This may be to some of our readers a startling question; for most of us have had that star pointed out to us many years; and perhaps those who directed our eyes to it little thought that there would ever be any other pole-star. It is well known that if the northern extremity of the axis of our earth were lengthened until it met the imaginary sphere of the heavens, it would come very near to our present pole-star, hence called Polaris; and if, for any cause, the direction of that axis were materially altered, that star would no longer be a true index of the north. We now propose to show that such a change of the direction of the earth’s axis is continually taking place; and that the terrestrial axis when thus lengthened describes a cone, the apex of which is the centre of the earth; and the circumference of the base of the cone is a circle described amongst the stars. When the axis has described one-half of its course, the angle between the two positions it occupies at the beginning and at the middle of the rotation is about forty-seven degrees. And thus the extremity of the axis will successively come near to other stars than our present pole-star; and in about twelve thousand years it will have as the Polaris the very conspicuous star Vega, or α in the constellation Lyra. We now proceed to explain the reason of this movement of the earth’s axis. It is well known that the earth is not a perfect sphere, but is flattened at the poles, being what astronomers call an oblate spheroid. Now, the sun’s attraction upon such a spheroidal body is not quite the same as it would be upon a perfect sphere. When the sun is at either equinox—that is, just over the equator—the attraction exercised upon our earth is the same as if that body were spherical; but when the sun is at or near the upper tropic, its action upon the terrestrial matter which bulges at the equator has a tendency to pull that matter towards the ecliptic, and to make the axis of the earth approach to a vertical to the ecliptic. The same influence is at work when the sun is near the lower tropic. And if this influence were not counteracted, the effect would be to cause the ecliptic and equator ultimately to coincide; and our annual succession of seasons would be done away with. But as no such catastrophe is threatening us, and the inclination of the ecliptic to the equator remains about twenty-three and a half degrees, there must be some force which neutralises the above tendency: this is the rotation of the earth on its own axis. No one but a good mathematician could _a priori_ tell the exact effect of these two forces combined. But any one may see how rotation may effect the motion of a body acted on by another force, by observing how a pegtop is kept upright by the rotation, whilst it falls as the rotation ceases. The influence of this rotation to keep a body from falling may be noticed by any one who carefully observes a spinning coin when about to fall. While the coin