The Planetary and Stellar Worlds

vatories at Washington, Cambridge, Philadelphia, and Georgetown, are amply provided with instruments, and an efficient corps of observers are constantly occupied in their use.

For a long time to come, one principal object will engage the instruments of the Cincinnati observatory, viz., the exploration of the heavens south of the equator, and the re-measurement of Sturve's double stars in that region. Should this work progress but slowly, let it be remembered that the director of the observatory has no assistant, out of his own immediate family, and must devote a large portion of his time to other duties, far more closely allied to the earth than the stars.

CINCINNATI OBSERVATORY,

Mount Adams, May, 1848.

CONTENTS.

CHAPTER I.-AN EXPOSITION OF THE PROBLEM WHICH THE

HEAVENS PRESENT FOR SOLUTION.

First revolution of the Heavens witnessed by man, 18. The

curiosity excited and its effects, 19. Object of the course, 20.

The astronomer lives in all ages, 21. First problem to dis-

tinguish between real and apparent motion, 23. The relations

of the sun, and earth, and moon, 24. The wandering stars or

planets, 25. Fixed stars, points of reference, 27. Com-

plexity of the planetary movements, 29. Discovery of the

true centre of Motion, 30. The planets form a system;

their orbits, laws, stability, 31. Perturbations, 32. Analytic

machinery, 32. Examination of the starry heavens, 33.

Distance of the fixed stars to be determined, ib. Motions

among the stars, 34. The binary systems; movement of the

sun in space, 35. Investigations yet to be made, and pro-

bable success, 37.

CHAPTER II.-DISCOVERIES OF THE PRIMITIVE AGES.

The founder of the science of astronomy unknown, 40.

First discovery of the moon, 41. Her motion among the

stars and her phases, 42. Cause of the phases sought; two

revolutions of the moon discovered, 43. First ideas of the

constellations; North Star, 44. Motions of the sun and moon

among the stars; the starry heavens surround the earth, 45.

First measure of the year, 47. A moving star discovered, ib.

Periods of the planets determined, 48. The sun's apparent

motion the subject of perplexity, 49. The equinoxes and

solstices, 52. Inequality in the sun's rays detected, 53. The

construction of the sphere, 54. Its uses in observing, 55.

Eclipses of the sun and moon, and their effects, 56. Explana-

tion of solar eclipses; discovery of the moon's reflective light;

and explanation of her phases, 63. Lunar eclipses explained;

prediction of the first eclipse, 62. Value of recorded eclipses,

64.

CHAPTER III.-MOTIONS OF THE HEAVENLY BODIES.

The names of early discoverers lost, 65. Chaldean period

found among many nations; the days of the week, and their

names, place of the vernal equinox, 66. Precession of the

equinoxes, 67. Astronomy of the primitive ages, and con-

dition of the mind at the beginning of the era reached by

history, 69. Causes retarding the progress of astronomy, 71.

The confounding of true and apparent motion; immobility of

the earth and its central position, 73. The Greek astrono-

mers, Pythagoras, Nicetas, Hipparchus, Ptolemy, 74. System

of Ptolemy, 76. Astronomy cultivated by the Arabs, 77.

The era of modern science commences, 78. Copernicus and

his discoveries, 79. His system promulged with great caution,

80. Kepler, the character of his mind, his mode of research,

84. His great discoveries, ib. Their great importance, 93.

CHAPTER IV.-LAWS OF MOTION AND GRAVITATION.

The philosophy of Aristotle-its hold on the mind, 94,

Characteristics of Galileo's mind, 95. He detects the errors

of Aristotle, ib. Attacks his theories, and demonstrates

their falsehood by experiment, 96. Driven from Pisa by his

enemies, 97. Discovers the law of falling bodies, 98.

Adopts the Copernican theory, 99. Constructs a telescope,

100. His discoverias in the moon, and among the planets

and fixed stars, 101. Phases of Venus, 102. Questions

relating to the planetary motions, 104. Laws of motion; the

centrifugal force, 106. Problem presented for solution to

Newton, 107. Discoveries of Descartes; conjectures of Kep-

ler, 109. Measure of the moon's distance and of the earth's

circumference, 110. The law of gravitation-Newton's first

effort to demonstrate the truth of this law, 112. He finally

shows that the moon is ever falling towards the earth, and

proves the law, 114. Enunciation of his great law, 116. Dis-

covers that the planets may revolve in conic sections, 117.-

CHAPTER V.-

-UNIVERSAL GRAVITATION APPLIED TO THE

SOLAR SYSTEM.

The era of physical astronomy commences, 121. A theore-
tic system proposed and discussed; a central sun and solitary
planet, 122. Planets and satellites added and their effects
considered, 124. How the imagined system may be made the
system of nature, 125. Discussion of the relative motions of
the sun, moon, and earth, under the action of their mutual
influences, 127. The moon's acceleration; motion of her
apsides, nodes, &c., and the discovery of the change in the
figure of the earth's orbit, 129. Perplexity occasioned by the

seeming discrepancy between the observed and computed

motion of the moon's perigee, 135. Finally removed by

Clairault, 138. Changes in the earth's figure occasioned by

its rotation, 141. The form of equilibrium reached, 142.

The precession of the equinoxes caused by the protuberant
matter at the earth's equator, 144. Moon affected by the
redundant matter at the earth's equator, 148. Wonderful
questions answered by an examination of the moon, 149.

CHAPTER VI.-STABILITY OF THE PLANETARY SYSTEM.

Rapid survey of the system, 141. General characteristics

of the planets, 152. What phenomena gravitation must

account for, 154. Stability not the sole object of the Creator,

155. Laws of matter selected in wisdom, 157. By how much

does the central force diminish the primitive velocity of a

planet? 157. Changes in the elements of the orbits of the

planets, 159. The eccentricity, 160. Stability of the princi-

pal axes, 161. Motion of the perihelion, ib. The inclina-

tions, 162. The lines of nodes, ib. The periodic times,

163. Stability of the great system, 163. Of the system of

the earth and moon, 166. Of Jupiter's system, 169. Of