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Zone, in astronomical geography, is applied to a division of the earth's surface by certain parallels of latitude.

The Zones are 5 in number, viz.

1. The torrid zone, lying between the two tropics. It comprehends the West India Islands, the greater parts of South America and of Africa, the southern parts of Asia, and the East India Islands.

2. The north frigid zone, lying round the north pole, and bounded by the north polar circle. It comprehends part of Greenland, of the northern regions of North America, and a little of the northern parts of Europe and Asia.

3. The south frigid zone, lying round the south pole, and bounded by the south polar circle. It contains no dry land, so far as yet discovered.

4. The north temperate zone, lying between the torrid and north frigid. It comprehends almost the whole of North America, Europe, and Asia, with the northern part of Africa.

5. The south temperate zone, lying between the torrid and south frigid. It comprehends the southern part of South America, of Africa, and of the great island of NewHolland.

In the torrid zone, the sun is vertical twice a year to every part of it, and there is very little diversity in the length of the day throughout the year, the longest day varying only from 12 to about 131 hours.

In the tempe rate zones the sun is never vertical, and the length of the longest day varies from about 131 to 24 hours. In the frigid zones, the length of the longest day (or time between the sun's rising and setting) varies from 24 hours to 6 months.

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Table of the Planets' motions, distances, &c.

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29.3216

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1 2 3 4 5 6 7

1.76914
3.55118
7.15455
16.68902

5.6973
9.0659
14.4616
25.436

0.94271
1.37024
1.88780
2.73948
4.51749
15.9453
79.3296

3.08
13.952
14.893
16.268
18.754
20.295,
59.154

5.8923
8.708
10.966
13.462
38.076
107.694

12.5
16.5
19.
22.
44.
88.

REMARKS. 1. There is a small variation in the inclination of planets' orbits, the longitude of
nodes, the longitude of perihelion, and excentricity of orbits, the amount of which in 100 years is
usually inserted in astronomical tables, and termed secular variations.

2. The diameter of the earth being 1. that of the sun will be 111.45 and that of the moon .2731.
The density of the sun, (water being !.) will be 1.1468, and that of moon, 3.339.

3. The inclination of the sun's axis is about 8°, and the time of his rotation about 25 days 6h.

4. The inclination of the moon's orbit to the ecliptic is about 5° 8', that of her axis about 2o. 18',
and the time of her rotation that of her revolution round the earth.

5. The periodical revolutions in the tables are those termed sidereal, and the distances of the
sateilitcs from their primaries are reckoned in semidiameters of their respective primaries.

6. The orbits of the 1st, 2d, and Sd, satellites of Jupiter are very nearly circular, and coincident
with the orbit of Jupiter : but that of the 4th is very sensibly elliptical, and inclined to the orbit of
Jupiter in an angle of about 1o. 448.

7. The elements of the above Tables are taken chiefly from Laplace and Lalande, the places
being calculated for the beginning of the year 1750.

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CONTENTS.

40

97

Page.

Explanation of the principal Terms relating to As.

tronomy, Chronology, and the astronomical

Parts of Geography, with occasional Illustra.

trations and Remarks,

5

Table of the Motions and Distances of the

Planets,

28

Table of the Satellites,

29

CHAP. I. Of Astronomy in general,

33

II. A brief Description of the SOLAR SYSTEM,

III. The COPERNICAN SYSTEM demonstrated to be

true,

77

IV. The Phenomena of the Heavens as seen from dif-

ferent Parts of the Earth,

89

v The Phenomena of the Heavens as seen from differ-

ent Parts of the Solar Sytem,

VI. The Ptolemean System refuted. The Motions and

Phases of Mercury and Venus explained, 102

VII. The physical Causes of the Motions of the Planets.

The Excentricities of their Orbits. The Times

in which the Action of Gravity would bring

them to the Sun. ARCHIMEDES' ideal Problem

for moving the Earth. The World not eternal, 109

VIII. Of Light. Its proportional Quantities on the dif-

ferent Planets. Its Refractions in Water and

Air. The Atmosphere ; its Weight and Proper.

ties. The horizontal Moon,

118

IX. The Method of finding the Distances of the Sun,

Moon, and Planets,

134

X. The Circles of the Globe described. The different

Lengths of Days and Nights, and the Vicissi.

tudes of Seasons, explained. The Explanation of

the Phenomena of Saturn's Ring, concluded, 142

XI. The Method of finding the Longitude by the

Eclipses of Jupiter's Satellites The amazing

Velocity of Light demonstrated by these Eclip-

ses,

154

XII. Of Solar and Sidereal Time,

162

XIII. Of the Equation of Time,

167

XIV. Of the Precession of the Equinoxes,

183

XV. The Moon's Surface mountainous: Her Phases

described : Her Path, and the Paths of Jupi.

ter's Moons delineated : The Proportions of the

Diameters of their Orbits, and those of Saturn's

Moons to each other, and to the Diameter of

the Sun,

219

XVI. The Phenomena of the Harvest Moon explained by

a common Globe: The Years in which the

Harvest Moons are least and most beneficial,

from 1751 to 1861. The long Duration of Moon-

light at the Poles in Winter,

235

XVII. Of the Ebbing and Flowing of the Sea,

251

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