These few examples will serve to indicate that we may advantageously amalgamate gold ores inside a ball or tube mill, either with coarse or fine grinding and that the success thus far attained opens a new field for the amalgamator whose prestige of late has been overshadowed by the cyanide chemist.

J. W. Finder states the four factors governing the success of amalgamation in tube mills or other mills that violently grind gold ores in the presence of mercury to be: The proper consistency of the pulp, the proper quantity of mercury, a subsequent mercury bath and the proper capacity of the machine.

He says:

"1. The pulp should be thick enough to hold the fine globules of mercury in thorough suspension as it revolves throughout the tube. About 75 per cent, (by volume) of water would, in most cases, result in the best consistence, although that must be determined by conditions and the character of the ore. When too thin, the pulp cannot be well amalgamated, and the mercury is likely to be whipped into a sickened condition. The consistence of soft mortar is therefore the best, and the safest. While grinding, the pulp should not be flooded for any purpose.

"2. The quantity of mercury to be used should be determined entirely by the content of the ore and consistence of the pulp. According to the facility with which the gold is amalgamated, the quantity of mercury should be regulated. If the ores contain zinc, lead, arsenic, antimony, talc, or graphite, or any other substance tending to affect the activity of the mercury, more mercury should be added to lessen such bad effects, in proportion to the detrimental material contained in the ores. In such cases it may become necessary to use as much as can possibly be carried, in fine globules, by the stiff pulp, in proper suspension without running together to form larger bodies in the mill. But with free ores, or comparatively so, half the quantity would suffice.

"3. The subsequent mercury bath is all important to the success of this operation. The lesson may be taken from the performance of the settler, in pan work, for collecting the amalgam and preventing the loss of mercury. This bath should be ample in capacity, and permanent, changed when showing signs of requiring quickening; and the proper dilution of the pulp as it enters the bath.

"4. The quantity of ore treated, within economical reason, should depend upon the quality of the work. The capacity of the machine is a matter of judgment, to be based upon results obtained. Amalgamation is a delicate and an important operation in itself. To do good work one should not try to make a tonnage record for grinding and expect to get the best extraction at the same time."