It may be well to remark that an amalgamator such as shown can be attached to any tube mill.

Mr. W. H. Hardinge says  that the mill superintendent stated that the loss of quicksilver was 0.025 oz. per ton of ore ground.

At the Amador Con. milling plant, California, the discharge from the Hardinge mills goes to Hardinge amalgamators, which are attached to and revolve with the mill. Mercury is fed into these amalgamators as required by the condition of the outside plates, in the same manner as feeding it into a stamp mortar. About a dozen small copper balls, made from 1/4- or 3/8-in. wire, are kept in the amalgamator. As these balls roll around they build up, forming good-sized amalgam balls which are removed daily while the mill is in operation; after removing the accumulated amalgam, the balls are returned to repeat the operation.

We are indebted to H. W. Hardinge for the conical mill and for some useful information contained in an article in Mining Press, Feb. 13, 1915, from which we quote the following:

"This matter of inside amalgamation was suggested by me to J. M. Elmer, in 1909, when he was in charge of a Mother Lode mine in Tuolumne, Cal. He then tried it out with highly satisfactory results. Mr. Elmer later reported that the amalgamation recovery advanced from 65 to between 80 and 85 per cent., and a total of over 90 per cent, was made with subsequent concentration. From information later gained, however, we must give A. D. Foote, of the North Star mine at Grass Valley, credit for a still earlier use of quicksilver in pebble mills for inside amalgamation. Some months after Mr. Elmer's resignation from the Tuolumne mine, we received a letter from Charles Maass, Mr. Elmer's successor, and from his letter I quote the following:

"The objection usually urged against inside amalgamation, where fine grinding is done, is that the mercury will granulate and thus become useless for amalgamating purposes. This is due to the mercury becoming foul through taking up soluble mineral salts. To prevent this, it is necessary to introduce some agent which will cause the liberation of hydrogen gas from the liquid in the mill, thus deoxidizing the salts when they no longer have an affinity for the mercury. In other words, it is simply necessary to keep the mercury as nearly chemically pure as possible. To accomplish this we have found that, in the case of the silex-lined mill, metallic sodium gives excellent results. In our ironlined mill the results were not as good, as the action of the metallic sodium was so violent that it caused the amalgam to adhere to such parts of the iron lining as had become brightened through wear. In this case we used an amalgam made up of zinc and aluminum. This also has the effect of liberating hydrogen gas, though the action is slower and will not cause^the amalgam to adhere to the polished iron. The objection to the^use of^this combination lies in the fact that it cannot be made up in quantities to keep, and as a consequence must be made up freshly whenever necessary to add any to the mill.