“It is a curious sight,” says Dr. Faraday, “to see a piece of wood or of beef, or an apple, or a bottle of water repelled by a magnet, or, taking the leaf of a tree, and hanging it up between the poles, to observe it take an equatorial position. Whether any similar effects occur in nature among the myriads of forms which, upon all parts of its surface, are surrounded by air, and are subject to the action of lines of magnetic force, is a question which can only be answered by future observation.”[187] At present, the bodies which are known to exhibit decided ferro-magnetic properties are the following, which stand arranged in the order of their intensity:-- Iron, Nickel, Cobalt, Manganese, Chromium, Cerium, Titanium, Palladium, Platinum, Osmium. It is interesting to know that there are evidences that two bodies which, when separate, are not magnetic, as iron is, become so when combined. Copper and zinc are both of the diamagnetic class, but many kinds of brass are discovered to be magnetic. The salts of the above metals are, to a greater or less extent, ferro-magnetic, but they may be rendered neutral by water, which is a diamagnetic body, being repelled by the magnet. It will be unnecessary, here, to enumerate the class of bodies which are diamagnetic; indeed, all not included in the preceding list may be considered as belonging to that class, with the exception of gases and vapours, which appear to exist, relatively to each other, sometimes in the one, and sometimes in the other condition.[188] To endeavour to reduce our knowledge of these facts to some practical explanation, we must bear in mind that particular spaces around the north and south geographical poles of the earth, are regarded as circles to which all the magnetic lines of force converge. Under circumstances which should prevent any interference with what is called ferro-magnetic action, all bodies coming under that class would arrange themselves according to the laws which would regulate the disposition of an infinite number of magnets, free to move within the sphere of each other’s influence. The north and south pole of one magnetic body would attach itself to the south and north pole of another, until we had a line of magnets of any extent; the two ends being in opposite states, like the magnetic points of convergence of the earth.