The precipitation room of the cyanide plant at the Portland mine, Colorado, contains 18 rows of zinc boxes, each row having six compartments 4 by 4 by 4 ft. and pyramidal in shape at the bottom. A 14-mesh wire screen supported by a 2-in. angle iron riveted on the inside, 20 in. above the lowest point of the pyramid forms the false bottom.
These boxes are supported on timbers high enough above the cement floor to permit a man to stand up to work about them. The solution enters the first box through a false compartment, flows under the screen, then up through the zinc and over into the next compartment; 28 in. is the distance from the screen to the overflow of each compartment.
A 12 by 12 in. wooden launder beneath each row of boxes carries the discharge to a launder of the same dimensions, which discharges into a steel vat with capacity for holding all of the solution from one row of zinc-boxes during a clean-up. It is connected to a 2-in. centrifugal pump which lifts the contents 30 ft. to a lead-lined tank. A hood having a 12 by 12-in. opening in the centre for the escaping fumes during a clean-up is built over the tank.
Twelve sets of zinc-boxes are in use; each compartment is packed with 200 lb. of zinc shavings previously dipped in a 2% acetate of lead solution. Strong solution having 0.6 lb. cyanide per ton and a protective alkalinity 0.5 to 1.0 lb. flows through six rows of boxes, and a weak solution—the strength of cyanide per ton of solution being 0.3 to 0.4 lb. and protective alkalinity, neutral to 0.2 lb.—flows through the other six boxes.

The Portland Gold Mining Co. will erect an experimental cyanide plant, with a view to determining whether the ores are adapted to that style of treatment.

Cripple Creek—Two of the Portland company's experts have selected a site for the new experimental cyanide plant to be erected at the mine.

Cripple Creek—The new Portland cyanide mill is in course of construction and it is expected to be ready for the installation of machinery, which is all on the ground, in the course of two or three weeks. It will have a capacity of 500 tons per day.

The foundations for the 10-stamp experimental mill which the Portland is building, at Cripple Creek, are practically completed. The plant is being built to sample the ores of the mines and also about a million tons of dump, which it is estimated will run $3 to $4.50 per ton.
The experimental plant will be under the direction of G. M. Taylor, who is superintendent of the Company's mill at Colorado City.

Work on the experimental plant of the Portland G. M. Co. is being pushed rapidly and it is expected that the mill will be in full operation some time during the present month.

Cripple Creek—When it finishes its experiments with the temporary 10-stamp mill, the Portland Co. will proceed to enlarge its capacity to treat not only the large dump, but the low-grade ore of the mine.

It is known that the Portland company has been experimenting on the dump ore for some time at Colorado City, and is now erecting a small plant (10-stamp mill) near the mine. They are proceeding carefully, spending probably not more than $15,000 on the outfit.
The method will be to convey the ore automatically to the mill for crushing, pass it over concentrating tables, and then
cyanide.
The tailing will be put over a second table. It is reported that they are going to very little expense in the matter and are obtaining the most up-to-date tables; by reason of many years of experience in milling their oxidized ores at Colorado City they should be able to devise the best and cheapest means for treating the dumps.

The Portland mill is to start immediately.

For several years past Colorado metallurgists have been attempting to solve the metallurgical puzzle presented by the low-grade ores of Cripple Creek. Millions of tons of ore running from $3 to $10 per ton have lain on the great dumps for years, while other millions were exposed in hundreds of miles of underground workings.
The Portland company alone had enough low-grade ore in its forty odd miles of workings to materially increase the Cripple Creek gold production provided a method of profitable treatment could be devised.
Shipping the ore to the Colorado Springs reduction plant of the company cost $1 per ton, roasting the ore cost $.76 per ton, and the other milling expenses ate up the small margin of profit.
Thus, for some years previous to 1907, the issues were clearly presented, first, to eliminate roasting the ores if possible, and, second, to eliminate freight charges by building mills at the mines.
It will, of course, be understood that until a way of eliminating the roasting of the tellurium ores was discovered, it would be useless to erect mills at the Cripple Creek mines where roasting costs even more than at Colorado Springs.

During the two years in which the Stratton Independence and Golden Cycle metallurgists have been evolving their plants, those of the Portland company have also been most active.
It is now common knowledge that the widely advertised Moore-Clancy process was given an extended trial at the experimental mill of the company but was evidently found unsuitable. The great amount of experimental work, however, did result in the evolution of what is known as the "Portland process," whose details are as yet unavailable.
It has been thoroughly tried out at the company's Cripple Creek 10-stamp experimental plant, however, with such success that a large mill is soon to be built close to the mines.
The annual report of the company recently issued says that from many tests the company is convinced that the problem of treating the low-grade dump ores has been solved.
The directors have decided to back up their judgment by the expenditure of at least $100,000 for a 300-ton mill, erected near the mine on Battle Mountain, to treat the great company dumps. These contain enough ore to run the mill for many years at an estimated net profit of from $1 to $2.50 per ton.

MILLING AND SAVING LOW-GRADE TELLURIDE ORES.
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The president of the Portland company, at Cripple Creek, Colo., in his annual report, stated that discoveries made by the company's metallurgist made possible the successful treatment without roasting of low-grade telluride ores.
The general manager of the Golden Cycle' also announced that his experts have a dry concentrating process which will effect the same end.
A mill has also been erected at the Stratton Independence for treating the low-grade ore of the dump.

At the Portland mill, another Chilean mill is being installed driven by a motor, and the transformer station is being enlarged.