[ 454 ]

by ,4.268, we have 9,372 for the gravity of the compound:The gravity of 'platina should be no more than this, if itscomposition was such as is supposed ; so that one part ofgold, wrapt up in three of ferrugineous matter, ?s very farfrom accounting for the great weight of the mineral. Tomake the gravity 17, the quantity of gold ought to be 10parts in 11 of the mass.

If it be supposed that the matter mixed with the gold isnot iron, but something of a heavier kind, let us investigatewhat its weight must be. If gold be blended with threetimes its weight of another matter, and the gravity of themixt be 17 ; then 4£ parts of gold, and i2|- of the othermatter, will together lose 1 in water : the 4 j or 4,25 ofgold lose ,22 in water, so that the 12,75 of the othejmatter must lose ,78,whence the gravity of this last comesout above 16. If platina therefore be supposed to containgold because it approaches to gold in specific weight, wemust still admit that there is a substance which does thesame though it contains no gold.

To this way of reasoning the degraded gold osMr.Boylohas been objected ; which however does not seem to meat all to affect the argument. For in Boy les process, ofwhich an account has been already given in the history ofgold, page 206 of this volume, the gravity of the gold, bythe mixture of an inconsiderable quantity of foreign mat-ter, was diminished between a fifth and a sixth part, proba-bly from accidental cavities in the mass ; whereas here,according to the supposition we have been speaking of,the gravity of the compound, instead of being diminished,is increased almost to double of what it ought to be. Theremay indeed be some variation of gravity from. the mixtureof two bodies with one another, but of such an increase asthis I believe it will not be pretended that there is anyinstance. The great weight of platinf therefore, instead'

of