(TWENTY-SIXTH MEMOIR.)

EXPERIMENTAL AND THEORETICAL.

487

eight-hundredth part of the half-crown must have consisted of iron, if its Magnetismwas due to the presence of that metal.

62. Again, the magnetic action of this half-crown was considerably more feeblethan that of the alloy, which has been chemically examined, and in which, if iron waspresent at all, that metal was in a less proportion than a twenty-thousandth part ofthe mass—which proportion, in a state of peroxide, and divided, as it necessarily musthave been, through the whole alloy, would scarcely yield the slightest perceptiblemagnetic action. Moreover, if iron to that amount were even pure or uncombined,its quantity was far too small for the display of those high magnetic powers of whichit was obviously possessed; and as there is a probability, at least, that the magneticpowers of iron become deteriorated by an alloy of that metal with silver or copper, orboth, there is not the slightest reason for supposing that the Magnetism of the alloyin question (32) was due to any iron that it could possibly contain. Nor do I believethat the magnetic actions displayed by the coinage are traceable to the presence of iron.

63. It has already been stated (42) that the magnetic action of nickel is consider-ably neutralized, when combined with zinc and copper, in the alloy constituting Ger-man silver. Since that part of this Memoir was read before this Society, I have hadan opportunity of alloying nickel with zinc alone, and have ascertained that, when thezinc is about eight or ten times the quantity of nickel, the alloy is perfectly neutral tothe magnet. This alloy has a zinc-coloured fracture, and partially crystallized in themanner of zinc; but it is extremely brittle, and easily pulverized in a mortar.

64. Nickel and antimony combine with facility, and in an extraordinary manner.If two pieces of the metals, one of each, be placed side by side in a crucible, so as totouch one another, especially at their upper ends, the moment the antimony assumesa dull red heat (even a lower heat than that which commences its fusion when alone)the nickel bursts out into a fine scarlet glow, fuses and spreads over the antimony in abeautiful fluid state, and insinuates itself into the pores of that metal, rendering thewhole mass soft, like paste or butter. If, whilst in this state, the crucible be removedfrom the fire, and permitted to cool gradually, the fracture of the button of this alloy,when broken, is of a much lighter colour than that of antimony. It is of a light grey,and very imperfectly crystallized. It is not so brittle as antimony, though still pul-verizable in a mortar. When one-fourth of the mass is nickel, the fracture is verycompact, and not unlike that of fine steel, but of a lighter colour. With these pro-portions, the alloy is somewhat malleable, and can be cut by a cold chisel.

65. From a retrospection of the facts developed by these researches, in connectionwith those previously known, we are led to observe a material difference in the mag-netic character of bodies, when in their simplest or natural conditions; and that thesenatural magnetic characters become considerably modified when the simple or elemen-tary bodies are variously combined—some simple magnetic bodies losing their natural