The magnetic principle which gives polarity to the needle, is believed to be regulated by the polar openings, and that the needle always points directly to the opening, and of course parallel to a line drawn perpendicular to the plane of the opening. And when the apparent verge shall be passed, the needle will seem to turn nearly round, so as to point in an opposite direction; having the contrary end north on the interior of the sphere, that was north on the exterior, the same end being north on the interior which was south on the exterior. Hence, when navigators arrive in the neighbourhood of the apparent verge, the variation of the needle becomes extreme; and when the verge is passed, the variation is more or less reversed. The meridians run from the highest northern to the highest southern point on the verges; hence, in tracing a meridian, or sailing due north, we would pursue that line which would conduct us directly from the sun at his greatest altitude; and when we come to the verge, the meridian would vary, and wind along the vicinity of the edge of the real verge, until it brought us to the highest point of the apparent verge. The magnetic needle, on arriving at the verge would appear to cease to pursue the same direction, but would in reality continue to maintain it, and lead directly into the polar opening. According to this formation of the sphere, a traveller or navigator might proceed true north any where west of the highest point of the verge, say on the continent of America, until he come to the verge. The meridian on which he was travelling would then wind along the verge to the right, until he arrived at the ninetieth degree; and by proceeding south, in the same direction, he would arrive at the coast of Siberia, without going far into the concavity of the sphere, and without knowing that he had been within the verge. Should such a journey be effected, it would appear to confirm the old theory of the form of the earth, and put the subject at rest; although pursuing the needle might have directed the traveller into the interior, and enabled him to discover those fine countries which Captain Symmes alleges to exist there. Each of the spheres composing the earth, as well as those constituting the other planets throughout the universe, is believed to be habitable both on the inner and outer surface; and lighted and warmed according to those general laws which communicate light and heat to every part of the universe. The light may not, indeed, be so bright, nor the heat so intense, as is indicated in high northern latitudes (about where the verge is supposed to commence) by the paleness of the sun, and darkness of the sky; facts, which various navigators who have visited those regions confirm; yet they are no doubt sufficiently lighted and warmed to promote the propagation and support of animal and vegetable life.