5. Let it be supposed that the earth and sea together form a spheroidal body, and preserve one and the same level in all the seas. For though some portions of the earth may be higher, yet this bears so small a relation to the size of the whole mass, as need not be noticed. The spheroid in consequence is not so minutely exact as one might be made by the aid of a turner’s instrument, or as would answer the definition of a geometer, still in general appearance, and looked at roughly, it is a spheroid. Let the earth be supposed to consist of five zones, with (1.) the equatorial circle described round it, (2.) another parallel to this,[709] and defining the frigid zone of the northern hemisphere, and (3.) a circle passing through the poles, and cutting the two preceding circles at right angles. The northern hemisphere contains two quarters of the earth, which are bounded by the equator and the circle passing through the poles. Each of these [quarters] should be supposed to contain a four-sided district, its northern side being composed of one half of the parallel next the pole; its southern, by the half of the equator; and its remaining sides, by [two] segments of the circle drawn through the poles, opposite to each other, and equal in length. In one of these quadrilaterals (which of them is of no consequence) the earth that we inhabit is situated, surrounded by sea, and similar to an island. This, as we said before, is evident both to our senses and to our reason. But should any one doubt thereof, it makes no difference so far as Geography is concerned, whether you suppose the portion of the earth we inhabit to be an island, or only admit what we know from experience, viz. that whether you start from the east or west, you may sail all round it. Certain intermediate spaces may have been left [unexplored], but these are as likely to be occupied by sea, as uninhabited lands. The object of the geographer is to describe known countries; those which are unknown he passes over equally with those beyond the limits of the inhabited earth. It will therefore be sufficient for describing the contour of the island we have been speaking of, if we join by a right line the utmost points which, up to this time, have been explored by voyagers along the coast on either side.