♈♋♎♑ is the Moon’s Orbit, in which she goes round the Earth, according to the order of the letters _abcd_, _ABCD_. When the Moon is at _a_ she is in her Third Quarter to the Earth at _e_, and just rising to the north Pole _n_; at _b_ she changes, and is at the greatest height above the Horizon, as the Sun likewise is; at _c_ she is in her First Quarter, setting below the Horizon; and is lowest of all under it at _d_, when opposite to the Sun, and her enlightened side toward the Earth. But then she is full in view to the south Pole _p_; which is as much turned from the Sun as the north Pole inclines towards him. Thus in our Summer, the Moon is above the Horizon of the north Pole whilst she describes the northern half of the Ecliptic ♈♋♎, or from her Third Quarter to her First; and below the Horizon during the progress through the southern half ♎♑♈; highest at the Change, most depressed at the Full. But in winter, when the Earth is at _E_, and it’s north Pole declines from the Sun, the New Moon at _D_ is at her greatest depression below the Horizon _NWS_, and the Full Moon at _B_ at her greatest height above it; rising at her First Quarter _A_, and keeping above the Horizon till she comes to her Third Quarter _C_. At a mean state she is 23-1/2 degrees above the Horizon at _B_ and _b_, and as much below it at _D_ and _d_, equal to the inclination of the Earth’s Axis _F_. _S_♋ and _S_♑ are, as it were, a ray of light proceeding from the Sun to the Earth; and shews that when the Earth is at _e_, the Sun is above the Horizon, vertical to the Tropic of Cancer; and when the Earth is at _E_, he is below the Horizon, vertical to the Tropic of Capricorn. [Illustration: Plate VIII. _J. Ferguson delin._ _J. Mynde Sculp._] [Illustration: Plate IX. _J. Ferguson delin._ _J. Mynde Sculp._] CHAP. XVII. _Of the ebbing and flowing of the Sea._ [Sidenote: The cause of the Tides discovered by KEPLER. PLATE IX. Their Theory improved by Sir ISAAC NEWTON.]