The following experiments are very instructive:--Suspend a magnetic needle by a silk cord, so that it will hang in a horizontal position. Then bring it over the centre of a large magnet lying upon a table, and it will still retain its position; but, as it is brought near to either end, it will be bent downwards, and, at the extremities, will be vertical. This experiment illustrates what is called the dip of the magnet. On the equator of the earth, the needle is horizontal, or nearly so, but as it is brought near the poles it dips, and over either magnetic pole would be vertical. The reason of this is evident from the former experiment: at the equator, each pole of the needle is attracted in an equal degree by the north and south poles of the earth; but, if we proceed northward, the north pole of the magnet will be more attracted than the south, and point towards it until at last it becomes vertical. The poles of the earth’s rotation, that is, the points which would form the terminations of its axis, did it revolve on one, are not the magnetic poles; nor is the equator of the earth the magnetic equator. They do not, however, greatly vary. Take, also, a bar magnet, and, placing it upon a table, cover it with a sheet of writing-paper. Then sprinkle upon it some fine iron filings, and they will arrange themselves in very beautiful curves round the magnet, showing, as it is supposed, the circulation of the magnetic fluid. From this experiment, we learn that the magnetic power is greatest at the poles; and this is true in reference to the magnetism of the earth, which increases in power from the magnetic equator to the magnetic poles of the earth, as determined by a great variety of interesting and delicate experiments. Sir Graves C. Haughton has communicated a paper to the June number of Brewster’s _Philosophical Magazine_, entitled “Experiments proving the common nature of Magnetism, Cohesion, Adhesion, and Viscosity.” This paper contains two separate sets of experiments, the first of which relates to the attraction the magnetic needle has for various mineral, vegetable, and animal substances: and it is not a little remarkable that antimony and bismuth, as well as copper, tin, and cadmium, are, in these experiments, shown to have attractive powers for the magnetic needle; though, in those made by Dr. Faraday, he has ranged them amongst the class of dia-magnetics, that is, of those that exhibited repulsion. Arsenic, too, which he found so intractable, was made, in the present experiments, to assume the real magnetic character, that is to say, the power of attracting and repelling, by being kept for a short time in contact with a bar magnet. Iodine, likewise, was found, on bringing it near the needle, to be able to attract it.