fierce fire, it is no longer pure platina, but a composition in which fusing matters are entered, and from which fire has taken the lightest parts. Platina, therefore, instead of being of a density almost equal to that of pure gold, as has been asserted, is only a density between that of gold and iron, and only nearer this first metal than the last. For supposing that the cube foot of gold weighed 1326 lb and that of iron 280, that of platina in grains will be found to weigh about 1194 lb. which supposes more than 3/4 of gold to 1/4 of iron in this alloy, if there is no penetration; but as we extract 6/7 by the loadstone, it might be thought, that there is more than 1/4 iron therein: especially as by continuing this experiment, I am persuaded, we should be able, with a strong loadstone to bring away all the platina even to the last grain. Nevertheless, we must not conclude that iron is contained therein in so great a quantity; for when it is mixed by the fusion with gold, the mass which results from this alloy is attractable by the loadstone, although the iron is in no great quantity therein. M. Baume had a piece of this alloy weighing 66 grains, in which was only entered 6 grains, that is, 1/11 of iron, and this button was easily taken up by the loadstone. Hence the platina might possibly contain only 1/11 iron, or 16/11 gold, and yet be attracted entirely by the loadstone; and this perfectly agrees with the specific weight which is 1/12 less than gold. But what makes me presume, that platina contains more than 1/11 of iron, or 16/11 of gold, is, that the alloy from this proportion is still of the gold colour, and much yellower than the highest coloured platina, and that 1/4 iron, or 3/4 gold is requisite for the alloy to be precisely of the natural colour of platina. I am, therefore, greatly inclined to think that there might possibly be this quantity of 1/4 iron in platina. We were assured by many experiments, that the sand of this pure iron which contained platina, is heavier than the filings of common iron. Thus, this cause, added to the effect of penetration, is sufficient for the reason of this great quantity of iron contained under the small volume indicated by the specific weight of platina. On the whole, it is very possible that I may be deceived in some of the consequences which I have drawn from my observations on this metallic substance: for I have not been able to make so profound an examination as I could wish; and what I say is only what I have observed, which may perhaps serve as a stimulus to other and better researches. Chance led me to tell my ideas to Conte de Milly, who declared himself nearly of my opinion. I gave him the preceding remarks to inspect, and two days after he favoured me with the following observations, and which he has permitted me to publish.