divisible by four, as the years 1600, 2000, 2400, &c. otherwise in length of time, the seasons would be quite reversed with regard to the months of the year; though it would have required near 23,783 years to have brought about such a total change. If the earth had exactly made 365 and diurnal revolutions on its axis, whilst it revolved from any equinoxial or solstitial point to the same again, the civil and solar years would always have kept pace together, and the style would never have needed any alteration. Interrogations for Section Eighth. In what time do the stars appear to go round the Earth? In what time does the Sun appear to go round the Earth? In what time do the stars gain one revolution? How many in a sydereal? Is the motion of the earth on its own axis uniform at all times of the year? Are the sydereal days always of the same length? Is the Sun's apparent diameter in the Heavens always equal? On what days of the year are the Sun and clock together? Between what periods will the clock be before the Sun ? Between what periods will the Sun be before the clock? What is called the Sun's apogee? What his perigee ? What the line of the Apsides? What is meant by the Sun's mean anamoly? How is his mean anamoly reckoned? What is meant by the precession of the equinoxes? Is there more matter accumulated at the equator than at any other part of the earth? What is the cause of such accumulation? What is the Equator? What effect is produced by this accumulation of matter? How many seconds of a degree do the equinoxial points recede westward every year? What are meant by the equinoxial points? What the solstitial? Which is the longest, the sydereal or solar year, and how much? How many degrees will the equinoxial points fall back in 2,160 years? Do the same signs always keep in the same points of the ecliptic ? Which is the longest, the Julian or the solar year, and how much? How many days difference will this make in 1.433 years? In what year of the Christian era was the Council of Nice held? What centuries were to be leap years? What is the difference between the old and new styles in the present century? SECTION NINTH. OF THE MOON'S PHASES. By looking at the Moon with an ordinary telescope, we perceive that her surface is diversified with long tracts of prodigious high mountains, and dark cavities. This ruggedness of the Moon's surface is of great use to us, by reflecting the Sun's light to all sides; for if the Moon were smooth and polished, she could never distribute the Sun's light all around. In some positions she would shew us his image no larger than a point, but with such lusture as would be hurtful to our eyes. The Moon's surface being so uneven, many have wondered why her edge does not appear jagged, as well as the curve, bounding the light and the dark places. But if we consider, that what we call the edge of the Moon's disk is not a single line, set round with mountains, in which case it would appear irregularly indented, but a large zone, having many mountains lying behind each other from the observer's eye, we shall find that the mountains in some rows will be opposite to the valves in others, and and so fill up the inequalities, as to make her appear quite round. The Moon being an opaque spherical body, (for her hills take off no more of her roundness, than the inequalities on the surface of an orange take off from its roundness,) we can only see that part of her enlightened half which is towards the earth. Therefore, when she is in conjunction with the Sun, her dark half is towards the earth, and she disappears; there being no light on that part to render it visible. When she comes to her first octant, or has gone over one eighth part of her orbit from her conjunction, a quarter of her enlightened side is seen towards the earth, and she appears horned. When she has gone a quarter of her orbit from between the earth and Sun; she shows us one half of her enlightened side, and then she is said to be a quarter old. When she has gone another octant, she shows us more of her enlightened side, and then she appears gibbous; and when she has gone over half her orbit, her whole enlightened side is towards the earth, and therefore she appears round: we then say it is full Moon, or the Moon is in opposition with the Sun. In her third octant, part of her dark side being towards the earth, she again appears gibbous, and is on the decrease. In her third quarter, she appears half decreased. When in her fourth octant, she again ap |