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Rh in Mexico; and that they could give, as yet, no explanation of the peculiarities of the process. Long practice had given the old Mexican amalgamators a perfect knowledge of the quantity of the different ingredients required by their ores, and they added to the Tortas, Salt, Magistral, and sometimes Lime, with a precision which a scientific man would be glad to attain, although unable to assign any reason for what they did. The only improvements which the Germans have been able hitherto to introduce, consist in preparing the ores, by the Concentrating Machine, either for smelting or amalgamation; and in collecting more carefully the quicksilver which may remain in the Tortas after the Amalgamation has taken place. The residue of the Torta is then washed, and carried afterwards, in troughs constructed for the purpose, round the whole Hacienda, until it is deposited in an open yard, where, after the earthy particles have been again separated by water, that which remains is called Polvillos, and on being smelted, is often found to produce from two to three Marcs of silver to the hundred weight. The little quicksilver which may remain is lost in this last operation.