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A TABLE of the Equation of Time, shewing

how much a Clock should be faster or slower
than the Sun, every Day of the Year, at Noon.

The Third Year after Leap-Year.
Jan. Feb. March. April. | May. | June.
M. S. | M. S. 1 M. S. M. S. M. S. M. S.
814 4/12 381 3

55/ 3 8/ 2 38 21 4 3614 111225 336 3 15 229 3 53 414 1717 12 37 18 37 22 219 4 5332114 # 23111 *59j 3500 3 * 28 2 5 5914

28/11 451 2 43] 3 34 1 59 6 25/14 32/11 31] 2

25/ 3 391 1 48 651 14 35 11 171 2 8 343 1037 8 17 14 37 11 2. 511 3 47) 1 326 9 777 42 143 39 10 46 i 34 351115 10 8 6114 4010 301 1 17 3 541 1 3 118

40110
14 I

11 3 56) o 51 391 9 58) O

451 3

58 0 1319

37 9
41| O

29; 3 59! O 27
38/14
351 9 24 O 13 4

00 O 15 15 9

59/14 31 9 7) C* 24 001 o 2
2014 27! 8

49
17! 3

591 0 * 10 39/14 23 8

32 3

58 0 23 58/14 17 8 141 461 3 56 036 16 14 1117 561 700 3 541 OF 49 34/14 51 7 37 1 131 3 52 1 2 51/13 57 7

19 1 261 3 49 1 14 7/13

49 7 00 1238 3 45 127 23/12 22/13 411 6

42 1501 3 40 140 36/13

32 6 23 2 2 3 351 153 25.12

221 6 41 2 13 3 301 2 6 26/13 3:13

125 461 2 23 3 24) 2 27/13

15 27 2 33 3 171 2 31 28/13 26/12

50 5 8 2 43] 3 101 2 43 29 13 37

4 501 2 52 3 3 2 56 30/13 471

4 31 3 001 2 55 3 8 31113 56

4 13

2 47

30/14 53/14 16/14

39

1419

32

16/10 1710 18/10 19/11 20/11

O O O

Cloc

21/11 22/12

44/12

50/13

18

15/13

Days.

A TABLE of the Equation of Time, shewing

how much a Clock should be faster or slower
than the Sun, every Day of the Year, at Noon.

The third Year atier Leap-Year.
July. | Aug. Sept. Oct. Nov. Dec.

M. S. M. S. M. S. M. S.M. S. M. S. 1 3 2015 541 0 * 15 10 23/16 1310 33 2 3 311 5 500 34 10 42 16 14110

10 31 3 425 346 0 5311

00/16 141 97 46 5741 1211 1816 13 9-22 4 5 35 1 3211 36 16 11 8 57

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A concise EQUATION-TABLE, adapted to the Second Year af

ter Leap-Year, and which will be within a Minute of the Truth for every Year; shewing, to the nearest full Minute, how much a Clock should be faster or slower than the Sun. By Mr. SMEATON.

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This table is near enough the truth for regulating common clocks and watches. It may be easily copied by the pen, and, being doubled, may be put into a pocket-book.

CHAP. XV.

The Moon's Surface mountainous : Her Phases de.

scribed: Her Path, and the Paths of Jupiter's Moons delineated: The Proportions of the Diameters of their Orbits, and those of Saturn's Moons, to each other; and the Diameter of the Sun.

B

VII.

surface

252.

Y looking at the Moon through an ordinary PLATE

telescope, we perceive that her surface is diversified with long tracts of prodigious high moun- The tains and deep cavities. Some of her mountains, by Moon's comparing their height with her diameter (which is

mountain. 2180 miles,) are found to be three times as high as ous. the highest mountains on our Earth. 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 like a looking-glass, or covered with water, she could never distribute the Sun's light all round: only, in some positions, she would shew us his image, no bigger than a point, but with such a lustre as might be hurtful to our eyes.

253. The Moon's surface being so uneven, many have wondered why her edge appears not jagged as well as the curve bounding the light and dark parts. But if we consider, that what we call the edge of the Why no Moon's disc is not a single line set round with moun. tains, in which case it would appear irregularly in- her edge. dented, but a large zone, having many mountains lying behind one another from the observer's eye, we shall find that the mountains in some rows will be opposite to the vales in others, and fill up the inequalities, so as to make her appear quite round; just as when one looks at an orange, although its roughness be very discernible on the side next the eye, especially if the Sun or a candle shines obliquely on that side, yet the line terminating the vie sible part still appears smooth and evep.

hills apo

pear on

PLATE
VII.

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254. As the Sun can only enlighten that half

of the Earth which is at any moment turned toward him, The Moon and being withdrawn from the opposite half, leaves it

in darkness; so he likewise doth to the Moon; only twilight.

with this difference, that the Earth being surrounded
by an atmosphere, and the Moon, as far as we know,
having none, we have twilight after the Sun sets;
but the Lunar inhabitants have an immediate transi-
tion from the brightest sunshine to the blackest dark-
ness, $ 177. For, let trk sw be the Earth, and A,

B, C, D, E, F, G, H, the Moon, in eight different
Fig. I. parts of her orbit. As the Earth turns round its

axis, from west to east, when any place comes to
t, the twilight begins there, and when it revolves
from thence to r, the Sun S rises; when the place
comes to s, the Sun sets, and when it comes to w,
the twilight ends. But as the Moon turns round
her axis, which is only once a month, the moment
that any point of her surface comes to r (see the
Moon at G) the Sun rises there without any pre-
vious warning by twilight; and when the same point
comes to s the Sun sets, and that point goes into

darkness as black as at midnight.
The 255. The Moon being an opaque spherical body
Moon's
phases. (for her hills take off no more from her roundness

than the inequalities on the surface of an orange take
off from its roundness), we can only see that part of
the enlightened half of her which is toward the Earth.
And therefore when the Moon is at A, in conjunction
with the Sun S, her dark half is toward the Earth,
and she disappears, as at a; there being no light on
that half to render it visible. When she comes to
her first octant at B, or has gone an eighth part of
her orbit from her conjunction, a quarter of her en-
lightened side is seen toward the Earth, and she ap-
pears horned, as at h. When she has gone a quarter
of her orbit from between the Earth and Sun to C,
she shows us one half of her enlightened side, as at
c; and we say, she is a quarter old. At D she is in
her second octant, and by shewing us more of her

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