the information and data which experience, diligent investigation, and careful study can bring to light; and while an engineer has a right to state probabilities from both

indications and analogy, he should never assume the gift of prophecy and thereby delude both himself and others.

Specific information gained in examination or research for one client should never be utilized for the benefit of another, unless there is no possibility that such use will in any wise injuriously affect the interests of any previous employer. This restriction applies with full force to the dealings of the engineer himself, as he should always remember that information gained by him at the cost of another, no matter how laboriously it has been obtained, belongs to the party who paid for it. No matter what success ability, industry, or chance may bring to an engineer, his career has been an absolute failure unless he can truthfully say in his heart of hearts: "No man is poorer because I am richer."

The Ruble Hydraulic Elevator.

BY J. McD. PORTER, SPOKANE, WASH.

(Spokane Meeting, September, 1909.)

IN many of the old placer-mining districts are still to be found large tracts of gold-bearing gravel not suitable to be worked with a dredge, because the bed is too shallow or the gulch too narrow. Frequently there is not enough grade to handle the gravel successfully by ground-sluicing or a bedrock flume, or it contains too many boulders to be worked successfully with the ordinary hydraulic pipe or tube elevator.

In southwestern Oregon, two practical placer-miners named Ruble, after working for years trying to make money out of placer-ground containing many large boulders, invented and patented a hydraulic elevator of an entirely new type, and one that has been found to work very successfully in flat ground and in gravel containing many large boulders. It is a very simple contrivance.

A few years ago I acquired the property near Pierce City, Idaho, known as the American placer-mine. Various attempts had been made to work this ground. A bed-rock flume had been installed by one company, an Evans elevator by another, and still other methods were tried on a smaller scale. All were