By means of electric or magnetic action we can separate bodies chemically combined, as well as unite them into chemical compounds; as will appear if we place a piece of blotting paper upon tinfoil, and this upon wool; if we then spread above these two pieces of test-paper, litmus and turmeric, the one the test of acids, and the other of alkalis, and saturate both with Glauber salt (which is by itself neither an acid nor an alkali, but a combination of the two), and, finally, connect each by means of a piece of zinc with the poles of a battery, the test-papers will immediately change colour, as they do the one in the presence of an acid simply, and the other of an alkali simply, but never in a compound where these are neutralised; thus proving that the compound has in this case been decomposed, and its elements disintegrated one from another. A very powerful magnet can be produced by coiling a wire round a bar of soft iron, and attaching its extremities to the poles of a galvanic battery, when it will be found that its strength will be proportioned to the strength of the current and the turns of the coil. This is especially the case when the bar is bent into the form of a horse-shoe, and the wires are insulated and coiled round its limbs. The force communicated to a magnet of this kind, which is often immense, is the product of the chemical action which goes on in the battery, and, in a certain sense, the measure of it. How great that is we may judge when we consider that, evanescent as it is in itself, it has imparted a virtue which is both powerful and constant, and ever at our service. _Summary_.--Thus, then, on a review of the whole, we find all things are endowed with attractive power, and that there is no particle which is not directly or indirectly related, in manifold ways, to the other particles of the universe. There is, first, the universal attraction of gravitation, under which every particle is, by a fixed law, drawn to every other within the sphere of existence. There is, secondly, the attraction of cohesion or aggregation, which acts at short distances, and unites the otherwise loose atoms of bodies into coherent masses. There is, thirdly, the power by which elements of different kinds combine into compounds with new and useful qualities, known by the name of chemical affinity. And, lastly, related to the action of affinity, aiding in it and resulting from it, there are those strange negative and positive, attractive and repellant polar forces which appear in the phenomena of electricity and magnetism, agencies of such potency and universal avail in modern civilisation.