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gold : in the quantity of one fourth and upwards, itgives a dull whitifhness.

Iron or steel, in very small proportion, render goldhard and eager, and on increasing the quantity of the iron,the mixt continues brittle : some of these mixtures are ofsuch a degree of hardness and closeness, as adapts themfor receiving a fine edge, and it is said that they have beenformed into razors. The colour of the gold is made paleby a small quantity of the iron : equal parts of the twoform a grey mass : if the quantity of the iron is three orfour times greater than that of the gold, the mixt provesof a white colour, approaching to that of silver.

All the rest of the metallic bodies give paleness, dullness,and brittleness, in different degrees, some more than othersin the same quantities. Of tin and lead the most minuteproportions, even the vapours which rife from them inthe fire, though not sufficient to add to the gold any weightsensible in the tenderest balance, make it so brittle that itflies in pieces under the hammer; though gold, contrari-wise, mixed with a small proportion of the lead or tin,does not appear to injure their malleability. Somethingof the same kind seems to happen in the mixtures of goldwith the metals which of themselves are brittle, as zinc,bismuth, and regulus of antimony ; a small proportionof these metals rendering gold extremely brittle, whereas,when the brittle metal is in large proportion, its fragilityis diminished by the gold: thus Mr. Hellot observes, in apaper on zinc published in the French memoirs for theyear 2735, that a mixture of three parts of zinc and oneof gold does not break so easily as a mixture of equal partsof the two. Some of these mixtures, particularly one ofequal parts of gold and zinc, bear a fine polish, and pro-bably, as the above mentioned author takes notice, would

be