“I neither wish to bring it about nor do I desire to witness it; but should it come to pass through the force of public opinion, I would second it to the full extent of my power. In such a case you will hear me spoken of. Adieu. I shall depart to-morrow; but pray leave me now, and let me have a little sleep.” Count du Saillant left the room without saying another word. Very early on the following morning Mirabeau was on his way to Paris. TERRESTRIAL MAGNETISM. (FROM CHAMBERS’S EDINBURGH JOURNAL.) It is proposed in the following article to give the reader some idea of one of the greatest and most extensive scientific works going on at the present time in this country—namely, the examination of the phenomenon of the earth’s magnetism; but before doing so, it will be necessary to make a few prefatory observations respecting magnetism generally. The attractive power of the natural magnet or loadstone over fragments of iron seems to have been known from the remotest antiquity. It is distinctly referred to by ancient writers, and Pliny mentions a chain of iron rings suspended from one another, the first being upheld by a loadstone. It is singular that although the common properties of the loadstone were known, and even studied, during the dark ages, its directive power, or that of a needle touched or rubbed by it, seems to be the discovery of modern times, notwithstanding the claims of the Chinese and Arabians to an early acquaintance with this peculiarity. There is no doubt that the mariner’s compass was known in the twelfth century, for several authors of that period make special allusion to it; but centuries elapsed before its variation from pointing precisely to the poles became noticed. If a magnet be suspended by a thread, in such a manner as to enable it to move freely, it will, when all other magnetic bodies are entirely removed from it, settle in a fixed position, which, in this country, is about 25° to the west of north; this deviation of the needle from the north is called its variation. Again, if, in place of suspending a magnetized needle, making it move horizontally on a pivot, we balance it upon a horizontal axis, as the beam of a pair of scales, we shall find that it no longer remains horizontal, but that one end will incline downward, or, as it is called, _dip_, and this dip or inclination from a horizontal line is about 70° in this country. Thus we are presented with two distinct magnetical phenomena: 1. The variation or declination of the needle; 2. Its dip or inclination; and to these we may add the intensity or force which draws the needle from pointing to the north, and which varies in different latitudes. These phenomena constitute what has been called terrestrial magnetism.