The idea will naturally suggest itself, what exactly does happen to the inhabitants living outside (on the one side or the other) of the strip of the Earth where the central line of shadow falls? This depends in every case on circumstances, but it may be stated generally that the inhabitants outside the central line but within 1000 to 2000 miles on either side, will see a larger or smaller part of the Sun concealed by the Moon’s solid body, simultaneously with the total concealment of the Sun to the favoured individuals who live, or who for the moment are located, within the limits of the central zone. [Illustration: FIG. 5.—PARTIAL ECLIPSE OF THE SUN.] Now we must advance one stage in our conceptions of the movements of the Earth and the Moon, so far as regards the bearing of those movements on the question of eclipses. The Earth moves in a plane which is called the “Plane of the Ecliptic,” and correspondingly, the Sun has an _apparent_ annual motion in the same plane. The Moon moving in a different plane, inclined to the first mentioned one to the extent of rather more than 5°, the Moon’s orbit will evidently intersect the ecliptic in two places. These places of intersection are called “Nodes,” and the line which may be imagined to join these Nodes is called the “Line of Nodes.” When the Moon is crossing the ecliptic from the S. to the N. side thereof, the Moon is said to be passing through its “Ascending Node” (☊); the converse of this will be the Moon passing back again from the N. side of the ecliptic to the S. side, which is the “Descending Node” (☋). Such changes of position, with the terms designating them, apply not only to the Moon in its movement round the Earth, but to all the planets and comets circulating round the Sun; and also to satellites circulating round certain of the planets, but with these matters we have no concern now. FOOTNOTES: [Footnote 1: D. Lardner, _Handbook of Astronomy_, 3rd ed., p. 288.] [Footnote 2: But not one of them was visible at Greenwich.] [Footnote 3: Latin _Annulus_, a ring.] CHAPTER III. THE “SAROS” AND THE PERIODICITY OF ECLIPSES.