[Page 273] Light of Unseen Stars.—From careful examination, it appears that three-fourths of the light on a fine starlight night comes from stars that cannot be discerned by the naked eye. The whole amount of star light is about one-eightieth of that of the full moon.

Lateral Movements of Stars, page 226-28.

Future Discoveries—A Trans-Neptunian Planet.—Professor Asaph Hall says: "It is known to me that at least two American astronomers, armed with powerful telescopes, have been searching quite recently for a trans-Neptunian planet. These searches have been caused by the fact that Professor Newcomb's tables of Uranus and Neptune already begin to differ from observation. But are we to infer from these errors of the planetary tables the existence of a trans-Neptunian planet? It is possible that such a planet may exist, but the probability is, I think, that the differences are caused by errors in the theories of these planets. * * * A few years ago the remark was frequently made that the labors of astronomers on the solar system were finished, and that henceforth they could turn their whole attention to sidereal astronomy. But to-day we have the lunar theory in a very discouraging condition, and the theories of Mercury, Jupiter, Saturn, Uranus, and Neptune all in need of revision; unless, indeed, Leverrier's theories of the last two planets shall stand the test of observation. But, after all, such a condition of things is only the natural result of long and accurate series of observations, which make evident the small inequalities in the motions, and bring to light the errors of theory."

Future discoveries will mostly reveal the laws and conditions of the higher and finer forces. Already Professor Loomis telegraphs twenty miles without wire, by the electric currents between mountains. We begin to use electricity for light, and feel after it for a motor. Comets and Auroras show its presence between worlds, and in the interstellar spaces. Let another Newton arise.

[Page 274] SOME ELEMENTS OF THE SOLAR SYSTEM Mean Dist. from Sun. - Mean Density. Earth's Diameter [Earth] Name. Sign. Masses. Dist. Millions in Miles. = 1. as 1. of Miles. - - Sun [Symbol] Unity 860,000 0.255 Mercury [Symbol] 1/5000000(?) 0.387 35-3/4 2,992 1.21 Venus [Symbol] 1/425000 0.723 66-3/4 7,660 0.85 Earth [Symbol] 1/326800 1. 92-1/3 7,918 1. Mars [Symbol] 1/2950000 1.523 141 4,211 0.737 Asteroids (No.) Jupiter [Symbol] 1/1047 5.203 480 86,000 0.243 Saturn [Symbol] 1/3501 9.538 881 70,500 0.133 Uranus [Symbol] 1/22600 19.183 1771 31,700 0.226 Neptune [Symbol] 1/19380 30.054 2775 34,500 0.204

- Gravity Axial at Orbital Revolu- Surface. Periodic Velocity Name. tion [Earth] Time. in Miles = 1 per sec. - - - Sun 25 to 26d 27.71 Mercury 24h 5m(?) 0.46 87.97d 29.55 Venus 23h 21m(?) 0.82 224.70d 21.61 Earth 23h 56m 4s 1. 365.26d 18.38 Mars 24h 37m 22.7s 0.39 686.98d 14.99 Asteroids Jupiter 9h 55m 20s 2.64 11.86yrs 8.06 Saturn 10h 14m 1.18 29.46yrs 5.95 Uranus Unknown. 0.90 84.02yrs 4.20 Neptune Unknown. 0.89 164.78yrs 3.36 -

[Page 275] EXPLANATION OF ASTRONOMICAL SYMBOLS.

SIGNS OF THE ZODIAC

0. [Symbol] Aries 0 deg. VI. [Symbol] Libra 180 deg. I. [Symbol] Taurus 30 VII. [Symbol] Scorpio 210 II. [Symbol] Gemini 60 VIII. [Symbol] Sagittarius 240 III. [Symbol] Cancer 90 IX. [Symbol] Capricornus 270 IV. [Symbol] Leo 120 X. [Symbol] Aquarius 300 V. [Symbol] Virgo 150 XI. [Symbol] Pisces 330

* * * * *

[Symbol] Conjunction. S. Seconds of Time. [Symbol] Quadrature. deg. Degrees. [Symbol] Opposition. ' Minutes of Arc. [Symbol] Ascending Node. " Seconds of Arc. [Symbol] Descending Node. R. A. Right Ascension. H. Hours. Decl. or D. Declination. M. Minutes of Time. N. P. D. Dist. From North Pole.

OTHER ABBREVIATIONS USED IN THE ALMANAC.

S., South, i.e., crosses the meridian; M., morning; A, Afternoon; Gr. H. L. N., greatest heliocentric latitude north, i.e., greatest distance north of the ecliptic, as seen from the sun. [Symbols] Inf., inferior conjunction; Sup., superior conjunction.

GREEK ALPHABET USED INDICATING THE STARS.

a, alpha. ae, eta. n, nu. t, tau. b, beta. th, theta. x, xi. u, upsilon. g, gamma. i, iota. o, omicron. ph, phi. d, delta. k, kappa. p, pi. ch, chi. e, epsilon. l, lambda. r, rho. ps, psi. z, zeta. m, mu. s, sigma. o, omega.



[Page 276] CHAUTAUQUA OUTLINE FOR STUDENTS.

As an aid to comprehension, every student should draw illustrative figures of the various circles, planes, and situations described. (For example, see Fig. 45, page 112.) As an aid to memory, the portion of this outline referring to each chapter should be examined at the close of the reading, and this mere sketch filled up to a perfect picture from recollection.

I. Creative Processes.—The dial-plate of the sky. Cause or different weights—on sun, moon. Two laws of gravity. Inertia. Fall of earth to sun per second. Forward motion. Elastic attraction. Perturbation of moon; of Jupiter and Saturn. Oscillations of planets.

II. Light.—From condensation. Number of vibrations of red; violet. Thermometer against air. Aerolite against earth. Two bolides against the sun. Large eye. Velocity of light. Prism. Color means different vibrations. Music of light. Light reports substance of stars. Force of; bridge, rain, dispersion, intensities, reflection, refraction, decomposition.

III. Astronomical Instruments.—Refracting telescope. Reflecting; largest. Spectroscope. Spectra of sun, hydrogen, sodium, etc. E made G by approach; C by departure. Stars approach and recede.

IV. Celestial Measurements.-Place and time by stars. Degrees, minutes, seconds. Mapping stars. Mural circle. Slow watch. Hoosac Tunnel. Fine measurements. Sidereal time. Spider-lines. Personal equation. Measure distance—height. Ten-inch base line. Parallax of sun, stars. Longitude at sea. Distance of Polaris, a Centauri, 61 Cygni. Orbits of asteroids.

V. The Sun.—World on fire. Apparent size from planets. Zodiacal light. Corona. Hydrogen—how high? Size. How many earths? Spots: 1. Motion; 2. Edges; 3. Variable; 4. Periodic; 5. Cyclonic; 6. Size; 7. Velocities. What the sun does. Experiments.

VI. The Planets from Space.—North Pole. Speed. Sizes. Axial revolution. Man's weight on. Seasons. Parallelism of axis. Earth near [Page 277] sun in winter. Plane of ecliptic. Orbits inclined to. Earth rotates. Proof. Sun's path among stars. Position of planets. Motion—direct, retrograde. Experiments.

VII. Meteors.—Size; number; cause of; above earth; velocity; colors; number in space; telescopic view of. Aerolites: Systems of; how many known. Comets: Orbits; number of comets; Halley's; Biela's lost; Encke's. Resisting medium. Whence come comets? Composed of what? Amount of matter in. [Symbol].

VIII. The Planets.—How many? Uranus discovered? Neptune? Asteroids? Vulcan? Distance from sun. Periodic time. Mercury: Elements; shapes, as seen from earth; transits. Venus: Elements; seen by day; how near earth? how far from? phases; Galileo. Earth: Elements; in space; Aurora; balance of forces. Tides: Main and subsidiary causes; eastern shores; Mediterranean Sea. Moon: Elements; hoax; moves east; see one side; three causes help to see more than half. Revolution: Why twenty-nine and a half days: heat—cold; how much light? Craters and peaks lighted; measured. Eclipses—Why not every new and full moon? Periodicity. Mars: Elements; how near earth? How far from? Apparent size; ice-fields; which end most? Satellites—Asteroids: How found? When? By whom? How many? Jupiter: Elements; trade-winds; how much light received? Own heat. Satellites: How many? Colors. Saturn: Elements; habitability; rings; flux; satellites. Uranus: Elements; discoverer; seen by; moon's motion. Neptune: Elements; discovered by; how? Review system.

IX. The Nebular Hypothesis.—State it; facts confirmatory. Objections—1. Heat; 2. Rotation; 3. Retrograde; 4. Martial moons; 5. Star of 1876. Evolution: Gaps in; conclusion.

X. The Stellar System.-Motto. Man among stars; open page; starry poem; stars located; named. Thuban. Etanin. Constellations: Know them; number of stars; double; e Lyrae, Sirius, Procyon, Castor, 61 Cygni, g Virginis. Colored stars; change color. Clusters: Two theories. Nebulae: Two visible; composed of; shapes; where? Variable stars. Sun. b Lyrae, Mira, Betelguese, Algol; cause. Temporary; 1572. New star of 1866: Two theories. Star of 1876. Movements of stars; Sirius; sun; 1830 Groombridge. Stars near Pleiades: Orion, Great Dipper, Southern Cross. Centre of gravity.

XI. The Worlds and the Word.—Rich. Number. Erroneous allusions. Truth before discovery: 1. A beginning; 2. Creation before arrangement; 3. Light before sun; 4. Mountains under water; 5. Order of development; [Page 278] 6. Sphere of earth; 7. How upheld; 8. Number of stars; 9. Weight of air; 10. Meteorology; 11. Queries to Job; 12. Sun to end of heaven; 13. View of Mitchell; 14. Herschel. What is matter? Force? End of earth. Way to knowledge. Work of light. Transfiguration of matter. Uniformitarianism. A whisper of Him. Man for mastery. Each a type of higher. Survival of fittest. Uranus. Worlds and Word one language.

XII. The Ultimate Force.—Universe shows power: 1. Rain; Niagara; 2. Vegetable growth; 3. Worlds carried; 4. Sun; fill dome with worlds; 5. Double suns; 6. Galaxies. Correlation. What ultimate? Mind and will. What continuous relation? Watch. Theories of gravitation: Newton's, Le Sage's, Bible's. High-class energy deteriorates. Search for atoms: 1. Microscope; 2. Gold; 3. Infusoria; 4. Musk. Properties of atoms: 1. Impenetrable; 2. Indivisible; 3. Shape; 4. Quality; 5. Crystallization; 6. Not touch each other; 7. Active; 8. Attractive; 9. Intelligent. Whose? Relation of matter to God; rock to soil. Push upward. Highest has mastery. Man advances by highest. Matter recapacitated. Refined habitations. Inhabitants. All force leads back to mind. Personal and infinite.



[Page 279] GLOSSARY OF ASTRONOMICAL TERMS AND INDEX.

ABBREVIATIONS used in astronomies, 275. ABERRATION OF LIGHT (a wandering away), an apparent displacement of a star, owing to the progressive motion of light combined with that of the earth and its orbit, 199. AEROLITE (air-stone), 122. AIR, refraction of the, 40. ALGOL, the variable star, 222. ALMANAC, Nautical, 71; explanation of signs used, 275. ALPHABET, Greek, 275. ALTITUDE, angular elevation of a body above the horizon. ANGLE, difference in directions of two straight lines that meet. ANNULAR (ring-shaped) ECLIPSES, 158; nebulae, 218, 220. APHELION, the point in an orbit farthest from the sun. APOGEE, the point of an orbit which is farthest from the earth. APSIS, plural apsides, the line joining the aphelion and perihelion points; or the major axis of elliptical orbits. ARC, a part of a circle. ASCENSION, RIGHT, the angular distance of a heavenly body from the first point of Aries, measured on the equator. ASTEROIDS (star-like), 162; orbits of interlaced, 74. ASTRONOMICAL INSTRUMENTS, 43. ASTRONOMY, use of, 57. ATOM, size of, 255; power of, 256. AURORA BOREALIS, 143. AXIS, the line about which a body rotates. AZIMUTH, the angular distance of any point or body in the horizon from the north or south points. BAILEY'S BEADS, dots of light on the edge of the moon seen in a solar eclipse, caused by the moon's inequalities of surface. BASE LINE, 68. BIELA'S COMET, 129. BINARY SYSTEM, a double star, the component parts of which revolve around their centre of gravity. BODE'S LAW of planetary distances is no law at all, but a study of coincidences. BOLIDES, small masses of matter in space. They are usually called meteors when luminous by contact with air, 120. [Page 280] CELESTIAL SPHERE, the apparent dome in which the heavenly bodies seem to be set; appears to revolve, 3. CENTRE OF GRAVITY, the point on which a body, or two or more related bodies, balances. CENTRIFUGAL FORCE (centre fleeing). CHROMOLITHIC PLATE of spectra of metals, to face 50. CIRCUMPOLAR STARS, map of north, 201. COLORS OF STARS, 214. COLURES, the four principal meridians of the celestial sphere passing from the pole, one through each equinox, and one through each solstice. COMETS, 126; Halley's, 128; Biela's lost, 129; Encke's, 130; constitution of, 131; will they strike the earth? 133. CONJUNCTION. Two or more bodies are in conjunction when they are in a straight line (disregarding inclination of orbit) with the sun. Planets nearer the sun than the earth are in inferior conjunction when they are between the earth and the sun; superior conjunction when they are beyond the sun. CONSTELLATION, a group of stars supposed to represent some figure: circumpolar, 201; equatorial, for December, 202; for January, 203; April, 204; June, 205; September, 206; November, 207; southern circumpolar, 208. CULMINATION, the passage of a heavenly body across the meridian or south point of a place; it is the highest point reached in its path. CUSP, the extremities of the crescent form of the moon or an interior planet. DECLINATION, the angular distance of a celestial body north or south from the celestial equator. DEGREE, the 1/360 part of a circle. DIRECT MOTION, a motion from west to east among stars. DISK, the visible surface of sun, moon, or planets. DISTANCE OF STARS, 70. DOUBLE STARS, 210. EARTH, revolution of, 109; in space, 142; irregular figure, 145. ECCENTRICITY OF AN ELLIPSE, the distance of either focus from centre divided by half the major axis. ECLIPSE (a disappearance), 157. ECLIPTIC, the apparent annual path of the sun among the stars; plane of, 106. EGRESS, the passing of one body off the disk of another. ELEMENTS, the quantities which determine the motion of a planet: data for predicting astronomical phenomena; table of solar, 274. ELEMENTS, chemical, present in the sun, 270. ELONGATION, the angular distance of a planet from the sun. EMERSION, the reappearance of a body after it has been eclipsed or occulted by another. [Page 281] EQUATOR, terrestrial, the great circle half-way between the poles of the earth. When the plane of this is extended to the heavens, the line of contact is called the celestial equator. EQUINOX, either of the points in which the sun, in its apparent annual course among the stars, crosses the equator, making days and nights of equal length. EVOLUTION, materialistic, 182; insufficient, 189. FIZEAU determines the velocity of light, 23. FORCES, delicate balance of, 144. GALILEO, construction of his telescope, 43. GEOCENTRIC, a position of a heavenly body as seen or measured from the earth's centre. GEODESY, the art of measuring the earth without reference to the heavenly bodies. GOD, relation of, to the universe, 258. GRAVITATION, laws of, 6; extends to the stars, 13; theories of, 253. GRAVITY on different bodies, 6, 274. HELICAL, rising or setting of a star, as near to sunrise or sunset as it can be seen. HELIOCENTRIC, as seen from the centre of the sun. HOOSAC TUNNEL, example of accuracy, 62. HORIZONTAL PENDULUM, 272. IMMERSION, the disappearance of one body behind another, or in its shadow. INCLINATION OF AN ORBIT, the angle between its plane and the plane of the ecliptic. INFERIOR CONJUNCTION, when an interior planet is between the earth and the sun. JUPITER, apparent path of, in 1866, 112; elements of, 164; satellites of, 165; positions of satellites, 166; elements of satellites, 166; the Jovian system, 167. KEPLER'S LAWS—1st, that the orbits of planets are ellipses, having the sun or central body in one of the foci; 2d, the radius-vector passes over equal spaces in equal times; 3d, the squares of the periodic times of the planets are in proportion to the cubes of their mean distances from the sun. LATITUDE, the angular distance of a heavenly body from the ecliptic. LIGHT, the child of force, 17; number of vibrations of, 18, 25; velocity of, 22; undulatory and musical, 26; chemical force of, 30; experiments with, 37; approach and departure of a light-giving body measured, 51; aberration of, 199. LIMB, the edge of the disk of the moon, sun, or a planet. LONGITUDE. If a perpendicular be dropped from a body to the ecliptic, its celestial longitude is the distance of the foot of the perpendicular from the vertical equinox, counted toward the east; mode of ascertaining terrestrial, 72. MAGELLANIC CLOUDS, 208. [Page 282] MARS, 159; snow spots of, 160; satellites of, 161. MASS, the quantity of matter a body contains. MEAN DISTANCE OF A PLANET, half the sum of the aphelion and perihelion distances. MEASUREMENTS, celestial, 57. MERCURY, 138. MERIDIAN, terrestrial, of a place, a great circle of the heavens passing through the poles, the zenith, and the north and south points of the horizon; celestial, any great circle passing from one pole to the other. METEORS, 119; swarm of, meeting the earth, 118; explosion of, 120; systems of, 123; relation of, to comets, 124. MICROMETER, any instrument for the accurate measurement of very small distances or angles. MIND, origin of force, 252; continuous relation of, to the universe, 252. MILKY WAY, 210, 215. MIRA, the Wonderful, 221. MOON, the, 151; greatest and least distance from the earth, 10; telescopic appearance of, 155. MURAL CIRCLE, 61. NADIR, the point in the celestial sphere directly beneath our feet, opposite to zenith. NEBULAE, 217. NEBULAR HYPOTHESIS, not atheistic, 182; stated, 182; confirmatory facts, 183; objections to, 185. NEPTUNE, elements of, 175. NODE, the point in which an orbit intersects the ecliptic, or other plane of reference; ascending, descending, line of, 107. OCCULTATION, the hiding of a star, planet, or satellite by the interposition of a nearer body of greater angular magnitude. OPPOSITION. A superior planet is in opposition when the sun, earth, and the planet are in a line, the earth being in the middle. ORBIT, the path of a planet, comet, or meteor around the sun, or of a satellite around a primary; inclination of, 106; earth's, seen from the stars, 70. OUTLINE FOR STUDENTS, 276. PARALLAX, the difference of direction of a heavenly body as seen from two points, as the centre of the earth and some point of its surface, 69. PARALLELS, imaginary circles on the earth or in the heavens parallel to the equator, having the poles for their centre. PERIGEE, nearest the earth; said of a point in an orbit. PERIHELION, the point of an orbit nearest the sun. PERIODIC TIME, time of a planet's, comet's, or satellite's revolution. PERSONAL EQUATION, 65. PERTURBATION, the effect of the attractions of the planets or other [Page 283] bodies upon each other, disturbing their regular motion; of Saturn and Jupiter, 11; of asteroids, 13; of Uranus and Neptune, 176. PHASES, the portions of the illuminated half of the moon or interior planet, as seen from the earth, called crescent, full, and gibbous. PHOTOSPHERE of the sun, 89. PLANET (a wanderer), as seen from space, 99; speed of, 101; size of, 102; movements retrograde and direct, 112. POINTERS, the, 197. POLE, NORTH, movement of, 198. POLES, the extremities of an imaginary line on which a celestial body rotates. QUADRANT, the fourth part of the circumference of a circle, or 90 deg.. QUADRATURE, a position of the moon or other body when 90 deg. from the sun. RADIANT POINT, that point of the heavens from which meteors seem to diverge, 118. RADIUS-VECTOR, an imaginary line joining the sun and a planet or comet in any part of its orbit. RAIN, weight of, 249. REFLECTING TELESCOPE, 44. REFRACTING TELESCOPE, 43. REFRACTION, a bending of light by passing through any medium, as air, water, prism. RETROGRADE MOTION, the apparent movement of a planet from east to west among the stars. REVOLUTION, the movement of bodies about their centre of gravity. ROTATION, the motion of a body around its axis. SATELLITES, smaller bodies revolving around planets and stars. SATURN, elements of, 167; revolution of, 168; rings of, 169; decreasing, 171; nature of, 171; satellites of, 172. SEASONS, of the earth, 102; of other planets, 105. SELENOGRAPHY (lunography), a description of the moon's surface. SIGNS OF THE ZODIAC, the twelve equal parts, of 30 deg. each, into which the zodiac is divided. SOLAR SYSTEM, view of, 100, 177. SOLSTICES, those points of the ecliptic which are most distant from the equator. The sun passes one about June 21st, and the other about December 21st, giving the longest days and nights. SPECTROSCOPE, 46. SPECTRUM OF SUN AND METALS, 50. STARS, chemistry of, 28; distance of, 70-73; mode of naming, 196; number of, 210; double and multiple, 210; colored, 214; clusters of, 215; variable, 220; temporary, new, and lost, 223; movements of lateral, 226; in line of sight, 269. STATIONARY POINTS, places in a planet's orbit at which it has no motion among the stars. [Page 284] STELLAR SYSTEM, the, 195. SUMMARY OF RECENT DISCOVERIES, 269. SUN, fall of two meteoric bodies into, 19; light from contraction of, 20; as seen from planets, 79; corona, 81; hydrogen flames of, 84; condition of, 89; spots, 90; experiments, 95; apparent path among the stars, 111; power of, 250. SYMBOLS USED IN ASTRONOMY, 275. TELESCOPE, refracting, 43; reflecting, 44; Cambridge equatorial, 46. TELESCOPIC WORK, clusters, 210; double stars, 212. TEMPORARY STARS, 223. TERMINATOR, the boundary-line between light and darkness on the moon or a planet. TIDES, 146. TRANSIT, the passage of an object across some fixed line, as the meridian, or between the eye of an observer and an apparently larger object, as that of Mercury or Venus over the disk of the sun, and the satellites of Jupiter over its disk; of a star, 65. ULTIMATE FORCE, the, 249. URANUS, elements of, 173; moons of, retrograde, 174; perturbed by Neptune, 176. VARIABLE STARS, 220. VENUS, 139. VERNIER, a scale to measure very minute distances. VERTICAL CIRCLE, one that passes through the zenith and nadir of the celestial sphere. The prime vertical circle passes through the east and west points of the horizon. VULCAN, discovery of, 137. WORLDS, THE, AND THE WORD, teach the same truth, 231-245. YEAR, the, length of, on any planet, is determined by the periodic time. ZENITH, the point in the celestial sphere directly overhead. ZODIAC, a belt 18 deg. wide encircling the heavens, the ecliptic being the middle. In this belt the larger planets always appear. In the older astronomy it was divided into twelve parts of 30 deg. each, called signs of the zodiac. ZODIACAL LIGHT, 80.



TO FIND THE STARS IN THE SKY.

Detach any of the following maps, appropriate to the time of year, hold it between you and a lantern out-of-doors, and you have an exact miniature of the sky. Or, better, cut squares of suitable sizes from the four sides of a box; put a map over each aperture; provide for ventilation, and turn the box over a lamp or candle out-of-doors. Use an opera glass to find the smaller stars, if one is accessible.

THE END