Again, while the Earth is moving from ♑ through ♒, ♓, to ♈, the Pole P begins to incline to the line, distinguishing light and darkness, in the same proportion that before it receded from it; and consequently the diurnal arches gradually lessen, until the Earth has arrived into ♈ where the Pole P will again fall on the horizon, and so cause the days and nights to be every where equal. But when the Earth has passed ♈, while she is going thro’ ♉, and ♊, _&c._ the Pole P will begin to fall in the obscure hemisphere, and so recede gradually from the light, until the Earth is arrived in ♋; in which position not only the Pole, but all the space within the arctic circle, are involved in darkness, and the diurnal arches of all the parallels, without the arctic circle, are equal to the nocturnal arches of the same parallels, when the Earth was in the opposite point ♑; and it is evident that the days are now at the shortest, and the nights the longest. But when the Earth has past this point, while she is going through ♌ and ♏, the Pole P will again gradually approach the light, and so the diurnal arches of the parallels gradually lengthen, until the Earth is arrived in ♎; at which time the days and nights will again be equal in all places of the World, and the Pole itself just see the Sun. [Illustration: Plate 4.] Here we only considered the phænomena belonging to the Northern parallels; but if the Pole P be made the South Pole, then all the parallels of latitude will be parallels of South latitude, and the days, every where, in any position of the Earth, will be equal to the nights of those who lived in the opposite hemisphere, under the same parallels. _Of the Phases of the Moon, and of her Motion in her Orbit._ [Sidenote: _Nodes._] [Sidenote: _Dragon’s Head._] [Sidenote: _Dragon’s Tail._] [Sidenote: _Retrograde Motion of the Nodes._] The orbit of the Moon makes an angle with the plane of the ecliptic, of above 5¼ degrees, and cuts it into two points, diametrically opposite (after the same manner as the equator and the ecliptic cut each other upon the globe, in ♈ and ♎) which points are called the _Nodes_; and a right line joining these points, and passing through the center of the Earth, is called the _Line of the Nodes_. That node where the Moon begins to ascend Northward above the plane of the ecliptic, is called the _Ascending Node_, and the _Head of the Dragon_, and is thus commonly marked [Symbol]. The other node from whence the Moon, descends to the Southward of the ecliptic, is called the _Descending Node_, and the _Dragon’s Tail_, and is thus marked [Symbol]. The line of nodes continually shifts itself from East to West, contrary to the order of the signs; and with this _retrograde_ motion, makes one revolution round the Earth, in the space of about 19 years. [Sidenote: _Periodical Month._] [Sidenote: _Synodical Month._]