\ /\ Rfl t-elleth ti;e number c f the Star*, and caUath them all by tlieir aamm ;; THK GEOGRAPHY OF THE HEAVENS, . * CLASS-BOOK OF ASTRONOMY : ACXX)M PARISH BY A {JKLESTIAL ATLAS BY ELIJAH H. BURRITT, A.M. GftBATLY ENLARGED, RETISKD AND ILLU8TBATBD, BY H. MATTISOST, A. M. SSW AND BBVISBD E D I T 1 N NEW YORK: PUBLISHED BY MASON BROTHERS. BOSTON : MASON & IIAULIN. PHILADELPHIA: J. B. LIPPINCOTT t CO. CINCINNATI : 8AP.CKNT, WILSON, & IIINKUE. SHTKRHD according to Act of Congress, in the year 1 ^56. bT . J. HUNT1NGTON, In the Clerk't )f&i.e ci toe District Court of the United Suites for the S-mthern D'?trict of New Yorl 1 . H. 1'ivson, Stereotyper. 0. A.. ALVORD, Printer LXDEX TO THE CONSTELLATIONS. PAG8 Andromeda ...... 18 Antinous 118 Anser et Velpecula . . . .121 Aries .... . 23 Argo Navis 62 Aquila 118 Aquarius 131 Auriga ....... 49 Bootes 84 Camelopardalua ..... 51 Oancer 64 Janes Venatiei . . .' . .83 Canis Major 59 Canis Minor 56 Oipricornus 127 Cassiopeia 22 Centaurus ...... 83 Cepheus 25 Cetus . 32 Columba 46 Coma Berenices 77 Corvus 78 Corona Australis 118 Corona Boreali* .... 94 Crater . ^ . .... 71 Cygnus 124 Delphinus 122 Draco . . . . . . .110 Kridanus ...... 47 Kquuleus 13 i Gemini 53 Gloria Frederica . . . 134 Hercules . . 108 Hydra 71 Lacerta 184 Leo 6 Leo Minor 69 Lupus (The Wolf) .... 90 Lepus i,The Hare) .... 45 Libra 91 Lynx 52 Lyra 112 Monoceros 53 Musca 82 Nocta 88 Ophiuchus 107 Oriou 41 Pegasus 129 'Perseus JJ5 Pisces 20 Pisces Australis 163 Sagittarius 116 Sagitta 121 Scutum Sobieski 116 Scorpio 100 Sceptrum Brandenburgium . . .'49 Serpentarius vel Ophiuchus . . 107 Serpens 93 Sextans 70 Taurus 88 Taurus Poniatowski . . . .115 Telescopium Herschellii ... 53 Triangulae 81 Ursa Major 78 Ursa Minor 96 Virgo 80 CONTENTS. PART I. -THE CONSTELLATIONS. CHA.PTER I. Constellations on the meridian in November, . . * . 18 ll. " " December, .... 23 HI. " ' " January, .... 38 w IV. " " February, .... 52 V. " * " March, .... 62 " VL " * " April, .... 66 " VII. " " " May, .... 73 " VUI. " " " June, . V . ' . 84 " IX. " " " July, .... 100 X. " " " August, .... 110 " XI. " " " September, .... 122 " XII. M " " October, .... 129 * Xni. Variable and Double Stars Clusters and Nebulae, .... 185 " XIV. Via Lactea, or Milky- Way, . ....... 141 " XV. Origin of the Constellations, ........ 143 " XVI. Number, Distances, and Economy of the Stars, .... 148 " XVII. Falling, or Shooting Stars, ........ 154 PART II. -THE SOLAR SYSTEM. CHAPTER I. General Phenomena of the Solar System, History, Ac., . ' ; 168 " H. The Sun His Distance, Magnitude, Ac., ..... 171 " III. The Primary Planets Mercury, Venus, Ac., ..... 177 IV. The Moon Her Distance, Motions, Phases, Ac., .... 203 V. Solar and Lunar Eclipses, ......... 214 " VI. Primary Planets continued Mars and the Asteroids, ... 224 " VII. Primary Planets Jupiter and Saturn, ...... 233 " VIII. Primary Planets Uranus and Neptune, .... . 245 " IX. Comets Their Nature, Motions, Orbits, Ac., ..... 249 " X. Of the Forces by which the Planets are retained in their Orbits, . 202 XI. Proper MotJon of the Sun in Space, ....... 2CS " XII. Precession of the Equinoxes Obliquity of the Ecliptic, . . . 270 " XIII. Philosophy of the Tides, ......... 2SO " XIV. The Seasons Different Lengths of the Days and Nights, . . 287 " XV. The Harvest Moon, and Horizontal Moon, ..... 293 " XVI. Refraction and Twilight, ......... 297 " XVII. Aurora Borealis and Parallax, ........ 802 "XVIII. Practical Astronomy Reflection and Rel action of Light, . . 808 " XIX. Refractors and Reflectors, ... ..... 818 " XX. Problems and Tables, .... . . . f334 PREFACE. THE rapid progress of the science of astronomy, for the last few years, has again rendered it necessary to revise the Geo- graphy of the Heavens a work, the popularity of which is suffi- ciently proved by a sale of 300,000 copies. The editor has, therefore, availed himself of the occasion to make such improve- ments, both in the book and maps, as seemed to be demanded by the progress of the science, and the most approved methods of instruction. Among these improvements we may mention the following : 1. The matter of the book has been thoroughly assorted ; the most important paragraphs being printed in large type, and numbered, as in most modern text-books ; while that which seemed in the main explanatory of the more important portions, is left in small print. By this means an agreeable variety is afforded to the eye, while the book is made to contain far more matter, and is, consequently, far more complete, than it could otherwise have been. 2. A new set of Questions has been prepared throughout. These are brief, topical and suggestive ; and numbered to answer to the paragraphs to which they relate. 3. A complete list of Telescopic Objects in each constellation has been inserted ; giving the Right Ascension and Declination of each object ; with a brief description of it ; and easy land- marks and directions by which it may be found ; and references to telescopic views of the same in the new maps. The color and relative magnitude of the components of the double stars, are also given. These Telescopic Objects, compiled with great labor from Smyth's Cycle of Celestial OJjects, will be found especially TV PREFACE. valuable to all institutions having an equatorial telescope Indeed, they greatly enhance the value of the work for i\t classes of students. 4. Several small constellations that were delineated on the maps, but were not described in former editions of the bock, have been described, and their history given in the preseiiu edition. 5. The page of the book has been greatly enlarged, for the double purpose of printing more matter and in larger type : and to afford scope for wood-cut illustrations. Of these, great numbers have been introduced into the second part of the work, adapting it, in this respect also, to the wants of both teacher and student. 6. Still further to illustrate the second part of the work, the first map of the atlas has been re-drawn and re-engraved, so as to illustrate more and better than the old map. 7. Two entirely new maps have been introduced into the Atlas, containing views of eighty different celestial objects ; such as Double Stars, Clusters, Nebulae, Comets, &c. These are all referred to in the book, and in turn refer from the objects back to the page of the book where they are described. These maps and the corresponding descriptions in the book will be found not only extremely interesting, but of incalculable value to the student. 8. A chapter on the history, structure and use of Telescopes, Transit Instruments, &c., has been introduced a subject which every student of astronomy should understand, but one to which no attention was given in the previous editions. Such are some of the principal new features of the present edition larger type, new questions, telescopic objects, new maps, new matter, and numerous illustrations, making it the most per- (ect and complete text-book of astronomy ever offered to the American public. H. MATTISON New York, July 18G6. INTRODUCTION 1. ASTRONOMY is the science of the heavenly bodies the Sun, Moon, Planets, Comets, and Fixed Stars. 2. In entering upon this study, the phenomena of the hea- vens, as they appear on a clear evening, are the first objects that demand our attention. Our first step is to learn the names and positions of the heavenly bodies, so that we can identify, and distinguish them from each other. In this manner they were observed and studied ages before books were written, and it was only after many careful and repeated observations, that systems and theories of Astronomy were formed. To the visible heavens, then, the attention of the pupil should be first directed, for it is only when he shall have become, in some measure, familiar with them, that he will be able to locate his Astronomical knowledge, or fully compre- hend the terms of the science. 3. For the sake of convenient reference, the heavens were early divided into constellations, and particular names assigned to the constellations and to the stars which they contain. A constellation may be defined to be a cluster or group of stars embraced in the outline of some figure. These figures are, in many cases, creations of the imagination ; but in others, the stars are in reality so arranged as to form figures which have some resemblance to the objects whose names have been assigned to them. These divisions of the celestial sphere bear a striking analogy to the civil divisions of the globe. The constellations answer to states and kingdoms, the most brilliant clus- ters to towns and cities, and the number of stars in each, to their respective population. The pupil can trace the boundaries of any constellation, and name all its stars, one by one, as readily as he can trace the boundaries of a state, or name the towns and cities from a map of New England. In this sense, there may be truly aaid to be a Geography of the Heavens. 4. The stars are considered as forming, with reference to 1. What is Astronomy? 2. What first studied? First step? 8. How are the heavens divided, and why? What is a constellation ? What of these figures ? In what sense may there really be a " Geography of the heavens f " 4. How are the stars classified, as respects their magnitudes? What expedient for designating their places in the heavens? ASTRONOMi'. their magnitudes, sixteen classes ; the brightest being called stars of the first magnitude, the next brightest, stars of the second magnitude, and so on to the sixth class, which consists of the smallest stars visible to the naked eye. The next teii classes are seen only through telescopes. In order to be able to designate with precision their situa- tions, imaginary circles have been considered as drawn in the heavens, most of which correspond to, and are in the same piano with, similar circles, supposed for similar purposes, to be drawn on the surface of the Earth, 5. In order to facilitate the study of Astronomy, artificial representations of the heavens, similar to those of the surface of the Earth, have been made. Thus, a Celestial Atlas, composed of several maps, accompanies this work. Before, however, pro- ceeding to explain its use, it is necessary to make the pupil acquainted with the imaginary circles alluded to, called the Cir- cles of the Sphere. CIRCLES OF THE SPHERE. 6. The Axis of the Earth is an imaginary line, passing through its centre, north and south, about which its diurnal revolution is performed. The Poles of the Earth are the extremities of its axis. The Axis of the Heavens is the axis of the Earth produced both ways to the concave surface of the heavens. The Poles of the Heavens are the extremities of their axis. The Equator of the Earth is an imaginary great circle pass- ing round the Earth, east and west, everywhere equally distant from the poles, and dividing it into northern and southern hemi- spheres. The Equator of the Heavens, or Equinoctial, is the great circle formed on the concave surface of the heavens, by producing the plane of the Earth's equator. A plane is that which has surface but not thickness. The plane of a circle is that ima- ginary superficies which is bounded by the circle. 7. The Rational Horizon is an imaginary great circle, whose plane, passing through the centre of the Earth, divides the hea- vens into two hemispheres, of which the upper one is called the 5. What helps to facilitate the study of the heavens? Circles? Called what? 6. Axis of the Earth? Poles? Axis of the heavens? Poles of the heavens? Equator of the Earth ? Equator of thu heavens, or Equ aoctial ? 7. Rational horizon ? Sensi- ble or apparent? CHICLES OF THE SPHERE. 11 visible hemisphere, and the lower one, the invisible hemisphere. It is the plane of this circle which determines the rising and set- ting of the heavenly bodies. The Sensible or Apparent Horizon, is the circle which termi- nates our view, where the Earth and sky appear to meet. To a person standing on a plain, this circle is but a few miles in diameter. If the eye he elevated five feet, the radius of the sensible horizon will be less than two miles and three quarters ; if the eye be elevated six feet, it will be just three miles. The observer being always in the centre of the sensible horizon, it will move as he moves, and enlarge or contract, as bis station is elevated or depressed. 8. The Poles oj the Horizon are two points, of which the one is directly overhead, and is called the Zenith; the other is directly underfoot, and is called the Nadir. Vertical Circles are circles drawn through the Zenith and Nadir of any place, cutting the horizon at right angles. The Prime Vertical is that which passes through the east and west points of the horizon. 0. The Ecliptic is the plane of the Earth's orbit ; or the great circle which the Sun appears to describe annually among the stars. It crosses the Equinoctial, a little obliquely, in two oppo- site points, which are called the Equinoxes. The Sun rises in one of these points on the 21st of March ; this point is called the Vernal Equinox. It sets in the opposite point on the 23d of September ; this point is called the Autumnal Equinox. One half of the Ecliptic lies on the north side of the Equinoctial, the other half on the south side, making an angle with it of 23^. This angle is called the obliquity of the Ecliptic. The axis of the Ecliptic makes the same angle with the axis of the heavens; so that the poles of each are 23^ apart. This angle is perpetually decreasing. At the commencement of the Christian era, it was about 23* 4o'. At the beginning of 1S36, it was only 23* 27' 38", showing an annual diminution of about half a second, or 45". 70 in a hundred years. A time will arrive, however, when this angle, having reached its minimum, will again increase in the same ratio that it had before diminished, and thus it will continue to oscillate at long periods, between certain limits, which are said to be comprised within the space of 20 42'. 10. The Ecliptic, like every other circle, contains 360, and it is divided into 12 equal arcs of 30 each, called signs, which the ancients distinguished by particular names. This division com- mences at the vernal equinox, and is continued eastwardly round t<> the same point again in the following order: Aries, Taurus, Gemini, Cancer, I^eo, Virgo, Libra, Scorpio, Sagittarius, Capri- 8. Poles of the horizon? Vertical circles? Prime Vertical? 9. Ecliptic? Equi- noxes? How is the Ecliptic situated with respect to the Equinoctial? Obliquity of Hcnptic? Is this angle permanent? 10. How is the Ecliptic divided? Where com- wnced, and how reckoned? Name sigl } in order? How does the Sun proceed tLr .ugh th. sigiH? 1* 12 ASTRONOMY. co-rnus, Aquarius, Puces. The Sun, commencing at the first degree of Aries, about the 21st of March, passes, at a mean rate, through one sign every month. 11. The Zodiac is a zone or girdle, about 16 degrees in breadth, extending quite round the heavens, and including all the heavenly bodies within 8 on each side of the ecliptic. It includes, also, the orbits of all the planets, except some of the asteroids, since they are never seen beyond 8 either north or south of the ecliptic. 12. Parallels of Latitude are small circles imagined to be drawn on the Earth's surface, north and south of the equator, and parallel to it. Parallels of Declination are small circles, imagined to be drawn on the concave surface of the heavens, north and south of the equinoctial, and parallel to it ; or they may be considered as circles formed by producing the parallels of latitude to the heavens. 13. The Tropic of Cancer is a small circle, which lies 234- north of the Equinoctial, and parallel to it. The Tropic of Capricorn is a small circle, which lies 23^ south of the Equi- noctial, and parallel to it. On the celestial sphere, these two circles mark the limits of the Sun's farthest declination, north and south. On the terrestrial sphere, they divide the torrid from the two temperate zones. That point in the ecliptic which touches the tropic of Cancer, is called the Summer Solstice ; and that point in the ecliptic which touches the tropic of Capricorn, is called the Winter Solstice. The distance of these two points from the equinoctial, is always equal to the obliquity of the ecliptic, which, in round numbers, is 23c ; but, as we have seen, the obliquity o-' tLe ecliptic is continually changing; therefore the position of the tropics must make a correspondent change. 14. The Colures are two great circles which pass through the poles of the heavens, dividing the ecliptic into four equal parts, and mark the seasons of the year. One of them passes through the equinoxes at Aries and Libra, and is thence called the Equi- noctial Colure; the other passes through the solstitial points or the points of the Sun's greatest declination north and south, a ad is thence called the Solstitial Colure. The Sun is in the equinoctial points the 21st of March and the 23d of September. He is in the solstitial points the 22d of June and the 22d of December. 15. The Polar Circles are two small circles, each about (561 11. What is the Zodiac? 12. Parallels of latitude? Of declination? 13. The tropics? Cancer? Capricorn? What do these circles mark in the celestial sphere* Ol ^ terrestrial? 14. The Colures? Where situated ? NVhen is the Sun at the equi- tioctia* pu'tits? The y>lstieiul? 15. What are the Polur Circles? CIRCLES OF THE SPHERE. 13 from the equator, being always at the same distance from the poles that the tropics are from the equator. The northern, is called the Arctic circle, and the southern the Antarctic circle. 16. Meridians are imaginary great circles drawn through the poles of the world, cutting the equator and the equinoctial at right angles. Every place op the Earth, and every corresponding point in the heavens, is considered as having a meridian passing through it; although astronomers apply but 24 to the heavens, thus dividing the whole concave surface into 24 sections, each 15* in width. These meridians mark the space which the heavenly bodies appear to describe, every hour, for the 24 hours of the day. They are thence sometimes denominated Hour Circles. In measuring distances and determining positions on the Earth, the equator and somo fixed meridian, as that of Greenwich, contain the primary starting points ; in the hea- vens these points are in the ecliptic, the equinoctial, and that great meridian which passes through the first point of Aries, called the equinoctial colure. 17. Latitude on the Earth, is distance north or south of the equator, and is measured on the meridian. Latitude in the Heavens, is distance north or south of the eclip- tic, and at right angles with it. Longitude on the Earth, is distance either east or west from some fixed meridian, measured on the equator. Longitude in the Heavens, is distance east from the first point of Aries, measured on the ecliptic. 18. Declination is the distance of a heavenly body either north or south of the equinoctial, measured on a meridian. Right Ascension is the distance of a heavenly body east from the first point of Aries, measured on the equinoctial. It is more convenient to describe the situation of the heavenly bodies by their decli- nation and right ascension, than by their latitude and longitude, since the former oor- responds to terrestrial latitude and longitude. Latitude and declination may extend 90 and no more. Terrestrial longitude may extend ISO* either east or west; but celestial longitude and right ascension, being reck- oned in only one direction, extend entirely round the circle, or 860. It is easy to convert right ascension into time, or time into right ascension, for if a heavenly body is one hou: in passing over 15, it will be one fifteenth of an hour, or four minutes, in passing over 1'. If the first point of Aries be on the meridian at 12 o'clock, the next hour line, whicfi is 15 E. of it, will come to the meridian at 1 o'clock; the second hour line at 2 o'clock ; the third at 3, &c. Of any two bodies whose right ascensions are given, that one will pass the meridian first which has the least right ascension. 19. In consequence of the Earth's motion eastward in its orbit, the stars seem to liave a motion westward, besides their apparent diurnal motion caused by the Earth's revolution on its axis ; so that they rise and set sooner every succeeding day by about four minutes, than they did on the preceding. This is 1(5. Meridians? How many? What other name? IIow measure distances on the earth? In the heavens? 17. What is latitude on the earth? In the heavens t Longitude on the earth ? In the heavens? IS. Declination? Right ascension Why describe by D. and R. A.? Extent of latitude? Declination? Longitude and R, A ? How convert II. A. into time? Which of two bodies given will first pass the merl. Jian? 19. What u, >pareut motion of etara ? Cause? Results? 14 ASTRONOMY. called their daily acceleration. It amounts to just two hours a month. On this account we have not always the same constel- lations visible to us throughout the year. While some, that were not visible before, are successively rising to view in the east, and ascending to the meridian, others sink beneath the western horizon, and are seen no more, until, having passed through the lower hemisphere, they again reaopear in the east. DESCRIPTION AND USE OF THE MAPS. 20. THE first map of the atlas represents, upon a large scale, general view of the solar system. This will be more fully described in the second part of the work. The next six maps represent different sections of the concave surface of the heavens. The first of these exhibits the principal constellations visible to us in October, November, and Decem- ber ; the second, those visible in January, February, and March; the third, those visible in April, May, and June ; and the fourth, those visible in July, August, and September ; with the excep- tion, however, of the constellations which lie beyond the 50th degree of north and south declination, of which, indeed, those around the North Pole are always, and those around the South Pole, never visible to us. 21. These constellations are represented on the sixth and seventh maps, called circumpolar maps, which are an exact con- tinuation of the others, and if joined to them at their correspond- ing degrees of right ascension and declination, they might be considered as constituting one map. The scale on which all the above-mentioned maps are drawn is that of a 16-inch globe. The lines drawn on the maps have been already defined ; and their use, being nearly the same with those in geography, will be readily understood. Those which are drawn from right to left, on each side of the equinoctial and parallel to it, are called Parallels of Declination. Those which are drawn up and down through the maps, at intervals of 15, are called Meridians of Hight Ascension, or Hour Circles. The scale at the top and bottom of the first four maps, and in the circumference of the circumpolar maps, indicates the daily progress of the stars in right ascension, and shows on what day of the month any star will be on the meridian at 9 o'clock in the evening. 20. What said of maps? First? Next six? 21. Sixth and seventh? Seal* f Describe lines? Scale indicates what? CLASSIFICATION OF bTARS, NEBLJLJ3, ETC. 15 22. The first four maps of the heavens are so constructed that the pupil in using them must suppose himself to face the south, and to hold them directly overhead in such manner that the top of the map shall be towards the north, and the bottom towards the south ; the right hand side of the map will then be west, and the left-hand east. In using the circumpolar maps he must suppose himself to face the pole, and to hold them in such a manner that the day of the given month shall be uppermost. The constellation called the Great Bear is an exception to this rule; in this constel- lation the principal stars are marked in the order of their right ascension. That point of projection for the maps which would exhibit each successive portion of the heavens directly overhead at 9 o'clock in the evening, was chosen, because in sum- mer at an earlier hour the twilight would bedim our observation of the stars, and a\ other seasons of the year it is easier to look up to stars that want an hour of their meridian altitude than to those which are directly overhead. CLASSIFICATION OF STARS, NEBULAE, &c. 23. FOR purposes of convenience in finding or referring to' par- ticular stars, recourse is had to a variety of artificial methods of classification. First, the whole concave of the heavens is divided into sections or groups of stars, of greater or less extent, called Constellations. (Of the origin of these figures see page 143). Next, they are classified according to their magnitudes, (as already stated art. 4), and designated on the maps accord- ingly. Thirdly, the stars of each constellation are classified according to their magnitudes in relation to each other, and with- out reference to other constellations. Thus, for instance, the largest star in Taurus is marked a, Alpha ; the next largest /?, Beta; the next, y, Gamma, &c., till the Greek alphabet is exhausted. Then the Roman (or English) is taken up, and finally, if necessary, recourse is had to figures. This useful method of designating particular stars by the use of the Greek and Roman alphabet, was invented by John Bayer, of Augsburg, in Germany, in 1603. It has been adopted by all succeeding astronomers, and extended by the addition of the Arabic notation 1, 2, 3, &c., wherever the stars in a constellation outnumber both alphabets. As Greek letters so frequently occur in catalogues and maps of the stars and on the celestial globes, the Greek alphabet is here introduced for the use of those who are unacquainted with it. The capitals are seldom used for designating the stars, but aro here given for the sake of regularity. 22. How use the first four maps of the hearsns? Circumpolar? What exception? What point of projection chosen, and why? 23 Classification or designation of stars? By whom invented, and when? 10 ASTRONOMY. THE GREEK ALPHABET. A a Alpha N v Nu ft Beta S | Xi F y Gamma O o Omicron A 6 Delta II TT Pi E e Epsilon P /o Rho Z C / Zeta 2 f Sigma H n Eta T T Tau Theta T v Upsilon 1 i Iota 4> Phi K K Kappa X ^ Chi A A Lambda * ^ Psi M fj, Mu 2 u Omega 24. As a further aid in finding particular stars, and especially in determining their number, and detecting changes, should any occur, catalogues of the stars have been constructed, one of which is over two thousand years old. Several of the principal stars have specific names, like the planets, as Sirius, Aldebaran, RegulttfS, &c. 25. The stars are still further distinguished, as single, doub 1 "., triple, multiple, binary, variable, new, and nebulous. A single star is one that appears as a unit under the most powerful telescopes. Double, triple, and multiple stars, are those that appear single to the naked eye, but by the aid of telescopes are found to consist of two or more stars. Binary stars are double stars revolving around each other, often called Binary Systems. Variable stars are those that are found to undergo certain fluctuations in their brightness, sometimes becoming quite invisible. In most cases these changes are periodical and regular, on which account they are called Periodical stars. New stars are those that suddenly blaze forth in some portion of the heavens previously void. Nebulous stars are those which are surrounded by a faint nebula, or halo of light or mist. 26. A duster of stars is an assemblage or group, thrown promiscuously together, like the Pleiades and Ilyades in Taurus, and the Bee Hive in Cancer. A Nebula is a cluster so remote as to appear only like a faint cloud or haze of light. Resolvable Nebulae, are those that can be resolved into distinct stars by the aid of a telescope. Irresolvable Nebula are those that have not 24. What further aid? Age? Names of stars? 25. Stars, how further distin- guished? Single stars? Double, &c.? Binary? What other name? Variable starsf What other name and why? New stars? Nebulous? 20. What are clusters ? Nebu IBB? Resolvable Nebulae? Irresolvable? Annular? Planetary? CLASSIFICATIO.N ? OF STARS, NEBULAE, ETC. 17 k? yet been thus resolved. Annular Nebula are those that have tlie form of an annulus or ring. Planetary Nebula are those that resemble planets in form, and in the sharpness of their out- line. Stellar Nebula are those with a star in the centre, the same as nebulous stars, already described (25). A more detailed account of the double stars, clusters and nebulas, will be given after the student has become somewhat familiar with the constellations. 27. We may now imagine the pupil ready to begin the study of the visible heavens. The first thing of importance is to fix upon the proper starting point. This, on many accounts, would seem to be the North Polar Star. Its position is apparently the same every hour of the night throughout the year, while the other stars are continually moving. Many of the stars also in that region of the skies never set, so that when the sky is clear, they may be seen at any hour of the night. They revolve about the pole in small circles, and never disappear below the horizon. On this account they are said to be within the circle of perpetual apparition. On the other hand, the identity of the North Polar Star, strange as it may appear, is not so easily determined by those who are just entering upon this study, as that of some others. For this reason, the point directly overhead, called the zenith, is preferable, since upon this point every one can fix with certainty in whatever latitude he may be. It will be alike to all the central point of the visible heavens, and to it the pupil will learn imper- ceptibly to refer the bearing, motion, and distances of trie heavenly bodies. That meridional point in each map, whose declination corresponds with the latitude of the place of observation, represents the zenith of the heavens at that place; and th^se constellations of stars which occupy this position en the maps, will be seen directly overhead, at 9 o'clock in the evening of the day through which the meridian pusses. Thus in Georgia, for instance, the starting point should be those stars which are situated in this meridian near the 33d degree of north declination, while in New England it should be those which are situated in it near the 42d degree. 28. We might, however, begin with the stars near either of the meridians represented on the maps, the only rule of selection being to commence at that which approaches nearest to being overhead at the time required. We have chosen for our starting point in this work that meridian which passes through the vernal er,uinox at the first point of Aries, not only because it is the meridian from which the distances of all the heavenly bodies are measured ; but especially because the student will thus be enabled to observe and compare th n progressive motion of the constellations according to the order in which they are always arranged in catalogues, and also to mark the constellations of the Zodiac passing overhead as they rise one after another in their order, and to trace among them the orbits of the Earth and of the other planets. 27. What first important in commenc'ng study of the heavens? What star would seem best starting point? Why? Whj not the best? What point preferable, ami why? Illustration from map. 23. With what stars might we begin? What rjerid'au thosen by the author? Why* PART I. THE CONSTELLATIONS CHAPTER I. CONSTELLATIONS ON THE MERIDIAN IN NOVEMBER. ANDROMEDA. MAP II.* 29. IF we look directly overhead at 10 o'clock, on the 10th of November, we shall see the constellation celebrated in fable by the name of ANDROMEDA. It is represented on the map by the figure of a woman having her arms extended, and chained by her wrists to a rock. It is bounded N. by Cassiopeia, E. by Perseus and the head of Medusa, and S. by the Triangles and the Northern Fish. It is situated between 20 and 50 of N. declination. Its mean right ascension is nearly 15; or one hour E. of the equinoctial colure. 30. It consists of G6 visible stars, of which three are of the 2d magnitude, and two of the 3d ; most of the rest are small. The stars directly in the zenith are too small to be seen in the pre- sence of the moon, but the bright star Almaack (y), of the 2d magnitude, in the left foot, may be seen 13 due E., and Merach (j3), of the same magnitude, in the girdle 7 south of the zenith. This star is then nearly on the meridian, and with two others N.W. of it forms the girdle. The three stars forming the girdle are of the 2d, 3d, and 4th magnitude, situated in a row, 3 and 4 apart, and are called x Merach, Mu, and Nu. 31. If a straight line, connecting Almaack with Merach, be * As the eastward motion of the earth in her orbit causes the sun to pass eastward annually around the heavens, and the constellations to rise earliar and earlier (19), the student will find it necessary to proceed eastward around the heavens, in studying the constellations. And as the right hand of the map is west, and the left hand east, we b^gin with the equinoctial colure, map II., and proceed to the left in the order in which tin- constellations successively arise. 29. What constellation? Maps, and why? (Note.) How Andromeda represented? Boundaries? Situation? Right ascension and declination? 30. Number of stars Magnitude? Almaack? Merach? "Girdle?" 31. Situation of Delta? Magnitude How otherwise known? Alpheratz? Substance of note ^fiue print)? ANDROMEDA. 19 produced south-westerly, 8 farther, it will reach to (? What clusters ;c nebula Shown on map, or not? 8<5. Pisces ? Where situated ? Wha^ now called 9 PISCES. %l in the heavens, and its outline at first is somewhat difficult to be traced. In consequence of the annual precession of the stars, the constellation Pisces has now come to occupy the sign Aries ; each constellation having advanced one whole sign in the order of the Zodiac. The Sun enters the sign Pisces, while the Earth enters that of Virgo, about the 19th of February, but he does not reach the constellation Pisces before the 6th of March. The Fishes, therefore, are now called the " Leaders of the Celestial Hosts." /See Aries. 37. That loose assemblage of small stars directly south of Meraeh, in the constellation of Andromeda, constitutes the Northern Fish, whose mean length is about 16, and breadth, 7. Its mean right ascension is 15, and its declination 25 N. Consequently, it is on the meridian the 24th of November ; and from its breadth, is more than a week in passing over it. 38. The Northern Fish and its ribbon, beginning at Merach, may by a train of small stars, be traced in a S. S. easterly direc- tion, for a distance of 33, until we come to the star El Rlscha, of the 3d magnitude, which is situated in the node, or flexure of the ribbon. This is the principal star in the constellation, and is situated 2 N. of the equinoctial, and 53 minutes east of the meridian. Seven degrees S. E. of El Rischa, passing by three cr four very small stars, we come to Mira, in the whale, a star of about the 8d magnitude, and known as the " Wonderful Star of 1596." El Rischa may be otherwise identified by means of a remarkable cluster of five stars in the form of a pentagon, about 15 E. of it. See Cetus. 39. From El Rischa the ribbon or cord makes a sudden flexure, doubling back across the ecliptic, where we meet with three stars of the fourth magnitude situated in a row 3 and 4 apart, marked on the map Zeta, Epsilon, Delta. From Delta the ribbon runs north and westerly along the Zodiac, arid termi- nates at Beta, a star of the 4th magnitude, 11 S. of Markab in Pegasus. This part of the ribbon, including the Western Fish at the end of it, has a mean declination of 5 N., and may be seen throughout the month of November, passing the meridian slowly to the W., near where the sun passes it on the 1st of April. 40. Twelve degrees W. of this Fish, there are four small stars situated in the form of the letter Y. The two Fishes, and the cord between them, make two sides of a large triangle, 30 and 40 in length, the open part of which is towards the N. W. When the Northern Fish is on the meridian, the Western is nearly two hours past it. This constellation is bounded N. by 37. Northern Fish? Length? Pec.? When on the meridian ? 38. How trace thu Northern Fish? To what star? Magnitude! Where situated? 89. From El Rischa ! From Delta* Mean declination of this part of the ribbon? 40. What 12* west of this fish? What do the two fishes, &c., make ? Boundaries of Pisces? 22 ASTRONOMY. Andromeda, W. by Andromeda and Pegasus, S. by the Cascad^ and E. by the Whale, the Ram and the Triangles. When, to enable the pupil to find any star, its direction from another is given, the latter is always understood to be on the meridian. After a little experience with' the maps, even though unaccompanied by directions, the ingenious youth will be able, of himself, t devise a great many expedients and facili- ties for tracing the constellations, or selecting out particular stars. In using a circumpolar map, face the pole, and hold it up in your hands in such a manner that the part which contains the name of the given month shall be uppermost, and you will have a portraiture of the heavens as seen at that time. The constellations about the Antarctic Pole are not visible in the United States; those about the Arctic or Northern Pole, are always visible. HISTORY. 41. The ancient Greeks, who have some fable to account for the origin of almog every constellation, say, that as Venus and her son Cupid were one day on the banks of the Euphrates, they were greatly alarmed at the appearance of a terrible giant, named Typhon. Throwing themselves into the river, they were changed into fi.shes, and by this means escaped danger. To commemorate this event, Minerva placed two fishes among the stars. According to Ovid, Homer, and Virgil, this Typhon was a famous giant. He had a hun- dred heads, like those of a serpent or dragon. Flames of devouring fire darted from hig mouth and eyes. He was no sooner born, than he made war against heaven, and so frightened the gods, that they fled and assumed different shapes. Jupiter became a ram: Mercury, an Ibis ; Apollo, a crow, Juno, a cow; Bacchus, a goat; Diy-na, a cat; Venus, a fish, <&c. The father of the gods, at last, put Typhon to llight, and crushed him under Mount ^tna. The sentiment implied in the fable of this hideous monster, is evidently this : that there is in the world a description of men whose mouth is so " full of cursing and bitter- ness," derison and violence, that modest virtue is sometimes forced to disguise itself, or flee from their presence. In the Hebrew Zodiac, Pisces is allotted to the escutcheon of Simeon. No sign appears to have been considered of more malignant influence than 7*iso*. The astrological calendar describes the emblems of this constellation as indicative of violence and death. Both the Syrians and Egyptians abstained from eating fish, out of dread and abhorrence ; and when the latter would represent anything as odious, or express hatred by hieroglyphics, they painted ajish. TELESCOPIC OBJECTS. 1. a PJSCIUM (El Bischn) A close double star in the eastern extremity of the ribbon, R. A. Ih. 53m. 46s. ; Dec. N. 1 59' 03". A. 5, pale green ; B. 6, blue ; a splendid object, and easily found. 2. PISCIUM A neat double star in the ribbon, about 13* north-west of a, R. A. Ih. 5m. 21 s. ; Dec. N. 6 43' 07". A. 6, silvery white ; B. 8, pale gray; a fine object. 3. PISCIUM A close double star in the space between the two fishes, about half-way between 77 Andromeda and Ceti ; R. A. Ih. 2m. 81s. ; Dec. N. 8" 42'. A. 8, white ; B. 14, pale blue. 4. A neat DOUBLE STAR, about 4 south of Algenib, in the wing of Pegasus, R. A. Oh. 1m. 53s. ; Dec. N. 10 14' 06". A. 6, silvery white ; B. 13J$, pale blue. 5. A FAINT NEBULA in the eye of the western Fish, about 10 south-half-east of Mar- kab, near y Piscium; R. A. 23h. 06in. 36s. ; Dec. 3 39' 1" : a very difficult object. CASSIOPEIA. MAP VI. 42. Cassiopeia is represented on the celestial map in regal state, seated on a throne or chair, holding in her left hand the branch 41. HISTORV? Greek account? Ovid's and others? Sentiment or moral? Hebrew Zodiac? Astrology? TELESCOPIC OBJECTS. Double stars Clusters? Nebula;? Shows on map, or not? 42. Cassiopeia? How represented Head? CASSIOPEIA. 23 of a palm tree. Her head and body are seeii in the Milky Way. H zr foot rests upon the Arctic Circle, upon which her chair is [laced She is surrounded by the chief personages of her royal family. The king, her husband, is on her right hand Perseus, her son-in-law, on her left and Andromeda, her daughter, just above her. 43. This constellation is situated 26 N. of Andromeda, and midway between it and the North Polar Star. It may be seen from our latitude, at all hours of the night, and may be traced out at almost any season of the year. Its mean declination is 60^ N. and its right ascension 12. It is on our meridian the 22d of November, but does not sensibly change its position for several days ; for it shoufd be remembered that the apparent motion of the stars becomes slower and slower, as they approxi- mate the poles. 44. Cassiopeia is a beautiful constellation, containing 55 stars that are visible to the naked eye ; of which four are of the 3d magnitude, and so situ'ated as to form, with one or two smaller ones, the figure of an inverted chair. " Wide ner stars Dispersed, nor shine with mutual aid improved; Nor dazzle, brilliant with contiguous flame : Their number fifty-five." 45. Caph, in the garland of the chair, is almost exactly in the equinoctial colure, 30 N.of Alpheratz, with which, and the Polar Star, it forms a straight line, j Caph is therefore on the meridian the 10th of November, and one hour past it on the 24th. It is the westernmost star of the bright cluster. Skedir, in the breast, is the uppermost star of the five bright ones, and is 5 S. E. of Caph : the other three bright ones, forming the chair, are easily distinguished, as they meet the eye at the first ghmee. There is an importance attached to the position of Caph that concerns the mariner and the surveyor. It is used, in connec- tion with observations on the Polar Star, for determining the latitude of places, and for discovering the magnetic variation of the needle. 40. It is generally supposed that the North Polar Star, so called, is the real immovable pole of the heavens : but this is a mistake. It is so near the true pole that it has obtained the 43. Situation? How seen? R. A. and Dec.? When on meridian? 44. Numbe-- of Btars? Magnitudes? Figure? Character of this constellation? 45. Caph? How situated? When on meridian? Sliedir? Importance attached to Caph? 46. Pole star? Is it the true pole? What variation? llow pole star situated with reference to 24 ASTRONOMY. appellation of the North Polar Star ; but it is, in reality, more than a degree, and a half distant from it, and revolves about the true pole every 24 hours, in a circle whose radius is 1 31'. It will consequently, in 24 hours, be twice on the meridian, once above, and once below the pole ; and twice at its greatest elonga- tion E. and W. The Polar Star not being exactly in the N. pole of the heavens, but one degree and 81 minutes on that side of it which is towards Caph, the position of the latter becomea important, as it always shows on which side of the true pole the polar star is. There is another important fact in relation to the position of this star. It is equidis- tant from the pole, and exactly opposite another remarkable star in the square of the Great Bear, on the other side of the pole, [tee Megrez.~\ It also serves to mark a spot in the starry heavens, rendered memorable as being the place of a lost star. Two hun- dred and fifty years ago, a bright star shone 5 N. N. E. of Caph, where now is a dark void ! On the Sth of November, 1572, Tycho Brahe and Cornelius Gemma saw a star in the constellation of Cassiopeia, which became, all at once, so brilliant, that it surpassed the splendor of the brightest planets, and might be seen even at noonday. Gradually, tliis great brilliancy diminished, until the 15th of March, 1573, when, without moving from its place, it became utterly extinct. Its color, during this time, exhibited all the phenomena of a prodigious flame first, it was of a dazzling white, then of a reddish yellow, and lastly of an ashy paleness, in which its light expired. It is impossible, says Mrs. Somerville, to imagine anything more tremendous than a conflagration that could be visible at such a distance. It was seen for sixteen months. Some astronomers imagined that it would reappear again after 150 years ; but it has never been discovered since. This phenomenon alarmed all the astronomers of the age, who beheld it; and many of them wrote dissertations con- cerning it. j Rev. Professor Vince, one of the most learned and pious astronomers of the age, has this remark : " The disappearance of some stars may be the destruction of that system at the time appointed by the Deity for the probation of its inhabitants ; and the appear- ance of new stars may be the formation of new systems for new races of beings then called into existence to adore the works of their Creator." Thus, we may conceive the Deity to have been employed from all eternity, and thus he may continue to be employed for endless ages ; forming new systems of beings to adore him; and transplanting beings already formed into happier regions, who will con- tinue to rise higher and higher in their enjoyments, and go on to contemplate system after system through th boundless universe. LA PLACE says : As to those stars which suddenly shine forth with a very vivid light, and then immediately disappear, it is extremely probable that great conflagrations, pro- duced by extraordinary causes, take place on their surface. This conjecture, continues he, is confirmed by their change of color, which is analogous to that presented to us on the earth by those bodies which are set on fire, and then gradually extinguished. The late eminent Dr. Good also observes that Worlds, and systems of worlds, are not only perpetually creating, but also perpetually disappearing. It is an extraordinary fact, that within the period of the last century, not less than thirteen stars, in different con- stellations, seem to have totally perished, and ten new ones to have been created. In many instances it is unquestionable, that the stars themselves, the supposed habitation of other kinds or orders of intelligent beings, together with the different planets by which it is probable they were surrounded, have utterly vanished, and the spots which they occupied in the heavens have become blanks ! What has befallen other systems will assuredly befall our own. Of the time and the manner we know nothing, but the fact is incontrovertible ; it is foretold by revelation ; it is inscribed in the heavens ; it is feit through the earth. Such is the awful and daily text ; what then ought to be the comment? The great and good lieza, falling in with the superstition of his age, attempted to prove that this was a comet, or the same luminous appearance which conducted the magi, or tvi.se men of the East, into Palestine, at the birth of our Saviour, and that it now appeared to announce his second coining. Caph ? What other important fact in relation to the position of Caph ? What remark- able fact stated? By whom attested? Describe phenomenon? Mrs. Souierville's remark? Other astronomers'? Professor Vince's remarks? The author's? La Place's ? Dr. Good's ? Beza'a ? CEPHEUS. S HISTORY. Cassiopeia was the wife of Cepheus, King of Ethiopia, and mother of Androraeaa. She was n queen of matchless beauty, and seemed to be sensible of it; for she even boasted herself fairer than Juno, the sister of Jupiter, or the Nereides a name given to the sea- nymphs. This so provoked the ladies of the sea, that they complained to Neptune of the insult, who sent a frightful monster to ravage her coast, as a punishment for her inso- lonce. But the anger of Neptune and the jealousy of the nymphs were not thus appeased They demanded, and it was finally ordained that Cassiopeia should chain her daughter Andromeda, whom she tenderly loved, to a desert rock on the beach, and leave her vxposed to the fury of this monster. She was thus left, and the monster approached , but just as he was going to devour her, Perseus killed him. " The saviour youth the royal pair confess. And with heav'd hands, their daughter's bridegroom bless." Eusden't Ovid. TELESCOPIC OBJECTS. 1. wi CASSIOPE^B (Shedir) A bright star, with a companion in the bosom of the figure: R. A Oh. 31m 29s.; Dec. 65 39' 05'. A 3, pale rose tint; B 10J$, small blue. S-./th and llerschell note Shedir as variable. 2. /? CASSIOPE^B (Citph) A bright star on the left side, with a minute companion; R. A. Oh. Om. 42s.; Dec. N. 58 16' 03'. A 2Jg, whitish; B 11%, dusky. Look diiectly opposite NegriSj in the great dipper, through the pole star, and about as far beyond. 3. y CASSIOPE.K A bright star with a distant companion on the right side of the figure : R. A. Oh. 4Im. 05s. ; Dec. N. 59" 50' OS'. A 3, brilliant white ; B 18, blue. Mat/ small stars in the field. 4. 77 CASSIOPE.K A BINARY STAR, about 4 from a towards Polaris; R. A. Oh. 39m. 27s.; Dec. N. 56" 57' 09". A. 4, pale white ; B. 733, purple. Estimated period 700 yeavs. 5. p. CASSIOPE,* A coarse TRIPLE STAR in the right elbow; R. A. Oh. 57 in. 23s. ; Dec. N. 54 3 OS' 01'. A 5^, deep yellow ; B 14, pale blue ; C 11, bluish. Several small stars in the field. 6. a CASSIOPE-* A beautiful double star in the left elbow; R. A. 23h. 50m. 55s. ; Dec. N. 54 51' OS". A 6, flushed white ; B 8, srnalt blue ; the colors clear and distinct. 7. A coarse QUADRUPLE STAR, just south of Cepheus' right hand; or about 27 south- Bouth-west of Polaris, on a line drawn over y Cephei. 11. A. 28h. 17m. 45s. ; Dec. N. 64' 24' 0-3'. A 5, pale yellow; B 9, yellowish; C 11, and D, 13, both blue. 8. A LARGB AND STRAGGLING CLUSTER, between the footstool of Cassiopeia and the head of Cepheus; R. A. Oh. 18m. 10s. ; Dec. N. 70 30' 03". A line from y Cassiopese, % the dh tance to y Cephei, will fall upon this object. A coarse double star in the field. 9. A RICH, BUT SOMEWHAT STRAGGLING CLUSTER; R. A. Oh. 24in. 5s. ; Dec. N. 62 23' 09*. Vicinity splendidly strewed with stars a double star in the centre. Look near the star K . 10. A LOOSE CLUSTER, including a small double star; R. A. Oh. 34m. 15s.; Dec. N. 60* &4' 07". A S%, B 11, both pale. Situated just half way between y and K . 1 1. A LOOSE CLUSTER of small stars ; R. A. Oh. 5Sm. 19s. ; Dec. N. 60 44'. On a line from , towards f: , about % the distance. 12. A CLUSTER and neat double star on a line from a through minute double star preceding. 3. y CKPHEI (Er JKai)A DOUBLE STAR in the knee of Cepheus, with a distant telescoj io companion on the preceding parallel. A3, yellow; B 14, dusky. R. A., 28h. 82m. 47s . Dec., N. 76 44' 7". This star will be the Pole star in about 2360 years. HISTORY. Who was CeptffM ? "Why placed in the heavens ? What said of the ri#in of otlii-r constellations? TELESCOPIC OBJKCTS. Alpha? Beta, &c. ? TV'hat clusters ? B.Cr. 2 28 ASTRONOMY. 4. rt CKPHEI (For) in the crown of Cepheus, a fine, though wide Dorm.K STAR ; R. A. ?2h. '28m. 14s. ; Dec., N. 57 35' 9". A 4%, orange tint; B 7, fine blue the colors in fine coa- trast. This star is 'Variable, with a period of 5d. Sh. 30m. 5. A LARGK AND RICH CLUSTER on the left elbow ; R. A., 20h. 2Sm. ]7s. ; Dec., N. 60* 06 9. . It is 12 due north of a Cygni; and 3 west-south-west of 7? Cephei. "A grand but distant collocation of suns bound together by mutual relations." . AN IRREGULAR CLUSTER between the head of Cepheus and the chain of Andromeda; R. A., 23h. 17m. 10s.; Dec., N. 60 e 43' 1". It is about one-third of the distance from 8 Cassiopeae to a Cephei ; and may be seen on Map VI., near the sceptre of Cepheua For a telescopic view, see Map V11L, Fig. 24. CHAPTER II. CONSTELLATIONS ON THE MERIDIAN IN DECEMBER. ARIES (THE BAM). MAP II. 50. TWENTY-TWO centuries ago, as Hipparclms informs us, this constellation occupied the first sign in the ecliptic, com- mencing at the vernal equinox. But as the constellations gain about 50" on the equinox, at every revolution of the heavens,* they have advanced in the ecliptic nearly 31 beyond it, or more than a whole sign : so that the Fishes now occupy the same place in the Zodiac, that Aries did in the time of Hipparchus ; while the constellation Aries is now in the sign Taurus, Taurus in Gemini, and Gemini in Cancer, and so on. ARIES is therefore now the second constellation in the Zodiac.^ It is situated next east of Pisces, and is midway between the Triangles and the Fly on the N. and the head of Cetus on the 8. It contains 66 stars, of which, one ia of the 2d, one of the 3d, and two of the 4th magnitudes. " First, from the east, the Ram conducts the year ; Whom Ptolemy with twice nine stars adorns, Of which two only claim the second rank ; The rest, when Cynthia fills the sign, are lost." Aries is readily distinguished by means of two bright stars in the head, about 4* apart, the brightest being the most north-easterly of the two. The first, which is of the 2J magnitude, situated in the right horn, is called Alpha Arietis, or simply Arietift; the other, which is of the 3d magnitude, lying near the left horn, is called Sheratan, and may be known by another star of the 4th magnitude, in the ear, 1 ^ S. of it, called Mesarthiin^ which is thejtfr*2 star in this constellation. Arietis and Sheratan, are one instance out of many, where stars of more than ordinary brightness are seen together in pairs, as in the Twins, the Little Dog, Ac., the brightest star being commonly on the east. * See " Precession of the Equinoxes," page 270. 60. Constellations in this chapter? Aries 22 centuries ago f Now; and why? How distinguished ? Arietis and Sheratan ? ARIES. 2$ 51. The position of Arictis affords important facilities to nautical science. Difficult to comprehend as it may be, to the unlearned, the skilful navigator who should be lost upon an unknown sea, or in the midst of the Pacific ocean, could, by measuring the distance between Arietis and the Moon, which often passes near it, determine at once not only the spot he was in, but his true course and distance to any known meridian or harbor on the earth. See Part II., page 206. Arietis comes to the meridian about 12 minutes after Sliera- lan, on the 5th December, near where the sun does in midsum- mer. Arietis, also, is nearly on the same meridian with Almaack, in the foot of Andromeda, 19 N. of it, and culminates only four minutes after it. The other stars in this constellation are quite small, constituting that loose cluster which we see between the Fly on the north, and the head of Cetus on the south. When Arietis is on the meridian, Andromeda and Cassiopeia are a little past the meridian, nearly overhead, and Perseus with the head of Medusa, is as far to the east of it. Taurus and Auriga are two or three hours lower down ; Orion appears in the S. E., and the Whale on the meridian, just below Aries, while Pegasus and the Swan are seen half-way over in the west. The manner in which the ancients divided the Zodiac into 12 equal parts, was both simple and ingenious. Having no instrument that would measure time exactly, " they took a vessel, with a small hole in the bottom, and having filled it with water, suffered the same to distill, drop by drop, into another vessel set beneath to receive it, beginning at the moment when some -3tar rose, and continuing till it rose the next following night, when it would have performed one complete revolution in the heavens. The water tailing down into the receiver they divided into twelve equal parts ; and having twelve other small vessels in readiness, each of them capable of containing one part, they again poured all the water into the upper vessel, and observing the rising of some star in the Zodiac, at the same time suffered the water to drop into one of the small vessels. And as soon us it was full, they removed it, and set an empty one in its place. Just as each vessel was full, they took notice what star of the Zodiac rose at that time, and thus continued the process through the year, until the 12 vessels were filled." Thus the Zodiac was divided into 12 equal portions, corresponding to the 12 months of the year, commencing at the vernal equinox. Each of these portions served as the visible representative or sign of the month it appeared in. All those stars in the Zodiac which were observed to rise while the first vessel was fill- ing, were constellated and included in the first sign, and called Aries, an animal held in great esteem by the shepherds of Chaldea. All those stars in the Zodiac which rose whi! tlie second vessel was filling, were constellated and included in the second sign, which, for a similar reason, was denominated Taurus; and all those stars which were observed to rise while the third vessel was filling, were constellated in the third sign, and called (jemini, in allusion to the twin Reason of the flocks. Thus each sign of 30 in the Zodiac, received a distinctive appellation, according to the fancy or superstition of the inventors; which names have ever since been retained, although the constellations themselves have since left their nominal signs more than 80 behind. The sign Aries, therefore, included all the stars embraced in the first 30 of the Zodiac, and no more. The sign Taurus, in like manner, included all those stars embraced 51. Position of Arietis? Importance to mariners? When come to meridian ? Where And wjeda and Cassiopeia then ? Perseus ? Taurus, Auriga, Orion, Pegasus and Swan ? What o. other stars hi Aries ? Aucwnt method of dividing the Zodiac ? Named of 30 ASTRONOMY. In tbe next 30" of the Zodiac, or those between 30" and 60% and so of the rest. Of tho who imagine that the twelve constellations of the Zodiac refer to the twelve tribes f Israel, some ascribe Aries to the tribe of Simeon, and others, to Gad. HISTORY. According to fable, this is the ram which bore the golden fleece, and carried Phryxns and hid sister Helle through the air, when they fled to Colchis from the persecution of their stepmother Ino. The rapid motion of the ram in his aerial flight high above the earth, caused the head of Helle to turn witli giddiness, and she fell from his back into that part of the sea which was afterwards called Hellespont, in commemoration of the dreadful event. Phryxus arrived safe at Colchis, but was soon murdered by his own father-in-law, ^tes, who envied him his golden treasure. This gave rise to the celebrated Argonautic expedition under the command of Jason, for the recovery of the golden fleece. Nephele, Queen of Thebes, having provided her children, Phryxus and Helle, with this noble animal, upon which they might elude the wicked designs of those who sought their lifej was afterwards changed into a cloud, as a reward for her parental solicitude; and the Greeks ever after called the clouds by her name. But the most probable account of the origin of this constellation is given in a preceding paragraph, where it ia referred to the flocks of the Chaldean shepherds. During the campaigns of the French army in Egypt, General Dessaix discovered among the ruins at Dendera, near the banks of the Nile, the great temple supposed by some to have been dedicated to Isis, the female deity of the Egyptians, who believed that the ris- ing of the Nile was occasioned by the tears which she continually shed for the loss of her brother Osiris, who was murdered by Typhon. Others suppose this edifice was erected for astronomical purposes, from the circumstance that two Zodiacs were discovered, drawn upon the ceiling, on opposite sides. On both these Zodiacs the equinoctial points are in Leo, and not in Aries ; from which it has been concluded, by those who pertina- ciously endeavor to array the arguments of science against the chronology of the Bible and the validity of the Mosaic account, that these Zodiacs were constructed when the sun entered the sign Leo, which must have been 97'20 years ago, or 4000 years before the inspired account of the creation. The infidel writers in France and Germany make it 10,OUO years before. But we may " set to our seal," that whatever is true in fact and coi- re^t in inference on this subject will be found, in the end, not only consistent with the Mosaic record, but with the common meaning of the expressions it uses. The discovery of Champollion has put this qucstion'for ever at rest ; and M. Lat- edly a rich stratum of fixed stars, presenting the most wonder- ful and sublime phenomenon of the Creator's power and great- ness. Kohler, the astronomer, observed a beautiful nebula near the face of Perseus, besides eight other nebulous clusters in dif- ferent parts of the constellation. The head and sword of Perseus are exhibited on the circumpolar map. That very bright star 3* E. of Algol, is Capella in the Charioteer. HISTORY Perseus was the son of Jupiter and Danae. He was no sooner born than he was cast Into the sea, with his mother ; but being driven on the coasts of one of the islands of the Cyclades, they were rescued by a fisherman, and carried to Polydectes, the king of the place, who treated them with great humanity, and intrusted them to the care of the priests of Minerva's temple. His rising genius and manly courage soon made him a favorite of the gods. At a great feast of Polydectes, all the nobles were expected to present the king with a superb and beautiful horse ; but Perseus, who owed his benefac- tor much, not wishing to be thought less munificent than the rest, engaged to bring him the head of Medusa, the only one of the three Gorgons, who was subject to mortali.y. The names of the other two were Stheno and Euryale. They were represented with ser- pents wreathing round their heads instead of hair, having yellow wings and brazen hands ; their bodies which grew indissolubly together, were covered with impenetrable scales, arid their very looks had the power of turning into stones all those on whom they fixed their eyes. To equip Perseus for this perilous enterprise, Pluto, the god of the infernal regions, lent him his helmet, which had the power of rendering the wearer invisible. Minerva, the goddess of wisdom, furnished him with her buckler, which was as resplendent as a polished mirror ; and he received from Mercury wings for his feet, and a dagger made 60. Algenib? Howknown? When on the meridian? W r here, then, are the Pleiades? What the general aspect of the heavens? 61. Milky Way around Perseus? Observa- tion of Kohler ? HISTORY. Who was Perseus? What fate at birth, &c.f PERSEUS, ET CAPUT MEDUSAE. *f diamonds. Thus equipped, he mounted into the air, conducted by Mircrva, and came upon the monsters who, with the watchful snakes about their heads, were all asleep, lie approached them, and with a courage which amazed and delighted Minerva, cut off with one blow Medusa's head. The noise awoke the two immortal sisters, but Pluto's helmet rendered Perseus iuvisible, and the vengeful pursuit of the Gorgous proved fruitless. " In the mirror of his polished shield Reflected, saw Medusa slumbers take, And not one serpent by good chance awake ; Then backward an unerring blow he sped, And from her body lopped at once her head." Perseus then made his way through the air, with Medusa's head yet reeking in his> hand, and from the blood which dropped from it as he flew, sprang all those innumerable serpents that have ever since infested the sandy deserts of Libya. " The victor Perseus, with the Gorgon head, O'er Libyan sands his airy journey sped, The gory drops distilled, as swift he flew, And from each drop envenomed serpents grew." The destruction of Medusa rendered the name of Perseus immortal, and he was changed into a constellation at his death, and placed among the stars, with the head of Medusa by his side. TELESCOPIC OBJECTS. 1. a PERSEI A FIXE DOUBLE STAR ; R. A. 3h. 12m. 55s. ; Dec. N. 49 17' 2". A 2%, bril- liant lilac ; B 9, cinereous. This is Algenib, in the hero's left side. 2. |3 PKKSEI, or Af-gol; R. A. 2h. 57m. 46s. ; Dec. N. 41* 20'. A variable DOUBLE STAR. A 2 to 4, whitish ; B 11, purple. The former varies in brightness periodically, from the i!d to the 4th magnitude, and back again to the~2d magnitude, period being 2d. 2Uh. 4Siu. 6Cs. ; an object of great interest. 3. j PERSEI A WIDE UNEQUAL DOUBLE STAR in the hero's left shoulder; R. A. 2h. 53m. 14s. ; Dec. N. 52 52' 4". A 4, flushed white ; B 14, clear blue. 4. 6 PERSEI A BRIGHT STAR with a companion in the hero's hip; R. A., 3h. 31m. 33s.; Dec., N. 47* 16' 2". About 3 south-west of a Persei. A 8}, white ; B 11, pale blue. 5. f PERSEI A NEAT DOUBLE STAR in the right knee ; R. A. 8h. 47in. 08s. ; Dec. N. 39* 82' 4". A 3%, pale white ; B 9, lilac ; a fine delicate object. 6. PfcRSBi A DELICATE QUADRUPLE STAR; R. A. 8h. 44m. 05s. ; Dec. N. 81 24' 2". A 3%, flushed white; B 10, smalt blue; C 12, ash-colored ; D 11, blue. It is situated in the r.ght foot, and is designated by Smyth as " an elegant group." 7. n PERSKI A FINE DOUBLE STAR in the head of the figure; R. A. 2h. 39m. 04s.; Dec. N. 55' 13' 5". A 5, orange ; B 8)6, smalt blue ; the colors in fine contrast. 8. A GORGEOUS CLUSTER in the sword handle of Perseus; R. A. 2h. 08m. 58s.; Dec. N. 56* 24' 4". It may be seen with the naked eye, and when seen through a good telescope, is one of the most magnificent objects in the heavens. Map VIII., Fig. 25. 9. An EXTENSIVE AND RICH CLUSTER on the right side of Perseus, in a rich portion of the galaxy. R. A. 8h. 04m. Ols.; Dec. N. 46* 87' 9". Smyth says "it has a gathering spot about 4' in diameter, where the star-dust glows among minute points of light." Herschel says, " the large stars are arranged in lines like interwoven letters. 10. An ELONGATED NEBULA ; R. A. 2h. 80m. 25s.; Deo. N. 38* 21' 8" ; supposed to be a vast ring, seen obliquely. Map VIII., Fig. 26. 11. A pretty compressed OVAL GROUP OF STARS, in the left knee of Perseus, nearly mi 1- way between /I and fi; R. A. 8h. 58m. lls.; Dec. N. 49* 04' 05". A well-marked object., surrounded by a curve of larger stars, somewhat in the form of the letter D. Map VII!., Fig. 27. TELESCOPIC OBJECTS. Alpha? Beta? Gamma? Delta? Epsilon? Zeta? Ktft? CltKitu-s? Nebula? Which shown on the map? S ASTKONOMY. CHAPTER III. CONSTELLATIONS ON THE MERIDIAN IN JANUARY. TAURUS (THE BULL). MAP III. 62. TAURUS is represented in an attitude of rage, as if about to plunge at Orion, who seems to invite the onset by provoca- tions of assault and defiance. Only the head and shoulders of the animal are to be seen ; but these are so distinctly marked that they caimot be mistaken. The constellations which pass our meridian in the months of January, February and March, present to us the most brilliant and interesting portion of the heavens ; embrac- ing an annual number of stars of the highest order and brightness, all so conspicuously situated, that the most inexperienced can easily trace them out. 63. Taurus is now the second sign and third constellation of the Zodiac ; but anterior to the time of Abraham, or more than 4000 years ago, the vernal equinox took place, and the year opened when the sun was in Taurus; and the Bull, for the space of 2000 years, was the prince and leader of the celestial host. The Ram succeeded next, and now the Fishes lead the year. The head of Taurus sets with the sun about the last of May, when the opposite constellation, the Scorpion, is seen to rise in the S. E. It is situated between Perseus and Auriga on the north, Gemini on the east, Orion and Eridanus on the south, and Aries on the west, having a mean declination of 16 N. 64. Taurus contains 141 visible stars, including two remark- able clusters called the PLEIADES and HYADES. The first is now on the shoulder, and the latter in the face of the Bull. The names of the Pleiades are Alciorie, Merope, Maia, Electra. Tayeta, Sterope and Celeno. Merope was the only one who married a mortal, and on that account her star is dim among her sisters. Although but six of these are visible to the naked eye, yet Dr. Hook informs us that, with a twelve feet telescope, he saw 78 stars; and Rheita affirms that he counted 200 stars in this small cluster. For its appearance through an ordinary tele- scope, see Map VIII., Fig. 28. The most ancient authors, such as Homer, Attalus, and Geminus, counted only sia Pleiades; but Siuionides, Varro, Pliny, Aratus, Hipparchus, and Ptolemy, reckon them 62. How is Taurus represented? How much of him seen? What constellations most brilliant' G3. In what si (in is Taurus ? What constellation? How 4000 years ago? What next led the year? What now? At what time does Taurus set with the sun? How situated? 64. How many visible stars in Taurus? Clusters? How situated? Names of the Pleiades? What said of Merope? How many of the Pleiades visible to the nyked ty^? Dr. Hook and Rheita? Ancient authors? TAURUS. oJ seven in number; fud it was asserted, that the seventh had been seen before the burn in}? of Trey; but this difference might arise from the difference in distinguishing them with the naked eye. 65. The Pleiades are so called from the Greek word, pk'ein, to sail; because at this season of the year, they were considered " the star of the ocean" to the benighted mariner. Virgil who flourished 1200 years before the invention of the magnetic needle, says that the stars were relied upon, in the first ages of nautical enterprise, to guide the rude bark over the seas. "Tune alnos primum fiuvii sensere cavatas ; Navita turn stellis nmneros, et nomina fecit, Pleiadas, Hyadas, claramque Lycaonis Arcton." " Then first on seas the shallow alder swam ; Then sailors quarter M heaven, and found a name For every fix'd and every wand'ring star The Pleiades, llyades, and the Northern Car." The same poet also ,. escribes Palinurus, the renowned pilot of the Trojan Beet, as watching the face of the nocturnal heavens. "Sidera cuncta notat tacito labentia ccelo, Arcturum, pluviasque Hyadas, geminosque Triones, Armatuiuque auro circumspicit Oriona." * Observe the stars, and notes their sliding course, r lhe Pleiades, llyades, and their wat'ry force; And both the Bears is careful to behold, And bright Orion, arm'd with burnished gold." Indeed, this sagacious pilot was once so intent in gazing upon the stars while at the helm, that he fell overboard, and was lost to his companions. *' Headlong he fell, and struggling in the main, Cried out for helping hands, but cried in vaiii." 66. Alcyone, of the 3d magnitude, being the brightest star in this cluster, is sometimes called the light of the Pleiades. The other five are principally of the 4th and 5th magnitudes. The Pleiades, or, as they are more familiarly termed, the seven stars, come to the meridian 10 minutes before 9 o'clock, on the even- ing of the 1st of January, and may serve in place of the sun, to indicate the time, and as a guide to the surrounding stars. According to Hesiod, who wrote about 900 years before the birth of our Savior, ttu heliacal rising of the Pleiades took place on the llth of May, about the time of liarvvst " When, Atlas-born, the Pleiad stars arise Before the sun above the dawning skies, Tis time to reap ; and when they sink below The morn-illumined west, 'tis time to sow." Thus, in all ages, have the stars been observed by the husbandman, for " signs and for seasons." Pliny says that Thales, the Miletan astronomer, determined the cosmical setting of the Pleiades to be i.'o days after tiie autumnal equinox. This would make a difference between the setting at that time and the present, of 35 days, and as a day answers to about 5!)' of the ecliptic, these days will make 34" 25'. This divided by the annual pre- cession (50^4"), will give 2465 years since the time of Thales. Thus does astronomy become the parent of chronology. Co. Why Pleiades so called? Remark, and quotations from Virgil? 60. What said of Alcyone f Of the ther five? When on the meridian? Serve what purpose? Period, and remark of Hesiod? Of Piiny? What calculation respecting the passage of ths Pit- iaJ<- over the meridian ? 40 ASTHONOMY. If it be borne in inind that the stars uniformly rise, come to the meridian, and set abo'U four minutes earlier every succeeding night, it will be very easy to determine at what time the seven stars pass the meridian on any night subsequent or antecedent to the 1st of January. For example: at what time will the seven slurs culminate on the 5th of January ? Multiply the 5 days by 4, and take the result from the time they culminate t>n the 1st, and it will give 30 minutes after 8 o'clock m the evening. 67. The Pleiades are also sometimes called Vergilice, or thu " Virgins of Spring ;" because the sun enters this cluster in the " season of blossoms/' about the 18th or May. He who made them alludes to this circumstance when he demands of Job : " Canst thou bind the sweet influences of the Pleiades," &c. (Job 38 : 31.) rian name of the Pleiades is Sitccoth, or Succoth-Benotli, derived from a Chal- daic word, which signifies "to speculate, to observe," and the "Men of SuccKh" (2 Kings IT : 30) have been thence considered observers of the stars. 68. The Hyades are situated 11 S. E. of the Pleiades, in the face of the Bull, and may be readily distinguished by means of five stars so placed as to form the letter V. (Map V11L, Fig. 29.) The most brilliant star is on the left, in the top of the letter, arid called Aldebaran ; from which the moon's distance is computed. " A star of the first magnitude illumes His radiant head ; and of the second rank, Another beams not far remote." The ancient Greeks counted seven in this cluster : "The Bull's head shines with seven refulgent flames, Which, (rrecia, Hyades, from their ^/towering names." 69. Aldebaran is of Arabic origin, and takes its name from two words which signify, " He went before, or led the way" alluding to that period in the history of astronomy when this star led up the starry host from the vernal equinox. It comes to the meridian at 9 o'clock on the 10th of January, or 48^ minutes after Alcyone, on the 1st. When Aries is about 27^ high, Aldebaran is just rising to the east. So MANILIUS : " Thus, when the Ram hath doubled ten degrees, And join'd seven more, then rise the Hyades." \ line 15 %" E. N. E. of Aldebaran will point out a bright star of the 2d magnitude in the extremity of the northern horn, marked Beta or Et Nath ; (this star is also in the foot of Auriga, and is common to both constellations.) From Beta in the northern horn, to Zeta, in the tip of the southern horn, it is 8, in a southerly direction. This star forms a right angle with Aldebaran and Beta. Beta and Zeta, then, in the button of the horns, are in a line nearly north and south, 8 apait, with the brightest on the north That very bright star 17% N. of Beta, is Capella, in the constellation Auriga. G7. What other name have the Pleiades, and why ? Citation from Job ? Syrian name ? 68. Where are the Hyades situated? How known? Where the most brilliant star? Name? Are they shown on the map? 69. Origin and import of the name Alrtebarant When does it come to the meridian at 9 o'clock p.m. ? Where is Beta? In what other constellation ? Zeta, and its distance? How situated with reference to AlCjbarar an I Beta? How Beta and /eta? Capella? . ORION. 4i HISTORY. According to the Grecian mythology, this is ih- animal which bore Europa over thg Beas to tliat country which derived from her its name. She was the daughter of Ageaor and princess of Phoenicia. She was so beautiful that Jupiter became enamoured of her and assuming the shape of a snow-white bull, he mingled with the herds of Agenor, while Europa, with her female attendants, were gathering flowers in the meadows. Kuropa caressed the beautiful animal, and at last had the courage to sit upon his back. The god now took advantage of her situation, and with precipitate steps retired towards the shore, and crossed the sea with Europa upon his back, and arrived safe in Crete. Some suppose she lived about 1552 years before the Christian Era. It is probable, however, that this constellation had a place in the Zodiac before the Greeks began to cultivate a knowledge of the stars; and that it was rather an invention of the Egyptians or Chal- deans. Both the Egyptians and Persians worshipped a deity under this figure, by the name of Apis ; and Belzoni is said to have found an embalmed bull in one of the notable sepulchres near Thebes. In the Hebrew Zodiac, Taurus is ascribed to Joseph. The Pleiades, according to fable, were the seven daughters of Atlas and the nymph Pleione, who were turned into stars, with their sisters the Hyades, on account of their amiable virtues and mutual affection. Thus we everywhere find that the ancients, with all their barbarism and idolatry, entertained the belief that unblemished virtue and a meritorious life would meet their reward in the sky. Thus Virgil represents Magnus Apollo as bending from the sky to address the youth lulus : 44 Macte nova virtute puer ; sic itur ad astra; Diis genite, et geniture Deos." " Go on, spotless boy, in the paths of virtue; it is the way to the stars; offspring of the gods thyself so shalt thou become the father of gods." Our disgust at their superstitions may be in some measure mitigated, by seriously reflecting, that had some of these personages lived in our day, they had been orna- ments in the Christian Church, and models of social virtue. TELESCOPIC OBJECTS. 1. a TAURI ( Aldtbaran) A star of the first magnitude with a telescopic companion' R. A. 4h. 2(Jm.'44s. ; Dec. N. 16 10' 9". A 1, pale rose tint ; B 12, sky blue. 2. /3 TAURI (7 A r at/t)R. A. 5h. 16m. 11s.; Dec. N. 28 28'. A fine star, with a distant companion. A 2, brilliant white; B 10, pale grey. 3. y TAURI One of the Hyades ; R. A. 4h. 10m. 4ts. ; Dec. 11 14' 1". A bright star, with a distant telescopic companion; A 3J^, yellow; B 11, pale blue. 4. 77 TAURI (Alcyone) One of the Pleiades; R. A. 3h. 37m. 57s.; Dec. N. 23" 36' 3". A 8, greenish yellow; B, pale white and distant. 5. A NKBULOUS STAR; R. A. oh. 59m. 06s. ; Dec. N. 30* 20' 5". A star of the eighth magnitude, with a faint luminous atmosphere surrounding it, and about 3' in diameter. This star and nebula led Sir William Herschel to adopt his Nebula Theory, or theory of condensation of gas or nebulous matter, into suns and worlds. 6. A LARGE NEBULA ; R. A. 5h. 24m. 51s. ; Dec. N. 21" 54' 2". It is about one degree iiorth-west of (in the tip of the Bull's southern horn. It is an oval form, with several luinute telescopic stars in its vicinity. For drawing, see Map VIII., Fig 80. Of the Pleiades and llyad&s, two prominent clusters, we have spoken at 64, 65. ORION. MAP III. 70. Whoever looks up to tins constellation and learns its Game, will never forget it. It is too beautifully splendid to need a description. When it is on the meridian, there is then above HISTORY. Story of Europa and Jupiter? What probability? What said of the Egyptians and Persians? Hebrew zodiacs? Fabulous paternity of the Pleiades? Why turned into stars? What remarks respecting the ancients? TKI.ESCOPIC OBJ ISCTS. Alpha? Beta? Gamma? Eta? Nebulae? Point out on th* map. 7u. What is said of Orion? Of the view when on the meridian? How is Cr'on repre- 42 ASTRONOMY. the horizon the most magnificent view of the celestial bodies that the starry firmament affords ; and it is visible to all the habitable world, because the equinoctial passes through the middle of the constellation. It is represented on celestial maps by the figure of a man in the attitude of assaulting the Bull, with a sword in his belt, a huge club in his right hand, and the skin of a lion in his left, to serve for a shield. Manillas, a Latin poet, who composed five books on astronomy a short time before the birth of our Saviour, thus describes its appearance : " First next the Twins, see great Orion rise, His arms extended stretch o'er half the skies ; His stride as large, and with a steady pace He marches on, and measures a vast space ; On each broad shoulder a bright star display'd, And three obliquely grace his hanging blade. In his vast head, immers'd in boundless spheres, Three stars, less bright, but yet as great, he bears, But farther off removed, their splendor's lost ; Thus graced and arm'd he leads the starry host." 71. The centre of the constellation is midway between the poles of the heavens and directly over the equator. It is also about 8 W. of the solstitial colure, and comes to the meridian about the 23d of January. The whole number of visible stars in this constellation is 78 ; of which, two are of the first magni- tude, four of the 2d, three of the 3d, and fifteen of the 4th. 72. Those four brilliant stars in the form of a long square or parallelogram, intersected' in the middle by the "Three Stars," or " Ell and Yard," about 25 S. of the Bull's horns, form the outlines of Orion. The two upper stars in the parallelogram are about 15 N. of the two lower ones ; and, being placed on each shoulder, may be called the epaulets of Orion. The brightest of the two lower ones is in the left foot, on the W., and the other which is the least brilliant of the four, in the right knee. To be more particular ; Bellatrix is a star of the 2d magnitude on the W. shoulder ; Betelguese is a star of the 1st magnitude, 7 E. of Bellatrix, of Diana he was placed among the stars directly opposite to the Scorpion that caused his death. Others say that Orion had no mother, but was the gift of the gods, Ju.pitt.-r, Neptune, and Mercury, to a peasant of Bceotia, as a reward of piety, and that he was invested with the power of walking over the sea without wetting his feet. In strength and stature he surpassed all other mortals. He was skilled in the working of iron, from which he fabricated a subterranean palace for Vulcan ; he also walled in the coasts of Sicily against the inundations of the sea, and built thereon a temple to its gods. Orion was betrothed to the daughter of (Enopion, but he, unwilling to give up hia daughter, contrived to intoxicate the illustrious hero and put out his eyes, on the sea'- ehore where he had laid himself down to sleep. Orion, finding himself blind when he awoke, was conducted by the sound to a neighboring forge, where he placed one of the workmen on his back, and, by his directions, went to a place where the rising sun wan seen with the greatest advantage. Here he turned his face toward the luminary, am , as it is reported, immediately recovered his sight, and hastened to punish the perfidiom cruelty of (Enopion. As the constellation Orion, which rises at noon about the 9th day of March, and sets a' noon about the 21st of June, is generally supposed to be accompanied, at its rising, with great rains and storms, it became extremely terrible to mariners, in the early adven- tures of navigation. Virgil, Ovid, and Horace, with some of the Greek poets, make mention of this. Thus Eneas accounts for the storm which cast him on the African coast on his way to Italy : "To that blest shore we steer'd our destined way, When sudden, dire Orion rous'd the sea; All charg'd with tempests rose the baleful star, And on our navy pour'd his wat'ry war." To induce him to delay his departure, Dido's sister advises her to "Tell him, that, charged with deluges of rain, Orion rages on the wintry main." The name of this constellation is mentioned in the books of Job and Amos, and in Homer. The inspired prophet, penetrated like the psalmist of Israel with the omni- science and power displayed in the celestial glories, utters this sublime injunction : " Seek Him that maketh the seven stars and Orion, and turneth the shadow of death into morning." Job also, with profound veneration, adores his awful majesty who "com- mandeth the sun and sealeth up the stars ; who alone spreadeth out the heavens, and maketh Arcturus, Orion, and Pleiades, and the chambers of the south:" and in anotner place, the, Almighty demands of him " Knowest thou the ordinances of heaven? Canst thou bind the sweet influences of the Pleiades, or loose the bands of Orion; canst thou bring forth Mazzaroth in his season, or canst thou guide Arcturus with his sons?" Calmet supposes that Mtizzmoth is here put for the whole order of celestial bodies in the Zodiac, which, by their appointed revolutions, produce the various seasons of fie year, and the regular succession of day and night. A ret if -us is the name of the prin- cipal star in Bootes, and is here put for the constellation itself. The expression, his yonn, doubtless refers to Asterion and Chara, the two greyhounds, with which he seems to be pursuing the Great Bear around the North pole. 7G. What stay mentioned west of Bellatrix? Remark respecting Orion? HISTORY. Story of parentage? Disposition and boasting? Punishment? What other account? What mention of by Virgil? By Job and Homer? Supposition of Cahuet? Wha' meant by "Arcturus and his sons?" LEPUS. 45 TELESCOPIC OBJECTS. 1. a ORIONIS (Betelguese)R. A. 5h. 46m. 30s. ; Dec. N. 7 22' 3'. A 1, orange tint; B 11, bluish. 2. /3 OKIONIS (Rigel} R. A. 5h. 6m. 51s ; Dec. S. S 23' 5". A 1, pale yellow; B 9, V sapphire blue. Map VIII. Fig. 3. 3. y OKIONIS (Bellatfix)^. A. 5h. 16m. 33s. ; Dec. N. 6 12'. A FINK STAB, with a minute distant companion. A 2, pale yellow ; 15 15, grey. 4. 6 OKIO.VIS (Miutaka)^ coarse DOUBLE STAB in the girdle of the figure; R. A. 51i. 23m. 50s. ; Dec. S. 25' 4". A 2, white ; B 7, pale violet. 5. e OHIONIS (Alnilam) in the centre of his belt ; K. A. oh. 2Sm. 06s. ; Dec. S. I 1 IS' 0" A 2}, white and nebulous; B. 10, pale blue. 6. C ORIOXIS (Altdtah) the last or lowest in the belt; R. A. 5h.32m. 41s.; Dec. 3. 2 O* A flue TRIPLE STAR. A 3, topaz yellow; B 6>6, light purple; and 10,-gray. 7. A minute DOUBLE STAR and cluster, in Orion's left hand ; R. A. 5h. 59m. 25s. ; Dec. N. 13 58' 6". A 7^, B SJi, both lucid white. 8. Another DOUBLE STAR in a cluster, in the left shoulder; R. A. 6h. 03m. 35s. ; Dec. N. 6 28' 9". A 9% and B 10, both pale yellow. A tolerably rich cluster, with numerous stragglers. 9. A PLANETAY NEBULA, of a bluish white tint, on the nape of Orion's neck small, pale, but quite distinct. R. A. 5h. 33m. 21s. ; Dec. N. 9 00' 2". 10. Two stars " in a \VISPY NEBULA," just above the left hip ; R. A. 5h. 38m. 33s. ; Dec. N. 00' 7". A 8% and B. 9, both white. A singular mass, between two small stars, about equi-distant, in a blaukish part of the heavens. 11. The GREAT NKBULA OF ORION The most conspicuous nebula in all the heavens. It is situated in the ticord of Orion, below the middle star of the belt; R. A. 5h. 27m. 25s.; Dec. S. 5 30'. For its position in the constellation see Map VIII., Fig. 31. It may be seen with a common telescope. There is an apparent opening in one side of this nebula, through which, as through a window, we seem to get a glimpse of other heavens, and brighter regions. (Map VIII., Fig. 32.) 12. The middle star in the sword is in the midst of this nebula, and with powerful tele- scopes is found to be sextuple. The writer has often seen the fifth star with a 6-inch refractor. These stars constitute the Trapezium of Orion. The region around this nebula is rich in stars, as shown on Map VIII., Fig. 33. LEPUS (THE HARE). MAP III. 77. This constellation is situated directly south of Orion, and conies to the meridian at the same time ; namely, on the 24th of January . It has a mean declination 18 S., and contains 19 Hiiall stars, of which, the four principal ones are of the 3d magni- tude. It may be readily distinguished by means of four stars of the 3d magnitude, in the form of an irregular square, or trapezium. 78. Zda, of the 4th magnitude, is the first star, and is situated in the back, 5 S. of Saiph, in Orion. About the same distance below Zeta are the four principal stars, in the legs and feet. These form the square. They are marked Alpha, Beta, Gamma, Delta. TKLK?UJOPIC OBJECTS. Alpha? Beta? Gamma? Delta, Ac.? What double staisT Nebulae? Point out on the map ? 77. Location of Lepus? Number and magnitude of stars? How may it be distiu- iruished? 78. Size and situation of Zt-ta? Other principal stars? How marked on ihe map ? 46 ASTRONOMY. 79. Alpha, otherwise called Ameb, and Beta form the N. W. end of the trapezium, and are about 3 apart. Gamma and Delta form the S. PI end, and are about 2 J apart. The upper right-hand one, which is Arneb, is the brightest of the four, and is near the centre of the constellation. Four or five degrees S. of Rigel are four very minute stars, in the ears of the iiare. HISTORY. Tliis constellation is situated about 18 west of the Great Dog, which, from the motion Of the earth, seen.s to be pursuing it, as the Greyhounds do the Bear, round the Circuit of the skies It was one of those animals whic.h Orion is said to have delighted in hunt- ing, and which, lor this reason, was made into a constellation and placed near hiin among the stars. TELESCOPIC OBJECTS. 1. a LEPORIS (Arneb') A distant DOUBLE STAB ; R. A. 5h. 25m. 40s. ; Dec. S. 17 56' 05*. A 8Jg, pale yellow ; B 9}$, grey. 2. ft LKPOKIS (Nihal) A STAR with a distant telescopic companion ; R. A. 5h. 21m. 23s. ; Dec. S. 20* f>3' 05". A 4, deep yellow; B 11, blue. 3. >' LKpoRib A wide TRIPLE STAR in a barren field; R. A. 5h. 37m. 4Ss. ; Dec. S. 22' 80 02". A *, light yellow ; B 6J, pale green ; C 13, dusky. 4. L LKPORIS A delicate DOL T BLK STAR in the Hare's left ear; R. A. 5h. 04m. 50s. ; Dec. S. 12' 03' 09'. A 4^, white; B 12, pale violet, with :i reddish distant star nearly north. 5. K LKPORIS A close DOUBLE STAR, at the root oSthe left ear; R. A. oh. 5m. 51s. ; Dec. 8. 13" US'. A 5, pale white ; B 9, clear grey. 6. A bright STELLAR NEBULA, under the Hare's feet ; R. A. 5h. 17m. 50s. ; Dec. S. 24," 39' 09". A fine object of a milky white tinge, and blazing towards the centre, Hersche'. describes it as "a beautiful cluster of stars, nearly 3' in diameter, of a globular form^ and extremly rich." An imaginary Jine run from Betelguese before a Leporis, and o^er S, will hit this object about 4 south-west of the latter. COLUMBA (NOAH'S DOVE). MAP III. 80. This constellation is situated about 16 S. of tlu- li-are, and is nearly on the same meridian with the " Three Stars," in the belt of Orion. It contains only 10 stars ; one of the 2d, one of the 3d, and two of the 4th magnitudes ; of these Phaet and Beta are the brightest, and are about 2 apart. Phaet, the principal star, lies on the right, and is the highest of the two ; Beta may be known by means of a smaller star just east of it,. marked Gamma. A line drawn from the easternmost star in the belt of Orion, 32 directly south, will point out Phaet ; it is also 11^ S. of the lower left-hand star in the square of the Hare, and makes with Sirius and Xaos, in the ship, a large equi- lateral triangle. 79. What other name has Alpha ; and with Beta what does it form? What further description ? HISTORY. Why was Lepus placed in the heavens? TELESCOPIC OBJECTS. Alpha? Beta] Gamma? Iota? Kappa? Nebula? SO. Situation of Columba? Number and size of stars? The two brightest, and skua- f-on f H.OW find Phaet ? What figure dues it help to form ? With what other star* ? ERiDANUS. 47 , HISTORY. This constellation is so called in commemorati'm of the dove wh ch Noah " sent forth to see if the waters were abated from off the face of the ground," after the ark had rested on mount Ararat. " And the dove cauie in to him in the evening, and lo, in her mouth was an olive leaf plucked off. -" The surer messenger, A dove sent forth once and again to spy Green tree or ground, whereon his foot may light : The second time returning in his bill An olive leaf he brings, pacific sign 1" ERTDANUS (THE RIVER PO). MAP III. 81. This constellation meanders over a large and very irregu- lar space in the heavens. It is not easy, nor scarcely desirable, to trace out all its windings among the stars. Its entire length is not less than 130 ; which, for the sake of a more easy refer- ence, astronomers divide into two sections, the northern and the southern. That part of it which lies between Orion and the Whale, including the great bend about his paws, is distinguished by the name of the Northern stream ; the remainder of it is called the Southern stream. 82. The Northern stream commences near Rigel, in the foot of Orion, and flows out westerly, in a serpentine course nearly 40 to the Whale, where it suddenly makes a complete circuit, and returns back nearly the same distance towards its source, but bending gradually down toward the south, when it again makes a similar circuit to the S. W., and finally disappears below the horizon. West of Rigel there are five or six stars of the 3d and 4th magnitudes, arching up in a semi-circular form, ami marking the first bend of the northern stream. About 8 below these, or 19 W. of Ripcl, is a bright sta~ of the 2d magnitude, in the second bend of the northern stream, marked Gamma. This star culminates \'6 minutes after the Pleiades, and one hour and a quarter before Rigel. Passing Gamma, and a smaller star west of it, there are four stars nearly in a row, which bring us to the breast of Otus. 8 N. of Gamma, is a small stai named Itied, which is thought by some to be considerably nearer the earth than Sirius. S Tkeemim, in the southern stream, is a star of the 3d magnitude, about 17 S. W. of the square in Lepus, and may be known by means of a smaller star.l above it. Achcr- n-ur is a brilliant star of the 1st magnitude, in the extremity of the southern stream; but having 58" of S. declination, can never be seen in this latitude. 83. The whole number of stars in this constellation is 84 ; of which, one is of the 1st magnitude, one of the 2d, and eleveu are of the 3d. Many of these cannot be pointed out by verbal description ; they must be traced from the map. HISTORY. Origin of this constellation ? 81. What said of Eridanus? Length? How divided? 82. Trace the Northern Stream? Gamma? Theemim? Achernar? 83. Whrlc number of stars in Eridanus F 48 ASTRONOMY. S4 In the upper part of the Northern stream, near tiie feet of Taurus, nay be seen a modern, but now discarded constella- tion, of which Captain Smyth says: "Abbe Hell (who also placed Herschel's Telescope among the celestials) has squeezed in his Harpa Georgii,to compliment a sovereign of those realms ; having filched from Eridanus about thirty or forty stars, some of vhe 4th magnitude, for the purpose. HISTORY. Eridanus is the name of a celebrated river in Cisalpine Gaul, also called Padus. Its modern name is Po. Virgil calls it the king of rivers. The Latin poets have rendered i memorable from its connection with the fable of Phaeton, who, being a son of Phoebus nd Clymene, became a favorite of Venus, who intrusted him with the care of one of er temples. This favor of the goddess made him vain, and he sought of his father a ublio and incontestable sign of his tenderness, that should convince the world of his rigin. Phoebus, after some hesitation, made oath that he would grant him whatever Le required, and no sooner was the oath uttered, than " The youth, transported, asks without delay, To guide the sun's bright chariot for a day. The god repented of the oath he took, For anguish thrice his radiant head he shook; My son, says he, some other proof require, Kash was my promise, rash was thy desire Not Jove himself, the ruler of the sky, That hurls the three-forked thunder from above, Dares try his strength ; yet who as strong as Jove? Besides, consider what impetuous force Turns stars and planets in a difi< rent course. I steer against their motions; nor am I Borne back by all the current of the sky: But how could you resist the orbs that roll In adverse whirls, and stem the rapid pole ?" Phcebus represented the dangers to which he would be exposed in rain. lie under- took the afirial journey, and the explicit directions of his father were forgotten. No sooner had Phaeton received the reins than he betrayed his ignorance of the manner of guiding the chariot. The flying coursers became sensible of the confusion of their driver, and immediately departed from the usual track. Phaeton repented too late of his rashness, and already heaven and earth were threatened with a universal confla- gration as the consequence, when Jupiter, perceiving the disorder of the horses, struck the driver with a thunderbolt, and hurled him headlong from heaven into the river Eridanus. His body, consumed with fire, was found by the nymphs of the place, whfr honored him with a decent burial, and inscribed this epitaph upon his tomb: "Iff 3 situs est Phaeton, currus aurigapaterni: Queue si non tenuit, magnis tamen excidit ausis." IRs sisters mourned his unhappy end, and were changeQ by Jupiter into poplars. "All the long night their mournful watch they keep, And all the day stand round the tomb and weep." OVID. It is said the tears which they shed turned to amber, with which the Phoenicians gnd Carthaginians carried on in secrecy a most lucrative trade. The great heat pro- duced on the occasion of the sun's departing out of his usual course, is said to have dried up the blood of the Ethiopians, and turned their skins black; and to have pro- duced sterility and barrenness over the greater part of Libya. " At once from life and from the chariot driven, Th' ambitious boy fell thunderstruck from heaven." ******* 84. What discarded constellation mentioned? Is it on the map? Remark of Capt. Smyth ? . Named after what? Modern name? Fable of Phaeton? It eviden* AURIGA. 49 *'The brekthless Phaeton, with flaming hah, Shot from the chariot like a falling star, That in a summer's evening from the top Of heaven drops down, or seems at least to drop, Till on the Po his blasted corpse was hurl'd, Far from his country, in the western world." The fable of Phaeton Evidently alludes to some extraordinary heats which wrra experienced in a very remote period, and of which only this confused tradition hui descended to later times. TELESCOPIC OBJECTS. 1. ft ERIDANI A bright star with a distant telescopic companion, on the shin bon? of Orion ; It. A. 4h. 5ym. 59s. ; Dec. S. 5 17' 9". A 3, topaz yellow ; B 12, pale blue. TLia star is just above Rigel, in the direction of the Hyades. 2. y ERIDANI A star with a distant companion ; It. A. 3h. 50m. 34s. ; Dec. S. 13 5S 1 . A 2 j, yellow ; B 10 pale grey. 3. A MB.K WHITE JSEBULA ; K. A. 3h. 83m. 02s. ; Dec. S. 19" 04' S". Pale, distinct, round, and bright in the centre. 4. A PI.ANKTARY NEBULA ; R. A. 4h. 06m. 60s.; Dec. S. 13 09' 1". About 433 from ) yisb in the direction of Kigel. A splendid though not very conspicuous object, of a grey white color. Map VIII., Fig. 34, represents it in its best aspects, highly magnifu with four telescopic stars in the field, two of which point exactly towards the nebula. SCEPTRUM BRANDENBURG IUM (SCEPTRE OF BRANDEXBUKGJ. MAP III. 85. This is a slender constellation, situated between the two streams of the River Po. It was constructed by Kirch, in 1688. and recognized by Bode a century afterwards; but is now gene- rally discarded, though retained on the map. It is composed of four stars of the 3d, 4th and 5th magnitudes, running north and south; and is usually included in Eridanus. AURIGA (THE CHARIOTEER). MAP III. 86. The Charioteer, called also the Wagoner, is represented on the celestial map by the figure of a man in a reclining posture, resting one foot upon the horn of Taurus, with a goat and her kids in his left hand, and a bridle in his right. It is situated N. of Taurus and Orion, between Perseus on the W. and the Lynx on the E. Its mean declination is 45 N. ; so that when on the meridian, it is almost directly overhead in New England. It is on the same meridian with Orion, and culminates at the same hour of the night. Both of these con- stellations are on the meridian at 9 o'clock on the 24th of TELESCOPIC OBJECTS. Beta? Gamma? Nebula? Point out on the map. 85. Describe the Sceptre of Brandenhurgh? Situation? When and by whom consti- tuted? Is it recognized by astronomers? Number and magnitude of stars? S6. lioV ! .Auriga reprvMOted? Situation? When on the meridian? 60 ASTRONOMY. January, and 1 hour and 40 minutes east of it on the 1st of January. 8t. The whole number of visible stars in Auriga, is 66, including one of the 1st and one of the 2d magnitude, which mark the shoulders. Capella is the principal star in this con- stellation, and is one of the most brilliant in the heavens. It takes its name from Capella, the goat, which hangs upon the left shoulder. It is situated in the west shoulder of Auriga, 24 E. of Algol, and 28 N. E. of the Pleiades. It may be known by a little sharp-pointed triangle formed by three stars, 3 or 4 this side of it, on the left. It is also 18 N. of El JN T ath, which is common to the northern horn of Taurus, and the right foot of Auriga. Capella comes to the meridian on the 19th of January, just 2 minutes before Rigel, in the foot of Orion, which it very much resembles in brightness. Menkalina, in the east shoulder, is a star of the 2d magnitude, 7J3" E. of Capella, and culminates the next minute after Betelguese, 37% S. of it. Thvta, in the right arm, is a star of the 4th magnitude, 8 directly south of Menkalina. It may be remarked as a curious coincidence, that the two stars in the shoulders of Auriga are of the same magnitude, and just as far apart as those in Orion, and opposite to them. Again, the two stars in the shoulders of Auriga, with the two in the shoulders of Orion, mark the extremities of a long, narrow parallelogram, lying N. and S., and whose length is just five times its breadth. Also, the two stars in Auriga, and the two in Orion, make two slender and similar triangles, both meeting in a common point, half way between them at El Nath, in the northern horn of Taurus. Delta, a star of the 4th magnitude in the head of Auriga, is about 9 N. of the two in the shoulders, with which it makes a triangle, about half the height of those just alluded to, with the vertex at Delta. The two stars in the shoulders are therefore the base of two similar triangles, one extending about 9" N. to the head, the other 18 . to the heel, on the top of the horn : both figures together resembling an elongated diamond. Delta in the head, Menkalina in the right shoulder, and Theta in the arm of Auriga, make a straight line with Betelguese in Orion, Delta in the square of the Hare, and Beta in Noah's Dove ; all being very nearly on the same meridian, 48 W. of the solstitial flolure. " See next the Goatherd with his kids ; he shines With seventy stars, deducting only four, Of which Capella never sets to us. And scarce a star with equal radiance beams Upon the earth : two other stars are seen Due to the second order." Eudosia* HISTORY. The Greeks give various accounts of this constellation; some supposed it to be Erich- thonius, the fourth king of Athens, and son of Vulcan and Minerva, who awarded him a place among the constellations on account of his many useful inventions. He was of H monstrous shape. He is said to have invented chariots, and to have excelled all others in the management of horses. In allusion to this, Virgil has the following lines " Primus Erichthonius currus et quatuor ausus Jungere equos, rapidisque rotis insistere victor." Georgic. Lib. iii. p. 11-3. " Bold Erichthonius was the first who join'd Four horses for the rapid race design'd, And o'er the dusty wheels presiding sat." Dryden. 87. Number of stars visible? .Magnitude and situation of Capella? How known? Menkalina? Delta compared wuh Theta? HISTORY. The first supposition ? Second? Third? Opinion of Jamiesou* CAMELOPARDALUS. 51 Other writers say that Bootes invented the chariot, and that Auriga was the son of Mercury, and charioteer to (Enomaus, king of Pisa, and so experienced, that he rendered his horses the swiftest in all Greece. But as neither of these fables seems to account for ilie goat and her kids, it has been supposed that they refer to Amaltluea and her sister Melissa, who fed Jupiter, during his infancy, with goat's milk, and that, as a reward for their kindness, they were placed in the heavens. But there is no reason assigned for their being placed in the arms of Auriga, and the inference is unavoidable, that mythology is at fault on this point. Jamieson is of opuiin that Auriga is a mere type or scientific symbol of the beautiful fp.ble of Phaeton, because he was the attendant of Phxebus at that remote period when Taurus opened the year. TELESCOPIC OBJECTS. 1- a A.UR\GiE(Capella) A fine star with two distant companions, on the right shoulder- blade of Auriga ; R. A. 5h. 04ru. 53s. ; Dec. N. 45" 49' UT". A 1, bright white ; B 12, pale blue ; C 9, grey. 2. j3 AURIGA (McnkdUna) A bright star in the left shoulder, with a distant com- panion ; R. A. 5h. 47m. 4Ss. ; Dec. N. 44 55' 3'. A 2, yellow; B 10%, bluish. 3. A RICH CLUSTER of minute stai;., on the left thigh ; R. A. 5h. 18m. 41s. ; Dec. N. 35* 44' 9" A singular figure, somewhat like a cross. Find by a line from Rigel, northwards through ft Tauri, and about 7 beyond. 4. A RESOLVABLE NEBULA ; R. A. Bt . 20ra. 5ls. ; Dec. N. 84 06' 9". Situated in a rich field of minute stars. CAMELOPARDALUS (THE OAMELOPARD). MAP VI. 88. This constellation was made by Hevelius out of the unformed stars which lay scattered between Perseus, Auriga, the head of Ursa Major, and the Pole star. It is situated directly N. of Auriga and- the head of the Lynx, and occupies nearly all the space between these and the pole. It contains 58 small stars ; the five largest of which are only of the 4th mag- nitude. 89. The principal star lies in the thigh, and is about 20 from Capella, in a northerly direction. It marks the northern boun- dary of the temperate zone ; being less than one degree S. of the Arctic circle. There are two other stars of the 4th magni- tude, near the right knee, 12 N. E. of the first mentioned. They may be known by their standing 1 apart and alone. The other stars in this constellation are too small, and too much scattered to invit observation. HISTORY. The Camelopard is so called from an animal of that name, peculiar to Ethiopia. This animal resembles both the camel and the leopard. Its body is spotted like that of the leopard. Its neck is about seven feet long, its fore and hind legs from the hoof to tiie* cecond joint, are nearly of the same length ; but from the second joint of the legs to the body, the fore legs are so long in comparison with the hind ones, that no person could sit uuon its back without instantly sliding off, as from a horse that stood up on his hind feet. TELESCOPIC OBJKCTS. Alpha? Beta? Cluster? Nebulae ? S3. Origin of Camelopardalus? Situation and extent? Number and size of its Slars? 69. Where is its prin -ipal star? The next two? llutv known? . Any mythological story? What said of the animal? E.G. 52 ASTRONOMY. TELESCOPIC OBJECTS. 1. a CAMELOPARDALI A neat DOUBLE STAR between the hind feet of the animal, half wa> between a Persei and f5 in the head of Auriga ; R. A. 4h. 19m. '23s. ; Dec. N. 53 83 3" A 7^, white; B 8%, sapphire blue. 2. Another close DOUBLE STAR, between the hind feet; R. A. 4h. 27m. 18s. ; Dec. N. 03* 09'. A 5), yellow ; B. 7}, pale blue. 3. A very delicate DOUBLE STAR in the animal's hind hoof; R. A. 4h. 44m. 28s. ; Dec. N 63 29' 3". A 5, white ; B 13, orange. 4. A fine DOUBLE STAR in the lower part of the back of the neck; R. A. 4h. 46m. 19s. Dec. N. 79 01' 8". A 5), light yellow ; B 9, pale blue. 5. A bright PLAXETABT NEBULA, of a bluish white tint, about 60" in diameter, in th* nind flank of the animal, R. A. 4h. 53m. 29s. Dec. N. 60 23' 5". A curious body, in a rich Held of small stars. CHAPTER IV. CONSTELLATIONS ON THE MERIDIAN IN FEBRUARY. THE LYNX. MAPS III. AND VI. 90. THIS constellation, like that of the Camelopard, exhibits no very interesting features by which it can be distinguished. It contains only a moderate number of inferior stars, scattered over a large space N. of Gemini, and between Auriga and Ursa Major. 91. The whole number of stars in this constellation is 44, including only three that are so large as the 3d magnitude. The largest of these, near the mouth, is in the solstitial colure, 14 N. of Menkaliua, in the E. shoulder of Auriga. The other two principal stars are in the brush of the tail, 3 S. W, of another star of the same brightness in the mouth of the Lesser Lion, with which it makes a small triangle. Its centre is on the meridian at 9 o'clock on the 23d, or at half-past 7 on the 1st of February. TELESCOPIC OBJECTS. 1. A close DOUBLE STAR, in the nose of the Lynx ; R. A. 6h. 07m. 51s. ; Dec. N. 59 25' 8* About 80" from the Pole star, on a line toward Sirius. A 6, and B 7%, both white. "An elegant but difficult object. 2. A close DOUBLE STAR in the eye of the Lynx, between Dubhi and Capella; R. A. 6h 38m. 57s. ; Dec. N. 59 37' 6". A 5}, golden yellow ; B 7, purple. A delicate and pretty object. 3. A coarse TRIPLE STAR on the animal's lower jaw; R. A. 6h. 12m. 50s. ; Dec. N. 58* 29' 7". A. 6, orange tinge ; B 13, blue ; and C 9, pale garnet. 4. A ROUND NEBULA, in the Lynx, or fore paws of Leo Minor; R. A. 9h. 14m. 82s. Dec. N. 35 11' 9*. It is pale white, sparkling in the centre. TELESCOPIC OBJECTS. Alpha? What other double stars? Nebula? i0. Describe the Lynx? Situation? 91. Number and size of its stars? Where is th tirgest situated? The otln>r two principal stars? TKLKSCOPIC OBJECTS. Wlmt double stars ? Triple? Nebula GEMINI. 53 TELESCOriUM liKRSCHELLII (HKKSCIIEL'B MAP III. 92. About midway between the body of the Lynx and Gemini, may be seen the rude figure of a refracting Telescope, with its stand. It was made out of a few unformed stars, by Abbe Hell, in honor of Sir William Herschel, but is now generally discarded. It is reta.aed on the map more as a matter of history than to perpetuate it as a constellation. GEMINI (THE TWINS). MAP III. 93. This constellation represents, in a sitting posture, the twin brothers, Castor and Pollux. It is the third sign, but fourth constellation in the order of the Zodiac, and is situated south of the Lynx, between Cancer on the east, and Taurus on the west. 94. The plane of the Ecliptic passes through the centre of Gemini ; and as the earth moves round in her orbit from the first point of Aries to the same point again, the sun, in the mean- time, will appear to move through the opposite signs, or those which are situated right over against the earth, on the other side of her orbit. Accordingly, if we could see, the stars as the sun appeared to move by them, we should see it passing over the constellation Gemini between the 21st of June and the 23d of July; but we seldom see more than a small part of any constellation through which the sun is then passing, because the feeble lustre of the stars is obscured by the superior effulgence of the sun. When the sun is just entering the outlines of a constellation eastward, its eastern limit may be seen in the evening twilight, just above the setting sun. So when the sun has irrived at the eastern limit of a constellation, the western part of it may be seen rising in the morning twilight, just before the rising sun. Under other circumstances, when the sun is said to be in, or to enter, a particular constellation, it is to be understood that that constellation is not then visible, but that those opposite to it are. For example: whatever constellation sets with the sun on any day, it is plain that the one oppo-ite to it must be then rising, and continue visible through the night. Also, whatever constel- lation rises and sets with the sun to-day, will, six months hence, rise, at sun-seUin, golden yellow ; B 8, lilac. 3. A fine TRIPLE STAR in the right fore-leg; R. A. 6h. 21m. 04s.; Dec. S. 6 56' 01'. A 6)3, white ; B 7, and C 8, both pale white. A ray shot from the Bull's eye through Bella- trix, and rather more than as far again, will pick it up. Supposed by Herschel to be a triple system, periods A B 17,000 ys. B C 1000. Shown double only on the map of the constellations. Telescopic view, Map VIII., Fig. 5. 4. A delicate TRIPLK STAR, in a magnificent stellar field, between the Unicorn's ears; R. A. 6h. 32m. 1fts. ; Dec. N. 10 02' 02". One-third the distance from Procyon to Aide- btt/'UK. A 6, greenish ; B 9^, pale grey ; C 15, blue. A fine object. 101. Character and situation of Monoceros? Extent? 102. Number and size of it? stars' How three of the largest situated? HISTORY. What said of the animal itself? Is it not wholly fabulous ? TKLKSCOPIC OBJECTS. Double stars ? Triple ? Any shown on the map ? CAN IS MAJOR 50 CANIS MAJOR (THE GKEAT DOG). MAP III. 103. This interesting constellation is situated southward and eastward of Orion, and is universally known by the brilliance of its principal star, Sirius, which is apparently the largest and brightest in the heavens. It glows in the winter hemisphere with a lustre which is unequaled by any other star in the firmament. Its distance from the earth, though computed at 20 millions of millions of miles, is supposed to be less than that of any other star : a distance, however, so great that a cannon ball, which flies at the rate of 19 miles a minute, would be two millions of years in passing over the mighty interval ; while sound, moving at the rate of 13 miles a minute, would reach Sirius in little less than three millions of years. It may be shown in the same manner, that a ray of light, which occupies only $ minutes and 13 seconds in coming to us from the sun, which is at the rate of nearly two hundred thousand miles a second, would be 3 years and 82 days in passing through the vast space that lies between Sirius and the earth. Consequently, were it blotted from the heavens, its light would continue visible to us for a period of 3 years and 82 days after it had ceased to be. If the nearsst stars give such astonishing results, what shall we say of those which are situated a thousand times as far beyond these, as these are from us? 104. In the remote ages of the world, when every man was his own astronomer, the rising and setting of Sirius, or the Dog Star, as it is called, was watched with deep and various solici- tude. The ancient Thebans, who first cultivated astronomy iu Egypt, determined the length of the year by the number of its risings. The Egyptians watched its rising with mingled appre- hensions of hope and fear ; as it was ominous to them of agri- cultural prosperity or blighting drought. It foretold to them the rising of the Nile, which they called Siris, and admonished them when to sow. 105. The Romans were accustomed yearly to sacrifice a dog to Sirius, to render him propitious in his influence upon their herds and fields. The eastern nations generally believed the rising of Sirius would be productive of great heat on the earth. Thus Virgil : " Turn sleriles exurere Sirius agros ; Ardebant herbse, et victura seges aegra negabat." " Parched was the grass, and blighted was the corn* Nor 'scape the beasts ; for Sirius from on high, With pestilential heat infects the sky." 103. Situation of Canis Major? How known? Supposed distance of Sirius ? Illus- trated by the speed of a cannon ball ? Of light ? 104. How was Sirius regarded by *Ji ancients? Use made of it by the Thebans? The Egyptians? 105. Practice or the Romans ? Of TH WITT B 60 ASTRONOMY. 106. Accordingly, to that season of the year when Sirius rose with the sun and seemed to blend its own influence with the heat of that luminary, the ancients gave the name of Dog-days, ( Dizs canicul 10, deep yellow, other distant small stars ia the field. 2. 6 CASIS MAJORIS A star with a distant companion in the loins ; R. A. 7h. Olm. 53s. ; Dec, S. 26 08' 6". A 3J6, light yellow ; B 7%, very pale. Other small stars in the Seld, A line from Betelguese through /Sirius intercepts it 12* below the latter star. 8. f CAMS MAJORIS (Adhara) A star with a distant companion in the belly ; R. A 6h. 52m. 20s. Dec. S. 28 45' 5". A 2}, pale orange : B 7, violet. Found by running a line from the middle of Orion's belt through j3 just west of Sirius, to about 14 beyond the latter star. 4. A CLUSTER in the back of the head ; R. A. 6h. 52m. 10s. ; Dec. S. 13 29' 2'. Tole- rably compressed; stars of the 8th to llth magnitudes, of which the four principal form the letter Y. 5. A CLUSTER between Sirius and Monoceros; R. A. 7h. 10m. 35s.; Dec. S. 15 21' 4* Stars principally of the 10th magnitude. Discovered by Miss Herschel in 1785. CHAPTER Y. CONSTELLATIONS ON THE MERIDIAN IN MARCH. AKGO NAVIS (THE SHIP ARGO). MAP III. 113. THIS constellation occupies a large space in the southern hemisphere, though but a small part of it can be seen in the United States. It is situated S. E. of Canis Major, and may be known by the stars in the prow and deck of the ship. 114. If a straight line joining Betelguese and Sirius, be pro- duced 18 to the southeast, it will point out Naos, a star of the 2d magnitude, in the rowlock of the ship. This star is in the S. E. corner of the Egyptian X, and of the large equilateral triangle made by itself with Sirius and the Dove. When on the meridian, it is seen from this latitude about 8 above the south- TELESCOPIC OBJECTS. Alpha ? Delta? Epsilon ? What clusters? 113. Size and situation of Argo Navis? How known? 114. llow n,ncl Jfavs, auJ here situated ? How high when on the meridian ? ARGO NAV13. C3 ern horizon. It comes to the meridian on the 3d of March, about half an hour after Procyou, and continues visible but a few hours. 115. Gamma, in the middle of the ship, is a star of the 2d magnitude, about 7 S. of Naos, and just skims above the south- ern horizon for a few minutes, and then sinks beneath it. The principal star in this constellation is called, after one of the pilots, Canopus; it is of the 1st magnitude, 36 nearly S. of JSirius, and comes to the meridian 17 minutes after it ; but hav- ing about 53 of S. declination, it cannot be seen in the Northern States. The same is true of Miaplacidns, a star of the 1st magni- tude in the oars of the ship, about 25 E. of Canopus, and 61 S. of Alphard, in the heart of Hydra. An observer in the northern hemisphere, can see the stars as many degrees south ol the equinoctial in the southern hemisphere, as his own latitude lacks of 90, and no wore. 116. Murkeb, is a star of the 4th magnitude, in the prow of the ship, and may be seen from this latitude 16 S. E. of Sirius, and about 10 E. of Wesen, in the back of the Dog. This star may be known by its forming a small triangle with two others of the same magnitude, situated a little above it, on the E., 3 and 4 apart. lit. This constellation contains 64 stars, of which two are of the 1st magnitude, four of the 2d, and nine of the 3d. Most of these are too low down to be seen in the United States. HISTORY. This constellation is intended to perpetuate the memory of the famous ship which car- ried Jason and his 54 companions to Colchis, when they resolved upon the perilous expedition of recovering the golden fleece. The derivation of the word Aryo has beeu often disputed. Some derive it from Argos, supposing that this was the name of the person who first proposed the expedition, and built the ship. Others maintain that it was built at Argos, whence its name. Cicero calls it Argo, because it carried GreciatiSj commonly called Argives. Diodorus derives the word from dpyb;, which signifies mcff't. Ptolemy says, but not truly, that Hercules built the ship, and called it Argo, after a son of Jason, who bore the same name. This ship had fifty oars, and being thus propelled must have fallen far short of the bulk of the smallest n/iip craft used by moderns. It is even said that the crew were able to carry it on their backs from the Danube to the Adriatic. According to many authors, she had a beam on her prow, cut in the forest of Dodona by Minerva, which had the power of giving oracles to the Argonauts. This ship was the first, it is said, that ever ventured on the sea. After the expedition was finished, and Jason had returned in triumph, he ordered her to be drawn ashore at the isthmus of Corinth, and consecrated to Neptune, the god of the sea. Sir Isaac Newton endeavors to settle the period of this expedition at about 80 yeais 115. Size and situation of Gamma? Name the principal star in this constellation? Its magnitude? Is it ever seen in the U. S. ? Wliat said of Miapla idus? Remark iu fine print? 116. What said of Markeb? How known? 117. Number of stars ia Aftfo Navis? Magnitudes? HisTunv. Design of th'.s constellation? Import of the term Argo? Size and strn*- tiwe of the ship? What myth respecting this ship? What remark respecting Hit lac Newton? Dr. Brya it's opinion? O4 ASTRONOMY. be-fore the destruction of Troy, and 43 years after the deuth of Solomon. Dr. Bryunt however, rejects the history of the Argonautic expedition as a mere liction of tiie Greeks, and supposes that this group of stars, which the poets denominate Argo Navis, refers to Noah's ark and the deluge, and that the fable of the Argoaautic expedition is founded oa cei'aia Egyptian traditions that related to the preservation of Noah aud his family during the Hood. TELESCOPIC OBJECTS. t ARGO NAVIS A star with a distant companion; R. A. Sh, 00m. 44s.; Dec. S. 23' 50' 6". A 3J3, pa'e yellow; B 1U, greyish. Other small stars in the field. 2. A SMALL GALAXY CLUSTER ; R. A. 7h. 37m. 44s ; Dec. S. 23 29' 1". 3. A neat DOUBLE STAR ovei the ship's stern ; R. A. 7h. 38m. OSs. ; Dec. S. 14 IS' 3". A 7, silvery white ; B 7), pale white. 4 A close DOUBLE STAR over the Argo's stern ; R. A. 7h. 40m. 27s. ; Dec. S. 11' 43' '6" A 7)6, pale yellow ; li 9, light blue. 5. A bright PLANETARY NEBULA ; R. A. 7h. 34m. 46s. ; Dec. S. 17' 50' 2". A fine object, pale bluish white, and may be identified by several small stars in its vicinity. See Map \ ill., Fig. 37. CANCER (TIIE CBAB). MAP IIJ- 118. Cancer is now the fifth constellation and fourth sign ot the Zodiac. It is situated in the ecliptic, between Leo on the E. and Gemini on the W. It contains 83 stars, of which one is of the 3d, and seven of the 4th magnitude. Some place the first- mentioned star in the same class with the other seven, and con- sider none larger than the 4th magnitude. 119. Beta is a star of the 3d or 4th magnitude, in the south- western claw, 10 N. E. of Procyou, and may be known from the fact that it stands alone, or at least has no star of the same magnitude near it. It is midway between Procyon and Acubeus. 120. Acubens, is a star of similar brightness, in the south- eastern claw, 10 N. E. of Beta, and nearly in a straight line with it and Procyon. An imaginary line drawn from Capella through Pollux, will point out Acubeus, at the distance of 24^ from Pollux. It may be otherwise distinguished by its standing between two very small stars close by it in the same claw. 121. The southern Asellus, marked Delta, is situated in the line of the ecliptic, and, in connection with Wasat and Tejat, marks the course of the earth's orbit for a space of 36 from the solstitial colure. A few degrees S. of Cancer, and about 17 E. of Procyon, are four stars of the 4th magnitude, 8* or 4 apart, which mark the head of Hydra. The rest of this constellation is delineated on Map IV. TKLESCOPIC OBJECTS. Iota? What cluster? Double stars? Nebula? Toint out on the .nap? 118. Tlace of Cancer in the Zodiac? In other respects? Naniber and size of if stars? 119. Beta? How known ? 120. Acubens? How found ? 121. Situation f Helta? Remarks respecting Hydra? Respecting the sign Caacer? CANCER. G5 The beginning of the sign Cancer (not the constellation) is called the Tropic of Can- cer, and when the sun arrives at tiiis point, it has reached its utmost limit of north decli- nation, where it seems to remain stationary a few days before it begins to decline again to the south. This stationary attitude of the sun is called the summer solstice; from two Latin words signifying the nun's standing still. The distance from the first point of Cancer to the equinoctial, which, at present, is 23 27? 3 ', is called the obliquity oj the ecliptic. It is a remarkable And well ascertained fact, that this is continually growing less and le?s. The tropics are slowly and steadily approaching the equinoctial, at the rate of about half a second every year; so that the sun does not now come so far north of the ' quator in summer, nor decline so far south in winter, as it must have done at the creation, by nearly a degree. HISTORY. In the Zodiacs of Esne and Dendera, and in most of the astrological remains of Egypt, a Seairabaeus, or Beetle, is used as the symbol of this sign; but in Sir William Joi.es' Oriental Zodiac, and in some others foud in India, we meet with the figure of a crab. As the Hindoos, in all probability, deriv<_ ] their knowledge of the stars trm the Chal- deans, it is sup 1 " >sed that the figure of the crab, in this place, is more ancient than the Beetle. In some extern representations of this sign, two animals, like asses, are found in this division of t. .e Zodiac; and as the Chaldaic name for the ass may be translated muddi- nefts, it is supposed to allude to the discoloring of the Nile, which river was rising when the sun entered Cancer. The Greeks, in copying this sign, have placed two asses as the appropriate symbol of it, which st.d remain. They explain their reason, however, for adopting this figure, by saying that these are the animals that assisted Jupiter in his victory over the giants. Dopuis accounts for the origin of the asses in the following words: "Le Cancer on sont les etoiles appellees les anes, forme I'eiapreinte du pavilion d' Issachar que Jacoo assimile a Pane." Mytholog sts give different accounts of the origin of this constellation. The prevail- ing opinion s, that while Hercules was engaged in his famous contest with the dreadful Lernaean monster, Juno, envious of the fame of his achievements, sent a sea-crab to bite and an joy the hero's feet, but the crab being soon dispatched, the goddess, to reward its services placed it among the constellations. " The Scorpion's claws here clasp a wide extent, And here the Crab's in lesser clasps are bent." TELESCOPIC OBJECTS. 1. (5 CANCRI A very delicate DOOBLR STAR, under the Crab's mouth; R. A. Sh. 35m. *>>s. ; Dec. J. 1S 44' 04". A 4}, straw color; B 15 blue, only seen by glimpses. 2. CANCRI A star with a distant companion, on the Crab's body; R. A. Sh. 31m. (6s.; Dec. N. 20 06' 02". A 6%, and B T, both pale white; and a third star in the field of nearly ihe same magnitude. 3. CANCRI A fine TRIPLE STAR, just below the after claws of the Crab; R. A. Sh. 03m. 02s. ; Dec N. 18 07' 05". A 6, yellow; B 7, orange tinge; C 7^, yellowish. Supposed to be a Ternary system. 4. Abort, 7 northeasterly from Tegmine, is a nebulous cluster of very minute stars, in Hie crest of Cancer, sufficiently luminous to be seen by the naked eye. It is situated in a triangular position with regard to the head of the Twins and the Little Dog. It is about 20 W. ol aeh. It may otherwise be discovered by means of two conspicuous stars of the 4th magnitude, lying one on either side of it, at the distance of about 2, called the northern and ftoiUhem AsMi. Bj some of the Orientalists, this cluster was denominated J'nwepe, .he Manger, a contrivance which their fancy filled up for the accommodation ,-,f the AnfUi or Asxex ; and it is so called by modern astronomers. The appearance 01 this group to the unassisted eye, in not unlike the nucleus of a comet, and it was repeat- edly mistaken for the comet of Is32, which, in the month of November, passed in itg ncighbo'^ood. Map VIII., Fig. 38. 5. A P'Cii EOT LOO.SK CLUSTER in the Crab's southern claw, where a line from Rigel through Procyon, into the east-northeast, will find it about 5 north of F in the Hy;id"s ; R. A. Sh. 4->!n. 20s.; Dec. N. 12" 2:J' 06". Stars mostly of the 9th and 10th magnitude* . fee Map VIII., Fig. 39. Ilisro' /.What other figures for Cancer? Egyptian ? Hindoo? Greek? Origin of this cor '!! ;ti AbTRONOMY. makes a right-a,nglcd triangle with Zozma on the N, and Dene- bola on the E., the right angle being at Theta. Nearly in a straight line with Zozma and Theta, and south of them, are three or four smaller stars, 4 or 5 apart, which mark one of the legs. '132. Denebola is a bright star of the first magnitude, in the brush of the tail, 10 S. E. of Zozma, and may be distinguished by its great brilliancy. It is 5 W. of the equinoctial colurc, and comes to the meridian 1 hour and 41 minutes after Regulus, on the 3d of May ; when its meridian altitude is the same as the sun's at 12 o'clock the next day. When Denebola is on the meridian, Regulus is seen 25* W. of it, and Phacl, in the square of Ursa Major, bears 89 N. of it. It forms, with these two, a large right-angled triangle; the right angle being at Denebola. It is so nearly on the same meridian with PI i ad that it culminates only four minutes before it. Denebola is 35%" W. of Arcturus, and about the same distance N. W. of Spica Vir- ginia, and forms, with them, a large equilateral triangle on the S. E. It also forms with Arcturus and Cor Caroli a similar figure, nearly as large on the N. E. These two triangles, being joined at their base, constitute a perfect geometrical figure of the form of a Rliombus, called by some, the DIAMOND OF VIRGO. A line drawn from Denebola through Regulus, and continued 7' or 8 further in the same direction, will point out Xi and Omicron, of the 3d and 4th magnitudes, situated in the foreclaws, and about 3 apart. There are a number of other stars of the 3d and 4th magnitudes in this constellation, which require no description, as the scholar will easily trace them out from the map. The position of Regulus and Denebola are often referred to in the geography of the heavens, as they serve to point out other clusters in the same neighborhood. HISTORY. According to Greek fable, this Lion represents the formidable animal which infested the forests of Nemuea. It was slain by Hercules, and placed by Jupiter among the stars in commemoration of the dreadful conflict. Some writers have applied the story of the twelve labors of Hercules to the progress of the sun through the twelve signs of the ecliptic; and as the combat of that celebrated herewith the Lion was his first labor, they have placed Leo as the^/'s sign. The figure of the Lion was, however, on the Egyptian charts long before the invention of the fables of Hercules. It would seem, moreover, according to the fable itself, that Hercules, who represented the sun, actually slew the Nemaean Lion, because Leo was already a zodiacal sign. In hieroglyphical writing the Lion was an emblem of violence and fury; and the representation of this animal in the Zodiac, signified the intense heat occasioned by the sun when it entered that part of the ecliptic. The Egyptians were much annoyt-d by lions during the heat of summer, as they at that season left the desert, and haunted tlu- banks of the Nile, which had then reached its greatest elevation. It was therefore natural for their astronomers to place the Lion whore we find him in the Zodiac. The figure of Leo, very much as we now have it, is in all the Indian and Egyptian Zodiacs. The overflowing of the Nile, which was regularly and anxiously expected every year by the Egyptians, took place when the sun was in this sign. They therefore paid more attention to it, it is to be presumed, than to any other. This was the principal reason, Mr. Green supposes, why Leo stands first in the zodiacs of Dendera. In the Hebrew Zodiac, Lt.-o is assigned to Judah, on whose standard, according to I! traditions, a Lion is painted. This is clearly intimated in numerous passages of the Hebrew writings : Ex. "Judah is a Lion's whelp; he stooped down, he couched as a 132. Size and position of Denebola? How known ? When does it come to the meri- dian as compared with Regulus? What said of its meridian altitude? When on the meridian where is Regulus seen? Phad? What triangle? How is Denebolo situatei 1 ; with respect to Arcturus and Spica Virginis ? To Cor Caroli ? What other large figures liisroKY. Greek fable? Egyptian? Hebrew Zodiacs? Scripture allusions to the LlDii ? LEO MINOR. 09 Lion, and as an Old Lion ; who shall rouse him up ?" Gen. xlix. 9. " The Lion of the tribe of Judah hath prevailed." Rev. v. 5. TELESCOPIC OBJECTS 1. a LKONIS (Reg til aft) A bright star with a distant companion; R. A. 9h. 59m. 51s. ; Dec. N. 12 44' OS". A 1, flushed white ; B SJ<, pale purple. 2. 8 LKONIS (Denebola)^ flue star with a distant companion; R. A. lib. 40m. 54s. ; Dec. N. 15-28' 0". A 2Ji, bluish; B S, dull red. 3. y ~LEoxts(Al Gieba)\ splendid DOUBLK STAB; R. A. lOh. lira. OSs. ; Dec. N. 20" 89' 0". A 2, bright orange; B 4, greenish yellow. A most beautiful object binary- period supposed about 1000 years. Map VIII., Fig. 6. 4. 6 LEONIS (Zozm)A. coarse TRIPLE STAR; R. A. llh. 05m. 85s.; Dec. N. 21 24 L". A 3, pale yellow ; B 13, blue ; C 9, violet. 5. E LEONIS A star with a distant companion in the mouth of Leo ; R. A. 9h. 30m. 46s ; Dec. N. 24" 30' 5". A 3, yellow; B 10, pale grey. ti. i LKONIS A BINARY STAR in the flank, 7 S. W. of Denebola (P on mapj; R. A. llh. 15m. 35a. ; Dec. N. 11* 24' 3". It forms a neat scalene triangle with j3 and #. A 4, pale yellow ; B 7J6, light blue ; a beautiful object. 7. fi LEONIS (lias Al Asad)A DOUBLE STAR; R. A. 9h. 43m. 39s. ; Dec. N. 26* 46' 5'. A 3, orange ; B 10, pale lilac. 8. A neat DOUBLE STAR near Zozma ; R. A. llh. 05in. 17s. ; Dec. 21 00' 3". Components both 7/$, and both faint yellow; a beautiful object. 9. A BRIGHT NEBULA near the hind paws ; R. A. lOh. 57m. 37s. ; Dec. N. 0" 49' 6". Larg, elongated, well-defined an enormous mass of luminous matter one of a vast number of spherical nebulas in the vicinity. 10. A bicentral WHITS NEBULA in the lower jaw, 2* south of A Leonis ; R. A. 9h. 23m. 07s. ; Dec. N. 22 1 '2' 1". May be classed as double small stars in field ; difficult object. See Map VI II., Fig. 40. 11. A lucid WHITE NEBULA on the Lion's ribs, about 9 due east of Regulus; R. A. lOh. .'/5m. 31s. ; Dec. N. 12" 31' 9". Round and bright, with two small stars in field. Another large pale white nebula, about 1 east of it. 12. A PAIR OF BRIGHT CLASS NEBUL.G in the Lion's belly; R. A. lOh. "9m. 49s. ; Dec. N. 13" 28'. Found south of line joining Regulus and & Leonis, about 10" east of, and nearly on a parallel with the latter. 13. A LARGB, Ki.oxr,ATKi> NF.mn.A, with a bripht nucleus on the Lion's haunch; R. A. llh. llm. 48s. ; Dec. N. 13 52' 4* ; just 3 southeast of $, with another smaller nebula, and several stars in the field. Map VIII., Fig. 41. LEO MINOR (THE LITTLE LION). MAP IV. 133. Leo Minor contains 53 stars, including only one of the 3d magnitude, and five of the 4th. The principal star is situated in the body of the animal, 13 JS T . of Gamma Leonis, in a straight line with Phad, and may be known by a group of smaller stars, a little above it on the N. W. It forms an equilateral triangle with Gamma and Delta Leonis, the vertex being in Leo Minor. This star is marked with the letter I, in modern catalogues, and being the principal representative of the constellation, is itself sometimes called the Little Lion : 8' K. of this star (the Little Lion) are two stars of the 4th magnitude, in the last pa\v of Ursa Major, and about 10* N. W. of it are U'o other stars ot the 3d magnitude, in the first hind paw. " The Smaller Lion now succeeds ; a cohort 0!' fifty stars attend his steps ; And three, to sight unarruM, invisible.'-* TELESCOPIC OBJECTS. Alpha? Beta? Gamma? Point out on the map. Delta? Kpsilon? Iota? Mu? What nebula? Which shown on the map? Point cut. 183. Describe Leo Minor? Its principal star? Helps form what triangle? 70 ASTRONOMY. 134. This constellation was formed by Hevelius, out o! the Stcllte informes, or unformed stars of the ancients, which lay scattered between the Zodiacal constellation Leo on the S., and Ursa Major on the N. Its mean right ascension is the same with that of Regulus, and it comes to the meridian at the same time on the Cth of April. The modern constellations, or those which have been added to our celestial maps e'nce the adoption of the Greek notation, in 1603, are referred to by the letters of the English alphabet instead of the Greek. This is the case in regard to Leo Minor, and all other constellations whose origin is subsequent to that period. TELESCOPIC OBJECTS. A BRIGHT OVAL NEBULA between Lynx and Cancer, but given to Leo Minor; R. A. Sh. 42in. 44s. ; Dec. N. 84 00' G". Direct telescope 10 north by east of Presepe in Cancer. SEXTANS (THE SEXTANT). MAP IV. 135. Sextans contains 41 very small stars, including only one as large as the 4th magnitude. This is situated very near the equinoctial, 13 S. of Regulus, and comes to the meridian about the same time on the 6th of April. The other stars in this con- stellation are too small to engage attention. A few of the largest of them may be traced out from the map. The SEXTANT, called also URANIA'S SEXTANT, is a modern constellation that Hevelius made out of the unformed stars of the ancients, which lay scattered between the Lion on the N., and Hydra on the S. Urania was one of the muses, and daughter of Jupiter and Mnemosyne. She pre- r'ded over astronomy. She was represented as a young virgin, dressed in an azure- colored robe, crowned with stars, holding a robe in her hands, and having many mathe- matical instruments about her. A sextant, in mathematics, is the sixth part of a circle, or an arc comprehending CO degrees. But the term is more particularly used to denote an astronomical instrument well known to mariners. Its use is the same as that of the quadrant : namely, to mea- sure the angular distance, and take the altitude of the sun, moon, planets, and fixed stars. It is indispensable to the mariner in finding the latitude and longitude at sea, and should be in the hands of every surveyor and practical engineer. It may serve the purpose of a theodolite, in measuring inaccessible heights and distances. It may gra- tify the young pupil to know, that by means of such an instrument, well adjusted, and with a clear eye and a steady hand, he could readily tell, within a few hundred yards how far north or south of the equator he was, and that from any quarter of the world, known or unknown. This constellation is so called, on account of a supposed resem- blance to this instrument. TELESCOPIC OBJECTS. 1. A DOUBLE STAR on the right fore leg of Leo, though crimped into the sextant. ; R. A 9h. 45m. 45s. ; Dec. N. 5 41' 8". It lies about one-third of the way from Regulus to Alphard. A 7, and B. 9, both blue, and well-defined. 134. Origin of Leo Minor? Mean R. A.? What remark respecting the notation of Oie stars ? TELESCOPIC OBJECTS. What nebula? Situation? How find? Io5. Describe Sextans? Situation of its principal star? What said of the remainder ? What said of the age of this constellation? Of Urania? Of the Sextant as a nautical instrument ? TELESCOPIC OBJECT?. What double stars? What nebula? What v narkable sigh* *oei\ near this nebula? HYDRA. 71 2. A neat DOUBLE STAR on the nnrth extreme of the prndunt^d limb of the instrument; and three-fifths of the distance oetween Alphard and Denebola ; R. A. lOh. 35in. 02s.; Dec. N. 5 e 35' 2". A 7, topaz yellow, B 8, smalt blue ; a fine object. 8. A bright class ROUND NEBULA on the frame of the instrument ; R. A. lOh. 05m. 58s.; Dec. N. 4* 15' 1". A good telescope shows another large but faint nebula near by. This object is on or near the spot where the Capuchin, De Rheita, fancied he saw the napkin of St. Veronica, in 17S3. Captain Smyth has a picture of this wonderful napkin ; and Sir J. Herschel remarks that " many strange things were seen among the stars before the us of powerful telescopes became coraiuon." HYDRA AND THE CUP. MAP IV. 136. HYDRA, (the. Water- Serpent,} is an extensive constella- tion, winding from E. to W. in a serpentine direction, over a space of more than 100 degrees in length. It lies south of Cancer, Leo and Yirgo, and reaches almost from Canis Minor to Libra. It contains sixty stars, including one of the 2d mag- nitude, three of the 3d, and twelve of the 4th. 137. Alphard or Cor Hydra, in the heart, is a lone star of the 2d magnitude, 23 S. S. W. of Regulus, and comes to the meridian at the same time with Lambda, in the point of the sickle, about 20 minutes before 9 o'clock on the 1st of April. There is no other considerable star near it, for which it can be mistaken. An imaginary line drawn from Gamma Leonis through Regulus, will point out Cor Hydra?, at the distance of 23 6 . 138. The head of Hydra may be distinguished by means of four stars of the 4th magnitude, 2^- and 4 apart, situated 6 S. of Acubens, and forming a rhomboidal figure. The three upper stars in this cluster form a small arch, and may be known by two very small stars just below the middle one, making with it a very small triangle. The three western stars in the head also make a beautiful little triangle. The eastern star in this group, marked Zeta, is about 6 directly S. of Acubens, and culminates at the same time. 139. When Alphard is on the meridian, AU:es, of the 4th mag- nitude, situated in the bottom of the Cup, may be seen 24 S. E. of it, and is distinguished by its forming an equilateral triangle with Beta and Gamma, stars of the same magnitude, 6 S. and E. of it. Alkes is common both to Hydra and the Cup. Beta, on the S., is in Hydra, and Gamma, on the N. E., is near the middle of the Cup. A line drawn from Zozma, through Theta 1B6. Describe Hydra? Its situation ? Number and magnitude of its stars? 137. Po siti< n and magnitude of Alphard? How pointed out? 133. How is the head of Hydra distinguished? 139. What said of Alkes? Of Beta and Gamma? How is Jteta found? V2 ASTRONOMY. Leouis, and continued 38J directly S. will reacb Beta ; it ia therefore on the same meridian, and will culminate at the samo time on the 23d of April. 140. The Cup itself (called also the Crater}, may be easily distinguished by means of six stars of the 4th magnitude, form- ing a beautiful crescent, or semicircle , opening to the W. The center of tbis group is about 15 below the equinoctial, and directly S. of the hinder feet of Leo. The crescent form of the stars in the Cup is so striking and well defined, when the mooa is absent, that no other description is necessary to point them out. Its center comes to the meridian about two hours after Alphard, on the same evening ; and consequently, it culminates at 9 o'clock, one month after Alphard does. The remainder of the stars in this constellation may be easily traced by aid of the map. 141. When the head of Hydra is on the meridian, its other extremity is many degrees below the horizon, so that its whole length cannot be traced out in the heavens until its center, 01 the Cup, is on the meridian. " Near the equator rolls The sparkling Hydra, proudly eminent To drink the Galttvtffi refulgent sea; Nearly a fourth of the encircling curve Which girds the ecliptic, his A ast folds involve; Yet ten, the number ot his stars diffused O'er the long track of his enormous spires ; Chief 'beams his heart, sure of the second rank, * But emulous to gain the first." Eudovia. HISTORY. ,ne astrologers of the east, in dividing the celestial hosts into various compartments, assigned a popular and allegorical meaning to each. Thus the sign Leo, which passei the meridian about midnight, when the sun is in Pisces, was called the Houae of Hit Lionfi, Leo being the domieil of Sol. The introduction of two serpents into the constellations of the ancients, had its origin, it is supposed, in the circumstances that the polar oite represented the oblique course of the stars, while the Hydra, or Great Snake, in the southern hemisphere, symbolized the moon's course ; hence the Nodes are called the Dragon^ head and tail to thin d<3, pale orange; B 11, pale blue other small stars in the field. 4. a HYHR.K (Cor Hydra,') A bright star in the heart of Hydra with a distant com- panion ; U. A. Ih. 19m. 44s. ; Dec. S. 1 5S' 1". A 2, orange tint; B 10, pale green. 5. () llYPRjE A star with a distant companion in the head of Hydra; R. A. Sh. 29m, 14s. ; Doc. N. 6 15' 5". A 4, light topaz; B 9, livid several other stars in the field. 6. f JlYDR.fi A double star in the head; R. A. 8h. 33m. ISs.; Dec. N. 7 00' 2'. A 4, pnle yellow; B S%, purple. 7 A PLANETARY NEBULA in the middle of the body; R. A. lOh. 17m. Ols.; Dec. S. IT* 60 6"; greyish white. CHAPTER VII. CONSTELLATIONS ON THE MERIDIAN IN MAY. UESA MAJOR (THE GREAT BEAR). MAPS IV. AND VI. 142. URSA MAJOR is situated between Ursa Minor on the north, and Leo Minor on the south. It is one of the most noted and conspicuous in the northern hemisphere. It has been an object of universal observation in all ages of the world. The priests of Belus and the Magi of Persia, the shepherds of Chaldea, and the Phoe- nician navigators, seem to have been equally struck with its peculiar outlines. And ii is somewhat remarkable, that a remote nation of American Aborigines, the Iroquois, and the earliest Arabs of Asia, should have given to the very same constellation the name of "Cirt.-at Be.tr, " when there had probably never been any communication between them ; and when the name itself is so perfectly arbitrary, there being no resem- blance whatever to a bear, or to any other animal. 143. It is readily distinguished from all others oy means of a remarkable cluster of seven bright stars, forming what is fami- liarly termed the Dipper, or Ladle. In some parts of England it is called " Charles' Wain," or wagon, from its fancied resem- TKLESCOPIC OBJECTS. Alpha? Gamma? Delta? Alpha Hydra;? Delta Ilydrae? Eta Hydra;? What Nebula? 'i42. Describe Ursa Major? What remarkable fact as to its name? 143. How dis- tinguished? What other names for the Dipper? What remark io saiull type? ^4 ASTRONOMY. blance to a wagon drawn by three horses in a line. Others call it the Plough. The cluster, however, is more frequently put foi the whole constellation, and called simply the Great Bear. We see no reason to reject the very appropriate appellation of the shepherds, for the resemblance is certainly in favor of the Dipper ; the four stars in the square forming the bowl, and the other three the handle. 144. When the Dipper is on the meridian, above the pole, the bottom lies toward us, with the handle on the right. Benetnasch is a bright star of the 2d magnitude, and is the first iu. the handle. The second, or middle star in the handle is Mizar, 7 distant from Benetnasch. It may be known by means of a very minute star almost touching it, called Alcor. 145. The third star in the handle is called Alioth, and is about 4|- W. of Mizar. Alioth is very nearly opposite Shedir in Cas- siopeia, and at an equal distance from the pole. Benetnasch, Mizar, and Alioth constitute the handle, while the next four in the square form the bowl of the Dipper. 146. Five and a half degrees W. of Alioth is the first star in the top 6f the Dipper, at the junction of the handle, called Megrez ; it is the smallest and middle one of the cluster, and is used in various observations both on sea and land for important purposes. When Megrez and Caph have the same altitude, and are seen in the same horizontal line east and west, the polar star is then at its greatest elongation from the true pole of the heavens; and this is the proper time for an observer to take its angle of elevation, in order to determine the latitude, and its azimuth or angle of declination, in order to determine the magnetic variation. 147. At the distance of 4J- S. W. of Megrez is Phad, the first star in that part of the bottom which is next the handle. The stars in this cluster are so well known, and may be so easily described without reference to their relative bearings, that they would rather confuse than assist the student, were they given with ever so much accuracy. The several bearings for this cluster were taken when Megrez was on the meridian, and will not apply at any other time, though their respective distances will remain the same. 148. At the distance of 8 W. of Phad, is the westernmost star in the bottom of the Dipper called Merak. The bright star 5 N. of it, toward the pole, is called Dubhe. These two, are. by common consent, called the Pointers, because they always point toward the pole; for, let the line which joins them be con- tinued in the same direction 28f further, it will just reach the north pole. The names, positions, and relative distances of the stars in this cluster should be well 144. How is the handle of the Dipper situated, when the Dipper is above the pole I 1 Describe Benetnasch? Mizar? How known? 145. Alioth? Megrez? Remark respecting? Phad? Remark iu small print? 148. Merak and Dubhe? Constitute what? Remark respecting the names, positions and distances of the stars in Ursa Major? Why should these distances be well understood? URSA MAJOR. 75 remembered, as they will be frequently adverted to. The distance of Dubhe, or tiio 1'oiuter nearest to the north pole, is 2S^. The distance between the two upper stars ii: the Dipper is 10; between the two lower ones is 8; the distance from the brim to the bottom next the handle, is 4^; between Megrez and Alioth, is 5% ; between Alioth and Mizar, 4^; and between Mizar and Benetnasch, 7. The reason why it is important to have these distances clearly settled in the mind is, that these stars, being always in view, and more familiar than any other, the student will never fail to have a standard un-asure before him, which the eye can easily make use of in determining the distances between other stars. 149. The position of Megrez in Ursa Major, and of Caph in Cassiopeia, is somewhat remarkable. They are both in the equi- noctial colurc, almost exactly opposite each other, and equally distant from the pole. Caph is in the colure, which passes through the vernal equinox, and Megrez is in that which passes through the autumnal equinox. The latter passes the meridian at 9 o'clock, on the 10th of May, and the former just six months afterward, at the same hour, on the 10th of November. 150. Psi, in the left leg of Ursa Major, is a star of the 4th magnitude, in a line with Megrez and Fhad, distant from the latter 12|- . A little out of the same line, 3 farther, is another star of the 4th magnitude, marked Epsilon, which may be dis- tinguished from Psi, from its forming a straight line with the two Pointers. 151. The right fore-paw, and the two hinder ones, each about 15 from the other, are severally distinguished by two stars of the 4th magnitude, between 1 and 2 apart. These three duplicate stars are nearly in a right line, 20 S. of, and in a direction nearly parallel with Phad and Dubhe, and are the only stars in this constellation that ever set in this latitude. There are a few other stars of equal brightness with those just described, but amidst the more splendid and interesting group with which they are clustered, they seldom engage our observation. The whole number of visible stars in this constellation is 87; of which five are of the 2d, two of the 3d, and about twice as many of the 4th magnitude. HISTORY. URSA MAJOR is said to be Calisto, or Helice, daughter of Lycaon, king of Arcadia. She was an attendant of Diana, and mother of Areas, by Jupiter, who placed her among the Constellation*, after the jealousy of Juno had changed her into a bear.' " This said, her hand within her hair she wound, Swung her to earth, and dragg'd her on the ground; The prostrate wretch lifts up her hand in prayer; Her arms grow shaggy, and deform'd with hair, Her nails are sharpen'd into pointed claws, Her hands bear half her weight, and turn to paws ; Her lips, that once could tempt a god, begin To grow distorted in an ugly grin ; 149. What said of Megrez and Caph? 160. Of Psi and Epsilon? 151. How find ihefeft of the figure? Number of stars in frsa Major? Magnitudes? Hi -STORY. Who was Ursa Mnjor b'-fore she became a boar? What other supposition? How are the two bears reprK.-.BMwd by the h^yptums? Wh;it further remarks? B.G. 4 70 ASTRONOMY. And lest the supplicating brute might reach The ears of Jove, she was deprived of speech. * * * * * * * How did she fear to lodge in woods alone, And haunt the Gelds and meadows, once her own ! How often would the deep-mouth'd dogs pursue, Whilst from her hounds the frighted hunters tlew." Ocid^s Met. Some suppose that her son Areas, otherwise called Bootes, was changed into Urs,i Minor, or the Little Bear. It is well known, that the ancients represented both these constellations under the figure of a wagon drawn by a team of horses ; hence the appel- lation of CluirletP Wain-, or wagon. This is alluded to in the Phenomena of Aratus, a Greek poem, from which St. Paul quotes in his address to the Athenians: " The one call'd Helix, soon as day retires, Observed with ease lights up his radiant fires. The other, smaller, and with feebler beams, In a less circle drives its laty teams; But more adapted for the sailor's guide, Whene'er, by night, he tempts the briny tide." In the Egyptian planispheres of remote antiquity, these two constellations are repre- tented by the figures of bears, instead of wagons; and the Grceks,who derived most of their astronomical symbols from the Kgyptians, though they usually altered them to emblems of their own history or superstition, have, nevertheless, retained the original form of the two bears, It is said by Aratus, that the Phoenician navigators made use of Ursa Minor in directing their voyages : " Observing this, Phoenicians plough the main :" while the Greeks confined their observations to Ursa Major. yome imagine that the ancient Kgyptians arranged the stars near the North Pole, withir the outlines of a bear, because the polar regions are the haunts of this animal, and also because it makes neither extensive journeys nor rapid marches. At what period men began to sail by the stars, or who were the first people that did so, is not clear; but the honoris usually given to the Phoenicians. That it was prac- ticed by the Greeks, as early as the time of the Trojan war, that is, about 1*200 years 1>. C., we learn from Homer; for he says of Ulysses, when sailing on his raft, that 41 Placed at the helm he sate, and mark'd the skies, Nor closed in sleep his ever watchful eyes." It is rational to suppose that the stars were first used as a guide to travellers by land, for we can scarcely imagine that men would venture themselves upon the sea by night, before they had first learned some safe and sure method of directing their course by land. And we find, according to Diodorus Siculus, that travellers in the sandy plains of Arabia were accustomed to direct their course by Vie Beam. That people travelled in these vast deserts at night by observing the stars, is directly proved by this passage of the Koran: "God has given you the stars, to be guided ii> the dark, both by land and by sea." TELESCOPIC OBJECTS. 1. tt URSA MAJORIS (I>ub7ie, on* of Vi pointers} A fine star with a distant compa- nion ; U. A. lOh. 53m. 4Ss. ; Dec. N. 62 86' 8". A 1 &, yellow ; B 8, yellow, 2. j3 URSA MAJORTS (Merak) A bright star with a distant companion ; R. A. 10h. 52m. 08"; Dec. N. 67 14' 2". A 2, greenish while; B 11, pale grey other stars in field. 8. y URSA MAJORIS (Phm. 23s. ; Dec. N. 64 86' 1". A 2, topaz yellow ; B 9, ashy paleness, with a fine group of stars in the field. ^ ^ 4. ft URSA MAJORIS (J//< / A norPt.K STAR in the right fo-epaw; R. A.Sh.4Sm. lls.; Dec. N.-k" :W >'. A o\>, topaz yellow ; B 18, purple. Bbf J. lIwnwlMl MppOted A might be a satellite, shining only by rctlection. S. !' UKSV M.VJOUTS A delicate ponu.K STAR in tho loft hind loot, just above 5 or > Vcola ; K. A. 1 Ih. 00m. 4Us. ; Dec. N. 30* 6S' 0'. A 4, orange tint ; B 12, cornelian blue; :i > lose but elegant object. '.'. A beautiful H.AXKTARY XKBI*LA, just south of .?; R. A. lOh. 2Sm. 4.V.; Pee. N. 51* '.' 4". A small, well defined object, bluish white, anil brightens towards the center. 10. A BRIGHT XKiu-t.A in the right fore leg; R. A. i>h. 10m. Ms.; D<-e. N. M* 40' 5'. Of a pale creamy whiteness, with several bright stars in the northern part of the field. Nduila large, elliptical and nucleated. 11. A bright-class ROUSP NKIU'! ^ above tlie Bear's ear ; 11. A. 9h.34m.82s. ; Dec. N. T:>* lh -". fe\eral stars in Held, of iHh to 12th magnitude. 12. A KINK OVAI. XKBCI.A in the ear ; U. A. 9h. 42m. 10s. ; Dec. N. 69* 51' S". r>. A I.AKUK MU.K-WHITK XKiu'LA on the body, about 1* south of $ or Merak ; K. A. llh. I'-.'-n. 02s. ; Dec. N. ;>C 81' S'. 14. A I.AIUIR n.AXKTARV XKRCt.A on the Hank, with several stars in the field, one of is pretty close; K. A. Uh. Oom. 21s. ; Dfttt. N. .\'i" ^ 1 J y- About 2* to the S. E. of .1. and just south of a line from & to ; ; a singular olyeet. circular, uniform, and seem- ingly of the sixe of Jupiter. W. llerscliel assigned this object to the SSOth order of dis- M ,|> Vlll.. Fig. 42. l.V A HI;H;!!T-CI.ASS NKiu-i.A in a poor field, behind the left hind leg, one-third the dis- :'rom <\ towards^Pen, l-.ola ; K. A. llh. TiSm. 51s.; Dec. N. 48* 57' 8'. Of a lucid white, various and elongated. Map Vlll.. K ; g. 4-S. lt>. A I.AI;K WIIITK SKBUI.A near the haunches ; K. A. 12h. llm. 04s.; Dec. N. 4S* 11' 1'. A noble-sized oval, with a bright nucleus, the lateral edges better lo lined than the ends) Found by running a diagonal line across the square, from a through }, and about 73$* beyond, into the S. E. COMA BERENICES (BERENICE'S HAIR). MAP IV. l.~>:2. This is a beautiful cluster of small stars, situated about V" K. of tin* equinoctial colure, and midway between Cor Caroli on the northeast, and IVnebohi on the southwest. If a straight line be drawn from Benetnaseh through Cor Caroli, and pro- dueed to IVnebola, it will pass through it. lf>3. The prineijnil stars are of between the 4th and f>th mau'- nitudes. Aeeording to Flamsted, there are thirteen of the 4th magnitude, and according to others there are seven ; but the student will find agreeably to his map, that there is apparently but <>Mf star in this group, entitled to that rank, and this is situated about 7 S. E. of the main cluster. Although it Is not easy to mistake this group for any other in the same repion of the skies, yet the stars which compos- it are all so small as to be rarely distinguished in the full presence of the moon. The confused lustre of this assemblage of small stars son.e- whal resembles that of the Milky Way. 1.V2 Describe Coma Berenices? How find itf 158. Its princii a' tars, the ir numbe; Ir. ? What remark in fine print ? 78 ASTRONOMY. 154. The whole number of stars in this constellation is 43 ; its mean right ascension is 185. It consequently is on the meridian the 13th of May. "Isow behold The glittering maze of Berenice's Hair ; Forty the stars ; but such as seem to kiss Thz flowing tresses with a lambent fire, Four to the telescope alone are seen." HISTORY. Berenice was of royal descent, and a lady of great beauty, who married Ptolemy Soter, or Evergetes, one of the kings of Egypt, her own brother, whom she loved with much tenderness. When he was going on a danpvcous expedition against the Assyrians, she vowed to dedicate her hair to the goddess of beauty, if he returned in safety. Some time after the victorious return of her husband, Evergetes, the locks, which, agreeably to her oath, she had deposited in the temple of Venus, disappeared. The king expressed great regret at the loss of what he so much prized ; whereupon Conon, his astronomer, publicly reported that Jupiter had taken away the queen's locks from the temple and placed them among the stars. " There Berenice's locks first rose so bright, The heavens bespangling with dishevelled light." Conon being sent for by the king, pointed out this constellation, saying, " There behold the locks of the queen." This group being among the unformed stars until that time, and not known as a constellation, the king was satisfied with the declaration of the astronomer, and the queen became reconciled to the partiality of the gods. Callimachus, a historian and poet, who flourished long before the Christian era, has these lines as translated by Tytler : " Immortal Conon, blest with skill divine, Amid the sacred skies behold me shine: E'en me, the bey Sir Charles Blagdon to a " Uack eye." Map VIII., Fig. 44. CORVUS (THE CROW). MAP IY. 155. This small constellation is situated on the eastern part of Hydra, 15 E of the Cup, and is on the same meridian with 154. What number of stars? HISTORY. Who was Berenice? Story of the loss of her hair, Ac.? TKLKnCoric OBJKCTS. What triple stars? Cluster? Nebula? Point out on the Map. 155. Where is Corvus situated? Number of visible stars? CO&YU8. l\f Coma Berenices, but as far S. of the equinoctial as Coma Bere- nices is N. of it. It therefore culminates at the same time, on the 12th of May. It contains nine visible stars, including three of the 3d magnitude, and two of the 4th. 156. This constellation is readily distinguished by means of three stars of the 3d magnitude and one of the 4th, forming a trapezium or irregular square, the two upper ones being about 3 apart, and the two lower ones 6 apart. 157. The brightest of the two upper stars, on the left, is called Algorab, and is situated in the E. wing of the Crow ; it has nearly the same declination S. that the Dog Star has, and is on the meridian about the 13th of May. It is 214- E. of Alkes in the Cup, 14^- S. W. of Spica Virginis, a brilliant star of the 1st magnitude, to be described in the next chapter. 158. Beta, on the back of Hydra, and in the foot of the Crow, is a star of the 3d magnitude, nearly 7 S. of Algorab. It is the brightest of the two lower stars, and on the left. The right- hand lower one is a star of the 4th magnitude, situated in the neck, marked Epsilon, about 6 W. of Beta, and may be known by a star of the same magnitude situated 2 below it, in the eye, and called Al Chiba. Epsilori is 21 S. of the vernal equinox, and if a meridian should be drawn from the pole through Megrez, and produced to Epsilon Corvi, it would mark the equi- noctial colure. )59. Gamma, in the W. wing, is a star of the 3d magnitude, 3^- W. of Algorab, and is the upper right-hand one in the square. It is but 1 E. of the equinoctial colure. 10 E. of Beta is a star of the 3d magnitude, in the tail of Hydra, marked Gamma ; these two, with Algorab, form nearly a right-angled triangle, the right angle being at Beta. HISTORY. The Crow, it is said, was once of the purest white, but was changed for tale-bearing to its present color. A lit punishment for such a fault. "The raven once in snowy plumes was drest, White as the whitest dove's unsullied br^.st, Fair as the guardian of the capitol, Soft a-) the Swan ; a large and lovely fowl; His tongue, his prating tongue, had changed him quti/t, To sooty blackness from the purest white." According to Greek fable the Crow was made a constellation by Apollo. This god be ; ng jealous of Oorouis (whom he tenderly loved), the daughter of Phlegyas and 1f.fi. How is it found? 157. What said- of Algorab? 153. Of Beta? Epsilon? Al Chiba? What said of the Pole, Megrez, and Epsilon? 159. Of Gamma? What triangle? HISTORY. Story of the original color of Corvus? Greek fable of the origin of th* constellation ? What other account ? 60 ASTRONOMl*. mother of JEscalapius, sent a crow to watch her behavior; the bird perceived her cri- minal partiality for Ischys the Thessalian, and immediately acquainted Apollo with h<-f conduct, which so finulhis indignation that he lodged an arrow in her breast, and killed her instantly. " T le god was wroth ; the color left his look, The wreath his head, the harp his hand forsook: The silver bow and feathered shafts he took, And lodged an arrow in the tender breast, That had so often to his own beeji prest." To reward the crow, he placed her among the constellations. Others say that this constellation takes its name from the daughter of Coronaeus, king of Phocis, who was transformed into a crow by Minerva, to rescue the maid from the pursuit of Neptune. The following, from an eminent Latin poet of the Augustan age, is her own account of the metamorphosis as translated into English verse by Mr. Addisori : " For as my arms I lifted to the skies, I saw black feathers from my fingers rise ; I strove to fling my garment on the ground ; My garment turned to plumes, and girt me round; My hands to beat my naked bosom try ; Nor naked bosom now, nor hands had I Lightly I tripp'd, nor weary as before Sunk in the sand, but skimm'd along the shore; Till, rising on my wings, I was preferr'd To be the chaste Minerva's virgin bird " TELESCOPIC OBJECTS. 1. $ CORVI A fine bright star nearly midway between two distant companions. A 2 J$, ruddy yellow ; B 7, greenish yellow ; C 8, dull grey. j3 is actually the lucida, or brightest star of the constellation. 2. <$ CORVI A DOUBLE STAR in the right wing ; R. A. 12h. 21m. 85s. ; Dec. S. 15' 37' 04*. A 3, pale yellow ; B 8%, purple. VIRGO (THE VIBGIN). MAP IV. 160. This is the sixth sign, and seventh constellation in the ecliptic. It is situated next east of Leo, and about midway between Coma Berenices on the N. and Corvus on the S. It occupies a considerable space in the heavens, and contains, according to Flamsted, one hundred and ten stars, including one of the 1st, six of the 3d, and ten of the 4th magnitudes. Its mean declination is 5 N., and its mean right ascension is 195. Its center is therefore on the meridian about the 23d of May. The sun enters the sign Virgo, on the 23d of August, but does not enter the COWlkttit- Hon before the 15th cf September. When the sun is in this sign, the earth is in Pisces ; and vice versa. 161. Alpha, or Spica Virgims, in the ear of corn which the virgin holds in her left hand, is the most brilliant star in this constellation, and situated nearly 15 E. N. E. of Algorab ir the Crow, about 35 S. E. of Denebola, and nearly as far S. S TELESCOprc OBJECTS. Beta ? Delta ? 160. Order and position of Virgo? Extent? Number of stars? Magnitudes? Hear declination of Virgo? Remark in fine priat ? 161. What said of Alpha, or Spica Vir 111 VIRGO. 81 W. of A returns three very brilliant stars of similar magnitude that form a large equilateral triangle, pointing to the S. Arc- turus and Denebola are also the base of a similar triangle on the north, terminating in Cor Caroli, which, joined to the former, constitutes the Diamond of Virgo. 162. The length of this figure, from Cor Caroli, on the north, to Spica Virginia on the south, is 50. Its breadth, or shorter diameter, extending from Arc-turns on the east to Denebola on the west, is 35^-. Spica may otherwise be known by its soli- tary splendor, there being no visible star near it except one of the 4th magnitude, situated about 1 below it, on the left. The position of this star in the heavens, has been determined with great exactness for the benefit of navigators. It is one of the stars from which the moon's distance is taken for determining the longitude at sea. Its situation is highly favoraHe for this purpose, s it lies within the moon's path, and little more than 2 below the etu 'h's orbit. Its right ascension being 199, it will come to our meridian at 9 o'clock about the 28th if Mrty, in that point of the heavens where the sun is at noon about the 20th of October. 1 63. Beta, called also Zavijava, is a star of the 3d magni- tude, in the shoulder of the wing, 7 W. of Eta, with which and Gamma it forms a line near the Earth's orbit, and parallel co it. Beta, Eta, Gamma and Spica, form the lower and longer side of a large spherical triangle whose vertex is in Beta. 164. Vindemialrix, is a star of the 3d magnitude, in the right arm, or northern wing of Virgo, and is situated nearly in a straight line with, and midway between Coma Berenices and Spica Virgiuis. It is 19J S. W. of Arcturus, and about the same distance S. E. of Coma Berenices, and forms with these two a large triangle, pointing to the south. It bears also 18 S. S. E. of Denebola, and comes to the meridian about 23 minutes before Spica Virginia. 165. Zeta, is a star of the 3d magnitude, 11^- N. of Spica, and very near the equinoctial. Gamma, situated near the left side, is also a star of the 3d magnitude, and very near the equi- noctial. It is 13 due west of Zeta, with which and Spica it forms a handsome triangle. Eta, is a star of the 3d magnitude in the southern wing, 5 W. of Gamma, and but 2 E. of the autumnal equinox. The other stars in this figure may be easily traced by means of the map. About 13 E. of Spica, there are two stars of the 4th magnitude, 3 apart, which mark the foot of Virgo. These two stars are on nearly the same meridian with Arcturus, ana culminate nearly at the same time. The lower one, marked iMnibda, is on the south, and but 8 W. of the principal star in Libra. Several other stars of the 3d magnitude lie scattered about In this constellation, and may be traced out by the map. finis? Diamond? 162. Length of Virgo? Breadth? How may Spica be known? Note in tine print? 1(53. Describe Beta? What triangle? 1G4. Vndematrix? ICo. Zeta, Gaumiu and Eta ? What other stars and how found? 82 ASTRONOMY. " Her lovely tresses glow with starry light ; Stars ornament the bracelet on her hand ; Her vest in ample fold, glitters with stars : Beneath her snowy feet they shine ; her eyes Lighten, all glorious, with the heavenly rays, Butjlrfltf the star which crowns the golden sheaf." HISTORY. According to the ancient poets, this constellation represents the Virgin Astrsea, *ha goddess of justice, who lived upon the earth during the golden age; but being offended at the wickedness and impiety of mankind during the brazen and iron ages of the world, she returned to heaven, and was placed among the constellations of the zodiac, with a pair of scales (Libra) in one hand and a sword in the other. llesiod, who flourished nearly a thousand years before the birth of our Saviour, and later writers, mention four ages of the world ; the golden, the silver, the brazen, and the iron age. In the beginning of things, say they, all men were happy, and all men were good; the earth brought forth her fruits without the labor of man; and cares, and wants, wars and diseases, were unknown. But this happy state of things did not last long. To the golden age, the silver age succeeded ; to the silver the brazen ; and to the brazen, the iron. Perpetual spring no longer reigned; men continually quarreled with each other; crime succeeded to crime; and blasphemy and murder stained the history of every day. In the golden age, the gods did not disdain to mix familiarly with the sons of men. The innocence, the integrity and brotherly love which they found among us, were a pleasing spectacle even to superior natures ; but as mankind degenerated, one god after another deserted their late beloved haunts; Astraia lingered the last; but finding the earth steeped in human gore, she herself flew away to the celestial regions. " Yicta jacet pietas ; et virgo caede madentes Ultima coelestum terras Astrsea reiiquit." Met. Lib. i. v. 1W. "Faith flees, and piety in exile mourns; And justice here oppr.es&'d, to heaven returns." Some, however, maintain, that Erigone was changed into the constellation Yirgo. The death of her father Icarus, an Athenian, who perished by the hands of some peasants, whom he had intoxicated with wine, caused a fit of despair, in which Krigone hung her- self; and she was afterward, as it is said, placed among the signs of the zodiac. She was directed by her faithful dog Mtera to the place where her father was slain. The first bough on which she hung herself breaking, she sought a stronger, in order to effect her purpose. "Thus once in Marathon's impervious wood, Ei'igone beside her father stood, When hastening to discharge her pious vows, She loos'd the knot, and cull'd the strongest boughs." LEWIS' Statius, 13. xi. The famous zodiac of Dendera, as we have already noticed, commences with the sigi? Leo ; but another zodiac, discovered among the ruins at Esne, in Egypt, commences with Virgo; and from this circumstance, some have argued, that the regular precession of the equinoxes established a date to this at least 2i)0i) years older than that at Dendera. The discoveries of Champollion, however, render it probable that this ancient relic of astrology at Esne was erected during the reign of the Emperor Claudius, and conse- quently did not precede the one at Dendera more than fourteen years. Of this, however, we maybe certain: the autumnal equinox now corresponds with the firt degree of Virgo; and, consequently, if we find a zodiac in which the summer solstice was placed where the autumnal equinox now is, that zodiac carries us back 9U nn the ecliptic; this divided by the annual precision 50 V must fix the date at about b'45o years ago. This computation, according to the chronology of the Sacred writings, carries us back to the earliest ages of the human species on earth, and proves, at least, that astronomy was among the first studies of mankind. The most rational way of accounting for this zodiac, says Jamieson, is to ascribe it to the family of Noah; or per- haps to the patriarch himself, who constructed it for the benefit of those who should live after the deluge, and who preserved it as a monument to perpetuate the actual state of the heavens immediately subsequent to the creation. HISTORY. Account of the poets? Ilesiod's ace junt? What other supposition 9 VVLal todia.cs mentioned, and what calculations, &c. ? CANES VENATICI. 83 TELESCOPIC OBJECTS. 1. a VIRGIXIS (Spica) A splendid star with a minute companion ; R. A. 13h. IGm. 47s. ; Dec. S- 10 19' 5". A 1, brilliant flushed white; B 10, bluish tinge. 2. p VIRGIXIS (Zarijun) A bright star with a small companion ; R. A. llh. 42m. 22s. ; Dec. N. 2 40' 0'. A 3}$, pale yellow ; B 11, light blue. 3. y VIRGIXIS A fine BIXAKY STAR in the Virgin's right side ; R. A. 12h. 38m. 33s. ; Dec. S. 34' 3'. A 4, silvery white; B 4, pale yellow. A Binary System with a period of about 157 years. Map. VIII. Fig. S. 4. (5 VIHGIXIS A star with a distant companion, on the left side, about 17 north-north' west of Spica, and nearly midway between y and Virginis ; R. A. 12h. 47m. 33s. ; Dec. N. 4 10' 1". A 3><>, golden yellow; B 10)<>, reddish; several small stars in the field. 5. e VIKGIXIS ( Veiideniidtrto') A star with a minute distant companion, on the upper extremity of the Virgin's left wing ; R. A. 12h. 54m. 13s. ; Dec. 11 49 03". A 3%, bright yellow; B 15, intense blue. This last color on so small an object is very striking. 6. A TRIPLE STAR in the lower part of the southern wing, 7 northwest of Spica; R. A. V3h. Olm. 40s.; Dec. S. 4 41 0". A4}, pale white; B 9, violet; C 10, dusky. 7. A LARGE, BUT RATHER PALE NEBULA, between Virgil's left wing and Leo's tail; R. A. I'2h. <:<>:,.. Ols. ; Dec. N. 15 47' 02". About 0% from tf Leonis, towards Arcturus, on the outskirts of a vast region of Nebula iu the Virgin's wing. It is elongated in the direction of two telescopic stars. S. A LOXG PALE-WHITE NEBULA, among telescopic stars, on the upper part of the Vir- gin's left wing ; It. A. 12h. 07m. 37s. ; Dec. N. 14 02' US". Situated one-third of the way from /3 Leonis to f Virginis, on the border of the vast nebulous region in Virgo. A curious object in the shape of a weaver's shuttle. 9. A LUCID WHITE ELLIPTICAL NEBULA, between the Virgin's right elbow and the Crow; R. A. 12h. 31m. 40s. ; Dec. S. 10 43' 07". Map VIII., Fig. 45. 10. A DOUBLE NEBI-LA in the center of Virgo's left wing ; R. A. 12h. 35m. 33s. ; Dec. N. 12 26' 01". It is 5 west of Vendemiatrix, toward Regulus, in a wonderful nebulous region. Map VIII., Fig. 40, shows it on the right, with two other nebulae, and several stars in the figure. 11. A PALE ELLIPTICAL NEBULA, in the middle of the left wing; R. A. 12h. 44m. 50s. , Dec. N. 12 05' 09". It looks like a paper kite, under an arch formed by three telescopic stars. Map. VIII., Fig. 47. 12. A WOXDFRFUL NEBULOUS REGION, about 2% from north to south, and 3 from east to west, is found on the left wing. It includes several of the objects described. For a in-awing of this remarkable field, see Map VIII., Fig. 48. CANES VENATICI (THE GREYHOUNDS). MAP IV. 1G6. This modern constellation, embracing two in one, was made by llevelius out of the unformed stars of the ancicMits which were scattered between Bootes on the east, and Ursa Major on the west, and between the handle of the Dipper on the north, and Coma Berenices on the south. These Hounds are represented on the celestial sphere as being in pursuit of the Great Bear, which Bootes is hunting round the pole of heaven, while he holds in his hand the leash by which they are fastened together. The northern one is called Asterion, and the southern one, Ckara. TELESCOPIC OB.TKCTS. Alpha? Beta? Gamma? Delta? Epsilon? What triple star? Nebula? Point out on the map. 166. Situation of Canal Venatici f By whom formed ? How represented? Naiuea of the hounds ? 4* 84 ASTRONOMY. 167. The stars in this group are considerably scattered, and are principally of the 5th and 6th magnitudes ; of the twenty- five stars which it contains, there is but one sufficiently large to engage our attention. Cor Caroli or Charles' Heart, so named by Sir Charles Scarborough, in memory of King Charles the First, is a star of the 3d magnitude, in the neck of Chara, the southern Hound. When on the meri lian, Cor Caroli is 17V directly S. of Alioth, the third star in the handle of the Dipper, and is so nearly on the same meridian that it culminates only one minute and a half af'er it. This occurs on the 20th of May. A line drawn from Cor Caroli through Alioth will lead to the N. polar star. This star may also be readily distinguished by its being in a straight line with, and midway between Benetnasch, the lirst star in the handle of the Dipper, and Coma Berenices ; and also by the fact that when Cor Caroli is on the meridian, Denebola bears 28 S. W. and Arcturus 26 S. E. of it, forming with these two stars a very large triangle, whose vertex is at the north ; it is also at the northern extremity of the large Diamond already described. The remaining stars in this constellation are too small and too much scattered to excite our interest. TELESCOPIC OBJECTS. 1 A DOUBI.R STAR near Chara's mouth ; R. A. 12h. 08m. 06s. ; Dec. N. 41* 33' 01*. A 6, yellow; B 9, blue. It is about 9 south of Cor Caroli, and one-third of the distance between that star and (5 Lconis. Map VIII., Fig. 10. 2. A MAGNIFICENT CLUSTER, between the southern Hound and the knee of Bootes; R. A. 13h. 84m. 4os. A splendid group, supposed to contain not less than 1,000 stars. Map VIII., Fig. 49. 3. A PAIR OF LUCID WIIITB NEBULAE, near the ear of the northern Hound ; R. A. 13h. 23rn. 06s. ; Dec. N. 48' 01' 07'. 4. A LAROR BRIGHT NEBULA, 2 %" north by west of Cor Caroli ; R. A. 12h. 43m. 22s. ; Dec. N. 41 59' 07". A fin i pale-white object, compressed toward the center, and with several email stars in the field. CHAPTER VIII. CONSTELLATIONS ON THE MERIDIAN IN JUNE. BOOTES (THE BEAB DEIVER). MAP IV. 168. THE BEAR-DRIVER is represented by the figure of a hunts- man in a running posture, grasping a club in his right hand, and holding up in his left the leash of his two greyhounds, Asterion and Chara, with which he seems to be pursuing the Great Bear round the polo of the heavens. He is thence called Arcto- phylax, or the " Bear-Driver." 167. Describe the stars in this group? Cor Caroli? TELESCOPIC OBJECTS. What double star ? Show on the map ? Clusters? Point out 011 the map? Nebulae? l(>3. Describe Bootes ? Why called the Bear-Driver ? BOOTES. 8b 169. This constellation is situated between Corona Borealis on the east, and Cor Caroli, or the Greyhounds, on the west. It contains fifty-four stars, including one of the 1st magnitude, seven of the 3d, and ten of the 4th. Its mean declination is 20 ]S T ., and its mean right ascension is 212 ; its center is there- fore on the meridian the 9th of June. It may be easily distin- guished by the position and splendor of its principle star, Arc- turns, which shines with a reddish luster, very rnu^h resembling that of the planet Mars. 170. Arcturus is a star of the 1st magnitude, situated near the left knee, 26 S. E. of Cor Caroli and Coma Berenices, with which it forms an elongated triangle, whose vertex is at Arc turus. It is 35|- E. of Denebola, and nearly as far N. of Spica Yirginis, and forms with these two, as has already been observed, a large equilateral triangle. It also makes, with Cor Caroli and Denebola, a large triangle whose vertex is in Cor Caroli. A great variety of geometrical figures may be formed of the stars in this bright region of the skies. For example : Cor Caroli on the N., and Spica Virginis on the S., constitute the extreme points of a very large figure in the shape of a diamond ; while Denebola on the W. and Arcturus on the E., limit the mean diameter at the other points. 111. Arcturus is supposed by some to be nearer the Earth than any other star in the northern hemisphere. Five or six degrees S. W. of Arcturus are three stars of the 8d and 4th magnitudes, lying in a curved line, about 2 apart, and a little below the left knte of Bootes ; and about 7 E. of Arcturus are three or four other stars of similar magnitude, situated in the other leg, making a larger curve N. and S. 172. Mirac, in the girdle, is a star of the 3d magnitude, 10 N. N. E. of Arcturus, and about 11 W. of Alphacca, a star in the Northern Crown. Seginus, in the west shoulder, is a star of the 3d magnitude, nearly 20 E. of Cor Caroli, and about the same distance N. of Arcturus, and forms with these two, a right- angled triangle, the right angle being at Seginus. The same star forms a right-angled triangle with Cor Caroli and Alioth, in Ursa Major, the right angle being at Cor Caroli. 173. Alkaturops, situated in the top of the club, is a star of the 4th magnitude, about 10 in an easterly direction from Seginus, which lies in the left shoulder ; and about 4 S. of Alkaturops is another star of the 4th magnitude, in the club, near the east shoulder, marked Delta. Delta is about 9 P dis- tant from Mirac, and 7 from Alphacca, and forms, with these two, a regular triangle. 109. How situated? How many stars, and their magnitude? Declination? How dis- tinguished ? 170. Describe Arcturus, and its position? What triangles? Whatdia- jiond? 171. Supposed nearness of Arcturus? 172. Describe Mirac and Seginus I 1 ' iangles? 173. Situation and magnitude of AlUaturops? Of Delta? > ASTRONOMY. 174. Nekkar is a star of the 3d magnitude, situated in the head, and is about 6 N. E. of Seginus, and ^ W. of Alkatu- rops ; it forms, with Delta and Seginus, nearly a right angled triangle, the right angle being at Nekar. These are the principal stars in this constt-llation, except the three stars of the 4th magnitude situated in the right hand. These stars m;iy be known by two of them being close together, and about 5 beyond Bem-tnasch, the Brat star in the handle of the Dip- per. About 6 E. of Benetnaseh is another star of the 4th magnitude, situated in the arm which forms, with Benetnaseh and the three in the hand, an equilateral triangle. 175. The three stars in the left hand of Bootes, the first in the handle of the Dipper, Cor Caroli, Coma Berenices, and Denebola, are all situated nearly in the same right line, running from northeast to southwest. "Bootes follows with redundant light; Ftfty-four stars he boasts ; one guards the Bear, Thence call'd AreturiM, of resplendent front, The pride of the./2/vtf order: eight are veil'd, Invisible to the unaided eye." MANILJUS thus speaks of this constellation : " And next Bootes comes, whose order'd beams Present a figure driving of his teams. Beiow his girdle, near his knees, he bears The bright Arcturw, fairest of the stars." If 6. Arcturusis mentioned by name in that beautiful passage in Job, already referred to, where the Almighty answers ''out of the whirlwind," and says : "Canst thou the sky's benevolence restrain, And cause the Pleiades to shine in vain? 0'', when Orion sparkles from his sphere, Thaw the cold seasons and unbind the year? Bid Mazzarotn his wonted station know, And teach the brignt Aretunts where to glow?" Young 1 8 Paraphrase. HISTORY. The ancient Greeks called this constellation Lycaon a name derived from which signifies a wolf. The Hebrews called it Caleb A nulach, the " Barking Dog;" while the Latins, among other names, called it Canix. If we go back to the time when Taurus opened the year, and when Virgo was the fifth of the zodiacal signs, we shall find that brilliant star Arcturus, so remarkable for its red and fiery appearance, corres- ponding with a period of the year as remarkable for its heat. Pythagoras, who intro- duced the true system of the universe into Greece, received it frcnn i-A DOUBLE STAR; R. A. 5h. 21m. 23s. ; Dec. S. 20 53' 5". A 4, deep yel- iow; B 11, blue. 3. y LCPI A wide TRIPLK STAR in a barren field; R. A. 5h. 37m. 4Ss. ; Dec. 22' 3u' 2". A 4, light yellow ; B 6J3, pale green ; C 13, dusky. A line from 6 Orionis through the second cluster, and carried 16 beyond, falls upon it. 4. A bright STELLAR NECCI.A, of a milky white tinge ; R. A. 5h. 17m. 50s. Dec S. 24 oO 9". A fine object biasing towards the centre. iSO. Situation of Lupus? Number and magnitude of its stars? Best time to observe? HISTORY. What was Lupus originally? Why changed and by whom? DescribuJ br what poet? TKLESCOPIC OBJECTS. Alpha? Beta? Gamma? What Nebula? LI7IRA. 91 LIBRA (THE SCALES). MAP IV. AND V. 181. This is the seventh sign, and eighth constellation, flora the vernal equinox, and is situated in the Zodiac, next east of Virgo. The sun enters this sign, at the autumnal equinox, on the 23d of September ; but does not reach the constellation before the 2 7 th of October. When the sun enters the sign Libra, the (lays and nights are equal all over the world, and seem to observe a kind of equilibrium, like a balance. When, however, it is said that the vernal and autumnal equinoxes are in Aries ami Libra, and the tropics in Cancer and Capricorn, it must be remembered that the signs Aries and Libra, "Cancer and Capricorn, and not the constellations of these names, are meant: for the equinoxes are now in the constellations Pisces and Virgo, and the tropics in Gemini and Sagittarius ; each c&lWteBation having gone forward one sign in the e clinic. About 22 centuries ago, the conntdlKtion Libra coincided with the sign Libra ; but having advanced 30 or more in the ecliptic, it is now in the sign Scorpio, and the con- stellation Scorpio is in the ttign Sagittarius, and so on. While Aries is now advanc -d a whole sign above the equinoctial point into north decli- nation, Libra has descended as far below it into south declination. 182. Libra contains fifty-one stars, including two of the 2d magnitude, two of the 3d, and twelve of the 4th. Its mean declination is 8 south, and its mean right ascension 226. Its center is therefore on the meridian about the 22d of June. It may be known by means of its four principal stars, forming a quadrilateral figure, lying northeast and southwest, and having its upper and lower corners nearly in a line running north and south. The two stars which form the N. E. side of the square, are situated about 1 apart, and distinguish the Northern Scale. The two stars which form the S. W. side of the square are situated about 6 apart, and distinguish the Southern Scale. lit in the Southern Scale, about 21 E. of Spica, and 8 E. of Lambda "Virgin is, is a star of the 2d magnitude, and is situated very near the ecliptic, about 4'2J<>* E. of the autumnal equinox. The distance from this star down to Theta Centauri is about 23% with which, ami Spica Virginia, it forms a large triangle, on the right. Xtif^nelffi-wfibi, the uppermost star in the Northern Scale, is also of the 2d magnitude, 9!<>" above Zubeneschamalj, toward the northeast, and it comes to the meridian about twenty-six minutes after it, on the 2ttd of June. Zubenelgemabi is the northernmost of the four bright stars in this figure, and is exactly opposite the lower one, which is 11* smith of it. 7.Hhrn?ntXral>i is a star of the 3d magnitude in the Northern Scale, 7 S. E. of Zubenel- g-.-mabi, and nearly opposite to /ubeneschamali, at the distance of 11 on the east. These two make the diagonal of the square east and west. /otii is a star of" the 4th magnitude, and constitutes the sout' ernmost corner of t'ie square. It is about 6 $. K. of /ubeneschamali, and 11 S. of Zuocnelgomabi. with which it forms, the other diagonal north and south. is a star of the '3d magnitude, situated below the Southern Scale, at the 1*\. Order and situation of Libra? What circumstance suggesting a balance? What remarks respecting the distinction between the (signs and the constellations? 1S2. Num- ber of stars in Libra? Its mean declination? Kight ascension? When on the meri- dian? How may it be known? Describe the four stars. Closing remarks? 92 ASTRONOMY. distance of 6 from Iota, and marks the southern limit of the Zodiac. It is situated In a right line with, and nearly midway between Spica Virginia and Beta Scorpionis : and comes to the meridian nearly at the same moment with Nekkar, in the head of Bootes. The remaining stars in this constellation are too small to engage attention. The scholar, in tracing out this constellation in the heavens, will perceive that Lambda and Mu, which lie in the feet of Virgo on the west, form, with Zubeneschamali and Zubenelgemabi, almost as handsome and perfect a figure, as the other two stars in the Balance do on the east. HISTORY. Virgo was the goddess of justice, and Libra, the scales, which she is usually repre- sented as holding in her left hand, are the appropriate emblem of her office. The Libra of the Zodiac, says Maurice, in his Indian Antiquities, is perpetually seen upon all the hieroglyphics of Egypt ; which is at once an argument of the great antiquity of this asterism, and of the probability of its having ueen originally fabricated by the astronomical sons of Misraim. In some few zodiacs, Astrzca, or the virgin who holds the balance in her hand as an emblem of equal justice, is not drawn. Such are the zodiacs of Esne and Dendera. Humboldt is of opinion, that although the Romans introduced this constellation into their zodiac in the reign of Julius Csesar, still it might have been used by the Egyptians and other nations of very remote antiquity. It is generally supposed that the figure of the balance has been used by all nations to denote the equality of the days and nights, at the period of the sun's arriving at this sign. It has also been observed, that at this season there is a greater uniformity in tho temperature of the air all over the earth's surface. Others affirm, that the beam only of the balance was at first placed among the stars, and that the Egyptians thus honored it as their Nllometer, or instrument by which they measured the inundations of the Nile. To this custom of measuring the waters of the Nile, it is thought the prophet alludes, when he describes the Almighty as incanuriii^ the waters in the hollmc of his hand. Isa. xl. 12. The ancient husbandmen, according to Virgil, were wont to regard this sign as indi eating the proper time for sowing their winter grain : " But when Astraca's balance, hung on high, Betwixt the nights and days divides the sky", Then yoke your oxen, sow your winter grain, Till cold December comes with driving rain." The Greeks declare that the balance was placed among the stars to perpetuate the memory of Mochus, the inventor of weights and measures. Those who refer the constellations of the Zodiac to the twelve tribes of Israel ascribe the Balance to Asher. TELESCOPIC OBJECTS. 1. a LIBR.E A wide DOUBLE STAR; R. A. 14h. 42m. 02s. ; Dec. S. 15 22' 3*. A 3, pal" ye. low; B 6, light grey. Carry a line from Arcturus to Spica; and from thence a rect- angular one about 22 to the eastward. 2. r? LIBRAE A loose DOUBLE STAR; R. A. 15h. OSm. 24s.; Dec. S. 8 47' 4*. A 2%, pale emerald ; B 12, light blue. 3. LIBRAE A fine TRIPLE STAR, between Libra and the right leg of Ophiuchus, 16 from Antares, towards Serpentis; R. A. 15h. 55m. 35s.; Dec. S. 10 55' 6". A 4%, bright white ; B 5, pale yellow ; C 1%, grey. Map VIII., Fig. 11. 4. A CLOSE CLUSTER, over the beam of the Scales ; R. A. ]5h. 10m. 26s. ; Dec. N. 2 41 ' 3". A superb object, with a bright central blaze, and outlines in all directions. Map IX., Fig. 51. Appears nebulous through small instruments. 5. A LARGE COMPRESSED CLUSTER of minute stars ; R. A. 15h. OSm. OCs. ; Dec. S. 20 26' 7". Faint and pale. HISTORY. Who was Virgo, ic.? Remark of Maurice? What general supposition ? What other explanations? TELESCOPIC OBJECTS. Alpha ? Beta? What triple star ? Map? Clusters and Map? ERPENS. 93 SERPENS (THE SERPEXT). PLATE V. 183. There are no less than four kinds of serpents placed among the constellations. The first is the Hydra, which is situ- ated south of the Zodiac, below Cancer, Leo and Virgo ; the second is Hydrus, which is situated near the south pole; the third is Draco, which is situated about the north pole ; and the fourth is the serpent called Serpens Ophiuchi, and is situated chiefly between Libra and Corona Borealis. A large part of this constellation, however, is so blended with Ophiuchus, the Serpent-Bearer, who grasps it in both hands, that the concluding description of it will be deferred until we coine to that constel- lation. " The Serpent Ophiiiclti winds his spire Immense : fewer by ten his figure trace ; One of the second rank ; ten shun the sight ; And seven, he who bears the monster hides." 184. Those stars which lie scattered along for about 25, in a serpentine direction between Libra and the Crown, mark the body and head of the Serpent. About 10 directly S. of the Crown there are three stars of the 3d magnitude., which, with several smaller ones, distinguish the head. 185. Unuk, of the 2d magnitude, is the principal star in this constellation. It is situated in the heart, about 10 D below those in the head, and may be known by its being in a line with, and between, two stars of the 3d magnitude the lower one, marked Epsilon, being 2, and the upper one, marked Delta, about 5 from it. The direction of this line is N. N. W. and S. S. B Unuk may otherwise be known by means of a small star, just above it, marked Lambda. In that part of the Serpent which lies between Corona Borealis and the Scales, about a dozen stars may be counted, of which five or six are conspicuous. Fur the remainder of this constellation, the student is referred to Serpentarius. "Vast as the starry Serpent, that on high Tracks the clear ether, and divides the sky, And southward winding from the Northern Wain. Shoots to remoter spheres its guttering train." Statiu*. HISTORY. The Hivites, of the Old Testament, were worshipers of the f'erpent, and were called Ophites. The idolatry of these Ophites was extremely ancient, and was connected with 1S3. How many serpents among the constellations? Describe each. Which here ivferred to? Is it fully described ? 1S4 What stars mark the body and head? 135. Name the principal star. Where situated and how known ? HISTORY. What said of the Hivites? Tradition respecting Ophiuchus? Supposed g iripture reference? 94 ASTRONOMY. Subf-ism, or the worship of the host of heaven. The heresy of the Ophites, mentioned by Moshoini, in his Ecclesiastical History, originated, perhaps, in the admission into the Christian church of some remnant of the ancient and popular sect of Sabeists, who adored the celestial Serpent. According to ancient tradition, Ophiuchus is the celebrated physician .Aesculapius, son of Apollo, who was instructed in the healing art by Chiron the Centaur; and the ser- pent, which is here placed in his hands, is understood by some to be an emblem of his sagacity and prudence; while others suppose it was designed to denote his skill in heal- ing the bite of this reptile. Biblical critics imagine that this constellation is alluded to in the following passage of the book of Job : " By his spirit lie hath garnished the Heavens ; his hand hath formed the crooked ser- pent." Mr. Green supposes, however, that the inspired writer here refers to Draco, because it is a more obvious constellation, being nearer the pole where the constellations were more universally noticed ; and moreover, because it is a more ancient constellation than the Serpent, and the hieroglyphic by which the Egyptians usually represented the heavens. TELESCOPIC OBJECTS. * 1. a SERPENTIS ( UnuK) A star with a minute companion on the heart of the Serpent ; R. A. I5h. 86m. 23s. ; Dec. N. 6 55' 9". A 2j, pale yellow ; B 15, fine blue. An extremely delicate object. 2. (3 SERPENTTS A delicate DOUBLE STAR in the Serpent's under jaw; R. A. 15h. 33m. 4Ss. ; Dec. N. 15 55' 7". A 8}, and B 10, both pale blue. 8. fi SKKPENTIS An elegant DOUBLE STAR in the bend of the neck ; R. A. 15h. 27m. 10s. ; Dec. N. 11 04' 7". A 3, bright white ; B 5, bluish white. A tine object, about 5 N. W. of Unak. 4. t] SIOKPENTIS A star with a minute companion in the Serpent's body, nearly midway oetween ?/ Ophiuchi and a Aquilae; R. A. ISh. 13m. 02s. ; Dec. S. 2 56 0. A 4, golden yellow; B 13, pale lilac. A delicate and difficult object. 5. r SKRPKNTIS A wide DOUBLE STAR in the middle of the Serpent, 4 northeast of ?/ > R. A. 17!i. llm. 49s.; Dec. S. 12 40' 7"' A 4^, pale sea-green; B 9, lilac, with a third siar in the field. 6. A delicate DOUBLE STAR; R. A. 15h. llm. 08s.; Dec. N. 2 22' 6". A 5 %, pale yellow B 10 J$, light grey, look 9 southwest of a Serpentis, 24 southeast of Arcturus. CORONA BORE ALTS (THE NORTHERN GROWN). MAP V. 186. This beautiful constellation may be easily known by means of its six principal stars, which are so placed as to form a circular figure, very much resembling a wreath or crown. It is situated directly north of the Serpent's head, between Bootes on the west, and Hercules on the east. This asterism was known to the Hebrews by the name of Atciroth, and by this nam<3 the stars in Corona Borealis are called, in the East, to this day. 187. Alphacca, of the 2d magnitude, is the brightest and middle star in the diadem, and about 11 E. of Mirac, in Bootes. It is very readily distinguished from the others both on account of its position and superior brilliancy. Alphaqca, Arcturus, and Seginus, form nearly an isosceles triangle, the vertex of which is at Arcturus. TELESCOPIC OBJECTS. Alpha? Beta? Delta? Eta? Nu? &c. 186. How may Corona Borealis be known? Where situated? Its Hebrew name? lS7. Describe Aiphacca? How distinguished? What triangle ? CORONA BOREALIS. 95 188. This constellation contains twenty-one stars, of which only six or eight are conspicuous ; and most of these are not larger than the 3d magnitude. Its mean declination is 30 north, and its mean right ascension 235; its center is therefore on the meridian about the last of June, and the first of July. " And, near to Ildiae, effulgent rays Beam, Ariadne, from thy starry crown : Twenty and one her stars; but eight alone Conspicuous ; one doubtful, or to claim The second order, or accept the third." HISTORY. This beautiful little cluster of stars is said to be in commemoration of a crown pre- sented by Bacchus to Ariadne, the daughter of Minos, second king of Crete. Theseus, king of Athens (12:35 B. 0.), was shut up in the celebrated labyrinth of Crete, to be devoured by the ferocious Minotaur which was confined in that place, and which usually fed upon the chosen young men and maidens exacted from the Athenians as a yearly tribute to the tyranny of Minos ; but Theseus slew the monster, and being furnished with a clew of thread by Ariadne, who was passionately enamored of him, he extricated himself from the difficult windings of his confinement. He afterward married the beautiful Ariadne according to promise, and carried her away ; but when he arrived at the island of Naxos, he deserted her, notwithstanding he had received from her the most honorable evidence of attachment and endearing tender- ness. Ariadne was so disconsolate upon being abandoned by Theseus, that, as some say, she hanged herself; but Plutarch says that she lived many years after, and was espoused to Bacchus, who loved her with much tenderness, and gave her a crown of seven star? which, after her death, .was placed among the stars. " Resolves, for this the dear engaging dame Should shine forever in the rolls of fame ; And bids her crown among the stars be placed, And with an eternal constellation graced. The golden circlet mounts; and, as it flies, Its diamonds twinkle in the distant skies ; There, in their pristine form, the gemmy rays Between Alcides and the Dragon blaze." Manilius, in the first book of his Axtronomicon, thus speaks of the Crown. " Near to Bootes the bright crown is view'd, \nd shines with stars of different magnitude: Or placed in front above the rest displays A vigorous light, and darts surprising rays. This shone, since Theseus first his faith betray'd, The monument of the forsaken maid." TELESCOPIC OBJECTS. . a CORONA BOREALIS (A!p7>acca)A. bright star with a distant companion; R. A. 15h. 27m. 54s. ; Dec. N. 27 15' 2". A 2, brilliant white ; B 8, pale violet. 2. y CORONA BOREALIS A most difficult BINARY STAR, 2>6 from Alphacca; R. A. lr>h. 30m. Ols. ; Dec. N. 2ti 48' 4"; with a distant companion. A 6, flushed white ; B, uncer- tain ; C 10, pale lilac. 3. C CORONA BOREALIS A fine DOUBLE STAR, 10" north and a little easterly from Alphacca ; R. A. 15h. 33ra. 21s. ; Dec. N. 87 09' 6". A 5, bluish white ; B 6, smalt blue A beauti- ful object. 4. r/ CORONA BOREALIS A BINARY STAR, midway between the Northern Crown and the club of Bootes ; R. A. 15h. 16m. 80s. ; Dec. N. 30" 52' 2". A north-northwest ray from a C.ronae, through /3, and half as far again, will hit it. A 6, white; B 6!, golden yellow. 1S8. How many stars in this constellation? Their magnitudes? Mean declinatioc and right ascension? HISTORY. SStory respecting Theseus and Ariadne? TKLESCOPIC OBJKCTS. Alpha? Gamma? Zeta? Eta? 9G ASTRONOMY. Sir John Ilerschel considered this the most remarkable binary star known, and tht on'y one that had completed a whole revolution since its discovery. Estimated period 4i>2 reara. URSA MINOR (THE LESSER BEAR). MAP VI. 189. This constellation, though not remarkable in its appear ance, and containing but few conspicuous stars, is, nevertheless, justly distinguished from all others for the peculiar advantage which its position in the heavens is well known to afford to nau- tical astronomy, and especially to navigation and surveying. The stars in this group being situated near the celestial pole, appear to revolve about it, very slowly, and in circles so small as never to descend below the horizon. Hence Ursa Minor will be above or below, to the right or left of the pole star, accord- ing to the hour; as he makes the entire circuit from east to west every 24 hours. 100. In all ages of the world, this constellation has been more universally observed, and more carefully noticed than any other, OM account of the importance which mankind early attached to the position of its principal star. This star, which is so near the true pole of the heavens, has from time immemorial been deno- minated the NORTH POLAR STAR. By the Greeks it is called Cynosyn ; by the Romans, Cynosura, and by other nations, Alruccabah. In most modern treatises it bears the name of Po- laris, or Alpha Polaris. 1 91 Polaris is of the 3d magnitude, or between the 2d and 3d, and situated a little more than a degree and a half from the true pole of the heavens, on that side of it which is toward Cas- siopeia and opposite to Ursa Major. Its position is pointed out by the direction of the two Pointers, Merak and Dubhe, which lie in the square of Ursa Major. A line joining Beta Cassio- pciffj, which lies at the distance of 32 on one side, and Megrez, which lies at the same distance on the other, will pass through the polar star. Or the Pole Star Capt. Smyth observes : At present It is only 1 33' from the polar point, Mid by its northerly precession in declination will gradually approach to within 26' 3ii* :>f it. This proximity to the actual pole will occur in A. D. 2095, but will not recur for 12,860 years. The period of the revolution of the celestial equinoctial pole about the pole of the ecliptic, is nearly 26,000 years ; the north celestial pole, therefore, will ba about 13,000 years ; hence, nearly 49 from the present polar star. 189. For what is Ursa Minor distinguished ? What said of its situation and change o( >ositi'm? 190. What said of the notice taken of it? Position of its principal star? Its Greek and Latin names, &c. ? 191. Describe Polaris? How found? Remarks of C;ipt. Smyth respecting? URSA MINOR J7 192. So general is the popular notion, that the North Polar Star is the true pole of the world, that even surveyors and navi- gators, who have acquired considerable dexterity in the use of the compass and the quadrant, are not aware that it ever had any deviation, and consequently never make allowance for any. All calculations derived from the observed position of this star, which are founded upon the idea that its bearing is always due north of any place, are necessarily erroneous, since it is in this position only twice in twenty-four hours ; once when above, and once when below the pole. 103. Hence, it is evident that the surveyor who regulates his compass by the North Polar Star, must take his observation when the star is on the meridian, either above or below the pole, or make allowance for its altered position in every other situa- tion. For the same reason must the navigator, who applies his quadrant to this star. for the purpose of determining the latitude he is in, make a similar allowance, according as its altitude is greater or less than the true pole of the heavens ; for we have seen that it is alternately half the time above and half the time Idow the pole. 194. The method of finding the latitude of a place from the altitude of the polar star, as it is very simple, is very often resorted to. Indeed, in northern latitudes, the situation of this star is more favorable for this purpose than that of any other of the heavenly bodies, because a single observation, taken at any hour of the night with a good instrument, will give the true lati- tude, without any calculation or correction, except that of its polar aberration. If the polar star always occupied that point in the heavens which is directly opposite the north pole of the earth, it would be easy to understand how latitude could be deter- mined from it in the northern hemisphere ; for in this case, to a person on the equator, the poles of the world would be seen in the horizon. Consequently, the star would appear just visible in the northern horizon, without any elevation. Should the person io\v travel one degree toward the north, he would see one degree below the star, and he would think it had risen one degree. And since we always see the whole of the upper hemisphere at one view, when there is nothing in the horizon to obstruct our vision, it follows that if we should travel 10 north of the equator, we should see just 10 below the pole, which would then appear to have risen 10 ; and should we stop in the 42d degree of north latitude we should, in like nnniier, have our horizon just 42 below the pole, or the pole would appear to have an elevation of 42. Whence we derive this general truth : The elevation of the pole of the equator in always equal to the latitude of the place of observation. Any instrument, then, which will give us the altitude of the north pole, will give us also the latitude of the place. The method of illustrating this phenomenon, is given in most treatises on the globe, T.KJ. What popular error? 193. When is the pole star a safe guide for the surveyor or mariner? What allowances should be made by each? 194. What said of finding the latitude by observations upon the pole star? What general rule stated f Wha* ommitted ? 93 ASTRONOMY. and as adopted by teachers generally, is to tell the scholar that the north pole risw higher and higher, as he travels farther and farther toward it. In other words, what- ever number of degrees lie advances toward the north pole, so many degrees will it rise above his horizon. Tins is not only an obvious error in principle, but it misleads the apprehension of the pupil. It is not that the pole in elc-Enlcd, but that our horizon is fffpr&Kted as we advance toward the north. The same objection lies against the artifi- cial globe ; for it ought to be so fixed that the /torison might be raised or depressed, and the pole remain in its own invariable position. 195. Ursa Minor contains twenty-four stars, including three of the 3d magnitude and four of the 4th. The seven principal stars are so situated as to form a figure very much resembling that iii the Great Bear, only that the Dipper is reversed, and about one half as large as the one in that constellation. 196. The first star in the handle, called Polaris, is the polar star, around which the rest constantly revolve. The two last in the bowl of the Dipper, corresponding to the Pointers in the Great Bear, are of the 3d magnitude, and situated about 15 from the pole. The brightest of them is called Kochab, which signifies an axle or hinge, probably in reference to its moving so near the axis of the earth. Kochab may be easily known by its being the brightest and middle one of the three conspicuous stars forming a row, one of which is about 2, and the other 3 from Kochab. The two brighest of these are situated in the breast and shoulder of the animal, about 3 apart, and are called the Giutrdx or Pointers of Ursa Minor. They are on the meri- dian about the 20th of June, but may be seen at all hours of the night, when the sky ia clear. 19t. Of the four stars which form the bowl of the Dipper, one is so small as hardly to be seen. They lie in a direction toward Gamma in Cepheus ; but as they are continually chang- ing their position in the heavens, they may be much better traced out from the map, than from description. Kochab is about 25 distant from Benetnasch, and about 24 from Dubhe, and hence forms with them a very nearly equi- lateral triangle. " The Lesser Bear Leads from the pole the lucid band : the stars Which form this constellation, faintly shine, Twice twelve in number; only one beams forth Conspicuous in high splendor, named by Greece The Cynosure; by us, the POLAR ,STAR." HISTORY. The prevailing opinion is that Ursa Major and Ursa Minor are the nymph Calisto and her son Areas, and that they were transformed into bears by the enraged and imperious Juno, and afterward translated to heaven by the favor of Jupiter, lest they might be destroyed by the huntsmen. The 'Chinese claim that the emperor Ilong-ti, the grandson of Noah, first discovered 195. Number of stars in Ursa Minor? Their magnitudes? How situated? 1%. De- scribe Polaris, Kochab, and the Guards or Pointers? 197. Are all the stars distinctly Visible? Direction? What triangle ? HISTORY. What prevailing opinion, or myth ? Chinese claim ? Phemcians ? Greets .' URSA MINOR. 99 the polar star, and applied it to purposes of navigation. It la certain that it was used for this purpose in a very remote period of antiquity. From various passaged in th^ ancients, it is manifest that the Phenicians steered by Cynosura, or the Lessor Bear; ^hereas, the mariners of Greece, and some other nations, steered by the Greater Bear, called Helice, or Helix. Lucan, a Latin poet, who flourished about the time of the birth of our Saviour, thai adverts to the practice of steering vessels by Cynosura : " Unstable Tyre now knit to firmer ground, With Sidon for her purple shells renown'd, Safe in the Cynosure their glittering guide With well-directed navies stem the tide." HOWE'S Translation, B. ill. The following extracts from other poets contain allusions to the same fact: " Phenicia, spurning Asia's bounding strand, By the bright Pole sttir's steady radiance led, Bade to the winds her daring sails expand, And fearless plough'd old Ocean's stormy bed." MA CRICK'S Elegy on Sir W. Jone*. "Ye radiant signs, who, from the ethereal plain Sidowutn* guide, and Greeks upon the main, Who from your poles all earthly things explore, And never set beneath the western shore." OVID'S Tristia. " Of all yon multitude of golden stars, Which the wide rounding sphere incessant bears. The cautious mariner relies on none, But keeps him to the constant pole alone." LUCAS'S Pharsalia, B. viii. v. 225. Ursa Major and Ursa Minor are sometimes called Triones, and sometimes the Greater and Lesser Wains. In Pennington's Memoirs of the learned Mrs. Carter, we have th following beautiful lines : " Here Cassiopeia fills a lucid throne, There, blaze the splendors of the Northern Crown ; While the slow Car, the cold Triones roll O'er the pale countries of the frozen pole : Whose faithful beams conduct the wandering ship Through the wide desert of the pathless deep." Thales, an eminent geometrician and astronomer, and one of the seven wise men of Greece, who flourished six hundred years before the Christian era, is generally reputed to be the inventor of this constellation, and to have taught the use of it to the Phenician navigators ; it is certain that he brought the knowledge of it with him from Phenice into Greece, with many other discoveries both in astronomy and mathematics. Until the properties of the magnet were known and applied to the use of navigation, and for a long time after, the north polar star was the only sure guide. At what time the attractive powers of the magnet were first known, is not certain ; they were known in Europe about six hundred years before the Christian era; and by the Chinese records, tt Is said that its polar attraction was known in that country at least one thousand years earlier. TELESCOPIC OBJECTS. 1. a URS MINORIS (Polaris) A DOUBLE STAR; R. A. Ih. 2m. 10s.; Dec. N. 88* 27' 4*. A 2>$, topaz yellow ; B 9J$, pale white. Map VIII., Pig. 12. 2. (3 URS^B MINORIS (Kochab) A star with a distant companion in the left shoulder; R. A. 14h. 51m. 14s.; Dec. N. 74 48' 2'. A 8, reddish; B 11, pale grey several small atars in the field 8. 6 URS.B MIMORIS A star with a very distant telescopic companion in the middle of the tail of the figure ; R. A. ISh. 23in. 56s. ; Dec. N. 86 86' 4'. A 8, greenish tinge ; B 12, grey. What proof? from the poets? What other names for Ursa Major and Ursa Minor? Whfci jaid of Tiiales? Use of the pole star? The magnet? TiLEscorie OBJKCTS. Alpha? Show on the map, Beta Delta Epsilon Zeta. B. i. 5 100 ASTRONOMY. 4. e URSM M.SOKIS A star with a minute companion, at the root of the tail; R. A. ]7h. 02m. 37s.; Dec. N. 82" 17' 01". A 4, bright yellow; B 12, pale blue; three ether telescopic stars in the field. It is easily found, being the third star from Polaris 5. URSA- MIDORIS A DOUBLE STAR in the middle of the body ; R. A. 15h. 4'Jm. 52s. ; Dec. N. 78 16' 07". A 4, flushed white ; B 11, bluish- with a yellow star of the 9th mag- nitude in the field. CHAPTER IX. CONSTELLATIONS ON THE MERIDIAN IN JULY. SCORPIO (THE SCOKPION). MAP V. 198. THIS is the eighth sign, and ninth constellation, in the order of the Zodiac. It presents one of the most interesting groups of stars for the pnpil to trace out that is to be found in the southern hemisphere. It is situated southward and east- ward of Libra, and is on the meridian the 10th of July. The snn enters this sign on the 23d of October, but does not reach the constellation before the 20th of November. When astronomy was first cultivated in the East, the two solstices and the two equinoxes took place when the sun was in Aquarius and Leo, Tau- rus and Scorpio, respectively. 199. Scorpio contains, according to Flamsted, fotty-four stars, including one of the 1st magnitude, one of the 2d, and eleven of the 3d. It is readily distinguished from all others by the pecu- liar luster and the position of its principal stars. Antares is the principal star, and is situated in the heart of the Scorpion, about 19 east of Zubenelgubi, the southernmost, star in the Balance. Antares is the most brilliant star in that region of the skies, and may be otherwise distinguished by its remarkably red appearance. Its declination is about 26 S It comes to the meridian about three hours after Spica Yirginis, or fifty minutes after Corona Borealis, on the 10th of July. It is one of the stars from which the moon's distance is reckoned for computing the longitude at sea. There are four great stars in the heavens, Ibmalhaut, Aldfl>aran, Rt.guht*, and An-tares, which formerly answered to the solstitial and equinoctial points, and which were much noticed by the astronomers of the East. 200. About 8-J- northwest of Antares, is a star of the 2d 198. Order of Scorpio among the signs, Ac.? Its comparative interest? Situation? When does the sun enter this sign ? When the constellation? How with the solstices and equinoxes anciently? Why not so now? 199. Number and magnitudes of the itarsin Scorpio? How distinguished? Name and position of its principal star? How known ? What use made of it ? What three other stars mentioned ? 2'uO. What other SCORPIO. 10J magnitude, in the head of the Scorpion, called Grajfias. It is but one degree north of the earth's orbit. It may be recognized by means of a small star, situated about a degree northeast of it, and also by its forming a slight curve with two other stars of the 3d magnitude, situated below it, each about 3 apart. The broad part of the constellation near Gramas, is powdered with numerous small stars, converging down to a point at Antares, and resembling in figure a boy's kite. 201. As you proceed from Antares, there are ten conspicuous stars, chiefly of the 3d magnitude, which mark the tail of the kite, extending down, first in a south-southeasterly direction about 17, thence easterly about 8 further, when they turn, and advance about 8 toward the north, forming a curve like a shepherd's crook, or the bottom part of the letter S. This crooked Hue of stars, forming the tail of the Scorpion, is very conspicuous, and may be easily traced. The first star below Antares, which is the last in the back, is of only the 4th magni- tude. It is about 2 southeast of Antares, and is denoted by the Greek name of T. Epsiloii, of the 3d magnitude, is the second star from Antares, and the first in the tail I* is situated about 7 below the star T, but inclining a little to the east. J/it, of the 3d magnitude, is the 3d star from Antares. It is situated 4% below Epsi- lon. It may otherwise be known by means of a small star close by it, on the left. Ztta, of about the same magnitude, and situated about as far below Mu, is the fourth star from Antares. Here the line turns suddenly to the east. Eta, also of the 3d magnitude, is the fifth star from Antares, and about 3V east of Zet.a. Theta, of the same magnitude, is the sixth star from Antares, and about 4 V east of Eta. Here, the line turns again, curving to the north, and terminates in a couple of stars. Iota is the seventh star from Antares, 3 V above Theta, curving a little to the left. It is a star of the 3d magnitude, and may be known by means of a small star, almost touching it, on the east. Kappa, a star of equal brightness, is less than 2 above Iota, and a little to the right. Letut/i, of the 8d magnitude, is the brightest of the two last, in the tail, and is situated about 3 above Kappa, still further to the right. It may readily be known by means of a smaller star, close by it, on the west. 202. This is a very beautiful group of stars, and easily traced out in the heavens. It furnishes striking evidence of the facility with which most of the constellations may be so accurately delineated, as to preclude everything like uncertainty in the knowledge of their relative situation. " The heart with luster of amazing force, Refulgent vibrates; faint the other parts, And ill-defined by stars of meaner note." HISTORY. This sign was anciently represented by various symbols, sometimes by a snake, and eometimes by a crocodile ; but most commonly by the scorpion. This last symbol is star described ? Size and position? How recognized? What said of the brojd part or body of Scorpio? 201. What stars form the tail of Scorpio? Are they conspicuous? Name and describe in detail? 2t)2. General remarks respecting thih constellation? HISTORY. How was Scorpio ancrently delineated? How regarded by ancint astro'.o- 102 ASTRONOMY. found on the Mithraic monuments, which is pretty good evidence that these monument* vsrc constructed when the vernal equinox accorded with Taurus. On ')oth the zodiacs of Dendera, there are rude delineations of this animal ; that on the portico differs considerably from that on the other zodiac, uow in the Louvre. Scorpio was considered by the ancient astrologers as a sign accursed. The Egyptians fixed the entrance of the sun into Scorpio as the commencement of the reign of Typhon, when, the Greeks fabled the death of Orion. When the sun was in Scorpio, in the month of Athyr, as Plutarch informs us, the Egyptians inclosed the body of their god Osiris in an ark, or chest, and during this oeremony a great annual festival was celebrated. Three days after the priests had inclosed Osiris in the ark, they pretended to have found him again. The death of Osiris, then, was lamented when the aun in Scorpio descended to the lower hemisphere, and when he arose at the vernal equinox, then Osiris was said to be born anew. The Egyptians or Chaldeans, who first arranged the Zodiac, might have placed Scorpio in this part of the heavens to denote that when the sun enters this sign, the diseases Incident to the fruit season would prevail; since Autumn, which abounded in fruit, often brought with it a great variety of diseases, and might be thus fitly represented by that venomous animal, the scorpion, who, as he recedes, wounds with a sting in his tail. Mars was the tutelary deity of the Scorpion, and to this circumstance is owing all that iargon of the astrologers, who say that there is a great analogy between the malign influence of the planet Mars and this sign. To this also is owing the doctrine of the alchemists, that iron, which metal they call Mars, is under the dominion of Scorpio ; BO ihat the transmutation of it into gold can be effected only when the sun is in this sign. The constellation of the Scorpion is very ancient. Ovid thus mentions it ia his beau* tiful fable of Phaeton : " There is a place above, where Scorpio bent, In tail and arms surrounds a vast extent ; In a wide circuit of the heavens he shines, And fills the place of two celestial signs.'' According to Ovid, this is the famous scorpion which sprang out of the earth at the command of Juno, and stung Orion ; of which wound he died. It was in this way the imperious goddess chose to punish the vanity of the hero and the hunter, for boasting that there was not on earth any animal which he could not conquer. " Words that provoked the gods once from him fell, 4 No beasts so fierce,' said he, 'but I can quell;' When lo ! the earth a baleful scorpion sent, To kill Latona was the dire intent ; Orion saved her, though himself was slain, But did for that a spacious place obtain In heaven : * to Viee my life,' said she, ' was dear, And/or thy merit shine illustrious there." Although both Orion and Scorpio were honored by the celestials with a place among the stars, yet their situations were so ordered that when one rose the other should set, juul vice vermi; so that they never appear in the same hemisphere at the same time. In the Hebrew zodiac this sign is allotted to Dan, because it is written, "Dan shall be a serpent by the way, an adder in the path." TELESCOPIC OBJECTS. 1. (i SCORPII (Antarc*) A bright star with a companion in the heart of Scorpio; R. A 10h. 19m. 80s. ; Dec. S. 26 04' 3". A 1, fiery red ; B 8, pale. Very close. '2. tf SCOKPII (, and the lower one Gamma. Theae stars in the head and shoulders of Serpentaiius, form ;i tri- angle, with the vertex in Ras Alhague, and pointing toward the northeast. 208 About 4 E. of Gamma, is a remarkable cluster of four or five stars, in the form of the letter V, with tne open part to the north. It very much resembles the Hyades. This beautiful little group mark the face of TAURUS PONIATOWSKI. The solsti- tial colure passes through the equinoctial about 2 E. of the 206. What other name has the Serpent Bearer? How represented? j?ituat ! on and extent? Number and size of its principal stars? 2 >7. Name of its principal star* Magnitude and situation? Rho, and its situation? Use of these two star*? What snid of lota and Kap|,a? Of Chelc-b and Gamma? 208. What remarkable cluster? Foi 5* 108 ASTRONOMY. lower star in the vertex of the V. The letter name of this star is k. There is something remarkable in its central position. It is situated almost exactly frn the inid-heavens, bemg nearly equidistant from the poles, and midway between the ver- nal and autumnal equinoxes. It is, however, about one and a third degrees nearer Mie north than the south pole, and about two degrees nearer the autumnal than the vernal equinox, being atout two degrees west of the solstitial colure. Directly south of the V, at the distance of about 12, are two very small stars, abou: 2" apart, situated in the right hand, where it grasps the serpent. About half-way between, and nearly in a line with, the two in the hand and the two in the shoulder, is another star of the 3d magnitude, marked Zeta, situated in the Serpent, opposite the right elbow. It may be known by means of a minute star just under it. J/a/vrtc, in the left arm, is a star of the 4th magnitude, about 10 S. W. of Iota and Kappa. About 7* farther in the same direction are two stars of the 3d magnitude, situ- ated in the hand, and a little more than a degree apart. The upper one of the two, which is about 16" N. of Graffias in Scorpio, is called Yed ; the other is marked Epsilon. These two stars mark the other point in the folds of the monster where it is grasped by Berpentarius. The left arm of S ^rpentarius may be easily traced by means of the two stars in the shoulder, the one (Marsic) near the elbow, and the two in the hand; all lying nearly in a line N. N. E. ard S. S. W. In the same manner may the right arm be traced, by stars very similarly situated; that is to say, first by the two in the east shoulder, just west of the V, thence 8 in a southerly direction inclining a little to the east, by Zeta, (known by a little star right under it,) and then by the two small ones in the right hand, situated about 6 below Zeta. About 1'2 from Antares, in an easterly direction, are two stars in the right foot, about 2 apart. The largest and lower of the two, is on the left hand. It is of between the 8d and 4th magnitudes, and marked Rho. There are several other stars in this constel- lation of the 3d aud 4th magnitudes. They may be traced out from the maps. " Thee, Serpentarius, we behold distinct, With seventy-four refulgent stars ; and one Graces thy helmet, of the second class: The Serpent, in thy hand grasp'd, winds his spire Immense ; fewer by ten his figure trace ; One of the second rank ; ten shun the sight; And seven, he who bears the monster hides." Eudosia. HISTORY. This constellation was known to the ancients twelve hundred years before the Chris- tian era. Homer mentions it. It is thus referred to in the Astronomicon of Miinilius - 14 Next, Ophiuchus strides the mighty snake, Untwists his winding folds, and smooths his back, Extends his bulk, and o'er the slippery scale His wide-stretch'd hands on either side prevail The snake turns back his head and seems to rage : That war must last where equal power prevails." ^sculapius Tras the son of Apollo, by Coronis, and was educated by Chiron the Cen- taur in the art of medicine, in which he became so skilful, that he was considered t>-? inrentor and god of medicine. At the birth of ^Esculapius, the inspired daughtei of Chiron uttered, "in sounding verse " this prophetic strain. 44 Hail, great physician of the world, all hail ! Hail, mighty infant, who, in years to come, Shall heal the nations and defraud the tomb! Swift be thy growth ! thy triumphs unconfined ! Make kingdoms thicker, and increase mankind : Thy daring art shall animate the dead, And draw the thunder on thy guilty head : Then shalt thou die, but from the dark abode Rise up victorious, and be twice a god." and resemblance? Marks what? What said of the lower star in the V. ? What stars outh of it? What cf Marsic? Of Yed and Epsilon ? How trace the left arm ? HISTORY. Antiquity of this constellation ? Proof? Who was ^Esculapius ? Account of his great skill ? His metamorphosis? Remarkable fact respecting Socrates and Plato! SERPENTAR1US. 109 He accompanied the Argonauts to Colchis, in the capacity of physician. He is said to toave restored many to Hie, insomuch that Pluto complained to Jupiter, that his dark dominion was in danger of being depopulated by his art. /Esculapius was worshiped at Epidaurus, a city of Peloponnesus, and hence he is styled by Milton " the god in Epidaurus." Being sent for to Rome in the time of a plague, he assumed the form of > serpent and accompanied the ambassadors, but though thus changed, he was JSscuiapius still, in serpents deu* the deity in a serpent and under that form he continued to be worshiped at Rome. The cock and the serpent were sacred to him, especially the latter. The ancient physicians used them in their prescriptions. One of tlie last acts of Socrates, who is accounted the wisest and best man of Pagan antiipaity, was to offer a cock to ^sculapius. He and Plato were both idolaters ; they conformed, and advised others to conform, to the religion of thir country ; to gross idolatry and absurd superstition. If the wisest and most learned >rere so blind, what must the foolish and ignorant have been ? TELESCOPIC OBJECTS. t. a OPHIUCHI (Ras Alhague)k bright star with a minute companion, in the head of the figure ; R. A. :.7h. 27m. 30s. ; Dec. N. 12" 40' 08". A 2, sapphire ; B 9, pale grey. A coarse triplet of snvill stars near them. 2. $, faint lilac ; C 6, white ; four other stars in view. 10. A BRIGHT-CLASS, OVAL NEBULA, under the body of Draco; R. A. 15h. 02m. 03s.; Dec. N. 56 28' 0". Faint at the edges, with four stars in the field ; one quite near it. 11. A PLANETARY NEBULA, between the second and third coil, on a line from Polaris to y Draconis : R. A. 17h. 58m. 38s. ; Dec. 66" 38' 01". A remarkably bright and pale blue object, with several telescopic stars in the field. Map IX., Fig. 56. It is situated exactly in tins pole of the ecliptic. LYRA (THE HARP). MAP V. 213. This constellation is distinguished by one of the most brilliant stars in the northern hemisphere. It is situated direct- ly south of the first coil of Draco, between the Swan on the TELKSCOPIC OBJECTS. Alpha ? Beta? Gamma? Delta? Epsilon? Eta? Mu? Triple stars ? Nebulae ? 213. How is Lyra distinguished? Where situated? Number and size of its princi- niil stars ? LYRA. 113 cast, and Hercules on the west ; and when on the meridian, is almost directly overhead. It contains twenty-one stars., includ- ing one of the 1st magnitude, two of the 3d, and as many of the 4th. There Lyra, for the brightness of her stars, More than their number, eminent ; thrice sevei She counts, and one of these illuminates The heavens tar around, blazing imperial In the first order." 214. This star "blazing imperial in the first order" is called Vega, and sometimes Wega ; but more frequently, Lyra, after the name of the constellation. There is no possibility of mistaking this star for any other. It is situated 14| S. E. of Eltanin, arid about 30 N. N. E. of Ras Alhague and Has Algethi. It may be certainly known by means of two small, yet conspicuous stars, of the 5th magnitude, situated about 2 apart, on the east of it, arid making with it a beautiful little triangle, with the angular point at Lyra. The northernmost of these two small stars is marked Epsilon, and the southern one ZftUBLB STAR about 2 3 south of e ; R. A. ISh. 89m. 15s. ; Dec. N. 87* 26' 05". A 5, topaz ; B 5%, greenish. 6. ;/ LYRA: A neat DOUBLE STAR 6 east of Vega; R. A. 19h. 08m 18s. ; Dec. N. 38" 52 05". A 5, sky blue; B 9, violet tint. A fine object for a moderate telescope. 1. v LYR^K A QUADRUPLE STAR in the cross-piece of the Lyre; R. A. ISh. 43m. 4Ss. ; Doc. N. 32 3S 0". A 9, pale yellow; B 13, bluish; C 11, pale blue ; D 15, blue; three other Itars in the field. A very delicate object. 8. A GLOBULAR CLUSTER, in a splendid field, between the eastern yoke of Lyra and the head of Cygnus; 11. A. 1%. 10m. 19s, ; Dec. N. 29 54' 02*. About 5% southeast of & Lyrss, towards pi Cygni, and 3V from the latter. Map IX., Fig. 57. 9. An ANNULAR NEBULA between (3 and y\ R. A. 18h. 47m. 37s.; Dec. N. 32* 50' OJ*. A wonderful object, in the form of an elliptical ring. Supposed by Herschel to be 900 times as distant as Sirius. A clear opening through its center, and several stars in the field. Map IX., Fig. 58. TAURUS PONIATOWSKIL MAP V. 215. This small asterism is between the shoulder of Ophin- clius and the Eagle. The principal stars are in the head, and of the 4th magnitude. They are arranged in the form of the letter V, and from a fancied resemblance to the zodiac Bull, and the Hyades, became another Taurus. See description of Ser- pentarius, article 206. OBJECTS. Alpha ? Beta ? Gamma ? Epsilon ? Point out on the map. Zeta? Eta? Nu? What cluster? Point out on the map. What nebula, and whert V>und on the map? 2lf>. Describe Taurus Poniatowskii. Where situated ? 116 ASTRONOMY. TELESCOPIC OBJECTS. 1. A neat DOUBLE STAR In the space between the Polish Bull, and the Eagle's wing, V east of a Ophiuchi, in a line towards Altair; R. A. 17h. 5Sm. 17s.; Dec. N. 11* 59' Go" A 8, straw-color; B S), sapphire blue. 2. A fine PLANETARY KEHULA, in a rich vicinity, in the shoulder; R. A. 18h. 04m. 2!s. , Dec. N. 6* 49' 02". A small but bright object, regarded by Prof. Struve as one of the most curious in the heavens. Many telescopic stars in the field. SCUTUM SOBIESKI (SOBIESKI'S SHIELD). MAP Y. 216. This small figure is between the head of the Polish Bull, and the head of Sagittarius. Its four principal stars are of the 5th magnitude ; and it is important chiefly for its Telescopic Objects. TELESCOPIC OBJECTS. 1. A DOUBLE STAR 1%" northeast of fi Sagittarii; R. A. ISh. 07m. 37s.; Dec. S. 19* 55' 05". A 8 %, and BIO, both grey. 2. A neat DOUBLE STAR, in a long and straggling assemblage below the Shield ; R. A. 18h. 10m. 36s. ; Dec. S. 17 11' 07". A 9, and B 11. both bluish. It is 4* from // Sagittarii, in a very rich vicinity ; several splendid fields lying only about 1 south of it. 3. A BEAUTIFUL CLUSTER below the base of the Shield ; R. A. ISh. 08m. 49s. ; Dec. S. 18* 27' 05". A line from a Aquilse, southwest over /I Antinoi, and continued as far again, will reach this object. 4. A SCATTERED BUT LARGE CLUSTER, north-half-east from yU Sagittarii 7* ; R. A. ISh. 09m. 44s. ; Dec. S. 13 50' 05". Stars disposed in pairs, the whole forming a very pretty object in a telescope of tolerable capacity. 5. A HORSE-SHOK NEBULA just below the Shield ; R. A. 18h. 1 1m. 23s. ; Dec. S. 16 15' 08". It has been compared to a Greek 12. Map IX., Fig. 59. Five stars, in the object, and others in the field, and the region around it particularly rich. Sir William Herschel computed that there were 285,000 stars in a space 10 long, and 2}$* wide; many of which were 2,300 times as far off as Sirius ! SAGITTAPJUS (THE ARCHER). MAP Y. 217. This is the ninth sign and the tenth constellation of the Zodiac. It is situated next east of Scorpio, with a mean decli- nation of 35 S., or 12 below the ecliptic. The sun enters this sign on the 22d of November, but does not reach the constel- lation before the 7th of December. It occupies a considerable space in the southern hemisphere, and contains a number of sub- ordinate, though very conspicuous stars. The whole number of its visible stars is sixty-nine, including five of the 3d magnitude, and ten of the 4th. TELESCOPIC OBJECTS. What double star ? What nebula ? 216. Situation and components of Scotum Sobieski ? For what chiefly important f TELESCOPIC OBJECTS. What double stars ? Clusters ? Nebula ? 217. Order of Sagittarius, in the signs and constellations? When does the sun eauu this siyn f The comUUation f Its extent ? Number and size ('f its stars t SAGITTAJUUS. ll/ 218. Sagittarius may be readily distinguished by means of five stars of the 3d and 4th magnitudes, forming a figure resem- bling a little, short, straight-handled dipper, turned nearly bot- tom upward, with the handle to the west, familiarly called the Milk-Dipper, because it is partly in the Milky-Way. This little figure is so conspicuous that it cannot easily be mistaken. It is situated about 33 E. of Antares, and comes to the meridian a few minutes after Lyra, on the 17th of Au- gust. Of the four stars forming the bowl of the Dipper, the two upper ones are only 3 apart, and the lower ones 5. The two smaller stars forming the handle, and extending westerly about 4J$*, and the easternmost one in the bowl of the Diaper, are all of the 4th magnitude. The star in the end of the handle, is marked Lambda, and is placed in the bow of Sagittarius, just within the Milky- Way. Lambda may otherwise be known by its being nearly in a line with two other stars about 4& apart, extending toward the S. E. It is also equidistant from P)d and Delhi, with which it makes a handsome triangle, with the vertex in Lambda. About 5 above Lambda, and a little to the west, are two stars close together i.i the end of the bow, the brightest of which is of the 4th magnitude, and marked Mu. This star serves to point out the winter solstice, being about 2 N. of the tropic of Capri- corn, and less than one degree east of the solstitial colure. If a line be drawn from Sigma through Phi, and produced about 6* farther to the west, it will point out Delta, and produced about 3 from Delta, it will point out Gamma; stars of the 3d magnitude, in the airow. The latter is in the point of the arrow, and may be known by means of a small star just above it, on the right. This star is so nearly on the game meridian with Etaain, in the head of Draco, that it culminates only two minutes after it. A few other conspicuous stars in this constellation, forming a variety of geometrical figures, may be easily traced from the map. HISTORY. This constellation, it is said, commemorates the famous Centaur Chiron, son of Philyra mid Saturn, who changed himself into a horse, to elude the jealous inquiries of his wife Fihea. C'hiron was famous for his knowledge of music, medicine and shooting. He taught mankind the use of plants and medicinal herbs; and instructed, in all the polite arts, the greatest heroes of the age. He taught Jisculapius physic, Apollo music, and Her cules astronomy; and was tutor to Achilles, Jason, and /Eneas. According to Ovid, h. was slain by Hercules, at the river Evenus, for offering indignity to his newly married bride. " Thou monf ter double shap'd, my right set free Swift as his words, the fatal arrow tlew; The Centaur's back admits the feather'd wood, And through his breast the barbed weapon stood ; Which, when in anguish, through the flesh he tore, From both the wounds gush'd forth the spumy gore." The arrow which Hercules thus sped at the Centaur, having been dipped in the blood of the Lernaean Hydra, rendered the wound incurable, even by the father of medicine himself, arid he begn'd Jupiter to deprive him of immortality, if thus he might escape liis excruciating pan. .5. Jupiter granted his request, and translated him to a place among the constellations. " Midst golden stars he stands refulgent now, And thrust? the Scorpion with his bended bow." This is the Grecian account of Sagittarius; but as this constellation appears on the ancient zodiacs of Egypt, Dendera, Ksne, and India, it seems conclusive that the Greek* 21S. How distinguished? Where is Lambda? How known? Where are Mu, Delta, and Gamma? HISTORY. What does Sagittarius commemorate? Story of Chiron ? What said of the antiquity of this constellation? Jk8 ASTilOiNOAIi'. only borrowed Vie figure, while they invented the fable. This is known to be true with respect to very many of the ancient coasteliacious. ilcuee the jargon of .the conttfciriu? accounts which have descended to us. TELESCOPIC OBJECTS. 1. /z SAGiTTARn A MULTIPLE STAR in the north end of the Archer's bow; R. A. ISh. tUm. 11s. ; Dec. S. 21" 05' OT" About 25* east-northeast of Antares. A 3#, pale yellow ; B 16, blue ; C 9^, and D 10, both reddish. 2. a SAGITTAKII A star with a distant companion in the Archer's right shoulder; R. A. 18h. 45m. 20s. ; Dec. S. 26" 29' 08'. A 3, ruddy ; B 9^, ash-colored. 8. A very delicate TRIPLE STAR, between the heads of Sagittarius and Capricorn, about 25* south-by-west of Altair, and 10 west of tf CaprScorni ; R. A. 19h. 31m. 33s. ; Dec. S. 16 39' 02". A 5%, yellow ; B 8, violet; C 16, blue. Other small stars in the field. 4. A LARGE AND COARSE CLUSTER of minute stars, close to the upper end of the bow, and In the Galaxy; R. A. 18h. 03m. 08s. ; Dec. S. 21 86' 01". Stars of the 10th to 13th mag- nitudes. A rich field of no particular form. 5. A LOOSE CLUSTER in the Galaxy, between the Archer's head and Sobieski's Shield; R. A. 18h. 22m. 14s. ; Dec. S. 19 10' 02". The most prominent are a pair of 8th magni- tude stars. It is about 5 northeast of ^ Sagittarii. 6. A FINE GLOBULAR CLUSTER between the head and bow, near the solsticial colure; R. A. ISh. 26m. 25s. ; Dec. S. 24" 01' 04". A fine group, compressed towards the ceuter, with several single stars in the field. Map IX., Fig. 60. CORONA AUSTPvALIS (THE SOUTHERN CROWN). MAP V. 219. This is a small and unimportant constellation near tho fore-legs of Sagittarius ; and between them and the Milky-Way. R. A. about 18h. 44m.; Dec. S. 40. Its four principal stars are of the 5th magnitude, situated near each other, and arranged in a gentle curve line, lying north and south. It has no Mytho- logical History, or Telescopic Objects worthy of notice. AQUILA ET AJSTINOUS (THE EAGLE AND ANTIXOUS). MAP V. 220. This double constellation is situated directly south of the Fox and Goose, and between Taurus Poniatowskii on the west, and the Dolphin on the east. It contains seventy-one fetars, including one of the 1st magnitude, nine of the 3d, and seven of the 4th. It may be readily distinguished by the position and superior brilliancy of its principal star. 221. Altair, the principal star in the Eagle, is of the 1st, or between the 1st and 2d magnitudes. It is situated about 14 c TELESCOPIC OBJECTS. Mu? Sigma? What triple star? What clusters? Which shown on the map? Point it out. 219. Describe Corona Australis. Its principal stars ? History and Telescopic Objects? 220. Situation of Aquila and Antinous? Number and size of its principal star** 8'21. Altair how known? Stars each side of it? Use of Altair in navigation* Whal AQUILA ET ANTINOUS. 119 S. W. of the Dolphin. It may be known by its being the largest and middle one of the three bright stars which are arranged in a line bearing N. W. and S. E. The stars on each side of Altair are of the 3d magnitude, and distant from it about 2. This row of stars very much resembles that in the Guards of the Lesser Bear. Altair is one of the stars from which the moon's distance is taken for computing longitude at sea. Its mean declination is nearly 8 N., and when on the meridian, it occupies nearly the same place in the heavens that the sun does at noon on the 12th day of April. It culminates about 6 minutes before 9 o'clock, on the last day of August. It rises acronically about the begin- ning of June. Ovid alludes to the rising of this constellation; or, more probably, to that of the prin- cipal star, Altair : " Now view the skies, And you'll behold Jove's hook'd-bill bird arise." Massey's Fasti. -" Among thy splendid group ONE dubious whether of the SECOND RANK, Or to the FIRST entitled ; but whose claim Seems to deserve the FIRST." Eudosia. The northernmost star in the line, next above Altair, is called Tarazed. In the wing of the Eagle, there is another row composed of three stars, situated 4 or 5 apart, extending clown toward the southwest; the middle one in this line is the smallest, being only of the fourth magnitude ; the next is of the 3d magnitude, marked 2>elta, and situated 8 S. W. of Altair. As you proceed from Delta, there is another line of three stars of the 3d magnitude, between 5 arid 6 apart, extending southerly, but curving a little to the west, which murk the youth Antiuous. The northern wing of the Eagle is not distinguished by anj conspicuous stars. Zrtit and EjMilon, of the 3d magnitude, situated in the tail of the Eagle, are about 2 apart, and 12* N. W. of Altair. The last one in the tail, marked Epsilon, is on the same meridian, and culminates the same moment with Gamma, in the Harp. From Epsilon, in the tail of the Eagle, to Theta, in the wrist of Antinous, may be trace! a long line of stars, chiefly of the 3d magnitude, whose letter names are Theta, Eta, Mu, Zeta and Epsilon. The direction of this line is from S. E. to N. W., and its length is about 25. Eta is remarkable for its changeable appearance. Its greatest brightness continues but 40 hours ; it then gradually diminishes for 66 hours, when its luster remains station- ary for 80 hours. It then waxes brighter and brighter, until it appears again as a star of the 3d magnitude. From these phenomena, it is inferred that it not only has spots on its surface, like our sun, hut that it also turns on its axis. Similar phenomena are observable in Algol, Beta, in the Hare, Delta, in Cepadus, and Omicron, in the Whale, and many others. " Aqu her with uila the next, Divides the ether with her ardent wing: Beneath the Swan nor far from Pegasus, POETIC EAGLE." poetic quotation? Where are Tarazed and Delta ? 7*ta and Epailon? Theta ? Kta F;r what remarkable ? 1 20 ASTRONOMY. HISTORY. Aqujla, or the Eagle, is a constellation usually joined with Antinous. Aquita is sup- posed to have been Merops, a king of the island of Cos, in ;ne Archipelago, and the hus- band of Clymene, the mother of I'haHon ; this monarch having been transformed into aa eagle, and placed among the constellations. Some have imagined that Aquila was the eagle vvnose form Jupiter assumed when he carried away Ganymede; others, that it represents the eagle which brought nectar to Jupiter while he lay concealed in the cave a* Urett, to avoid the fury of his father, Saturn. Some of the ancient poets say, that this is the eagle which furnished Jupiter with weapons in big war with the giants: " The towering Eagle next doth boldly soar, As if the thunder in his claws he bore; He's worthy Jove, since he, a bird, supplies The heaven with sacred bolts, and arms the skies." MttnOftu. The eagle is justly styled the "sovereign of birds," since he is the largest, strongest, and swiftest of all the feathered tribe that live by prey. Homer calls the eagle, " the sirong sovereign of the plumy race ;" Horace styles him " The royal bird, to whom the king of heaven The empire of the feathered race has given :" Ami Milton denominates the eagle the "Bird of Jove." Its sight is quick, strong and piercing, to a proverb : Job xxix., 23, Ac. " Though strong the hawk, though practised well to fly, An eagle drops her in the lower sky ; An eagle when deserting human sight. She seeks the sun in her unwearied flight ; Did thy command her yellow pinion lift So high in air, and set her on the clift Where far above thy world she dwells alone, And proudly makes the strength of rock? her own ; Thence wide o'er nature takes her dread survey, And with a glance predestinates her prey? She feasts her young with blood ; and hovering o'er The unsiaughtered host, enjoys the promise^ gore." ANTINOUS. Antinons is a part of the constellation Aquili, and wg, and B 8, both white ; C 16, blue ; D 9, yellowish ; several other small stars in the field. Map VIII., Fig. 17. 5. A SMALL BRIGHT CLUSTER, in the Dolphin's tail, 8% south of ; R. A. 20h. 26m. 21s. ; Dec. N. 6 53' 02". Just east of a 9th magnitude star a coarse telescopic pair at a distance, and several minute stars in the field. 6. A small PLANETARY NKBULA, betwen the pectoral fin and the arrow head, 6* north- northwest of a, and exactly on a line towards Vega Lyrae ; R. A. 20b. 15m. 15s. ; Dec. N. 1 ( J 35, 1/6". It it in a coarse cluster, in the center of which are too, irr^picuou* tiara. HISTORY. Accounts of the origin of Delphinus? What aid of Hesiod? Of Taras? Df the natural shape, &c.? TELESCOPIC OBJKCTS. Alpha? Beta? Gamma? What quadruple star? Point ouf )Q the map. What clustery Nebula,? 124 ASTRONOMY. CYGNUS (THE SWAN). MAP V. 226. This remarkable constellation is situated in the Milky- Way, directly E. of Lyra, and nearly on the same meridian with the Dolphin. It is represented on outspread wings, flying down the Milky-Way, toward the southwest. The principal stars which mark the wings, the body and the bill of Cygnus, are so arranged as to form a large and regular Cross ; the upright piece lying along the Milky- Way from N. E. to S. W., while the cross piece, representing the wings, crosses the other at right angles, from S. E. to N. W. 227. Arided or Demb Cygni, in the body of the Swan, is a rtar of the second magnitude, 24 E. N. E. of Lyra, and 30 directly N. of the Dolphin. It is the most brilliant star in the constellation. It is situated at the upper end of the cross, and comes to the meridian at 9 o'clock on the 16th of September. S((d > r is a star of the 8d magnitude, 6* S. W. of Deneb, situated exactly in the cross, or where the upright piece intersects the cross piece, and is about 20 E. of Lyra. Dtlta^ the principal star in the west wing, or arm of the cross, is situated N. W. of Siid'r, at the distance of little mere than 8, and is of the 3d magnitude. Beyond Delta, toward the extremity of the wing, are two smaller stars about 5' apart, and inclining a little obliquely to the north ; the last of which reaches nearly to the first coil of Draco. These stars mark the west wing ; the east wing may be traced by means of stars very similarly situated. Gienah is a star of the 3d magnitude, in the east wing, just as far east of Sad'r in the center of the cross, as Delta is west of it. This row of three equal stars, Delta, Sad'r and Gienah, form the bar of the cross, and are equi-distant from each other, being about 8" apart. Beyond Gienah on the east, at the distance of 6 or 7 s , there are two other stars of the 3d magnitude; the last of which marks the extremity of the eastern wing. The stars in the neck are all too small to be noticed. There is one, however, in the beak of the Swan, at the foot of the cross, called Albireo, which is of the 3d magnitude, and can be seen very plainly. It is about 16 S. W. of Sad'r, and about the same dis- tance S. E. of Lyra, with which it makes nearly a right angle. " In the small space between Sad'r and Albireo," says Dr. Herschel, u the stars in the Kilky-Way seem to be clustering into two separate divisions ; each division containing more than one hundred and sixty-Jive thcnutand stars." Albireo bears northerly from Altair, about 20*. Immediately south and southeast of Albireo, may be seen the Fox and GOOSE; and about midway between Albireo and Altair, there may be traced a line of four or five minute stars, called the ARROW ; the head of which is on the S. W., and can be distinguished by means of two stars situated close together. 228. According to the British catalogue, this constellation contains eighty-one stars, including one of the 1st or 2d magni- tude, six of the 3d, and twelve of the 4th. The author of the following beautiful lines says there are one hundred and seven. "Thee, silver Swan, who, silent, can o'erpass? A hundred with seven radiant stars compose Thy graceful form : amid the lucid stream 226. Situation of Cygnus? How represented? Figure made by its principal stars? Its position? 227. Which is the brightest of its stars? Describe Sad'r, Delta, Gienah, Albireo. Remark of Dr. Herschel? 223. Number of stars in Cygnus? Variable tars ? What are they supposed to indicate ? CYCNUS. 125 Of the fair Milky- Way distingui* \ed : one Adorns the second order, where she cuts Tlie waves that follow in her utmost track ; This never hides its fire throughout the night, And of the rest, the more conspicuous mark Her snowy pinions and refulgent neck." JSudosia, b. IT. Astronomers have discovered three variable stars in the Swan. Chi, situated in the Beck, between Beta and Sad'r, was first observed to vary its brightness in 1686. Jts peri- odical changes of light are now ascertained to be completed in 405 days. Sad'r is also changeable. Its greatest luster in somewhat less than that of a star of the Sd magnitude, and it gradually diminishes till it reaches that of the 6th. Its changes are far from being regular, and, from present observations, they do not seem to recur till after a period of ten years or more. A third variable star was discovered in the head on the 20th of June, 1670, by Anthelmc. It appeared then to be of the 3d magnitude, but was so far diminished in the following October, as to be scarcely visible. In the beginning of April, 1671, it was again seen, and was rathrr brighter than at first. After several changes, it disappeared in March, 1672, and has rot been observed since. These icmarkable facts seem to indicate, that there is a brilliant planetary system iu this constellation, which, in some of its revolutions, becomes visible to us. HISTORY. M/thologists give various accounts of the origin of this constellation. Some suppose it is Orpheus, the celebrated musician, who, on being murdered by the cruel priestess of Bacchus, was changed into a Swan, and placed near his Harp in the heavens. Others suppose it is the swan into which Jupiter transformed himself when he deceived Leda, wile of Tyndarus, king of Sparta. Some affirm that it was Cycnus, a son of Neptune, who was so completely invulnerable that neither the javelins nor arrows, nor even the blows of Achilles, in furious combat, could make any impression. 41 Headlong he leaps from off his lofty car, And in close fight on foot renews the war ; But on his flesh nor wound nor blood is seen, The sword itself is blunted on the skin." But when Achilles saw that his darts and blows had no effect on him, he Immediately threw him on the ground and smothered him. While he was attempting to despoil him ef his armor, he was suddenly changed into a swan. "With eager haste he went to strip the dead; The vanished body from his arms was fled. His sea-god sire, to immortalize his fame, Had turned it to a bird that bears his name." According to Ovid, this constellation took Its name from Cycnus, a relative of Phaeton, who deeply lamented the untimely fate of that youth, and the melancholy end of his Bisters, who, standing around his tomb, wept themselves into poplars. " Cycnus beheld the nymphs transformed, allied To their dead brother on the mortal side, In friendship and affection nearer bound ; He left the cities, and the realms he owned, Through pathless fields, and lonely shores to range; Ami woods made thicker by the sisters' change: While here, within the dismal gloom alone, The melancholy monarch made his moan ; His voice was lessened as he tried to speak, And issued through a long-extended neck : His hair transforms to flown, his fingers meet In skinny films, and shape his oary feet; From both his sides the wings and feathers break: And from his mouth proceeds a blunted beak; All Cycnus now into a swan was turned." Ovid's Met. b. if. . . Various accounts? Story of Cycnus and Achilles ? Grid's account? Vir- gil's remarks respecting the Swan ? 126 ASTRONOMY. Ylrgil, also, in the 10th book of his JEneid, alludes to the same fable: ** For Cycnus loved unhappy Phaeton, And sung his loss in poplar groves alone Beneath the sister shades to soothe his grief; Heaven heard his song, and hasten'd his relief And changed to snowy plumes his hoary hair, And wing'd his flight to sing aloft iii air." Of all the feathered race, there is no bird, perhaps, which makes BO beautiful and majetuic an appearance as the.swan. Almost every poet of eminence has taken notice of it. The swan has, prob.-ibly, in all ages, and in every country where taste and ele- gance have been cultivated, been considered as the emblem of poetical dignity, purity, and ease. By the ancients it was consecrated to Apollo and the Muses ; they also enter- tained a notion that this bird foretold its own end, and sang more sweetly at the approach of death. "She, like the swan Expiring, dies in melody." -dSschylui. " So on the silver stream, when death is nigh, The mournful swan sings its own elegy." Ovid's Tristia. TELESCOPIC OBJECTS. 1. a CTGNI (Deneb) A bright star on the back of the Swan, with a telescopic com- panion ; R. A. 20h. 85m. 57s. ; Dec. N. 44 42' 07'. A 1, brilliant white ; B 12^, pale blue. 2. ,3 CVGNI (Albireo) A bright DOUBLK STAB on the bill of the figure; R. A. 19h. 24m. 16s. ; Dec. N. 27" 87' 07". About 13 V south-southeast of Vega. A 3, topaz yellow ; B 7, sapphire blue ; the colors in brilliant contrast. A Sue object, and the first double star ever seen by the present editor. 3 6 CYGNI A most delicate DOUBLB STAR in the middle of the left wing, 14* west of a Cygni; R. A. 19h. 39m. 58s.; Dec. N. 44 44' 06'. A 3J$, pale yellow; B 9, sea green. Another beautiful object. 4. C CYGNI A star with a distant companion, on the tip of the right wing ; R. A. 21h. OCm. 07s. ; Dec. N. 29 34' 05*. A 3, pale ye.low; B 10, sky blue; the field rich in sinalf stars. 5 7i CYGNI A close DOUBLE STAR in the right or lower wing, with a distant companion ; R. A. 20h. 41in. 11s. ; Dec. N. 85' 54' 03". A 5, B 10, and C 6, all bluish. 6 U CYGMI A beautiful DOUBLE STAR, with a distant companion, on the very tip of the right wing; R. A. 21h. 3Um. 59s.; Dec. N. 2S 01' 04". A 5, white; B 6, and C 7>$, both blue. 7. A BINARY STAR (61 Cygni) the most remarkable known in the heavens. It Is situ- ated on the inner tip of the right wing of Cygni, 1% south-by-east of Deneb, and nearly east of Vega ; R. A. 20h. 59m. 43s. ; Dec. N. 37" 53' 0". A 5J4, and B 6, both yellow, but the latter of the deepest tint. From the great rapidity of its proper motion, this star ia regarded as one of the nearest to our system. It affords a positive instance of a double star which, besides the individuals revolving round each other, or about their common center of gravity, has a progressive uniform motion towards some determinate region. It ia supposed to be not less than 412,000 times the diameter of the earth's orbit from us; or 88,190,000,000,000 miles distant; and to be moving through space 60,000 times as fast aa Mercury the swiftest body known to our system. The period of 61 Cygni as a binary system, is about 450 years. For orbit, &c., see Map VIII., Fig. 18, and 19. 8. A fine DOUBLB STAR on the tip of the left wing, 10 northwest of a Cygni, and within 1" of 0; R. A. 19h. 37m. 34s. ; Dec. N. 50 09' 8'. A 6H and B 7, both pale fawn color. 9. A WIDE QUADRUPLE STAR in a rich field, on the Swan's left thigh, about 8* west by north of Deueb ; R. A. 20h. 08m. 86s. ; Dec. N. 46* 15' 6'. A 4, orange ; B 16, livid ; C 7%, and D 5J$, both cerulean blue. Not the effect of contrast. 10. A NKAT SMALL CLUSTER in the root of the neck, about 2 south of y; R. A. 20h. 18m. 17s. ; Dec. N. 37* 59' 9". A 8, yellow ; B 11, dusky. 11. A LOOSK SPLASHT CLUSTER in & rich vicinity, between the Swan's tail and the Lizard, due south of (3 Cephei, and east -northeast of Deneb; R. A. 21h. 26m. 29s.; Dec. N. 47* 43' 8'. TELESCOPIC OBJECTS. Alpha? Beta? Delta? Zeta? Lambda? Mu? What cele- brated binary star? Remarks respecting? Period? Point out on the map. What ether double star ? Quadruple? What clusters? Nebula? CAPRICORNUS. 127 12. A VERY SIKGDLAR NEBULA on the tip of the northern wing, about 5Ji* north of d; R. A. 19h. 40m. 85s.; Dec. N. 50*07' 6*. Seen to be nebulous only with good instru- ments. Several telescopic stars in the field. The Herschels considered this as a con necting link between planetary nebula and nebulous stars. CAPRICORNUS (THE GOAT). MAP V. 229. This is the tenth sign, and eleventh constellation, in the order of the Zodiac, and is situated south of the Dolphin, and next east of Sagittarius. Its mean declination is 20 south, and its mean right ascension 310. It is therefore on the meridian about the 18th of September. It is to be observed that the first point of the sign Capricorn, not the constellation, marks the southern tropic, or winter solstice. The sun, therefore, arrives at this point of its orbit the 21st of December, but does not reach the constellation Capricorn until the 16th of January. The sun, having now attained its utmost declination south, after remaining a few days apparently stationary, begins once more to retrace its progress northwardly, affording to the wintry latitudes of the north a grateful presage of returning spring. At the period of the winter solstice, the sun is vertical to the tropic of Capricorn, and the southern hemisphere enjoys the same light and heat which the northern hemisphere enjoys on the 21st of June, when the sun is vertical to the tropic of Cancer. It is, at this period, mid-day at the south pole, and midnight at the north pole. 230. The whole number of stars in this constellation is fifty- one ; none of which are very conspicuous. The three largest are only of the 3d magnitude. There is an equal number of the 4th. The head of Capricorn may be recognized by means of two stars of the 3d magnitude, situated a little more than 2 apart, called Giedi and Dabih. They are 28 from the Dolphin, in a southerly direction. Giedi is the most northern star of the two, and is double. If a line be drawn from Lyra through Altair, and produced about 23* farther, it will point out the head of Capri- corn. These two stars come to the meridian the 9th of September, a few minutes after Sad'r, in Cygnus. A few other stars of inferior note may be traced out by reference to the maps. The sign of the Goat was called by the ancient orientalists the " Southern gate of the Sun," as Cancer was denominated the " Northern gate." The ten stars in the ttign Capricorn, known to the ancients by the name of the " Tower of Gad," are probably now in the constellation Aquarius. HISTORY. Capricornus is said to be Pan, or Bacchus, who, with some other deities, were feasting near the banks of the Nile, when suddenly the dreadful giant Typhon came upon them, and compelled them all to assume a different shape, in order to escape his fury. Ovid relates, " How Typhon, from the conquer'd skies, pursued Tlieir routed godheads to the seven-mouth'd flood : 229. Position of Capricornus? When does the sun enter it? What said of his place and motion at that time? Of the winter solstice? 230. Number of stars in Capri- corn? Their magnitudes? How recognize the figure? What said of Giedi? Ancient name of this sigu ? 128 ASTRONOMY. Forced every god (his fury to escape), Some beastly form to take, or earthly shape. Jove (sings the bard) was changed into a ram, From whence the horns of Libyan Arrmon caine; JSacchus a goat ; Apollo was a crow ; Phuebe a cat ; the wife of Jove a cow, Whose hue was whiter than the falling snotr; Mercury to a nasty ibis turned While Venus from a fish protection craves, And once more plunges in her native waves." On this occasion it is further related that Bacchus, or Pan, led the way and plunged into the Nile, and that the part of his body which was under the water assumed the form of a fish, and the other part that of a goat; and that to preserve the memory of this frolic, Jupiter made him into a constellation, in his metamorphosed shape. Some say that this constellation was the goat Amalthea, who supported the infan Jupiter with her milk. To reward her kindness, the father of the gods placed her arnon* the constellations, and gave one of her horns to the nyrnphs who had taken care of him in his infantile years. This gift was ever after called the horn of plenty; as it possessed the virtue of imparting to the holder whatever she desired. On this account the Latin term Cornucopia, denotes plenty, or abundance of good things. The word Amalihea, when used figuratively, has also the same meaning. The real sense of tnis fable, divested of poetical embellishment, appears to be this ; that in Crete, some say in Libya, there was a small territory shaped very much like a bullock's horn, and exceedingly fertile, which the king presented to his daughter Amal- thea, whom the poets feigned to have been Jupiter's nurse. " The bounteous Pan," as he is styled by Milton, was the god of rural scenery, shep- herds, and huntsmen. Virgil thus addresses him '. " And thou, the shepherd's tutelary god, Leave, for a while, Pan ! thy loved abode." The name of Pan is derived from a Greek word signifying aU tJiingt; and he was often considered as the great principle of vegetable and ani ual life. He resided chiefly in Arcadia, in woods and the most rugged mountains. As Pan usually terrified the inhabi- tants of the adjacent country, even when he was nowhere to be seen, that kind of fear which often seizes men, and which is only ideal or imaginary, has received from him the name of Panic. Pales, the female deity corresponding to Pan, was the goddess of sheepfolds and of pastures among the Romans. Thus Virgil : " Now, sacred Pales, in a lofty strain, 1 sing the rural honors of thy reigu ' The shepherds offered to this goddess milk and honey, to gain her protection over their flocks. She is represented as an old woman, and was worshiped with great solemnity at Home. Her festivals, which were called Pulilia, were celebrated on the 20th of April, the day on which Romulus laid the foundations of the city. TELESCOPIC OBJECTS. 1. a CAPRICORNT A QUINTUPLE STAR in the right horn ; R. A. 20h. 09m. 10s. ; Dec. S. 13* 02' 1". A 8, pale yellow ; B (or a 1) 4, yellow ; 016, blue; I) 9, ash-colored; E 9J, lilac tinge. Few telescopes will reveal all these components. 2. /3 CAPRICORNI A wide PAIR OF STARS in the right horn, 2^ 8 south-half-east of a; R. A. 20h. 12m. Ols. ; Dec. S. 15 16' 9". A 8^, orange yellow; B 7, sky blue. Other small stars in the field. It requires, a powerful instrument, and the most favorable cir- cumstances to detect the minute star 5. (See Map VIII., Fig. 20.) 3. A GLOBULAR CLUSTER between Aquarius and the neck of Capricorn, 9" due east of rt Capricorni, about J^ from a 6th magnitude star; R. A. 20h. 44m. 89s. ; Dec. S. 13 07' 6". Many stars iu the field, two of which are close to the cluster, or the east. Map IX., Fig. 63. HISTORY. Who was Capricornus? What proof cited? What further? What other myth ? Meaning of this fable ? What said of Pales? TELESCOPIC OBJECTS. Alpha? Beta? Point out on the map ? What clusters ? Where ghown on the map ? PEGASL'S \2\) 4. A fine PALK WHITK CLUSTER, about 20* west-northwest of Fomalhxut; R. A. 2''.. Blm. 16s. ; Dec. S. 23* 52' 4"- A bright object, with strapping streams of stars, and bui few outliers iu the field. Seen with small instruments. Map IX., Fig. 64. CHAPTER XII. CONSTELLATIONS ON THE MERIDIAN IN OCTOBER. PEGASUS (THE FLTIXG HORSE). MAP IT. 231. THIS constellation is represented in an inverted posture, with wings. It occupies a large space in the heavens, between the Swan, the Dolphin and the Eagle, on the west, and the Nor- thern Fish and Andromeda, on the east. Its mean right ascen- sion is 340, or it is situated 20 W. of the prime meridian. It extends from the equinoctial N. 35. Its mean length E. and W. is about 40, and it is six weeks in passing our meridian, viz., from the 1st of October to the 10th of November. 232. We see but a part of Pegasus, the rest of the animal being, as the poets imagined, hid in the clouds. It is readily distinguished from all other constellations by means of four remarkable stars, about 15 apart, forming the figure of a square called the Square of Pegasus. The two western stars in this square corae to the meridian about the 23d of October, and are 18 apart. The northern one, which is the brightest of three triangular stars in the martingale, is of the 2d magnitude, and is called Schedt. Its declination is 26V. J/t/rA-afc, also, of the 2d magnitude, situated in the head of the wing, is 13" S. of Scheat, and passes the meridian 11 minutes after it. The two stars which form the eastern side of the square, come to the meridian about an hour after those in the western. The northern one has already been described as Alpheratz in the head of Andromeda, but it also belongs to this constellation, and is 14* E. Scheat. 14* S. of Alpheratz, is Algenib, the last star in the wing,situated 16)$' E. of Markab. 233. Algenib in Pegasus, Alpheratz in Andromeda, and Caph In Cassiopeia are situated on the prime meridian, and point out its direction through the pole. For this reason they are some- times called the three guides. They form an arc of that great circle in the heavens from which the distances of all the heavenly bodies are measured. 281. What constellations in this chapter? Describe Pegasus, its size, position, &c. 232. Do we see the whole of the figure ? How is it distinguished? What said of Scheat and Markab? Of Alpheratz and Algenib? 233. Remark respecting Algenib, Alphe- ratz and Caph? What sometimes called, and why? They form what? Rem^rki 130 ASTRONOMY. It Is an arc of the equinoctial ;olure which passes through the vernal equinox, and which the sun crosses about the 2 1st of March. It is, in astronomy, what the meridian of Greenwich is in geography. If the sun, or a planet, or a star, be said to have so many degrees of right ascension, it means that the sun or planet has ascended so many degrees from this prime meridian. Enif, sometimes called Enir, is a star of the 3d magnitude in the nose of Pegasus, about 20* W. S. W. of Markab, and half-way between it and the Dolphin. About half of the distance from Markab toward Enif, but a little to the S., there is a star of the 8d mag- nitude situated in the neck, whose letter name is Zfta. The loose cluster directly S. of the line joining Enif and Zeta, forms the head of Pegasus. In this constellation there are eighty-nine stars visible to the naked eye, of which U.ret are of the second magnitude and three of the third. HISTORY. This, according to fable, is the celebrated horse which sprung from the blood of Medusa, after Perseus had cut off her head. He received his name according to Hesiod, from his being born near the sources (7r?/y?7, Pege) of the ocean. According to Ovid, he fixed his residence on Mount Helicon, where, by striking the earth with his foot, he raisfd the fabled fountain called Hippocrene. He became the favorite of the Muses ; and being tamed by Neptune or Minerva, he was given to Bellerophon, son of Glaucus, king of Ephyre, to aid him in conquering the Chimajra, a hideous monster that continually vom- ited flames. This monster had three heads, that of a lion, a goat, and a dragon. The fore parts of its body were those of a lion, the middle those of a goat, and the bin ter those of the dragon. It lived in Lycia, of which the top, on account of its desolate wil- derness, was the resort of lions, the middle, winch was fruitful, was covered with goats, and at the bottom, the marshy ground abounded with serpents. Bellerophon was the first who made his habitation upon it. Plutarch thinks the Chimsera was the captain of some pirate who adorned their ship with the images of a lion, a goat, and a dragon. After the destruction of this monster, Bellerophon attempted to fly up to heaven upon Pegasus ; but Jupiter was so displeased at this presumption, that he sent an insect to sting the horse, which occasioned the melancholy fall of his rider. Bellerophon fell to the earth, and Pegasus continued his flight up to heaven, and was placed by Jupiter among the constellations. " Now heav'n his further wand'ring flight confines, Where, splendid with his num'rous stars, he shines." Ovid's Fasti. TELESCOPIC OBJECTS. 1. a PKGASI (MarkaV) A star with a distant companion, at the junction of the wing and shoulder, 13 south of Scheat ; R. A. 22h. 56m. 47s. ; Dec. N. 14 20' US'. A 2, white ; B 11, pale grey. 2. [3 PKGASI (Scheat) A bright star with a minute distant companion, on the left fore- leg; R. A. 22h. 56m. Ols. ; Dec. N. 27" 13' 0". A 2, deep yellow ; B 15, blue ; with two other stars in the field. 3. y PKGASI (Algenib} A star with a distant companion, on the edge of the wing; R. A. Oh. 05m. Os. ; Dec. N. 14 17' 07'. A 2>$, yellow ; B 13, pale blue. 4. PKGASI (Enif} A star with two distant companions, in the nose of the figure ; R. A. 2th. 36m. 19s. ; Dec. N. 9 OS' 07". A 2%, yellow ; B 14, blue ; C 9, violet; and a 9th magnitude star of a violtt tinge, at a distance east. 5. PKGASI A star with a minute companion in the middle of the neck ; R. A. 22h. 33m 29s. ; Dec. N. 9 59' 9". A line from Alpheratz over M?rkab, and carried 7 further, will reach . A3, light yellow ; B 13, dusky; with other stars in the field. 6. A DOUBLE STAR between the head of Pegasus and the hind legs of the Fox ; or about 10 V south by east of Cygni ; R. A. 21h. 14m. 41s. ; Dec. N. 19 07' 4". A 4, pale orange, and considered variable ; B 9, purplish. respecting the prime meridian? What said of Enif? Of Zeta? Of the head of Pegasus Number of stars in the constellation, and their magnitudes ? HISTORY. Story of his origin and name? Residence, &c. ? How he came among the stars ? TELESCOPIC OBJKCTS. Alpha? Beta? Gamma? Epsilon? Zeta? What double starf What cluster V Point out on the map. What nebula? AQUARIUS. 131 7. A GLOBULAR CLUSTER between the mouths of Pegasus and Equleus, about 4* north- west of e ; II. A. 21h. 22m. 13s. ; Dec. N. IT 27' 4'. Map IX., Fig. 65. It is laid down as a nebula on Map II., but with a good instrument it is resolved into stars, with straggling outliers, as shown in the diagram. 8. An ELONGATED NEBULA in the animal's mane, about 8* due south of Markab ; R. A. 22h. 56in. 58s. ; Dec. N. 11 27' 9". A very faint and difficult object. EQULEUS, YEL EQUI SECTIO (THE LITTLE HOESE, OK THE HOUSE'S HEAD). MAP II. 234. This Asterism, or small qluster of stars, is situated about 7 W. of Euif, in the head of Pegasus, and about half-way between it and the Dolphin. It is on the meridian at 8 o'clock, on the llth of October. It contains ten stars, of which the four principal are only of the 4th magnitude. These may be readily distinguished by means of the long irregular square which they form. The two in the nose are much nearer together than the two in the eyes : the former being 1 apart, and the latter 2|-. Those in the nose are uppermost, being 4 N. of those in the eyes. This figure also is in an inverted position. These four stars are situated 10 or 12 S. E. of the diamond iu the Dolphin's head. Both of these clusters are noticeable ou account of their figure rather than their brilliancy. HISTORY. This constellation is supposed to be the brother of Pegasus, named Celeris, given by Mer- cury to Castor, who was so celebrated for his skill in the management of horses ; othe3 take him to be the celebrated horse which Neptune struck out of the earth with his tri- dent, when he disputed with Minerva for superiority. The head only of Celeria ia visible, and this, also, is represented in an inverted position. TELESCOPIC OBJECTS. Four of the principal stars in this little group are double namely, /?, d, t and 2.. ft fs rather a star with a companion; II. A. 21h. 14m. 578.; Dec. N. 6* 07' 9". The other three will easily be found from their proximity to 8. AQUARIUS (THE WATER-BEAKER). MAP II. 235. This constellation is represented by the figure of a nun pouring out water from an urn. It is situated in the Zodiac, immediately S. of the equinoctial, and bounded by the Little 234. Situation of Eqiileus? When on the meridian ? Number of stars, and how dis- tinguished? What further description ? HISTORY. What suppositions respecting the origin of Eqiileus f TKI.KSCOPIC OUJKCTS. What double stars? How found T 2o5. How is Aquarius represented? Its boundaries? 6* 132 ASTRONOMY. Horse, Pegasus, and the Western Fish on the ST., the Whale on the E., the Southern Fish on the S. and the Goat on the W. 236. Aquarius is now the 12th in order, or last of the Zodiacal constellations ; and is the name of the llth sign in the ecliptic. Its mean declination is 14 S., and its mean right ascension 335, or 22 hours, 20 min. ; it being 1 hour and 40 rain. W. of the equinoctial colure ; its center is, therefore, on the meridian the 15th of October. It contains one hundred and eight stars ; of which the four largest are all of the 3d magnitude. " His head, his shoulders, and his lucid breast, Glisten with stars ; and where his urn inclines, Rivers of light brighten the watery track." 237. The northeastern limit of Aquarius may be readily dis- tinguished by means of four stars of the 4th magnitude, in the hand and handle of the urn, so placed as to form the letter Y, very plainly to be seen, 15 S. E. of Enif, or 18 S. S. W. of Markab, in Pegasus ; making with the two latter nearly a right angle. About 4V W. of the figure is El Melik, a star of the 8d magnitude, in the E. shoulder, and the principal one in this constellation. 10 S. W. of El Melik, is another star of the same magnitude, situated in the W. shoulder, called Sad es Saud. Ancha, of the 4th magnitude, is in the right side, 8* S. of El Melik. 9* E. of Ancha, is another star of the 4th magnitude, whose letter name is Lambda. Scheat, of the 3d magnitude, lying below the knee, is situated 8J* S. of Lambda ; and U S. of Scheat, the brilliant star Fomalhaut, of between the 1st and 2d magnitudes, ter- minates the cascade in the mouth of the Southern Fish. This star is common to bo f h these constellations, and is one of those from which the lunar distance is computed for iscertaining the longitude at sea. It culminates at 9 o'clock on the 22d of October. Fomalhaut, Deneh Kaitos, and Alpha in the head of the Phoenix, make a large triangle, whose vertex is in Deneb Kaitos. Those two stars of the fourth magnitude, situated 4" S. of Sad es Saud, and nearly the same distance from Ancha, are in the tail of Capricorn. They .are about 2 apart. The western one is called Deneb Algedi. The rest of the stars in the cascade are quite small ; they may be traced from the letter Y, in the urn, in a southeasterly direction toward the tail of Cetus, from which the cascade suddenly bends off near Scheat, in an opposite course, and finally disappears iu the mouth of the Southern Fish, 30" S. of Y. HISTORY. This constellation is the famous Ganymede, a beautiful youth of Phrygia, son of Tros, king of Troy, or, according to Lucian, son of Dardanus. He was taken up to heaven by Jupiter as he was tending his father's flocks on Mount Ida, and became the cup-bearer of the gods in place of Hebe. There are various opinions, however, among the ancients respecting its origin. Some suppose it represents Deucalion, who was placed among the stars after the celebrated deluge of Thessaly, 1500 years before the birth of our Saviour ; while others think it designed to commemorate Cecrops, who came from Egypt to Greece, founded Athens, established science, and introduced the arts of polished life. The ancient Egyptians supposed the setting or disappearance of Aquarius caused th Nile to rise, by the sinking of his urn in the water. In the Zodiac of the Hebrews, Aquarius represents the tribe of Reuben. Its order in the signs and constellations? Number and size of its stars? 237. How distinguish the northeast limit? What said of El Melik? Of Sad es Saud? Of Ancha, Lambda, Scheat, <$, white ; B 10, violet. 4. A DELICATE TRIPLE STAR in the space between the Lizard's back and the left hand of Andromeda; R. A. 22h. 49m. 06s.; Dec. N. 40 45' 1". A 6, bright white; B. 15, pale blue; C 9)6, reddish ; a fourth star at a distance. A very difficult object; claimed by aome for Andromeda, but usually classed as belonging to the Lizard. HISTORY. Supposed origin of this constellation ? TELESCOPIC OBJECTS. Alpha? Where situated? 289. Describe Lacerta. Where situated ? 240. What other small constellation near? By whom inserted, when and why? Of what does it consist? To represent what? Is it recognized by astron'omers? TKLKSOOPIC OBJECTS. What double stars in Lacerta? What triple star? Quadruple? Cluster ? Any of them shown on the map? VARIABLE AM) DOUI3LE STARS. 135 5. A QUADRUPLE STAR, the western one of the three forming the triangle at the end of the tail ; R. A. 22h. 29m. 46s. ; Dec. N. 38 43 5". About 20 northwest of Aipheratz. A and B 65^, both white ; C 11, greenish ; D 10, blue. 6. A LARGB LOOSE CLUSTER in the Lizard's mouth ; R. A. z,.h. OSm. 59s. ; Dec. N. 49 05' 1". Stars from the 9th to the 14th magnitudes. A line carried from Polaris through tin tiara of Cepheus, and 8 beyond, strikes it. CHAPTER XIII. VARIABLE AND DOUBLE STAES CLUSTERS AND NEBULJE. 241. THE periodical variations of brilliancy to which some of the fixed stars are subject, may be reckoned among the most remarkable of their phenomena. Several stars, formerly distin- guished by their splendor, have entirely disappeared ; others are now conspicuous which do not seem to have been visible to the ancient observers ; and there are some which alternately appear and disappear, or, at least, of which the light undergoes great periodic changes. Some seem to become gradually more obscure, as Delta in the Great Bear ; others, like Beta in the Whale, to be increasing in brilliancy. 242. Some stars have all at once blazed forth with great splen- dor, and, after a gradual diminution of their light, again become extinct. The most remarkable instance of this kind is that of the star which appeared in 1572, in the time of Tycho Brahe. It suddenly shone forth in the constellation Cassiopeia, with a splendor exceeding that of stars of the first magnitude, even of Jupiter and of Venus, at their least distances from the earth ; and could be seen with the naked eye, on the meridian, in full day! Its brilliancy gradually diminished from the time of its first appearance, and at the end of sixteen months it entirely disappeared, and has never been seen since. ( See a more par- ticular account of this phenomenon, page 35.^) Another instance of the same kind was observed in 1604, when a star of the first ma#- nitude suddenly appeared in the right foot of Ophiuchus. It presented, like the former, all the phenomena of a prodigious flame, being, at first, of a dazzling white, then of a reddish yellow, and, lastly, of a leaden palenes? ; in which its light expired. These instances prove that the stars are subject to great physical revolutions. (Page oO) 243. A great number of stars have been observed whose ligit seems to undergo a regular periodic increase and diminution. '241. What said of the periodical variations of the stars? 242. What other remark*- bit; phenomenon? What instances cited ? What do these instances prove? 243. What 136 . v ASTRONOMY. They are properly called Variable Stars. One in the Whale has a period of 344 days k ad is remarkable for the magnitude of its variations. From oeing a star of the second magnitude, it becomes so dim as to be seen with difficulty through powerful telescopes. Some are remarkable for the shortness of the period of their variation. Algol has a period of between two and three days ; Delta Cephei, of 5-J days ; Beta Lyra, of 6 2-5 days ; and Mu Antinoi, of 7 days. The regular succession of these variations precludes the supposition of rn actual destruction of the stars; neither can the variations be supposed to arise from a change of distance ; for, as the stars invariably retain their apparent places, it would be neces- sary to suppose that they approach to, and recede from the earth in straight lines, which is very improbable. The most probable supposition is, that the stars revol/e, like the sun and planets, about an axis. "Such a motion," says the elder Herschel, "may be as evidently proved, as the diurnal motion of the earth. Dark spots, or large por- tions of the surface, less luminous than the rest, turned alternately in certain directions, either toward or from us, will account for all the phenomena of periodical changes in the luster of the stars, so satisfactorily, that we certainly need not look for any other cause.'' DOUBLE STARS. 244. On examining the stars with telescopes of considerable power, many of them are found to be composed of two or more stars, placed contiguous to each other, or of which the distance subtends a very minute angle. This appearance is, probably, in many cases, owing solely to the optical effect of their position relative to the spectator ; for it is evident that two stars will appear contiguous if they are placed nearly in the same line of vision, although their real distance may be immeasurably great. STARS OPTICALLY DOUBLE. Apparent position. True position. lT' ::r::: .............. - ...... * .................................................. * A B Here the observer on the left sees a large and small star at A, apparently near toge- ther the lowest star being much the smallest. But instead of their being situated as uiey appear to be, with respect to each other, the true position of the smaller star m;iy be at B instead of A; and the difference in their apparent magnitudes may be wholly owing to the greater distance of the lower star. Upon this subject Dr. Herschel remarks, that this nearness of the stars to each other, in certain cases, might be attributed to some accidental cause, did it occur only in a few instances ; but the frequency of this companionship, the extreme closeness, and, in many cases, the near equality of the stars so conjoined, would alone lead to a strong suspicion of a more near and intimate relation than mere casual juxtaposition. 245. There are, however, many instances in which the angle of position of the two stars varies in such a manner as to indi- are these unsteady stars called ? What specimens referred to, and- their periods ? What does this regular succession, Ac., prov?? What theory did Dr. Herschel adopt respect- .ng the variable stars? 244. What said of double stars? Are they always really near -> in 1S2G. Sir John Herschel, io addition to the above, published an account ol 1000, before he left England for the Cape of Good Hope, where he went to push his discoveries in the southern hemisphere. Professor Struve, with the great Dorpat telescope, has given a catalogue of 3,068 of the most remarkable of these stars. The object of these catalogues is not merely to fix the place of the star within such limits us will enable us easily to discover it at any future time, but also to record a description ;ver really near each other? What motion? What do these constitute? Is it certain that stars are ever thus in motion around a common center? '240. What remarkable instance cited? Its annual angular motion? Period? What other binary systems? Are these planetary systems like our own ? 247. Who first undertook the examination o"U> double stars, and witli what view? What number did he observe? What culii- 138 ASTRONOMY. of the appearance, position, and mutual distances of the individual stars composing the system, in order that subsequent observers may have the means of detecting their con nected motions, or any changes which they may exhibit. Professor Struve has also taken notice of 52 triple stars, among which No. 11 of the Unicorn, Zeta of Cancer, and Zi of the Balance, appear to be ternary systems in motion. Quadruple and quintuple star? have likewise been observed, which also appear to revolve about a common center of gravity ; in short, every region of the heavens furnishes examples of these curious phe- nomena. COLOR OF THE STARS. 248. Many of the double stars exhibit the curious and beau- tiful phenomenon of contrasted colors, or complimentary tints. In such instances, the larger star is usually of a ruddy or orange hue, while the smaller one appears blue or green, probably in virtue of that general law of optics, which provides that when the retina is under the influence of excitement by any bright colored light, feebler lights, which, seen alone, would produce no sensation but that of whiteness, shall for the time appear colored with the tint complimentary to that of the brighter. Thus, a yellow color predominating in the light of the brighter star, that of the les-8 brigh; one, in the same field of view, will appear blue; while, if the tint of the brighter star verge to crimson, that of the other will exhibit a tendency to green or even appear a vivid green. The former contrast is beautifully exhibited by Iota, in Cancer; the latter by AlJna.. What remarks respecting red and green suns, &c. ? Of insulated stars of a red color f 250. What said of clusters * What specimen referred to T Pleiades f NEBULA. 139 The Pleiades are an instance of this kind, in which six or seven stars may be seen in near proximity, by the naked eye ; and even more if the eye be turned carelessly upon it; for it is a remarkable fact that the center of the eye is far less sensible to feeble impressions of light, than the exterior portion of the retina, liheita affirms that by the aid of a telescope he counted over 200 stars in this small cluster. See Map VIII., Fig. 28. In the constellation called Coma Berenices there is another group more diifused, and consisting of much larger stars. In Cancer there is a nebulous cluster of very minute stars, called Prasepe., or the Beehive, which is sufficiently luminous to be seen by the naked eye, in the absence of the moon, and which any ordinary spyglass will resolve into separate stars. In the sword-handle of Perseus, also, is another such spot, crowded with stars. It requires, however, rather a better telescope to resolve it into individual stars. See p. 65, and Map VIII., Fig. 39. Whatever be the nature of these clusters, it is certain that other laws of aggregation prevail in them, than those which have determined the scattering of stars over the gene- ral surface of the sky. Many of them, indeed, are of an exactly round figure, and con- vey the idea of a globular space filled full of stars, and constituting, in itself, a family or society apart, and subject only to its own internal laws. '' It would be a vain task," says the younger llerschel, " to attempt to count the stars in one of these globular clusters. They are not to be reckoned by hundreds ; for it would appear that many clusters of this description must contain, at least, ten or twenty thou- rind stars, compacted and wedged together in a round space, not more than a tenth part as la ** us that which is covered by the moon. NEBULAE. 251. The Nebula, so called from their dim, cloudy appearance, form another class of objects which furnish matter for curious speculation and conjecture respecting the formation and struc- ture of the sidereal heavens. When examined with a telescope of moderate powers, the greater part of the nebulae are dis- tinctly perceived to be composed of little stars, imperceptible to the naked eye, because, on account of their apparent proximity, the rays of light proceeding from each are blended together, in such a manner as to produce only a confused luminous appear- ance. In other nebulie, however, no individual stars can be perceived, even through the best telescopes; and the nebula; exhibit only the appearance of a self-luminous phosphores- cent patch of gaseous vapor, though it is possible that even in this case, the appearance may be owing to a congeries of stars so minute, or so distant, as not to afford, singly, sufficient light to make an impression on the eye. Remarks upon their r.ature and the Inws that govern them? Remarks of llerschel? 251. What are fte&u&v, and why so called? llow appear through telescopes? Are they all resolvable into stars? 140 ASTRONOMY. 252. One of the most remarkable nebulas is in the sword- handle of Orion. It is formed of little flocky masses, like wisps of cloud, which seem to adhere to many small stars at its out- skirts. It is not very unlike the mottling* of the sun's disc, but of a coarser grain, and with darker intervals. These wisps of light, however, present no appearance of being composed of small stars ; but in the intervals between them, we fancy that we see stars, or that, could we strain our sight a little more, we should see them. These intervals may be compared to openings in the firmament, through which, as through a window, we seem to get a glimpse of other heavens, and brighter regions, beyond. See page 45, and Map VIII., Fig. 32. 253. Another very remarkable nebula is that in the girdle of Andromeda, which, on account of its being visible to the naked eye, has been known since the earliest ages of astronomy. It is often mistaken for a comet, by those unacquainted with the heavens. See page 20, and Map VIII., Fig. 22. Marius, who noticed it in 1612, describes its appearance as that of a candle shining through horn; and the resemblance is certainly very striking. Its form is a long oval, increasing, by insensible gradations of brightness, from the circumference to a central point, which, though very much brighter than the rest, is not a star, but only a nebula in a high state of condensation. It occupies an area comparatively large equal to that of the moon in quadrature. This nebula may be considered as a t3*pe, on a large scale, of a very numerous class of nebulae, of a round or oval figure, increasing more or lsp in density toward the center. 254. Annular nebula are those in the form of a ring, but are among the rarest objects in the heavens. The most conspicuous of this class is to be found exactly half-way between the stars Beta and Gamma Lyrae, and may be seen with a telescope of moderate power. It is small, and particularly well defined ; appearing like a flat oval ring. The central opening is not entirely dark, but is filled with a faint, hazy light, uniformly spread over it, like a fine gauze stretched over a hoop. 255. Planetary nebula are very extraordinary objects. They have, as their name imports, the appearance of planets, with round or slightly oval discs, somewhat mottled, but approaching, in some instances, to the vividness of actual planets. Some of them, upon the supposition that they are equally distant from us with the stars, must be of enormous magnitude. That one, for instance, which is situated in the left hand of Aquarius, must 252. What remarkable nebula mentioned? Describe it? Point out on the map. 253. What other? How long known, and why? Show on the map. How described hy Harius? Its form and extent? How considered? 254. What are Annular Nebula ? tit-e they common? What specimen referred to? 255. Planetary nebulas? Their character and magnitude? Specimen? Stellar nebulae ? General remarks respecting VIA LACTEA. 141 have a volume vast enough, upon the lowest computation, to fill the whole orbit of Herschel ! In some instances a nebula presents the appearance of a faint, luminous atmosphere, of a circular form, and of large extent, surrounding a central star of considerable brilliancy. These are denominated Stellar Nebula. The nebulas furnish an inexhaustible field of speculation and conjecture. That by far the larger number of them consists of stars, there can be little doubt; and in the inter- minable range of system upon system, and firmament upon firmament, which we thus catch a glimpse of, the imagination is bewildered and lost. Sir William Herschel con- jectured that the nebulae might form the material out of which nature elaborated new suns and systems, or replenished the wasted light of older ones. But the little we know of the physical constitution of these sidereal masses, is altogether insufficient to warrant such a conclusion. (For a Spiral Nebula recently discovered by Lord fiosse, see Map IX., Fig. 68.) CHAPTER XIY. VIA LACTEA (THE MILKY-WAT). " Throughout the Galaxy's extended line, Unnumber'd orbs in gay confusion shine : Where every star that gilds the gloom of night With the faint tremblings of a distant light, Perhaps illumes some system of its own, With the strong influence of a radiant sun." Mrs. Carter. 256. THE VIA LACTEA, or Milky-Way, is that luminous zone or pathway of singular whiteness, varying from 4 to 20 in width, which passes quite around the heavens. The Greeks called it GALAXY, on account of its color and appearance : the Latins, for the same reason, called it VIA LACTEA, which, in our tongue, is Milky-Way. Of all the objects which the heavens exhibit to our view, this fill* the mind with the most indescribable grandeur and amazement. When we consider what unnumbered millions of mighty suns compose this stupendous girdle, whose distance is so vast that the strongest telescope can hardly separate their mingled twilight into distinct specks, and that the most contiguous of any two of them may be as far asunder as our sun is from them, we fall as far short of adequate language to express our ideas of such immen- sity, as w do of instruments to measure its boundaries. 257. It is one of the achievements of astronomy that has resolved the Milky-Way into an infinite number of small stars, whose confused and feeble luster occasions that peculiar white- ness which we see in a clear evening, when the moon is absent. It is also a recent and well-accredited doctrine of astronomy, the Nebulae? Sir Wm. Herschel's conjecture? 256. What is the Via Lactca? Its Greek name? What said of its magnificence and grandeur? 257. What said of the achievements of astronomy t Its doctrine respecting the structure of the universe * Of the sun, and its relation to the fixed star*? 142 ASTRONOMY. that all the stars in the universe are arranged into clusters, 01 groups, which are called NEBULA or STARRY SYSTEMS, each of which consists of myriads of stars. The fixed star which we call 00R SUN, belongs, it is said, to that extensive nebula, the Milky -Way; and although apparently at such an inmeasurable distance from its fellows is, doubtless, as near to any one of them, as they are to one another. 258. Of the number and economy of the stars which compose this group, we have very little exact knowledge. Dr. Herschel informs us that, with his best glasses, he saw and counted 588 stars in a single spot, without moving his telescope ; and as the gradual motion of the earth carried these out of view and intro- duced others successively in their places, while he kept his tele- scope steadily fixed to one point, " there passed over his field of vision, in the space of one quarter of an hour, no lest than one hundred and sixteen thousand stars, and at another time, in forty-one minutes, no less than two hundred and fifty-eight thou- sand." In ?,11 parts of the Milky- Way he found the stars unequally dispersed, and appearing to arrange themselves into separate clusters. In the small space for example, between Beta and Sad'r, in Cygni, the stars seem to be clustering in two divisions ; each division conta ning upwards of one hundred and sixty-five thousand stars. At other observations, when examining a section of the Milky- Way, not apparently more than a yard in breadth, and six in length, he discovered fifty UioiUHmd stars, large enough to be distinctly counted ; and he suspected twice as many more, which, for want of sufficient light in his telescope, he saw only now and then. 259. It appears from numerous observations, that various changes are taking place among the nebulae that several nebu- Ise are formed by the disolution of larger ones, and that many nebulae of this kind are at present detaching themselves from the Milky-Way. In that part of it which is in the body of Scorpio, there is a large opening, about 4 broad, almost desti tute of stars. These changes seem to indicate that mighty movements and vast operations are continually going on in the distant regions of the universe, upon a scale of magnitude and grandeur which baffles the human understanding. More than two thousand five hundred nebulae have already been observed; and, if each af them contains as many stars as the Milky-Way, several hundreds of millions of stars must exist, even within that portion of the heavens which lies open to our obser- vation. " what a confluence of ethereal fires. From urns unnumber'd down the steep of heaven Streams to a point, and centers on my sight." 260. Although the Milky-Way is more or less visible at all seasons of the year, yet it is seen to the best advantage during '258 Number and economy of the stars? Dr. Herschel's statements? What number passed the field of his instrument in a 'juarter of an hour? In forty-one minutes? In space apparently only a yard in breadth? 259. What changes observed in the nebu- lie? What do they indicate? Number of nebulse? Estimated number of stars? 260. When is the Via Lactea seen to the best advantage? Direction when Lyra is on the ORIGIN OF THE CONSTELLATIONS 143 the months of July, August, September, and October. When Lyra is on, or near the meridian, it may be seen stretching obliquely over the heavens from northeast to southwest, gradu- ally moving over the firmament in common with other constel- lations. (For views of our cluster, see Map IX., Figs. 69, 70, 71.) Its form, breadth and appearance are various, in different parts of its course. In some places it is dense and luminous ; in others, it is scattered and faint. Its breadth is often not more than five degrees ; though sometimes it is ten or fifteen degrees, and even twenty. In some places it assumes a double path, but for the most part it is singl*:. It may be traced in the heavens, beginning near the head of Cepheus, about 30 from the north pole, through the constellations Cassiopeia, Perseus, Auriga, and part of 0/ion and the feet of Gemini, where it crosses the Zodiac; thence over the equinoctial into the southern hemisphere, through Monoceros, and the middle of the ship Argo, where it is most luminous, Charles' Oak, the Cross, the feet of the Centaur, and the Altar. Here it is divided into two branches, as it passes oyer the Zodiac again into the northeni hem- isphere. One branch runs through the tail of Scorpio, the bow of Sagittarius, the shield of Sobieski, the feet of Antinous, Aquila, Delphinus, the Arrow and the Swan. Th<; other branch passes through the upper part of the tail of Scorpio, the side of Serpentarius, Taurus Poniatowskii, the Goose and the neck of the Swan, where it again unites with the other branch, and passes on to the head of Oepheus, the place of its beginning. Some of the pagan philosophers maintained that the Milky-Way was formerly the sun's path, and that its present luminous appearance is the track which its scattered beams left visible in the heavens. The ancient poets, and even philosophers, speak of the Galaxy, or Milky -Way, as the path which their deities used in the heavens, and which led directly to the throne of Jupiter. Thus, Ovid, in his Metamorphoses, Book i. : " A way there is in heaven's extended plain, Which, when the skies are clear, is seen belowr, And mortals, by the name of Milky, know; The groundwork is of stars, through which the road Lies open to the Thunderer's abode." Milton alludes to this in the following lines : " A broad and ample road, whose dust is gold, And pavement, stars, as stars to thee appear, Seen in the Galaxy, that Milky- Way, Which nightly as a circling zone, thou seest Powdered with stars." CHAPTER XY. ORIGIN" OF THE CONSTELLATIONS. 261. THE science of astronomy was cultivated by the imme- diate descendants of Adam. JOSEPHTJS informs us that the sons of SETH employed themselves in the study of astronomy ; and that they wrote their observations upon two pillars, one of brick meridian? Its form, breadth, Ac.? How traced in the heavens? Notion of the Pagac philosophrs ? Of the poets T What citations? 261. How early was astronomy cultivated? i44 ASTRONOMY. and the other of stone,* in order to preserve them against the destruction which A DAM had foretold should come upon the earth. He also relates, that Abraham argued the unity and poorer of God, from the orderly course of things both at sea and land, in their times and seasons, and from hia observa- tions upon the motions and influences of the sun, moon and stars ; and that he read lec- tures in astronomy and arithmetic to the Egyptians, of which they understood nothing till Abraham brought these sciences fromChaldea to Egypt; from whence they passed to the Greeks. 262. BEROSUS also observes that Abraham was a great and just man, and famous for his celestial observations ; the making of which was thought to be so necessary to the human welfare, that he assigns it as the principal reason of the Almighty's prolong- ing the life of man. This ancient historian tells us, in his account of the longevity of the antediluvians, that Providence found it necessary to prolong man's days, in order to promote the study and advancement of virtue, and the improvement of geometry and astronomy, which required, at least, six hundred years for making and perfecting observations.! 263. When Alexander took Babylon, Calisthenes found that the most ancient observations existing on record in that city, were made by the Chaldeans about 1903 years before that period, which carries us back to the time of the dispersion of mankind by the confusion of tongues. It was 1500 years after this that the Babylonians sent to Hezekiah, to inquire about the shadow's going back on the dial of Ahaz. It is, therefore, very probable that the Chaldeans and Egyptians were the original inventors of astronomy; but at what period of the world they marked out the heavens into constellations, remains in uncertainty. La Place fixes the date thirteen or fourteen hundred years before the Christian era, since it was about this period that Eudoxus con- structed the first celestial sphere upon which the constellations were delineated. Sir Isaac Newton was of opinion, that all the old constellations related to the Argonautic expedition, and that they were invented to commemorate the heroes and events of that memorable enterprise. It should be remarked, however, that while none of the ancient constellations refer to transactions of a later date, yet we have various accounts of them of a much higher antiquity than that event. 264. Some of the most learned antiquarians of Europe have searched every page of heathen mythology, and ransacked all the legends of poetry and fable for the purpose of rescuing this subject from that impermeable mist which rests upon it, and they have only been able to assure us, in general terms, that they are Chaldean or Egyptian hieroglyphics, intended to per- petuate, by means of an imperishable record, the memory of the times in which their inventors lived, their religion and manners, *Josephus affirms, that "he saw himself that of stone to remain in Syria in his owu lim?." t Vince's Complete System of Astronomy, Vol. ii. p. 244. What proof? What said of Abraham? 262. What further proof? What reason assigned for the longevity of the antediluvians? 263. What discovery by Calisthenes? Wnat conclusion from this discovery? La Place's date of the origin of the constdla tions? Sir Isaac Newton's opinion? Kemark? 264. What researches, and whaJ results? ORIGIN OF THE CONSTELLATIONS. 145 their achievements in the arts, and whatever in their history was riost worthy of being commemorated. There was, at least, a moral grandeur in this idea ; for an event thus registered, a custom thus canonized, or thus enrolled among the stars, must needs survive all other traditions of men, and stand forth in per- petual characters to the end of time. 265. In arranging the constellations of the Zodiac, for instance, it would be natural for them, we may imagine, to represent those stars which rose with the sun in the spring of the year, by such animals as the shepherds held in the greatest esteem at that season ; accordingly, we find Aries, Taurus, and Gemini, as the symbols of March, April, and May. 266. When the sun enters the sign Cancer, at the summer solstice, he discontinues his progress towards the north pole, and begins to return towards the south pole. This retrograde mo- tion was fitly represented by a Crab, which is said to go back- ward. The sun enters this sign about the 22d of June. The heat which usually follows in the next month was repre- sented by the Lion ; an animal remarkable for its fierceness, and which at this season was frequently impelled by thirst tc leave the sandy desert, and make its appearance on the banks of the Nile. 267. The sun entered the sixth sign about the time of harvest, which season was therefore represented by a Virgin, or female reaper, with an ear of corn in her hand. At the autumnal equinox, when the sun enters Libra, the days and nights are equal all over the world, and seem to observe an equilibrium or balance. The sign was therefore represented under the symbol of a pair of Scales. 268. Autumn, which produces fruit in great abundance, brings with it a variety of diseases, and on this account was represented by that venomous animal, the Scorpion, which, as he recedes, wounds with a sting in his tail. The fall of the leaf, was tiie season for hunting, and the stars which mark the sun's path at this time were represented by a huntsman, or archer, with his arrows and weapons of destruction. The Goat, which delights in climbing and ascending some mountain or precipice, is the emblem of the winter solstice, when the sun begins to ascend from the southern tropic, and gradually to increase in height for the ensuing half year. 2t>5. Origin of Aries, Taurus, and Gemini? 266. Of Cancer and Leo 207. 0' Virgo and Lib.-a ? '2(53. Of Scorpio and Capricorn ? [TTIXVIRSlTr o* 146 ASTRONOMY. 269. Aquarius, or the Water Bearer, is represented by the figure of a man pouring out water from an urn, an emblem of the dreary arid uncomfortable season of winter. The last of the zodiacal constellations was Pisces, or a couple of fishes, tied back to back, representing the fishing season. The severity of winter is over ; the flocks do not afford suste- nance, but the seas and rivers are open and abound with fish. " Thus monstrous forms, o'er heaven's nocturnal arch, Seen by the sage, in pomp celestial march ; See Aries there his glittering bow unfold, And raging Taurus toss his horns of gold ; With bended bow the sullen Archer lowers, And there Aquarius conies with all his showers ; Lions and Centaurs, Gorgons, Hydras rise, And gods and heroes blaze along the skies." Whatever may have led to the adoption of these rude names at first, they are now retained to avoid confusion. The early Greeks, however, displaced many of the Chaldean constellations, and sub- stituted such images in thsir place as had a more special reference to their own history. The Romans also pursued the same course with regard to their history; and hencs the contradictory accounts that have descended to later times. 270. Some, moreover, with a desire to divest the science of the stars of its pagan jargon and profanity, have been induced to alter both the names and figures of the constellations. In doing this, they have committed the opposite fault ; that of blending them with things sacred. The " venerable Bede," for example, instead of the profane names and figures of the twelve constellations of the Zodiac, substituted those of the twelve apostles. Julius Schillerius, fol- lowing his example, completed the reformation in 1627, by giv- ing Scripture names to all the constellations in the heavens. Weigelius, too, a celebrated professor of mathematics in the University of Jena, made a new order of constellations, by converting the firmament into a coxcx HERALDICOM, in which he introduced the arms of all the princes of Europe. But astronomers, generally, never approved of these innovations ; and for ourselves, we had as lief the sages and heroen of antiquity should continue to enjoy their fianced honors in the sky, as to see their places supplied by the princes of Europe. 271. The number of the old constellations, including those of the Zodiac, was only forty-eight. As men advanced in the knowledge of the stars, they discovered many, but chiefly in southern latitudes, which were noc embraced in the old constel- lations, and hence arose that mixture of ancient and moderr names which we meet with in modern catalogues. 272. Astronomers divide the heavens into three parts, called the Northern and Southern Hemispheres, and the Zodiac. In the 2C-9. Of Aquarius and Pisces? Course of the Greeks and Romans, in displacing con- stellations? 270. What other reform attempted? What particular instances cited? Bede? Schillerius? Weigelius? How are these innovations regarded by astronomers! 871. Number of the old constellations? How others added? JT2. How do astrono ORIGIN OF THE CONSTELLATIONS. 147 .northern hemisphere, astronomers usually reckon thirty-four con- stellations, in the Zodiac twelve, and in the southern hemisphere forty-seven ; making in all ninety-three. Besides these, there are a few of inferior note, recently formed, which are not con- sidered sufficiently important to be particularly described. 273. About the year 1603, John Bayer, a native of Germany, invented the convenient system of denoting the stars in each constellation by the letters of the Greek alphabet, applying to the largest star the first letter of the alphabet ; to the next largest the second letter, and so on to the last. Where there are more stars in the constellation than there are Greek letters, the remainder are denoted by the letters of the Roman alphabet, and sometimes by figures. By this system of notation, it is now as easy to refer to any particular star in the heavens, as to any particular house in a populous c'ty, by its street and number. Before this practice was adopted, it was customary to denote the stars by referring them to their respective situations in the figure of the constellation to which they severally belonged, as the head, the arm, the foot, Ac. It is hardly necessary to remark that these figures, which are all very curiously depicted upon artificial globes and maps, are purely a fanciful invention answering many con- venient ends, however, for purposes of reference and classification, as they enable us to designate with facility any particular star, or cluster of stars ; though these clusters very rarely, if ever, represent the real figures of the objects whose names they bear. Atid yet it is somewhat remarkable that the name of "Great Bear," for instance, should have been given to the very same constellation by a nation of American aborigines (the Iroquois), and by the most ancient Arabs of Asia, when there never had been any com- munication between them! Among other nations, also, between whom there exists no evidence of any intercourse, we find the Zodiac divided into the same number of constel- lationt, and these distinguished by nearly the same names, representing the twelve months, or seasons of the year. 274. The constellations, or the uncouth figures by which they are represented, are a faithful picture of the ruder stages of civilization. They ascend to times of which 110 other record exists ; and are destined to remain when all others shall be lost. Fragments of history, curious dates and documents relating to chronology, geography and languages, are here preserved in imperishable characters. The adventures of the gods, and the inventions of men, the exploits of heroes, and the fancies of poets, are here spread out in the heavens, and perpetually celebrated before all nations. The Seven stars, and Orion, present themselves to us, as they appeared to Amos and Homer: as they appeared to Job, more than 3000 years ago, when the Almighty demanded of him " Knowest thou the ordinances of heaven? Canst thou bind the sweet influences of the PLEIADES, or loose the bands of ORION? Canst thou bring forth MAZZAROTH in his season, or canst thou guide ARCTURCS with his sons?" Here, too, are consecrated the lyre of Orpheus and the ship of the Argonauts; and, in the same firmament, glitter the Mariner's Compass and the Telescope of Herschel. mers divide the constellations? Number in each division? Total? What others? 273. John Bayer's invention? Utility of it? How before it was adopted? What remark respecting the figures on maps and globes, and their use? What remarkable facts Btated? 274. Historical use of the constellations? Illustrations? B.G. MS ASTRONOMY. . CHAPTER XVI. NUMBER, DISTANCE AND ECONOMY OF THE STARS. 275. THE first conjecture in relation to the distance of the fixed stars is, that they are all placed at an equal distance from the observer, upon the visible surface of an immense concave vault, which rests upon the circular boundary of the world, and which we call the Firmament. We can, with the unassisted eye, form no estimate of their respective distances ; nor has the tele- scope yet enabled us to arrive at any exact results on this sub- ject, although it has revealed to us many millions of stars that are as far removed beyond those which are barely visible to the naked eye, as these are from us. Viewed through the telescope, the heavens become quite another spectacle not only to tiie understanding but to the senses. New worlds burst upon the sight, and old ones expand to a thousand times their former dimensions. Several of those little stars which but feebly twinkle on the unassisted eye, become immense globes, with land and water, mountains and valleys, encompassed by atmospheres, enlightened by moons, and diver- sified by day and night, summer and winter. Beyond these are other suns, giving light and life to other systems, not a thousand, or two thousand merely, but multiplied without end, and ranged all around us, at immense distances from each other, attended by ten thousand times ten thousand worlds, all in rap.d motion ; yet calm, regular and harmonious all space seems to be illuminated, and every particle of light a world. 276. It has been computed that one, hundred millions of stars which cannot be discerned by the naked eye, are now visible through the telescope. And yet all this vast assemblage of suns and worlds may bear no greater proportion to what lies beyond the utmost boundaries of human vision, than a drop of water to the ocean ; and, if stricken out of being, would be no more missed, to an eye that could take in the universe, than the fall of a single leaf from the forest. We should therefore learn, says Dr. Chalmers, not to look on our earth as the universe of God, but as a single, insignificant atom of it; that it is only one of the many mansions which the Supreme Being has created for the accommodation of his worshipers ; and that he may now be at work in regions more distant than geometry ever measured, creat- ing won Is more manifold than numbers ever reckoned, displaying his goodness, and spreading over all the intimate visitations of his care. 277. The immense distance at which the nearest stars are known to be placed, proves that they are bodies of a prodigious size, not inferior to our sun, and that they shine, not by reflected rays, but by their own native light. It is therefore concluded, 275. What is the first conjecture as to the distance of the stars? Can we form no just estimate? What said of the heavens when seen through a telescope? 276. What computation as to the number of stars invisible to the naked eye, but visible through telescopes ? Is this probably the whole universe ? Remark of Chalmers ? 277. What NUMBER, DISTANCE, AND ECONOMY OF THE STARS. 149 with good reason, that every fixed star is a sun, no less spacious than ours, surrounded by a retinue of planetary worlds, which revolve around it as a center, and derive from it light and heat, and the agreeable vicissitudes of day and night. These vast globes of light, then, could never have been designed merely to diversify the voids of infinite space, nor to shed a few glimmering rays on our far distant world, for the amusement of a few astronomers, who, but for the most powerful telescopes, had never seen the ten thousandth part of them. We may therefore rationally conclude, tha* wherever the All-wise Creator has exerted his creative power, there also he has placed intelligent beings to adore his goodness. 278. The greatest possible ingenuity and pains have been taken by astronomers to determine, at least, the approximate distance of the nearest fixed stars. If they have hitherto been unable to arrive at any satisfactory result, they have, at least, established a limit beyond which the stars must necessarily be placed. If they have failed to calculate their true distances from the earth, it is because they have not the requisite data. The solution of the problem, if they had the data, would not be more difficult than to compute the relative distances of the planets a thing which any schoolboy can do. Tn estimating so great a distance as the nearest fixed star, it is necessary that we employ the longest measure which astronomy can use. Accordingly, we take the whole diameter of the earth's orbit, which, in round numbers, is 190 millions of miles, and endeavor, by a simple process in mathematics, to ascertain how many measures of this length are contained in the mighty interval which separates us from the stars. The method of doing this can be explained to the apprehension of the pupil, if he does not shrink from the illustration, through an idle fear that it is beyond his capacity. For example ; suppose that, with an instrument constructed for the purpose, we should tliis night take the precise bearing or angular direction from us of some star in the northern hemisphere, and note it down with the most perfect exactness, and, having waited just six months, when the earth shall have arrived at the opposite point of its orbit, 190 millions of miles east of the place which we now occupy, we should then repeat our observation upon the same star, and see how much it had changed its position by oui traveling so great a distance one side of it. Now, it is evident, that if it changes its apparent position at all, the qua-nlity of the change will bear some proportion to the distance gone over ; that is, the nearer the star, the greater the angle ; and the more remote the star, the fe** the angle. It is to be observed, that the angle thus found, ig called the star's Annual Parallax. 279. But it is found by the most eminent astronomers of the age, and the most perfect instruments ever made, that the paral- lax of the nearest stars does not exceed the four thousandth part of a degree, or a single second ; so that, if the whole great orbit of the earth were lighted up into a globe of fire 600 millions of miles in circumference, it would be seen by the nearest star only as a twinkling atom ; and to an observer placed at this distance, proof that the stars are large bodies? What conclusion, therefore? What other inference? 278. What effort to determine the twinkling of the most tiny star to the broad glare of the sun. The whole heavens seemed in motion, and suggested to some the awful grandeur of the image employed in the apocalypse, upon the opening of the sixth seal. when " the stars of heaven fell unto the earth, even as a fig-tree casteth her untimely ligs, when she is shaken of a mighty wind." 298. One of the most remarkable circumstances attending his display was, that the meteors all seemed to emanate from 296. What other similar phenomenon cited ? 297. What still more sublime spectacle? Its extent? Its appearance ? 158 ASTRONOMY. one and the same point, a little southeast of the zenith. Follow ing the arch of the sky, they ran along with immense velocity, describing, in some instances, an arc of 30 or 40 in a few METEORIC 8HOWKB OF NOVEMBER, 1333. seconds. On more attentive inspection it was seen, that the meteors exhibited three distinct varieties ; the first, consisting of phosphoric lines, apparently described by a point ; the second, of large fire-balls, that at intervals darted along the sky, leaving luminous trains, which occasionally remained in view for a num- ber of minutes, and, in some cases, for half an hour or more ; the third, of undefined luminous bodies, which remained nearly Btationary in the heavens for a long time. Those of the first variety were the most numerous, and resembled a shower of fiery mow driven with inconceivable velocity to the north of west. The second kind appeared more \\kefdlling stars a spectacle which was contemplated by the more unenlightened beholders with great amazement and terror. The trains which they left were commonly white, but sometimes were tinged with various prismatic colors, of great beauty. 299. These fire-balls were occasionally of enormous size. Dr. Smith, cf North Carolina, describes one which appeared larger than the full moon rising. " I was," says he, " startled by the '?08 What remarkable circumstance attended this phenomenon? Variety of meteors? 299. What said of the fireballs seen? Of their size? FALLING OR SHOOTING STARS. 150 splendid light in which the surrounding scene was exhibited, ren- dering even small objects quite visible." The same ball, or a similar one, seen at New Haven, passed off in a northwest direction, and exploded a little northward of the star Capella, leaving, just behind the place of ;ap explosion, a train of peculiar beauty. BfifiN^ The line of direction was at first nearly straight ; but it. soon began to SWj;^-- contract in length, to dilate in breadth, and to assume the figure of a serpent SCROLLING itself up, until it appeared like a luminous cloud of vapor, float- ing gracefully in the air, where it remained in full view for several luinutos. If this body were at the distance of lit) miles from the observer, it must have had a diameter of one mile; if at the distance of 11 miles, its diame- A LARGK METEOR. fer was 5'2S feet; and if only one mile off, it must have been 48 feet in diameter. These tonsiderations leave no doubt that many of the meteors were bodies of lurge size. 300. Of the third variety of meteors, the following are remark- able examples : At Poland, Ohio, a luminous body was dis- tinctly visible in the northeast for more than an hour. It was very brilliant, in the form of a priming-hook, and apparently twenty feet long, and eighteen inches broad. It gradually settled toward the horizon, until it disappeared. At Niagara Falls, a large luminous body, shaped like a square tttlil?.. was seen near the zenith, remaining for some time almost stationary, emitting large streams of light. 301. The point from which the meteors seemed to emanate, was observed, by those who fixed its position among the stars, to be in constellation Leo ; and, according to their concurrent testimony, this RADIANT POINT was stationary among the stars, during the whole period of observation ; that is, it did not move along with the earth, in its diurnal revolution eastward, but accompanied the stars in their apparent progress westward. A remarkable change of ioe(ttJt*r, from warm to cold, accompanied the meteoric rhower, or immediately followed it. In all parts of the United States, this change was remarkable for its suddenness aud intensity. In many places, the day preceding had been unusually warm for the season, but, before the next morning, a severe frost ensued, unparalleled lor the time of year. 302. In attempting to explain these mysterious phenomena, it is argued, in the first place, that the meteors had their origin beyond the limits of our atmosphere ; that they of course did not belong to this earth, but to the regions of space exterior to it 800. What other variety of meteors described? Where? 801. Point from which .heyseemed to emanate? What change of weather foil: ved ? go-2. What fact asserted as 1o the distance from which thorfe meteors came I'rofessor Oliasted's estimate of i ? 150 ASTRONOMY. The reason on which the conclusion is founded is this : All bodies near the earth, Including the atmosphere itself, have a common motion with the earth aroumi its axis from west to east; but the radiant point, that indicated the source from which the nieteors emanated, followed the course of the stars from east to west; therefore, it was independent of the earth's rotation, and consequently, at a great distance from it, and beyond the limits of the atmosphere. The height of the meteoric cloud, or radiant point, above the earth's surface, was, according to the mean average of Professor Oliusted's observations, not less than 2233 mile?. 303. That the meteors were constituted of very light, combus- tible materials, seems to be evident, from their exhibiting the actual phenomena of combustion, they being consumed, or con- verted into smoke, with intense light ; and the extreme tenuity of the substance composing them is inferred from the fact that they were stopped by the resistance of the air. Had their quan- tity of matter been considerable, with so prodigious a velocity, they would have had sufficient momentum to dash them upon the earth ; where the most disastrous consequences might have followed. The momentum of even light bodies of such size, and in such numbers, traversing the atmosphere with such astonishing velocity, must have produced extensive derangements in the atmospheric equilibrium. Cold air from the upper regions would be brought down to the earth; the portions of air incumbent over districts of country remote from each other, being mutually displaced, would exchange places, the air of the warm latitude." be transferred to colder, and that of cold latitudes to warmer regions. 304. Various hypotheses have been proposed to account for this wonderful phenomena. The agent which most readily suggests itself in this, and in many other unexplained natural appearances, is electricity. But no known properties of electricity are adequate to account for the production of the meteors, for their motions, or for the trains which they, in many instances, left behind them. Others, again, have referred their proximate cause to magnttism. and to phosphureted hydrogen ; both of which, however, seem to be utterly insufficient, so far as their properties are known, to account for so unusual a phenomenon. 305. Professor Olmsted, of Yale College, who has taken much pains to collect facts, and to establish a permanent theory for the periodical recurrence of such phenomena, came to the con- clusion, that The meteors of November IBth, 1833, emanated from a nebulous body, which was then pursuing its way along with the earth around the sun ; that this body continues to revolve around the sun, in an elliptical orbit but little inclined to the. plane of the ecliptic, and having its aphelion near the orbit of the earth; and finally, that 803. Supposed composition of these meteors? Why? 304. Hypotheses for explain* 'ig phenomenon? Are they satisfactory? 805. Professor Olmsted's conclusion? FALLING OR SHOOTING ST UlS. 161 (he body has a period of marly six months, and that its perihelion is a little below the orbit of Mercury* This theory at least accommodates itself to the remarkable fact, that almost all the phenomena of this description, which are known to have happened, have occurred in the two opposite months of April and November. A similar exhibition of meteors to that of November, 18*3, was observed on the same day of the week, April 20th, 18(13, at Kich- aiond, Virginia ; Stockbridge, Massachusetts ; and at Halifax, in British America. Another n-as witnessed in the autumn of ISIS, in the North Sea, when, in the language of the observers, " all the surrounding atmosphere was enveloped in one expansive sea of fire, exhibiting the appearance of another Moscow, in flames." * After the Jirat edition of this work went to press, the author was politely fur- nished, by Professor (Minuted, with the following communication. " I am happy to hear that you propose to stereotype your ' Geography of the Heavens.' it has done much, I believe, to diflfuse a popular knowledge of astronomy, and I am pleased that your efforts are rewarded by an extended patronage. " Were I now to express my views on the subject {Meteoric Showers) in as condensed a form as possible, I should state them in some such terms as the following : The meteoric showers which have occurred for several years past on or about the 13th of November, are characterized by four peculiarities, which distinguish them from ordinary shooting stars. First, they are far more numerous than common, and are larger and brighter. Secondly, they are in much greater proportion than usual, accompanied by luminous trains. Thirdly, th-^y mostly appear to radiate from a common center; that is, were their paths in the heavens traced backward, they would meet in the same part of the heavens: this point has for three years past, at least, been situated in the constellation Leo. Fourthly, the greatest display is everywhere at nearly the same time of night, namely, from three to four o'clock a time about half-way from midnight to sunrise. The meteors are inferred to consist of combustible matter, because they are seen to take fire and burn in the atmosphere. They are known to be very light, because, although they full toward the earth with immense velocity, few, if any, ever reach the earth, but are arrested by the air, like a wad fired from a piece of artillery. Some of them are inferred to be bodies of comparatively great size, amounting in diameter to several hundred feet, at least, because they are seen under so large an angle, while they are at a great distance from the spectator. Innumerable small bodies, thus consisting of extremely light, thin, combustib'e matter, existing together in space far beyond the limits of the atmosphere, are believed to compose a body of immense extent, which has been called ' the nebulous body.' Only the skirts or extreme portions of this are brought down to the earth, while the entire extent occupies many thousands, and perhaps several millions of miles. Thin nebulous body is inferred to have a revolution around the sun, as well as the earth, and to come very near to the latter about the 13th of November each year. This annual meeting every year, for several years in succession, could not take place unless the periodic time of the nebulous body is either nearly a year, or half a year. Various rea- sons have induced the belief that half a year is the true period ; but this point is con- Bidered somewhat doubtful. The zodiacal light, a faint light that appears at different seasons of the year, either immediately preceding the morning or following the evening twili/,ht, ascending from the sun in a triangular form, is, with some degree of probability, thought to be the nebular body itself, although the existence of such a body, revolving in tie solar system, was inferred to be the cause of the meteoric showers, before any connection of it with the zodiacal light was even thought of." \\> what remarkable fact does his theory accord ? Substance of letter from Professor OluiKted? 162 ASTRONOMY. 306. Exactly one year previous to the great phenomenon of 1833, namely, on the 12th of November, 1832, a similar meteoric display was seen near Mocha,, on the Red Sea, by Capt. Ham- mond and crew of the ship Restitution. A gentleman in South Carolina thus describes the effect of the phenomenon of 1S;>5. jjmii his ignorant blacks : " I was suddenly awakened by the most distressing cries thai ever fell on my ears. Shrieks of horror, and cries of mercy, I could hear from most of the negroes of three plantations, amounting in all to about six or eight hundred. While earnestly listening for the cause, I heard a faint noise near the door calling my name ; I arose, and taking my sword, stood at the door. At this moment, I heard the same voice still beseeching me to rise, and saying, 'O, my God, the world is on tare !' I then opened the door, and it is difficult to say which excited me most the awfulness of the scene, or the distressed cries of the negroes; upward of one hundred lay prostrate on the ground some speechless, and some with the bitterest cries, but most with their hand* raised, imploring God to save the world and them. The scene was truly awful ; foi never did ruin fall much thicker, than the meteors fell toward the earth ; east, w :st north, and south, it was the same !" 306. What similar meteoric shower referred to? Description of that of Novcioiei 1S33, and its effects upon certain persons ? PART II. THE SOLAR SYSTEM CHAPTER I. GENERAL PHENOMENA OF THE SOLAR SYSTEM, HISTORY, &c. 307. OUR attention has hitherto been directed to those bodies which we see scattered everywhere throughout the whole celes- tial concave. These bodies, as has been shown, twinkle with a reddish and variable light, and appear to have always the same position with regard to each other. We know that their num- ber is very great, and that their distance from us is immeasur- able. We are also acquainted with their comparative brightness, and their situation. In a word, we have before us their few visible appearances, to which our knowledge of them is well-nigh limited ; almost all our reasonings in regard to them being founded on con ~ par approach the sun, however, their faint and nebulous light becomes * more and more brilliant, and their train increases in length until they arrive at their nearest point of approximation, when -s? they shine with their greatest brilliancy. As they recede from '' the Sun, they gradually lose their splendor, resume their faint and nebulous appearance, and their train diminishes, until they s ' entirely disappear. They have no well-defined figure ; they seem to move in every possible direction, and are found in every . rt of the heavens. From their train they were called by the <~ -Greeks Kouqrai, cornets, which signifies bearded, or having '. long hair. ^ The causes of these various phenomena must have early constituted a very natural f subject of inquiry. Accordingly, we shall find, if we examine the history of the science, j that, in very early times there were many speculations upon this subject, and that dilfer- v cut theories were adopted to account for these celestial appearances. 315. The Egyptians, Chaldeans, Indians, arid Chinese, early * possessed many astronomical facts, many observations of impor- tant phenomena, and many rules and methods of astronomical calculation ; and it has been supposed, that they had the ruins of a great system of astronomical science, which m the earliest ages of the world had been carried to a great degree of perfec- tion, and that while the principles and explanations of the phe- 314. Any other bodies described? How distinguished? What called, and why ? Is it probable that these phenomena were early observed ? 315. What said of the Egyptians, Chaldeans, rt> ,X * PHENOMENA OF THE SOLAR SYSTEM. 167 who had preceded him, spread oat before him, composed a work in thirteen books, called the MeyaA?/ Zvvra&c;, or Great System. 318. Rejecting the doctrine of Pythagoras, who taught that the Sun was the center of the universe, and that the Earth had a diurnal motion on its axis arid an annual motion around the Sun, as contrary to the evidence of the senses, Ptolemy endea- vored to account for the celestial phenomena, by supposing the Earth to be the center of the universe, and all the heavenly bodies to revolve around it. He seems to have entertained an idea, in regard to the supposition, that the Earth revolved on its axis, similar to one which some entertain even at the present day. "If," says he, "there were any motion of the Earth common to it and all other heavenly bodies, it would certainly precede them all by the excess of its mass being so great; and animals and a certain portion of heavy bodies would be left behind, riding upon the air, and the earth itself would very soon be completely carried out of the heavens." 319. In explaining the celestial phenomena, however, upon his hypothesis, he met with a difficulty in the apparently station- ary attitude and retrograde motions which he saw the planets sometimes have. To explain this, however, he supposed the planets to revolve in small circles, which he called epicycles, which were, at the same time, carried around the Earth in larger circles, which he called deferents, or carrying circles. In following out his theory, and applying it to the explanation of different phenomena, it became necessary to add new epicycles, and to have recourse to other expedients, until the system became unwieldy, cumbrous, and complicated. This theory, although astro- nomical observations continued to be made, and some distinguished astronomers appeared fron time to time, was the prevailing theory until the middle of the 15th century. It was not, however, always received with implicit confidence ; nor were its difficulties alw(ty^ entirely unappreciated. Alphonso X., king ot Castile, who flourished in the 13th century, when contemplating the doctrine of the epicycles, exclaimed, ' Were the universe thus constructed, if the J'eity had called me to his councils at the creation of the world, I could have given him good advice." He did not, however, mean any impiety or irreverence, except what was directed against the system of Ptolemy. 320. About the middle of the 15th century, Copernicus, a native of Thorn in Prussia, conceiving a passionate attachment to the study of astronomy, quitted the profession of medicine, and devoted himself with the most intense ardor to the study of this science. " His mind," it is said, " had long been imbued with the idea that simplicity and harmony should characterize the arrangements of the planetary system. In the complication and disorder which he saw reigned in the hypothesis of Ptolemy, he perceived insuperable objections to its being considered as a representation of nature." 318. His system of astronomy? What singular idea and reasoning? 819. What difficulty did he meet with, and how explain it? What further difficulty? How long did this theory prevail? What anecdote of the King of Castile? 320. What dis- tinguishd student of astronomy now arose? liis impressions in regard to the Ptolemaic theory ? His own earlier convictions? What other theories did he study? i 68 ASTRONOMY. In the opinions of the Egyptian sages, in those of Pythag ras, Philolaus, Aristaichtw, and Nicetus, he recognized his own earliest conviction that the Earth was not the center of the universe. His attention was much occupied with the speculation of Martinus Capella, who placed the Sun between Mars and the Moon, and made Mercury and VeniM revolve round him as a center, and with the system of Appollonius Pergceus who made ill the planets revolve around the Sun, while the Sun and Moon were carried around tha Earth iu the center of the universe. 321. The examination, however, of various hypotheses, by Copernicus, gradually expelled the difficulties with which the subject was beset, and after the labor of more than thirty years, he was permitted to see the true system of the universe. The Sun he considered as immovable, in the center of the system, while the Earth revolved around him, between the orbits of Yenus and Mars, and produced by its rotation about its axis all the diurnal phenomena of the celestial sphere. The other planets he considered as revolving about the Sun, in orbits exterior to that of the Earth. ( See the Relative Distances of the Planets 7 Orbits, Map I. of the Atlas.} Thus, the stations and retrogradations of the planets were the necessary consequence Df their o-.vn motions, combined with that of the Earth about the Sun. He said that " by long observation, he discovered that, if the motions of the planets be compared with that of the Earth, and be estimated according to the times in which they perform their revolutions, not only their several appearances would follow from this hypothesis, but that it would so connect the older of the planets, their orbits, magnitudes, and distances, and even the apparent motion of the fixed stars, that it would be impossible to remove one of these bodies out of its place without disordering the rest, and even the whole of the universe also." 322. Soon after the death of Copernicus, arose Tycho Brahs, born at Knudstorp, in Norway, in 1546. Such was the distinc- tion which he had attained as an astronomer, that when, dissa- tisfied with his residence in Denmark, he had resolved to remove, the King of Denmark, learning his intentions, detained him in the kingdom, by presenting him with the canonry of Rothschild, with an income of 2,000 crowns per annum. He added to this sum a pension of 1,000 crowns, gave him the island of Hucn, and established for him an observatory at an expense of about 200,000 crowns. Here Tycho continued, for twenty-one years, to enrich astronomy with his observations. His observations upon the Moon were important, and upon the planets numerous and precise, and have formed the data of the present generalizations in astronomy. He, however, rejected the system of Copernicus; considering the Earth as immovable in the center of the system, while the Sun, with all the planets and comets revolving around him, performed his revolution around the earth, and, in the course of twenty-four hours, the stars also revolved about the central body. This theory was not so simple as that of Copernicus, and involved the absurdity of making the Sun, planets, Ac., revolve around a body comparatively insignificant. 321. How was Copernicus led to discover the true system of astronomy ? What is that system ? Does it account for the stations and retrogradations of the planets ? 323 What distinguished astronomer next arose? What said of his detention in Dwmarlt Via observations? His theory PHENOMENA OF THE SOLAR SYSTEM. 1 (>fl 323. Near the close of the 15th century, arose two men, who wrought most important changes in the science ; Kepler and Galileo, the former a German, the latter an Italian. Previous to Kepler, all investigations proceeded upon the supposition that i he planets moved in circular orbits which had been a source of much error. This supposition Kepler showed to be false. He discovered that their orbits were ellipses. The orbits of their secondaries or moons he also found to be the same curve. He next determined the dimensions of the orbits of the planets, and found to what their velocities in their motions through their orbits, and the times of their revolutions, were proportioned; all truths of the greatest importance to the science. 824. While Kepler was making these discoveries of facts, very essential for the explanation of many phenomena, Galileo was discovering wonders in the heavens never before seen by the eye of man. Having improved the telescope, and applied it to the heavens, he observed mountains and valleys upon the surface of our Moon ; satellites or secondaries were discovered revolving about Jupiter ; and Venus, as Copernicus had predicted, was seen exhibiting all the different phases of the Moon, waxing and waning as she does, through various forms. Many minute stars, not visible to the naked eye, were described in the Milky- Way ; and the largest fixed stars, instead of being magnified, appeared to be small brilliant points, an incontrovertible argument in favor of their immense distance from us. All his dis- coveries served to confirm the Copernican theory, and to show the absurdity of the hypothesis of Ptolemy. 825. Although the general arrangement and motions of the planetary bodies, together with the figure of their orbits, had been thus determined, the force of power which carries them around in their orbits, was as yet unknown. The discovery of this was reserved for the illustrious Newton, though even his discovery was in some respects anticipated by Copernicus, Kepler and Hooke. By reflecting on the nature of gravity that power which causes bodies to descend toward the center of the earth since it does not sensibly diminish at the greatest- distance from the center of the earth to which we can attain, being as powerful on the loftiest mountains as it is in the deepest caverns, he was led to imagine that it might extend to the Moon, and that it might be. the power which kept her in her orbit, and caused her to revolve around the Earth. He was next led t > suppose that perhaps the same power carried the 823. What two noted astronomers ifect arose? What did Kepler discover? 824. Galileo and his discoveries? What theory did they serve to establish? 825 What f7at discovery next made, and by whom? llow l^i to it ? Successive steps? 170 ASTRONOMY. primary planets around the Sun. By a series of calculations, he was enabled at length to establish the fact, that the same force which determines the fall of an apple to the Earth, carries the moons in their orbits around the planets, and the planets and comets in their orbits around the Sun. To recapitulate briefly : The system (not hypothesis, for much of it has been established by mathematical demonstration) by which we are now enabled to explain with a beauti- fu' simplicity the different phenomena of the Sun, planets, moons, and comets, is, that tho Sun is the central body in the system: that the planets and comets move round him in elliptical orbits, whose planes are more or less inclined to each other, with velocities bearing to each other a certain ascertained relation, and in times related to their dis- tances ; that the moons, or secondaries, revolve in like manner about their primaries, and at the same time accompany them in their motion around the Sun ; all meanwhile revolving on axes of their own ; and that these revolutions in their orbits are produced by the mysterious power of attraction. The particular mode in which this system is applied to the explanation of the different phenomena, will be exhibited as we proceed to consider, one by one, the several bodies above mentioned. 326. These bodies, thus arranged and thus revolving, consti- tute what is termed the Solar System. The planets have been divided into two classes, primaries and secondaries. The latter are also termed moons, and sometimes satellites. The primaries are those that revolve about the Sun, as a center. The seconda- ries are those which revolve about the primaries. There have been discovered to this date (1854), thirty-five primary planets, viz.: Mercury, Venus, the Earth, Mars, Flora, Clio, Yesta, Iris, Metis, Eunomia, Psyche, Thetis, Melpomene, Fortuna, Massiiia, Lutetia, Calliope, Thalia, Hebe, Parthenope, Irene, Egeria, Astrsea, Juno, Ceres, Pallas, Hygeia, Jupiter, Saturn, Uranus, Neptune, and four other Asteroids, whose names and places have not yet been determined. Mercury is the nearest to the Sun, tmd the others follow in the order in which they are named. The seventeen small planets from Flora to Hygeia, inclusive, were dis- covered by means of the telescope, and, because they are very small, compared with the others, are called Asteroids. Neptune, also, is a telescopic planet, though much larger than any of the Asteroids. There have been discovered twenty secondaries. Of these, the Earth has one, Jupiter four, Saturn eight, Herschel six, and Neptune one, All these, except our Moon, as well as the Aste- roids and Neptune, are invisible to the naked eye. Map I. of the Atlas, " exhibits a plan of the Solar System," comprising the relative magnitudes of the Sun and Planets ; their comparative distances from the Sun, and from each other; the position of their orbits, with respect to each other; the Earth and the gun ; together with many other particulars which are explained on the map. There, the Describe the Copernican theory? 826. What do the bodies mentioned constitute? How are the planets divided ? Describe eacn ? What number of primaries ? Name them ic order from the Sun ? Which are the Asteroids ? Which telescopic ? How many econdary planets ? How distributed? Are they visible to the naked eye ? What said THE SUN HIS DISTANCE, MAGNITUDE, ETC. 171 Crft and most prominent object which claims attention, is the representation of the Hun's circumference, with its deep radiations, bounding the upper margin of the map. It is apparent, however, that this segment is hardly one-sixth of the whole circumference of which it is a part. Were the map sufficiently large to admit the entire orb of the Sun, even upon so diminutive a scale as there represented, we should then see the Sun and Planets in their just proportions the diameter of the former being 112 times the diameter of the Earth. It was intended, originally, to represent the Earth upon a scale of one inch in diameter and the other bodies in that proportion ; but it was found that it would increase the map to four times its size ; and hence it became necessary to assume a scale of half an inch for the Earth's diameter, which makes that of the Sun 56 inches, and the other bodies, as represented upon the map. The relative position of the Planets' orbits is also represented, on a scale as large aa the sheet would permit. Their relative distances from the Sun as a center, and from each other, are there shown correctly. But had we wished to enlarge the dimensions of these orbits, so that they would exactly correspond with the scale to which we have drawn tho planets, the map must have been nearly two miles in length. "Hence," says Sir John Herschel, " the idea that we can convey correct notions on this subject, by drawing circles on paper, is out of the question." To illustrate this Let us suppose ourselves standing on an extended plane, or field o( ice, and that a globe 4 feet 8 inches in diameter is placed in the center of the plane, to represent the Sun. Having cut out of the map the dark circles representing the planets, we may proceed to arrange them in their respective orbits about the Sun, as follows : First, we should take Mercury, about the size of a small currant, and place it on the circumference of a circle 194 feet from the Sun; this circle would represent the orbit of Mercury, in the proper ratio of its magnitude. Next, we should take Venus, about the size of a rather small cherry, and place it on a circle 862 feet from the Sun, to represent the orbit of Venus. Then would come the Earth, about the size of a cherry, revolving in an orbit 500 feet from the Sun. After the Earth we should place Mars, about the size of a cranberry, on a circle 762 feet from the Sun. Neglecting the Asteroids, some of which would not be larger than a pin's head, we should place Jupiter, hardly equal to a mode- rate-sized melon, on a circle at the distance of half a mile (2601 feet) from the Sun ; Saturn, somewhat less, on a circle nearly a mile (4768 feet) from the Sun ; Herschel, about the size of a peach, on the circumference of a circle nearly 2 miles (9591 feet) from the Sun ; and last of all Neptune, a little larger than Herschel, and on a circle of nearly 3 miles (15,366 feet) from the Sun. To imitate the motions of the planets in the above-mentioned orbits, Mercury must describe its own diameter in 41 seconds ; Venus, in 4 minutes 14 seconds ; the Earth, in 7 minutes; Mars, in 4 minutes 48 seconds; Jupiter, in 2 hours 56 minutes; Saturn, in 8 hours 13 minutes ; Herschel, in 12 hours 16 minutes ; and Neptune, in 23 hours 25 min. Many other interesting subjects are embraced in Map I. ; but they are either explained on the map, or in the following chapters, to which they respectively relate. CHAPTER II. THE SUN HIS DISTANCE, MAGNITUDE, &o. 321. THE Sun is a vast globe, in the center of the solar sys- tem, dispensing light and heat to all the planets, and governing all their motions. It is the great parent of vegetable life, giv- ing warmth to the seasons, and color to the landscape. Its rays are the cause of various phenomena on the surface of the earth and in the atmosphere. By their agency, all winds are pro- of Mnp I. ? Its scale ? Remark of Dr. Herschel ? What illustrations of the S^lar System does ao .'urnish? Gi7. Sucj^t of Chapter II.? Describe the Sun? 13.G. b 172 ASTRONOMY. dneed, and the waters of the sea are made to circulate in vnpnr through the air, aiid irrigate the land, producing springs and rivers. 328. The Sun is by far the largest of the heavenly bodies whose dimensions have been definitely ascertained. Its diameter is about 889,000 miles. Consequently, it contains a volume of matter equal to fourteen hundred thousand globes of the size of the Earth. Of a body so vast in its dimensions, the human mind, with all its efforts, can form no adequate conception TUB SDN AND THE MOON'S ORBIT. Were the Sun a hollow sphere, perforated with a thousand openings to admit the twinkling of the luminous atmosphere around it and were a globo as large as the Earth placed at its center, with a satellite as large as our Moon, and at the same distance from it as she is from the earth, there would be present to the eye of a spectator on the interior globe, a universe as splendid MS that which now appears to the uninstructed eye a universe as large and extensive as the whole creation was conceived to be in the infancy of astronomy. The mean distance of the Moon from the Earth is 240,000 miles, consequently the average diameter of her orbit is 480,000 miles; and yet, were the Sun to take the place of the Earth, lie would fill the whole orbit of the Moon, and extend 200,000 miles beyond it in every direc- tion ! To pass from side to side through his center, at railroad speed (30 miles an hour), would require nearly three and a half years , and to traverse his vast circumference nearly eleven years. Here let the student refer to Map I., where the Relative Magnitudes of the Sun and Planets are exhibited. Let him compare the segment of the Sun's circumference, as there represented, with the entire circumference of the Earth. They are both drawn upon the same scale. The segment of the Sun's circumference, since it is almost a straight line, must be a very small part of what the whole circumference would be, were it repre- sented entire. Let the student understand this diagram, and he will be in some measure able to conceive how like a mere point the Earth is, compared with the Sun, and to form in his mind some image of the vast magnitude of the latter. 329. The next thing which fills the mind with wonder, is the distance at which so great a body must be placed, to occupy, apparently, so small a space in the firmament. The Sun's mean distance from the Earth is twelve thousand times the Earth's diameter, or a little more than 95,000,000 of miles. We may derive some faint conception of such a distance, by considering that the swiftest steamboats, which ply our waters at the rate of 200 miles a day, would not traverse it in thirteen hundred years ; and, that a cannon ball, flying night and day, at the rate of 16 miles a minute, would not reach it in eleven years. 330. The Sun, when viewed through a telescope, presents the appearance of an enormous globe of fire, frequently in a state of violent agitation or ebullition ; dark spots of irregular form, 828. His magnitude? Diameter? Compare*with the Earth ? What illustration given? What reference to the Map? 329. Distance of the Sun? What illustration given? 830 How does the Sun appear through a telcdW'pe ? Describe these spots? THE SUN HIS DISTANCE, MAGNITUDE, ETC. 173 rarely visible to the naked eye, frequently pass over his disc, from east to west, in the period of nearly fourteen days. Th^se spots are usually surrounded by a SPOTS ON THB S.CN. penumbra, or !ess deeply shaded border, and that, by a margin of light more bril- liant that that of the Sun. A spot when first seen on the eastern edge of the Sun, appears like a line which progressively ex- tends in breadth, and increases its appa- rent velocity, till it reaches the middle, when it begins to contract, and to move less rapidly, till it ultimately disappears at the western edge. In some rare instances, the same spots re-appear on the east side, ?u id are permanent for two or three revo- lutions. But, as a general thing, the spots on the Sun are neither permanent nor uni- form. Sometimes several small ones unite into a large one; and, again, a large one separates into numerous small ones. Some continue several days, weeks, and even months, together; while others appear and disappear, in the course of a few hours. Those spots that are formed gradually, are, for the most part, as gradually dissolved; whilst those that are suddenly formed, generally vanish as quickly. 331. It is the general opinion, that spots on the Sun were first discovered by Galileo, in the beginning of the year 1611 ; though Schemer, Harriot, and Fabric-ins, observed them about the same time. During a period of 18 years from this time, the Sun was never found entirely clear of spots, excepting a few days in December, 1624 : at other times, there were frequently seen twenty or thirty at a time, and in 1625, upwards of fifty were seen at once. From 1650 to 1670, scarcely any spots were to be seen ; and, from 1676 to 1684, the orb of the Sun pre- sented an unspotted disc. Since the beginning of the eighteenth century, scarcely a year has passed, in which spots have not been visible, and frequently in great numbers. In 1799, Dr Ilerschel observed one nearly 30,000 miles in breadth. A single second of angular measure, on the Sun's disc, as seen from the Earth, corre- sponds to 462 miles ; and a circle of this diameter (containing therefore nearly 220,000 square miles) is the least space which can be distinctly discerned on the Sun as a viMbla area, even by the most powerful glasses. Spots have been observed, however, whose linear diameter has been more than 44,000 miles; and, if some records are to be trusted, of even still greater extent. DR. DICK, in a letter to the author, says : " I have for many years examined the solar (pots with considerable minuteness, and have several times seen spots which were not less than the one twenty-fifth part of the Sun's diameter, which would make them about 92,192 miles in diameter, yet they were visible neither to the naked eye, nor through an opera glass magnifying about three times. And, therefore, if any spots have been visi- ble to the naked eye which we must believe, unless we refuse respectable testimony- they could not have been much less than 50,000 miles in diameter." 331 Who first saw them ? When? How was it for the next IS years ? How in 1625* From 1650 to 1670? From 1676 to 1684? How since the beginning of the eighteenth, century? Dr. Herschel's measurements? Dr. Dick's remarks and conclusion? 174 ASTRONOMY. 332. The apparent direction of these spots over the Sun's disc is continually varying. Sometimes they seem to move across it in straight lines, at others in curve lines. Sometimes the spots seem to move upward, as they cross from east to west, while at other times they incline downward, while the curve lines are sometimes convex towards one pole of the Sun, and sometimes towards the other. 333. All these phenomena are owing to the fact that the axis of the Sun is inclined to the ecliptic, so that viewing him from different points in the Earth's orbit, the apparent direction of the spots must necessarily vary. serve to illustrate : The following diagrams may VARIOUS DIRBCTIOHS OF TBB SOLAR SPOTS. B C I March. June. September. December. Let E F represent the plane of the ecliptic. In March, the spots describe a curve, which is convex to the south, as shown at A. In June, they cross the Sun's disc in nearly straight lines, but incline upward. In September, they curve again, though in the oppo- site direction ; and in December, pass over in straight lines, inclining downward. The figures B and D show the inclination of the Sun's axis. The following diagram will serve still further to illustrate the cause of the change of direction of the solar spots. BOLAR SPOTS OBSERVED FROM DIFFERENT POISTS. DEC. Let the student imagine himself stationed upon the earth at A, In March, looking upon t v a sun in the center, whose north or upper pole is now inclined toward him. The spots will then curve a^^^inard. TJiree months afterward vis., in June the earth will be 332. In what general direction do these spots move ? What variations ? is the cause of these varying phenomena? 833. What THE SUN HIS DISTANCE, MAGNITUDE, ETC. 175 at B ; when the sun's axis will incline to tlit left, and the spots seem to pass upward to the right. In three months longer, the observer will be at C, when the north pole of the sun will incline/row fiim, and the spots seem to curve upward; and in three months longer, he will be at D, when the axis of the sun will incline to the riffM, and the spots seem to incline downward. 334. From the regularity with which these spots revolve, it is concluded, with good reason, that they adhere to the surface of the Sun and revolve with it. They are all found within 30 of his equator, or within a zone 60 in width. 335. The apparent revolution of a spot, from any particular point of the Sun's disc, to the same point again, is accomplished in 27 days, 7 hours, 26 minutes, and 24 seconds ; but during *fiat time, the spot has, in fact, gone through one revolution, together with an arc, equal to that described by the Earth in iier orbit in the same time ; which reducest he time of the Sun's actual rotation on his axis, to 25 days, 9 hours, and 36 minutes. Let S represent the sun, and A SIDEHBAL AND SYNODIC REVOLUTIONS OF THE sus. the earth in her orbit. When she is at A, a spot is seen upon the disc of the sun at B. The sun re- volves in the direction of the ar- rows, and in 25 days 10 hours the spot conies round to B again, or opposite the star E. This is a side- real revolution. During these 25 days 8 hours, the earth has passed on in her orbit some 25, or nearly, to C, which will require nearly two days for the spot at B to get directly toward the earth, as shown at D. This last is a synodic revolution. It consists of one complete revolu- tion of the sui upon his axis, and about 27 over. 336. The part of the Sun's disc not occupied by spots, is far from being uniformly bright. Its ground is finely mottled with an appearance of minute dark dots, or pores, which, attentively watched for several days in succession, are found to be in a con- stant state of change. What the physical organization of the Sun may be, is a ques- tion which astronomy, in its present state, cannot solve. It seems, however, to be surrounded by an ocean of inexhaustible flame, with dark spots of enormous size, now and then floating upon its surface. From these phenomena, Sir W. Herschel sup- posed the Sun to be a solid, dark body, surrounded by a vast 334. Are these spots supposed to adhere to the body of the Sun ? On what part of the Sun are they found ? 885. What is their time of apparent, revolution ? The actiuil time? How arrived at? 336. What said of the part of the Su:i about his poles? Of his physical organization? What iocs it seem to be 9 How did Sir W. Herso.h^J regard it? 176 ASTRONOMY. . atmosphere, almost always filled with luminous clouds, occasion- ally opening and disclosing the dark mass within. 337. The speculations of Laplace were different. He im- agined the solar orb to be a mass of fire, and the violent effer- vescences and explosions seen on its surface, to be occasioned by the eruption of elastic fluids, formed in its interior, and the spots to be enormous caverns, like the craters of our volcanoes. Others have conjectured that these spots are the tops of solar mountains, which are sometimes left uncovered by the luminous fluid in which they are immersed. 338. Among all the conflicting theories that have been advanced, respecting the physical constitution of the Sun, there is none entirely free from objection. The prevailing one seems to be, that the lucid matter of the Sun is neither a liquid sub- stance, nor an elastic fluid, but that it consists of luminous clouds, floating in the Sun's atmosphere, which extends to a great distance, and that these dark spots are the opaque body of the Sun, seen through the openings in his atmosphere. Her- schel supposes that the density of the luminous clouds need not be greater than that of our Aurora Borealis, to produce the effects with which we are acquainted. 339. The similarity of the Sun to the other globes of Jie sys- tem, in its supposed solidity, atmosphere, surface diver' Jed with mountains and valleys, and rotation upon its axis, has .ed to the conjecture that it is inhabited, like the planets, by beings whose organs are adapted to their peculiar circumstances. Such was the opinion of the late Dr. Herschel, who observed it unremit- tingly, with the most powerful telescopes, for a period of fifteen years. Such, too, was the opinion of Dr. Elliot, who attributes to it the most delightful scenery ; and, as the light of the Sun is eternal, so, he imagined, were its seasons. Hence he infers that this luminary offers one of the most blissful habitations for intelligent beings of which we can conceive. 887. Laplace's speculations? What other opinions? 838. Is there a satisfactory theory of the physical nature of the Sun? State the prevailing ( ne ? Herschel's suppo- sition? 839. What conjecture in regard to the inhabitants of the Sun, and UJKII what ft unded? Who held to this idea? THE PRIMARY PLANETS MERCURY AND VENUS. H7 CHAPTER III. THE PRIMARY PLANETS MERCURY AND VENUS. 340. MERCURY is the nearest planet to the Sun that has yet been discovered^, and with the exception of the asteroids, is the smallest. Its diameter is about 3,000 miles. Its bulk, therefore, is about sixteen times less than that of tlic Earth. It would require more than twenty millions of such globes to compose a body equal to the Sun. Here the student should refer to the diagrams, exhibiting the relative magnitudes and distances of the Sun and Planets, Map I. And whenever this subject recurs in the course of this work, the student should rmir to the figures of thi Map, until he is able to form in his mind distinct conceptions ot tne relative magnitudes and distances of all the planets. The Sun and planets being spheres, or nearly so, their relative bulks are esti- mated by comparing the cubes of their diameters: thus, the diameter of Mercury being 8,140 miles, and that of the Earth 7,912 ; their bulks are as the cube of 3,140, to the cube of 7,912, or as 1 to 16, nearly. 341. Mercury revolves on its axis from west to east in 24 hours, 5 minutes, and 28 seconds ; which makes its day about 10 minutes longer than ours. It performs its revolution about the Sun in a few minutes less than 88 days, and at a mean dis- tance of nearly 37,000,000 of miles. The length of Mercury's year, therefore, is equal to about three of our months. The rotation of a planet on its axis, constitutes its day ; its revolution about the Sua constitutes its year. 342. Owing to the dazzling brightness of Mercury, the swift- ness of its motion, and its nearness to the Sun, astronomers have made but comparatively few discoveries respecting it. When viewed through a telescope of considerable magnifying power, it exhibits at different periods all the various phases of the Moon ; except that it never appears quite full, because its enlightened hemisphere is never turned directly towards the Earth, only when it is behind the Sun, or so near to it as to be hidden by the splendor of its beams. Its enlightened hemisphere being thus always turned towards the Sun, and the opposite one being always dark, prove that it is an opaque body, similar to the Earth, shining only in the light which it receives from the Sun. 343. Mercury is not only the most dense of all the planets, but receives from the Sun six and a half times as much light arid 840. Subject of Chapter III.? Size and position of Mercury? What map illustrate* this subject? 841. State the time of Mercury's revolution upon his axis? How does tlt.'i compare with the Earth? lli.s period of revolution around the Sun ? 842. What said of discoveries upon Mercury, his phases, &c. ? What proof that he is opaque? 178 ASTRONOMY. beat as the Earth. The truth of this estimate, of course, depends upon the supposition that the intensity of solar light and heat at the planets, varies inversely as the squares of their dis- tances from the Sun. PHILOSOPHY OF TUK DIFFUSION OF LIGHT. TBIT In this diagram the light is seen passing in right lines, from the sun on the left toward the several planets on the right. It is also shown that the surfaces A, B, anil C receive equal quantities of light, though B is four times, and C nine times as large as A; and as the light falling upon A is spread over four times as much surface at B, and nine times as much at 0, it follows that it is only one-ninth as intense at C, and one-fourth at Pi, as it is at A. Hence the rule, that the light and heat oft fa planet is, inversely^ (istlies present century. The dark line running east and west across the Sun's center represents the plane of the ecliptic, and the dotted lines the apparent paths of Mercury in the several transits. The planet is shown at its nearest point to the Sun's center. Its path in the last transit and in the next will easily be found. The last transit of Mercury was observed in this country by Pro- fessor Mitchel, - at the Cincinnati Observatory, and by many others both in America and in Europe. The editor had made all necessary preparation for observing the phe- nomenon at his residence, near Oswego, New York ; but, unfor- tunately, his sky was overhung with clouds, which hid the sun from his view, and disappointed all SOUTH his hopes. 353. By comparing the mean motion of any of the planets with the mean motion of the Earth, we may readily determine the periods in which they will return to the same points of their orbit, and the same positions with respect to the Sun. The knowledge of these periods will enable us to determine the hour when the planets rise, set, and pass the meridian, and in general all the phenomena dependent upon the relative position of the Earth, the planet and the Sun ; for at the end of one of these periods they commence again, and all recur in the same order. We have only to find a number of sidereal years, in which the planet completes exactly, or very nearly, a certain number of revolutions; that is, to find such a number tt planetary revolutions, as, when taken together, shall be exactly equal to one, or any lumber of revolutions of the Earth. In the case of Mercury this ratio will be as 87.969 e to 305.256. Whence find that, node montlw of a planet? The node months of Mercury? 852. When did the last transit of Mercury occur? When will the next take place? What others during the present century? What said of the last transit of Mercury? 858. How may we deter- loine when *n>nsi^ will occur ? What ratio is found between the revolutions of Mercury ASTRONOMY. 7 periodical revolutions of the Earth are equal to 29 of Mercury : 13 periodical revolutions of the Earth are equal to 54 of Mercury: 83 periodical revolutious of the Earth are equal to 137 of Mercury : 46 periodical revolutions of the Earth are equal to 191 of Mercury. Therefore, transits of Mercury, at the same node, may happen at intervals of 7, 13, 33, 46, &c. years. Transits of Venus, as well as eclipses of the Sun and Moon, are calculateu upon the same principle. The following is a list of all the Transits of Mercury from the time the first was observed by Gassendi, November 6, 1631, to the end of the present century : 1631 Nov. 6. 1644 Nov. 6. 1651 Nov. 2. 1661 May 8. 1664 Nov. 4. 1674 May 6. 1677 Nov. 7. 1690 Nov. 9. 1697 Nov. 2. 1707 May 5. 1710 Nov. 6. 1723 Nov. 9. 1736 Nov. 10. 1740 Nov. 2. 1743 Nov. 4. 1753 May 5. 1756 Nov. 6. 1769 Nov. 9. 1776 Nov. 2. 1782 Nov. 12. 1786 May 3. 1789 Nov. 5. 1799 May 7. 1802 Nov. 8. 1815 Nov. 11. . 1822 Nov. 4. 1832 May 5. 1835 Nov. 7. 1845 May 8. 1848 Nov. 9. 1S01 Nov. 11. 1S68 Nov. 4. "1878 May 6. 1881 Nov. 7. 1891 May 9. 1894 Nov. 10. 354. The sidereal revolution of a planet respects its absolute motion ; and is measured by the time the planet takes to revolve from any fixed star to the same star again. The synodical revo- lution of a planet respects its relative motion ; and is measured by the time that a planet occupies in coming back to the same position with respect to the Earth and the Sun. SIDEREAL AHD SYNOWO REVOLUTIOKS. In the adjoining cut the revolution of _,- ' "**"".. the Earth from A, opposite the star 1!, .."' around to the same point again, would be a sidereal revolution. Suppose the Earth and Mercury to start together from the points A (where Mer- cury would be in inferior conjunction with the Sun), and to proceed in the direction of the arrows. In 88 days Mercury would come around to the same point again ; but as the Earth requires more than four times that number of days for a revolu- tion, she will only have reached the point D when Mercury arrives at C again; so that they will not be in conjunction, and a synodic revolution will not be completed by Mercury. He starts on, however, in hiss second round, and constantly gaining upon the Earth, till in 27 days from the time he left C the second time, he over- takes the Earth at E and F, and is again in inferior coiyunction. SVom this illustration, it will be seen that the synodic revolution of a planet must always require more time than the sidereal. 355. The absolute motion of Mercury in its orbit is 109,757 miles an hour ; that of the Earth is 68,288 miles ; the differ- ence, 41,469 miles, is the mean relative, motion of Mercury, with respect to the Earth. The sidereal revolution of Mercury is 87d. 23h. 15m. 44s. Its synodical revolution 13 and the Enrth? 354. What is a sidereal revolution of a planet? A synodical 1 855. What is the absolute motion of Mercury in his orbit? What is that of the Earth? The difference, or relative motion of Mercury? What is b,js $ider*ql period? Hi* tyiwdicf IJ'W is the lattsr ascertained? THE PRIMARY PLANETS MERCURY AND VENUS. 1S3 found by dividing the wh< fe circumference of 360 by its relative motion in respect to the Earth. Thus, the mean daily motion of Mercury is 14732". 555; that of the Earth is 8543".318 ; and their difference is 111S4".237, being Mercury's relative motion, or what it gains on the Earth every day. Now by simple proportion, 111S4".237 ia to 1 day, as 3oO* is to 115d. 21 h. 3', 24", the period of a synodical revolution of Mercury. VENUS. 356. There are bat few persons who have not observed a beautiful star in the west, a little after sunset, call the evening star. This star is Terms. It is the second planet from the Sun. It is the brightest star in the firmament, and on this account easily distinguished from the other planets. If we observe this planet for several days, we shall find that it does not remain constantly at the same distance from the Sun, but that it appears to approach, or recede from him, at the rate of about three-fifths of a degree every day ; and that it is some- times on the east side of him, and sometimes on the west, thus continually oscillating backwards and forwards between certain limits. 357. As Venus never departs quite 48 from the Sun, it is never seen at midnight, nor in opposition to that luminary ; being visible only about three hours after sunset, and as long before sunrise, according as its right ascension is greater or less than that of the Sun. At first, we behold it only a few minutes after sunset ; the next evening we hardly discover any sensible change in its position ; but after a few days, we perceive that it has fallen considerably behind the Sun, and that it continues to depart farther and farther from him, setting later and later every evening, until the distance between it and the Sun is equal to a little more than half the space from the horizon to the zenith, or about 46. It now begins to return toward the Sun, making the same daily progress that it did in separating from him, and to set earlier and earlier every succeeding evening, until it finally sets with the Sun ; and is lost in the splendor of his light. 358. A few days after the phenomena we have now described, we perceive, in the morning, near the eastern horizon, a bright star which was not visible before. This also is Venus, which is now called the morning star. It departs farther and farther from the Sun, rising a little earlier every day, until it is seen 85(5. Describe Venus. What called? Distance from the Sun? What change of posi- tion observable ? 857. Greatest distance to which she departs from the Sim? What ioiisequence ' How and wheii ?ecn? 858. \Vhut next after thee phenomena? 184 ASTRONOMY. about 46 west of him, where it appears stationary for a few days ; then it resumes its course towards the Sun, appearing later and later every morning, until it rises with the Sun, and we cease to behold it. In a few days, the evening star again appears in the west, very near the setting sun, and the same phenomena are again exhibited. Such are the visible appear- ances of Yenus. 359. Yenus revolves about the Sun from west to east in 224| days, at the distance of about 69,000,000 of miles, moving in her orbit at the rate of 80,000 miles an hour. She turns around on her axis once in 23 hours, 21 minutes, and 7 seconds. Thus her day is about 25 minutes shorter than ours, while her year is equal to 7|- of our months, or 32 weeks. 360. The mean distance of the Earth from the Sun is estimated at 95,000,000 of miles, and that of Yenus being 69,000,000, the diameter of the Sun, as seen from Yenus, will be to his diameter as seen from the Earth, as 95 to 69, and the surface of his disc as the square of 95 to the square of 69, that is, as 9025 to 4761, or as 2 to 1, nearly. The intensity of light and heat being inversely as the square of their distances from the Sun (No. 342), Yeiius receives twice as much light and heat as the Earth. 361. The orbit of Yenus is within the orbit of the Earth ; for if it were not, she would be seen as often in opposition to the Sun, as in conjunction with him ; but she was never seen rising in the east while the Sun was setting in the west. Nor was she ever seen in quadrature, or on the meridian, when the Sun was either rising or setting. Mercury's greatest elongation being about 23 from the Sun, and that of Yenus about 46, the orbit of Yenus must be outside of the orbit of Mercury. 362. The diameter of Venus is about 7.900 miles; blither apparent diameter and brightness are constantly varying, accord. ing to her distance from the Earth. When Yenus and tho Earth are on the same side of the Sun, her distance from th Earth is only 26,000,000 of miles ; when they are on opposite sides of the Sun, her distance is 164,000,000 of miles. Were the whole of her enlightened hemisphere turned towards us, when she is nearest,, she would exhibit a light and brilliancy 859. What is Venus' sidereal period? Distance from the Sun? Rate of motion ? Time of rotation upon her axis? How, then, do her day and year compare with ours? 800. How must the Sun appear from Venus, and why? What of her light and heat! 861. Where Is the orbit of Venus situated? What proof of this? 362. Venus' diame- ter? H'jr apparent diameter? State her least and greatest distances from the Earth THE PRIMARY PLANETS MERCURY AND VENUS. 185 twenty-five times greater than she generally does, and appear like a smaU brilliant moon ; but, at that time, her dark hemi- sphere is turned towards the Earth. When VenUo approaches nearest to the Earth, her apparent, or observed diameter is 61".2; when most remote, it is only 9". 6 ; now 61".2-i-ir.6=6?-8. hence when nearest the Earth her apparent diameter is 6? g times greater than when most distant, and surface of her disc (,4)- or nearly 41 times greater. In this work, the apparent size of the heavenly bodies is estimated from the apparent surface of their discs, which is always proportional to the squares of their apparent diameters. 363. Mercury and Venus are called Interior planets, because their orbits are within the Earth's orbit, or between it and the Sun. The other planets are denominated Exterior, because their orbits are without or beyond the orbit of the Earth. (Map I.) As the orbits of Mercury and Yenus lie within the Earth's orbit, it is plain, that once in every synodical revolution, each of these planets will be in conjunction on the same side of the Sun. In the former case, the planet is said to be in its inferior conjunc- tion, and in the latter case, in its superior conjunction ; as in the following tigure. MARS IN CONJUNCTION --... 8 MARS IN OPPOSITION Let the student imagine him- self stationed upon the earth in the cut. Then the sun and three planeta above are in conjunc- tion. The inferior and supe- rior are distinguished ; while at A, a planet is shown in quaf.lrd- ture, and at the bottom of the cut the planet Mars in opposi- tion with the sun and interior planet. The period of Venus' synodi- cal revolution is found in the same manner as that of Mer- cury ; namely, by dividing the whole circumference of her orbit by her mean relative motion in a day. Thus, Venus' absolute mean daily motion is 1 36' 7".S, the Earth's is 59' S".3, and their difference u, 36' 51T.5. Divide 860 by 36' 59".5, and it gives 5S3.920, or nearly 584 days fur Venus' synodical revolution, or the period in which she is twice in conjunction with the Eurth. 364 When Yenus' right ascension is less than that of the Sun, she rises before him ; when greater, she appears after his setting. She continues alternately morning and evening star, for a period of 292 days, each time. How would she appear if we saw her enlightened side when nearest to us? What com- putation in the fine print? 863. How are Mercury and Venus distinguished, and why? What said of conjunctions f Describe the inferior and superior t How is the period of Venus' synodieai revolution found? 864. When is Venus evening star? Morning? 186 ASTRONOMY. To those -ilio are but little acquainted with astronomy, it will seem strange, at first, that Venus should apparently continue longer on the east or west side of the Sun, than the whole time of her periodical revolution around him. But it will be easily understood, when it is considered, that while Venus moves around the Sun, at the rate of about 1* 36' of angular motion per day, the Earth follows at the rate of 59' ; so that Venus actually gains on the Earth, only 37' in a day. Now it is evident that both planets will appear to keep on the same side of the Sun, until Venus has gained half her orbit, or 180 in advance of the Earth; and this, at a mean rate, will require 292 days, since 292 x 37' = 10304', or 180 nearly. 365. Terms passes from her inferior to her superior conjunc- tion in about 292 days. At her inferior conjunction, she is 26,000,000 of miles from the Earth ; at her superior conjunc- tion, 164,000,000 of miles. It might be expected that her bril- liancy would be proportionally increased, in the one case, and diminished in the other ; and so it would be, were it not that her enlightened hemisphere is turned more and more from us, as she approaches the Earth, and comes more and more into view as she recedes from it. It is to this cause alone that \\e must attribute the uniformity of her splendor, as it usually appears to the naked eye. 366. Mercury -and Yenus present to us, successively, the various shapes and appearances of the Moon ; waxing and waning through different phases, as shown in the following cut, from the beautiful crescent to the full rounded orb. This fact shows, that they revolve around the Sun, and between the Sun and the Earth. PHASES OF VESUS AS SHE REVOLVES AROCKD It should be remarked, however, that Venus is never seen when she is entirely/W, except once or twice in a century, when she passes directly over the Sun's disc. At every other conjunction, she is either behind the Sun, or so near him as to be hidden by the splendor of his light. The preceding diagram better illustrates the various appear- ances of Venus, as she moves around the Sun, than any description of them could do. 367. From her inferior to her superior conjunction, Venue, appears on the west side of the Sun, and is then our morning How long each? How is it that Venus is east or west of the Sun 292 days, when her periodic revolution is performed in about 225 days? 365. What is the time from one conjunction of Venus to another ? Is her brilliancy in proportion to her nearness? Why not? 366. What phases do Mercury and Venus exhibit, and what do they prove? Are they ever seen entirely fullf 8C7. When is Venus morning star? When evening" THE PRIMARY PLANETS MERCURY AND VENUS. 187 star ; from her superior to her inferior conjunction she appears on the east side of the Sun, and is then our evening star. These phenomena are illustrated by the following diagram. VENUS AS MORNING AND EVENING STAR. Let the student hold the book up south of him, and he will at once see why Venns is alternately morning and evening star. Let the plane A B represent the sensible or visi- ble horizon, C D the apparent daily path of the Sun through the heavens, and K the Earth in her apparent position. The Sun is shown at three different points namely, rising in the east, on the meridian, and setting in the west; while Venus is seen revolving around him from west to east, or in the direction of the arrows. Now it is obvious that when Venus is at F, or went of the Sun, she sets before him as at G, and rises before him as at H. She must, therefore, be morning star. On the other hand, when she is edt of the Sun, as at J, she lingers in the west after the Sun has gone down, as at K T and is consequently evening xtar. In this cut, Venus would be at her greatest elongation eastward at J, and tcextward at F, HIM! in both cases would be "stationary." At L and M she would be iu conjunc- tion with the Sun. Were the earth to suspend her daily rotation, with the Sun on the meridian of th i ; observer, as represented at L, we might readily watch Venus through her whole circuit around the Sun. 368. Like Mercury, Yenus sometimes seems to be stationary. Her apparent motion, like his, is sometimes rapid ; at one time, direct, and at another, retrograde; vibrating alternately back- wards and forwards, from west to' east, and from east to west. These vibrations appear to extend from 45 to 47, on each side of the Sun. Consequently she never appears in the eastern horizon more than three hours before sunrise, nor continues \onger in the western horizon after sunset. Any star or planet therefore, however brilliant it may appear, which is seen earlier or later than this, cannot be Venus. 369. In passing from her western to her eastern elongation, 269. Is she ever stationary? AVhat other irregularities in her apparent motion? 869. When is her motion direct? When retrograde? When most rapid? When 188 ASTRONOMY. her motion is from west to east, in the order of the signs; it is thence called direct motion. In passing from her eastern to her western elongation, her motion with respect to the Earth is from east to west, contrary to the order of the signs ; it is thence denominated retrograde motion. Her motion appears quickest about the time of her conjunctions ; and she seems sta- tionary at her elongations. She is brightest about thirty-six days before and after her inferior conjunction, when her light is so great as to project a visible shadow in the night, and some- times she may be seen with the naked eye even at noon-day. DIRECT AND RKTROGSADK MOTIONS. The cause of the apparent re- trogression of the interior planets is the fact that they revolve much more rapidly than the earth, from \which we view them ; causing \ / their direct motion to appear to \ / be retrograde. Suppose the earth to be at A, and Venus at B, she would appear to be at C, among the stars. If the earth remained at A while Venus was passing from B to D, she would seem to retrograde from C to E; but as the earth passes from A to F while Venus goes from B to D, Venus will appear to be at G ; and the amount of her apparent westward motion will only be from C to G. 370. If the orbit of Venus lay exactly in the plane of the Earth's orbit, she would pass centrally across the Sun's disc, like a dark round spot, at every inferior conjunction ; but, as one-half of her orbit lies about 3^ above the ecliptic, and the other half as far below it, she will always pass the Sun a very little above or below it, except when her inferior conjunction happens in, or near one of her nodes ; in which case she will make a transit. (See cuts, pages 179 and 180.) This phenomenon, therefore, is of very rare occurrence ; it can happen only twice in a century ; because it is only twice in that time that any number of complete revolutions of Venus are just or nearly equal to a certain number of the Earth's revolutions. The principle which was illustrated in predicting the transits of Mercury, applies equally well to those of Venus ; that is, we must find such sets of numbers (representing brightest? State the cause of the apparent retrograde motion? 370. Why have we not i transit at every revolution of Venus? How frequent, therefore? How predicted! When do her nodes cut th ecliptic? THE PR' MARY PLANETS MERCURY AND VENUS. 181) complete revolutions of the Earth and Venus) as shall be to each other in the ratio cf their periodical times, or as 365.256 is to 224.7. Thus : the motion of Venus, in the Julian years, is 21o659r.52; that of the Earth for the same period being 129627".45, the ratio will be V^W^V ''ft' As the two terms of this fraction cannot be reduced by a coir, tnon divisor, we must multiply them by such numbers as will make one a multiple of th other; accordingly, 13 times the denominator will be nearly equal to 8 times the nume- rator ; and 475 times the denominator will equal 291 times the numerator. By combining these two periods and their multiples by addition and subtraction, we shall obtain the period of all the transits that have ever happened. Thus : 291 S x 7=2:35, another period ; and 2916 x 8=243, another period, and so on. Whence we find that 8 periodical revolutions of the Earth are equal to 18 of Venus : 235 periodical revolutions of the Earth are equal to 382 of Venus: 243 periodical revolutions of the Earth are equal to 395 of Venus: 251 periodical revolutions of the Earth are equal to 408 of Venus : 291 periodical revolutions of the Earth are equal to 475 of Venus. Hence a transit of Venus may happen at the same node, after an interval of S years, but if it do not happen then, it cannot take place again at the same node, in less than 235 years. The orbit of Venus crosses the ecliptic rear the middle of Gemini and Sagit- tarius; and these points mark the position of her nodes. At present, her ascending node is in the 14th degree of Gemini, and her descending node in the same degree of Sagit- tarius. 371. The node months of Venus are December and Jane. The line of her nodes lies in Gemini ( n ) and Sagittarius ( ) ; and as the Earth always passes those points in the mouths named, it follows that all transits of Venus must occur in those months for ages to come. This proposition will be well understood by consulting the cut on page Q% ; for as the line of Venus' nodes is only one sign ahead of that of Mercury, the Earth will reach that ]>omt in the ecliptic in one month after she passes the line of Mercury's nodes; so that if his transits occur in May and November, hers should occur in June and December, as In always the case. 272. The first transit ever known to have been seen by any human being, took place at the ascending node, December 4th, 1639.* If to this date we add 235 years, we shall have the * This phenomenon was first witnessed by Horrox, a young gentleman about 21 years of age, living in an obscure village 15 miles north of Liverpool. The tables of Kepler, constructed upon the observations of Tycho Brahe, indicated a transit of Venus in 1C31, but none was observed. Horrox, without much assistance from books and instruments, set himself to inquire into the error of the tables, and found that such a phenomenon might be expected to happen in 1639. He repeated his calculations during this interval, with all the carefulness and enthusiasm of a scholar ambitious of being the first to predict and observe a celestial phenomenon, which, from the creation of the world, had never been witnessed. Confident of the result, he communicated his expected triumph to a confidential friend residing in Manchester, and desired him to watch for the event, and to take observations. So anxious was Horrox not to fail of witnessing it himself, that he commenced his observations the day before it was expected, and resumed them at the rising of the Sun on the morrow. liut the very hour when his calculations led him to expect the visible appearance of Venus on the Sun's disc, wntt also the appointed hour for the, public -tco^ufdp of God on the Sabbath. The delay of a few minutes might deprive him for ever of an opportunity of observing the transit. If its very commence- ment were not noticed, clouds might intervene, and conceal it until the Sun should set: a. id nearly a century and a half would elapse before another opportunity would occur. He had l>een waiting for the event with the most ardent anticipation for eight years, and the result promised much benefit to the science. Noticithxtawlhig all Mi*, Hnrrof tu-ice (tuxpended his observation* and twice repaired to the House of God, the Great Author of the bright works he delighted to contemplate. When his duty was thus per- 871. "Which are her node months? 872. When was the first transit observed * What interesting anecdote? 130 ASTRONOMY. time of the next transit at the same node, which will accordingly happen in 1874. There will be another at the same node in 1882, eight years afterwards. It is not more certain that this phenomenon will recur, than that the event itself will engross the attention of all the astronomers then living upon the Earth. It will be anticipated, and provided for, and observed, in every inhabited quarter of the globe, with an intensity of solicitude which no natural phenomenon, since the creation, has ever excited. 373. The reason why a transit of Yenus should excite so great an interest is, because it may be expected to solve an important problem in astronomy, which has never yet been satisfactorily done : a problem whose solution will make known to us the magnitudes and masses of all the planets, the true dimensions of their orbits, their rates of motion around the Sun, and their respective distances from the Sun, and from each other. It mny be expected, in short, to furnish an universal standard of astro- nomical measure. Another consideration will render the obser- vation of this transit peculiarly favorable ; and that is, astrono- mers will be supplied with better instruments, and more accurate means of observation, than on any former occasion. So important, says Sir John Herschel, have these observations appeared to astronomers, that at the last transit of Venus, in 1769, expeditions were fitted out, on the most efficient scale, by the British, French, Russian, and other governments, to the remotest corners of the globe, for the express purpose of making them. The celebrated expedition of Captain Cook to Otaheite, was one of them. The general result of all the observations made on this most memorable occasion, gives 8" .5776 for the Sun's horizontal parallax. 374. The phenomena of the seasons of each of the planets, like those of the Earth, depend upon the inclination of the axis of the planet to the plane of its orbit, and its revolution around the Sun. The inclination of the axis of Venus to the plane of her orbit, though not precisely known, ia commonly estimated at 75, as represented to the eye in the following cut : formed, and he had returned to his chamber the second time, his love of science was gratified with full success ; and he saw what no mortal eye had observed before ! If anything can add interest to this incident, it is the modesty with which the young astronomer apologizes to the world, for #U#jjendifiy his observations at all. "I observed it," says he, "from sunrise till nine o'clock, again a little before ten, ard lastly at noon, and from one to two o'clock ; the rest of the day being devoted to higher duties, which might not be neglected for these pastimes." When the next? When another ? How will it be regarded? 87-3. Why should such an event excite general interest? Remark cf Sir John Herschel ? What expedition and what results? 374. Upon what do the se tsons of the planets depend? What is the inclination of Venus' axis tc the piane ler orbit? How is her orbit situated with reference to the ecliptic? THE PRIMARY PLANETS MERCURY ANb VENUS. 191 WCUJUTION OF VKNU3' A XII. The orbit of Venus departs from the ecliptic 8J$% while her axis is inclined to the plane of her orbit 75", as shown in the above figure. This distinction should be kept definitely in view by the student. 375. The declination of the Sun on each side of Yenus' equa- tor, must be equal to the inclination of her axis ; and if this extends to 75, her tropics are only 15 from her poles, and her polar circles only 15 from her equator. It follows, also, that the Sun must change his declination more in one day at Yenus, than in five days on the Earth ; and, consequently, that he never shines vertically on the same places for two days in succession This may, perhaps, be providentially ordered, to prevent the too great effect of the Sun's heat, which, on the supposition that it is in inverse proportion to the square of the distance, is twice as great on this planet as it is on the Earth. 376. At each pole of Yenus, the Sun continues half of her year without setting in summer, and as long without rising in winter ; consequently, her polar inhabitants, like those of the Earth, have only one day and one night in the year ; with this difference, that the polar days and nights of Yenus are not quite two-thirds as long as ours. Between her polar circles, which are but 15 from her equator, tli ere are two winters, two summers, two springs, and two autumns, every year. But because the Sun stays for some time near the tropics, and passes so quickly over the equator, the win- ters in that zone will be almost twice as long as the summers. The north pole of Yenus' axis inclines towards the 20th degree oJ Aquarius ; the Earth's towards the beginning of Can- cer ; consequently, the northern parts of Yenus have summer in the signs where those of the Earth have winter, and vice versA. 377. When viewed through a good telescope, Yenus exhibits not only all the moon-like phases of Mercury, but also a variety of inequalities on her surface ; dark spots, and brilliant shades, hills and valleys, and elevated mountains. But on account of 375. What is the amount of the Sun's declination upon Venus ? What resu'ts ? What supposed design in this arrangement? 376. What said of the polar regions of Venus f What of her seasons? How is her north pole situated with respect to the heaveu*? What consequence? 817. llow does Yenus appear through a telescope-* 192 ASTRONOMY. the great density of her atmosphere, these inequalities arc per- ceived with more difficulty than those upou the other planets. 378. The mountains of Yenus, like those of Mercury and th? Moon, are highest in the southern hemisphere. According to M. Schroeter, a celebrated German astronomer, who spent more than ten years in observations upon this planet, some of her mountains rise to the enormous height of from ten to twenty- two miles. The observations of Dr. Herschel do not indicate so great an altitude ; and he thinks, that in general they are con- siderably overrated He estimates the diameter of Venus at 8649 miles ; making her bulk more than one-sixth larger than that of the Earth. Several eminent astronomers affirm, that they have repeatedly seen Yenus attended by a satellite, and they have given circumstantial details of its size and appearance, its periodical revolution and its distance from her. It is said to resemble our Moon in its phases, its distance, and its magnitude. Other astronomers deny the existence of such a body, because it was not seen with Yenus on the Sun's disc, at the transits of 1761 and 1769. It probably does not exist. THE EARTH. 379. The Earth is the place from which all our observations of the heavenly bodies must necessarily be made. The apparent motions of these bodies being very considerably affected by her ligure, motions, and dimensions, these hold an important place in astronomical science. It will, therefore, be proper to consider, first, some of the methods by which they have been determined. If, standing on the sea-shore, in a clear day, we view a ship leaving the coast, in any direction, the hull or body of the vessel Why less distinct than the other planets? 878. Where are her highest mountains Jituated? Their height ? Remark of Dr. Herschel ? His estimate of Venus' diameter ? What said about a satellite around Venus? 379. Relation of the earth to the other planets in the study of astronomy? What necessary, therefore? What proof of th convexity of her surface? THE PRIMARY PLANETS THE EARTH. 193 first disappears ; afterwards the rigging, and lastly the top of the mast vanishes from our sight. CONVKXITT OF TUB EARTH'S Sr/HFlCB. Here the observer upon the shore at A sees only the topmasts of the ship, whi.e the maft standing upon the pillar at B sees the masts and sails, and part of the hull. Now, if the water between A and the ship were exactly flat instead of convex, the vision of A would extend along the line C, and he could see the whole ship as well as B. The advan- tage of B over A, in consequence of hia elevation, shows that the surface of the water is convex between A and the ship. 380. Again : navigators have sailed quite around the Earth, and thus proved its convexity. CONVEXITY OF THE EARTH'S SURFACE. Ferdinand Magellan, a Portuguese, was the first who carried this enterprise into execution. Jle embarked from Seville, in Spain, and directed his course towards the west. After a long voy- age, he descried the continent of America. Not finding an opening to enable him to continue his course in a westerly direction, he sailed along the coast towards the south, till, coming to its south- ern extremity, he sailed around it, and found himself in the great Southern Ocean. He then resumed his course towards the west. After some time he arrived at the Molucca Islands, in the Edntern Hem ixpJiere ; and sailing con- tinually towards the west, he made Europe from the east, arriving at the place from which he set out.* The next who circumnavigated the Earth was Fir Francis Drake, who sailed from Plymouth, December 18, 1577, with five small vessels, and arrived at the same place, September 26, 1580. Since that time, the circumnavigation of the Earth has beeii performed by Cavendish, Cordes, Noort, Sharten, Heremites, Dampier, Woodes, Rogers, Schovten, Roggewin, Lord Ar.sou, Byron, Carteret, Wallis, Bougainville, Cook, King, Clerk, Vancouver, and many others. 381. These navigators, by sailing in a westerly direction, allowance being made for promontories, &c., arrived at the coun- try they sailed from. Hence the Earth must be either cylindri- cal or globular. It cannot be cylindrical, because, if so, the meridian distances would all be equal to each other, which is * Magellan sailed from Seville, in Spain, August 10, 1519, in the ship called the Victory, accompanied by four other vessels. In April, 1521, he was killed in a skirmish with the natives, at the island of /Sebu, or Zebu, sometimes called Matan, one of the Philippines. One of his vessels, however, arrived at St. Lucar, near Seville, September 7, 1522. 880. What secor.d proof stated ? Who first sailed around the world? Who next? 31. In what direction did they sa : l? How did these voyages prove the earth to be 194 ASTRONOMY. contrary to observation. The figure of the Earth is, therefore, spherical. 382. The convexity of the Earth, north and south, is proved by the variation in the altitude of the pole, and of the circum- polar stars ; this is found uniformly to increase as we approach them, and to diminish as we recede from them. LATITCDK FOUND BY THE NORTH STAR. Suppose an observer standing upon the Earth, and viewing the pole star from the 45 of North latitude; it would, of course, appear elevated 45 above his visible horizon. But let him recede southward, and as he passed over a degree of latitude, the pole star would settle one degree towards the horizon, or more properly, his northern horizon would be elevated one degree towards the pole star, till at length, as he crossed the equator, the North star woulc" sink below the horizon, and become invisible. Whence we derive the general rule, that the altitude of one pole, or the depression of the other, at any l,fac.e on the Earth's surface, is equal to the latitude of that place. 383. The form of the Earth's shadow, as seen upon the Moon ;n an eclipse, indicates the globular figure of the Earth, and the consequent convexity of its surface. FORM OF THE EARTH'S SHADOW. 382. What further proof have we that the earth Is spherical? What rule btaed tpon this phenomenon? 383. What other evidence that the earth is a globe What remarks respecting the curvature of the earth's surface? What rules laid down based upon this curvature ? THE PRIMARY PLANETS THE EARTH. 195 Were the Earth a cube as shown at. A, or in the form of a prism, as represented at B, her shadow would be more or less cubical or prismatic, as seen in the cut ; but instead of this, it is convex on all sides, as represented at C, plainly indicating the convexity of the Earth by which it is caused. The curvature of the Earth for one mik is 8 inches ; and this curvature Increases with the square of the distance. From this general law it will be easy to calculate the distance at which any object whose heights given, may be seen, or to determine the height of an object when the distance is known. 1st. To find the height of the object when the distance is given. RULE. Find the square of the distance in miles, and take two-thirds of that number for the height in feet. Ex. 1. How high must the eye of an observer be raised, to see the surface of the ocean at the distance of three miles? Ans. The square of 3 ft. is 9 ft., and % of 9 ft. is 6 ft. Ex. 2. Suppose a person can just see the top of a spire over an extended plain of ten miles, how high is the steeple ? Ans. The square of 10 is 100, and % of 100 ia 66 % feet. 2. To find (he distance when the height is given. RULE. Increase ttie height in feet one-half, and extract the square root, for the dis tance in milts. Ex. 1 . How far can a person see the surface of a plain, whose eye is elevated six feet above it? Ans. 6, increased by half, is 9, Snd the square root of 9 is 3: the distance is then 3 miles. Ex. 2. To what distance can a person see a lighthouse whose height is 96 feet from the level of the ocean ? Ans. 96 increased by its half, is 144, and the square root of 144, is 12; the distance is therefore 12 miles. 3. To find the curvature of the Earth when it exceeds a mile. KuLK. Multiply the square of the distance by .000126. 384. Although it appears from the preceding facts, that the Earth is spherical, yet it is not a perfect sphere. If it were, the length of the degrees of latitude, from the equator to the poles, would be uniformly the same ; but it has been found, by the most careful measurement, that as we go from the equator towards the poles, the length increases with the latitude. These measurements have been made by the most eminent mathematicians of different countries, and in various places, from the equator to the arctic circle. They have found that a degree of latitude at the arctic circle was ninj-sixteenths of a mile longer than a degree at the equator, and that the ratio of increase for the intermediate degrees was nearly as the squares of the sines of the latitude. Thus the theory of Sir Isaac Newton was confirmed, that the body of the Earth was more rounded and convex between the tropics, but considerably flattened towards the poles. Places of Observation, Latitude. Length of a degree in English miles. Observers. Peru Pennsylvania Italy France England B-reden Equator. 39 12' N. 43 01 46 51 29 54' 66 20 10 63.732 68.896 68.998 69.054 69.146 69.292 Bouguer, Mason and Dixon, Boscovich and Lemaire, Delambre and Mechain, Mudge, Swamberg. 385. These measurements prove the Earth to be an ollate spheroid, whose longest or equatorial diameter is 7926 miles, and polar diameter, 7899 miles. The mean diameter is, therefore, about 7912, and their difference 27 miles. The French Acade- 884. Cut is the earth a sphere? What proof to the contrary? 885. What, then, ! tha earth's real figure ? What difference in her polar and equatorial diameters? Waat demonstration that the earth is not an exact sphere? B.G 9 196 ASTRONOMY. my have determined that the mean diameter of the Earth, from the 45th degree of north latitude, to the opposite degree of south latitude, is accurately 7912 miles. If the Earth were an exact sphere, Its diameter might be determined by its curvature, from a single measurement. Thus, - in the adjoining figure, we have A B equal to 1 mile, and B I) / f\ equal to 8 inches, to find A E, or B E, which does not sensibly / / \ differ from A E, since B D is only 8 inches. Now it is a propo- sition of Euclid (B. 3, prop. 36), that, when from a point with- out a circle, two lines be drawn, one cutting and the other touching it, the touching line (B A) is a mean proportional be- tween the cutting line (B E) and that part of it (B D) without the circle. BD: BA: : BEorAE very nearly. That is, 1 mile being equal to 63,360 inches, 8 : 63,360 : : 1 : 7,920. miles. This is very nearly what the most elaborate calculations make the Earth's equatorial diameter. 386. The Earth, considered as a planet, occupies a favored rank in the Solar System. It pleased the All-wise Creator to assign its position among the heavenly bodies, where nearly all the sister planets are visible to the naked eye. It is situated next to Venus, and is the third planet from the Sun. To the scholar who for the first time takes up a book on astronomy, it will no doubt eem strange to find the Earth classed with the heavenly bodies. For what can appear more unlike, than the Earth, with her vast and seemingly immeasurable extent, and the stars, which appear but as points? The Earth is dark and opaque, the celestial bodies are brilliant. We perceive in it no motion ; while in them we observe a continual change of place, as we view them at different houra of the day or night, or at different seasons of the year. 387. It moves round the Sun from west to east, in 365 days, 5 hours, 48 minutes, and 48 seconds ; and turns the same way, on its axis, in 23 hours, 56 minutes, and 4 seconds. The former is called its annual motion, and causes the vicissitudes of the seasons. The latter is called its diurnal motion, and produces the succession of day and night. The Earth's mean distance from the Sun is about 95,000,000 of miles. It consequently moves in its orbit at the mean rate of 68,000 miles an hour. Its equatorial diameter being 7926 miles, it turns on its axis at the rate of 1040 miles an hour. Thus, the Earth on which we stand, and which has served for ages as the unshaken foundation of the firmest structures, is every moment turning swiftly on its center, aru, Kt the same time, moving onwards with great rapidity through the empty space. This compound motion is to be understood of the whole Earth, with all that it hold* within its substance, or sustains upon its surface of the solid mass beneath, of the ocean which flows around it, of the air that res>ts upon it. and of the clouds which float above it in the air. 336. What said of the position of the earth in the system ? "What remark as to class? fying the earth as a planet? 887. State the time of the earth's revolution around the Bun? On her own axis? What are they called, respectively ? What is the earth's mean distance from the sun? Its mean rate of motion in its orbit? Hourly motion of Vodies at the equator? What twofold motion there? Includes what? THE PRIMARY PLANETS THE EARTH. 197 388' That the Earth, iii common with all the planets, revolves around the Sun as a center, is a fact which rests upon the clear- est demonstrations of philosophy. That it revolves, like them, upon its own axis, is a truth which every rising and setting sun illustrates, and which very many phenomena concur to establish. Either the Earth moves around its axis every day, or the whole universe moves around it in the same time. There is no third opinion that can be formed on this point. Either the Earth must revolve on its axis every twenty-four hours, to produce the alternate succession of day and night, or the Sun, Moon, planets, comets, fixed stars, and the whole frame of the universe itself, must move around the Earth, in the same time. 389. To suppose the latter case to be the fact, would be to cast a reflection on the wisdom of the Supreme Architect, whose laws are universal harmony. As well might the beetle, that in a moment turns on its ball, imagine the heavens and the earth had made a revolution in the same instant. It is evident, that in proportion to the distance of the celestial bodies from the Earth, must, on this supposition, be the rapidity of their move- ments. The Sun, then, would move at the rate of more than 400,000 miles in a minute ; the nearest stars, at the inconceiv- able velocity of 1,400,000,000 of miles in a second; and the most distant luminaries, with a degree of swiftness which no numbers could express, and all this, to save the little globe we tread upon, from turning safely on its axis, once in twenty -four hours. 390. The idea of the heavens revolving about the Earth, is encumbered with innumerable other difficulties. We will men- tion only one more. It is estimated on good authority, that there are visible, by means of glasses, no less than 100,000,000 of stars, scattered at all possible distances in the heavens above, beneath, and around us. Now, is it in the least degree probable, that the velocities of all these bodies should be so regulated, that, though describing circles so very different in dimensions, they should complete their revolutions in exactly the same time? In short, there is no more reason to suppose that the heavens revolve around the Earth, than there is to suppose that they revolve around each of the other planets, separately, and at the same time ; since the same apparent revolution is common to them all, for they all appear to revolve upon their axis, in differ- ent periods. 388. What two motions has the e irth ? What proof of her diurnal revolution ? 889. Wby not suppose the heavens revolve around us ? 890. What further proof? 198 ASTRONOMY. 391. The rotation of the Earth determines the length of the day, and may be regarded as one of the most important ele- ments in astronomical science. It serves as an universal measure of time, and forms the standard of comparison for the revolu- tions of the celestial bodies, for all ages, past and to come. Theory and observation concur in proving, that among the innu- merable vicissitudes that prevail throughout creation, the period of the Earth's diurnal rotation is immutable. SOLAR AND SIDEREAL TIME. 392. The Earth performs one complete revolution on its axis hi 23 hours, 56 minutes, and 4.09 seconds, of solar time. This is called a sidereal day, because, in that time, the stars appear to complete one revolution around the Earth. But, as the Earth advances almost a degree eastward in its orbit, in the time that it turns eastward around its axis, it is plain that just one rotation never brings the same meridian around from the Sun to the Sun again ; so that the Earth requires as much more than one complete revolution on its axia to complete a solar day, as it has gone forward in that time. SOLAS AND SI&BREAL TIMK. To the man at A the Sun (S) is exactly on the meridian, or it ia twelve o'clock, noon. The Earth passes on from B to D, and at the same time revolves on her axis. When she roaches D, the man who has stood on the same meridian has made a complete revolution, as determined by the star G- (which was also on his meridian at twelve o'clock the day before) ; but the Sun is now eaat of tfte meridian, and he must wait/owr minutes for the Earth to roll a little further eastward, and bring the Sun again over his north and south Hue. If the Earth was not revolving around the Sun, her solar and sidereal days would be the same ; but ao U Is, she has to perform a little more than one complete revolution each solar day, to bring the Sun on the meridian. 393. It is obvious, therefore, that in every natural or solar day, the Earth performs one complete revolution on its axis, and the 365th part of another revolution. Consequently, in 365 days, the Earth turns 366 times around its axis. And as every 891. What relation ha* the earth's diurnal revolution to time f What said of its regu- arity ? 392. What is the time required for a complete revolution ? Explain the differ- ence between solar and sidereal time? 893. Is a solar day more than a comple** revolution of the earth on her axis? To what does this excess amount in a year? THE PRIMARY PLANETS THE EARTH. 199 revolution of the earth on its axis completes a sidereal day, there must be 366 sidereal days in a year. And, generally, since the rotation of any planet about its axis is the length of a sidereal day at that planet, the number of sidereal days will always exceed the number of solar days by one, let that number be what it may, one revolution being always lost in the course of an annual revolution. This difference between the sidereal and solar days may be illustrated by referring to a watch or clock. When both hands set out together, at 12 o'clock for instance, the minute hand must travel more than a whole circle before it will overtake the hour hand, that is, before they will come into conjunction again. 394. In the same manner, if a man travel around the Earth eastwardly, no matter in what time, he will reckon one day more, on his arrival at the place whence he set out, than they do who remain at rest ; while the man who travels around the Earth westwardly will have one day less. From which it is manifest^ that if two persons start from the same place at the same time v but go in contrary directions, the one traveling eastward and the other westward, and each goes completely around the globe, although they should both arrive again at the very same hour at the same place from which they set out, yet they will disagree two whole days in their reckoning. Should the day of their return, to the man who traveled westwardly, be Monday, to the man who travelled eastwardly, it would be Wednesday ; while to those who remained at the place itself, it would be Tuesday. 395. Nor is it necessary, in order to produce the gain or loss of a day, that the journey be performed either on the equator, or on any parallel of latitude : it is sufficient for the purpose, that all the meridians of the Earth be passed through, eastward or westward. The time, also, occupied in the journey, is equally unimportant ; the gain or loss of a day being the same, whether the Earth be traveled around in 24 years, or in as many hours. 396. It is also evident, that if the Earth turned around its axis but once in a year, and if the revolution was performed the same way as its revolution around the Sun, there would be per- petual day on one side of it, and perpetual night on the other. Hence what general rule? What illustration referred to? 894. What effect has tra- veling east or west, upon time? Hence what result? 895. Ts it important that the sup- posed journeys be performed in n short period? 896. How would it be if the Earth revolveU oo her axis but once a*year? 200 ASTRONOMY. From these facts the pupil will readily comprehend the principles involved in a curious problem which appeared a few years ago. It was gravely reported by an American ship, that, in sailing over the ocean, it chanced to find six Sundays in February. The fact was insisted on, and a solution demanded. There is nothing absurd in this. The man who travels around the earth eatttwardli/, will see the Sun go down a little earlier every succeeding day, than if he had remained at rest; or earlier than they do who live at the place from which he set out. The faster he travels towards the rising sun, the soont-r will it appear above the horizon in the morning, and so much sooner will it set in the evening. What he thus gains in time, will bear the same proportion to a solar day, as the distance traveled does to the circumference of the Earth. As the globe is 360 degrees in circumference, the Sun will appear to move over one twenty-fourth part of its surface, or 14 every hour, which is 4 minutes to one degree. Consequently, the Sun will rise. come to the meridian, and set, 4 minutes sooner, at a place 1 east of us, than it will with us; at the distance of 2 the Sun will rise and set 8 minutes sooner; at the distance of 3", 12 minutes sooner, and so on. Now the man who travels one degree to the east, the first day will have the Sun on his meridian 4 minutes sooner than we do who are at rest ; and the second day 8 minutes sooner, and on the third day 12 minutes sooner, and so on ; each successive day being completed 4 minutes earlier than the preceding, until he arrives again at the place from which he started : when this continual gain of 4 minutes a day will have amounted to a whole day in advance of our time : he having seen the Sun rise and set once, more than we have. Consequently, the day on which he arrives at home, whatever day of the week it may be, is one day in advance of ours, and he must needs live that day over again, by calling the next day by the same name, in order to make the accounts harmonize. If this should be the last day of February in a bissextile year, it would also be the same day of the week that the Jlrst was, and be six times repeated, and if it should happen on Sunday, he would, under these circumstances, have six Sundays in February. Again : whereas the man who travels at the rate of one degree to the east, will have all his days 4 minutes shorter than ours, so, on the contrary, the man who travels at the same rate towards the west, will have all his days 4 minutes longer than ours. When he has finished the circuit of the Earth, and arrived at the place from which he first set out, he will have seen the Sun rise and set once fcMth&a we have. Consequently, the day he gets home will be one day after the time at that place; for which reason, if he arrives at home on Saturday, according to his own account, he will have to call the next day Monday ; Sunday having gone by before he reached home. Thus, on whatever day of the week January should end, in common years, he would find the same day repeated only three times in February. If January ended on Sunday, he would, under these cir- cumstances, find only three Sundays in February. 397. The Earth's motion about its axis being perfectly equable and uniform in every part of its annual revolution, the sidereal days are always of the same length, but the solar or natural days vary very considerably at different times of the year. This varia- tion is owing to two distinct causes, the inclination of the Earth's axis to its orbit, and the inequality of its motion around the Sun. From these two causes it is, that the time shown by a well-regu- lated clock and that of a true sun-dial are scarcely ever the same. The difference between them, which sometimes amounts to 16^ minutes, is called the Equation of Time, or the equation of solar days. What curious facts accounted for ? What supposition of a man traveling eastward one degree a day? What effect upon the time of the Sun's passing the meridian? Upon the lengiti of his daj ? What change of name may it require ? 897. Are the solar and sidereal days alik s uniform as to length ? Why do solar days vary in length? Wliy do not a dial and cluck agree ? What is the Equation of Time t THE PRIMARY PLANETS THE EARTH 20 1 EQUATION OF TIMB The difference between N mean and apparent time, or, in other words, between Equinoctial and Ecliptic time, may be further shown by this figure, which repre- sents the circles of the sphere Let it be first pre- mised, that equinoctin F Remarks respecting this phenomenon f THE M00> HER MOTIONS, PHASES, ETC. 209 MOON'S REVOLUTION. t 415. Th? Moon revolves once on her axis exactly in the time that she performs her revolution around the Earth. This is evi- dent from Ler always presenting the same side to the Earth for if she had no rotation upon an axis, every part of her surface would be presented to a spectator on the Earth, in the course of her synodical revolution. It fol- lows, then, that there is but one day and night in her year, containing, both together, 29 days, 12 hours, 44 minutes, and 3 seconds. Suppose a monument erected upon the Moon's surface, so as to point toward the Earth at New Moon, AS represented at A. From the Earth it would appear in the Moon's center. Now if the Moon so revolve upon her axis, in the direction of the arrows, as to keep the pillar pointing directly toward the Earth, as shown at A, B, C, and D, and the intermediate points, she must make just one revolution on her axis during her periodic revolu- tion. At A, the pillar points from the Sun, and at C toward him : showing that, in going half-way round the Earth, she has performed half a revolu- tion upon her axis. 416. Though the Moon always presents nearly the same hemi- sphere toward the Earth, it is not always precisely the same. Owing to the ellipticity of her orbit, and the consequent inequality of her angular velocity, she appears to roll a little on her axis, first one way and then the other thus alternately revealing and hiding new territory, as it were, on her eastern ami west- ern limbs. This rolling motion east and west is called her libration in longitude. MOOX'S UBRATION. f> to' The Accompanying cut will illustrate the subject of the Moon's llbrations in longitude. From A around to C, the angular motion is flower than the- average, and the diurnal motion gains upon it, so that the pillar points wtst of the Earth, and we see more of the eastern limb of the moon. From C to A, again, the Moon advances./hsfcr than a mean rate, and gain* upon the diurnal revolution; go that the pillar points east of the Earth, and we see more of the Moon's wwtern li'.ub. Thus she seems ^ librate or roll, first o ic way and then tL<; other, during every periodic revolution. At B, we see most of her eastern limb ; and at D, most of her western. 417. The axis of .the Moon is inclined to the plane of her orbit only about one and a half degrees (1 30' 10.8"). But this 415. How often does the Moon revolve on her axis? How is it known ? What follows from this fact? 416. What are the Moon'i librations? In Lonaitudet 417. In 210 ASTRONOMY. slight inclination enables us to see first one pole and then the other, in her revolution around the Earth. These slight rolling motions are called her librations in latitude As Ine inclination of the Earth's axis brings first one pole and then the other toward the Sun, and produces the seasons, so the inclination of the Moon's axis brings first one pole and then the other in view from the Earth. But as her inclination is only 1%, the libration in latitude is very slight. 418. As the Moon turns on her axis only as she moves around the Earth, it is plain that the inhabitants of one half of the lunar world are totally deprived of the sight of the Earth, unless they travel to the opposite hemisphere. This we may presume they will do, were it only to view so sublime a spectacle ; for it is certain that from the Moon the Earth appears ten times larger than any other body in the universe. 419. As the Moon enlightens the Earth, by reflecting the light of the Sun, so likewise the Earth illuminates the Moon, exhibit- ing to her the same phases that she does to us, only in a con- trary order. And, as the surface of the Earth is 13 times as large as the surface of the Moon, the Earth, when full to the Moon, will appear 13 times as large as the full Moon does to us. That side of the Moon, therefore, which is towards the Earth, may be said to have no darkness at all, the Earth constantly shining upon it with extraordinary splendor when the Sun is absent ; it therefore enjoys successively two weeks of illumina- tion from the Sun, and two weeks of earth-light from the Earth. The other side of the Moon has alternately a fortnight's light, and a fortnight's darkness. 420. As the Earth revolves on its axis, the several continents, seas, and islands, appear to the lunar inhabitants like so many spots of different forms and brightness, alternately moving over its surface, being more or less brilliant, as they are seen through intervening clouds. By these spots, the lunarians can not only determine the period of the Earth's rotation, just as we do that of the Sun, but they may also find the longitude of their places, as we find the latitude of ours. 421. As the full Moon always happens when the Moon is directly opposite the Sun, all the full moon;? in our winter, must happen when the Moon is on the north side of tne equinoctial, 418. Can all the Lunarians see the Earth? llc-w large must she appear from the Moon ? 419. What said of her light and phases ? How, then, are the two hemispheres of the Moon enlightened ? 420. How must the Earth appear to the Lunarians, and what may they infer from the motion of the spots seen on her surface? 421. Where is the Moon at the full in winter? In summer? Why? What result as to moonlight at th# poles ? THE MOON HER MOTIONS, PHASES, ETC 211 because then the Sun is on the south side of it ; consequently, at the north pole of the Earth, there will be a fortnight's moon- light and a fortnight's darkness by turns, for a period of six months, and the same will be the fact during the Sun's absence the other six months, at the south pole. 422. The plane of the Moon's orbit is very near that of the ecliptic. It departs from the latter only about 5 (5 8' 48".) INCLINATION OF THE MOON'S ORBIT TO THB PLANK OF THK ECLIPTIC. Let the line A B represent the plane of the Earth's orbit, and the line joining the Moon at C and D would represent the inclination of the Moon's orbit to that of the Earth. At C the Moon would be wWiin the Earth's orbit, and at D exterior to it; and it would be Fuil Moon at D, and New Moon at C. 423. The Moon's axis being inclined only about 1 to her orbit, she can have no sensible diversity of seasons ; from which we may infer, that her atmosphere is mild and uniform. The quantity of light which we derive from the Moon when full, is at least 300,000 times less than that of the Sun. Tin's is Monsieur Bouquer's inference, from his experiments, as stated by La Place, in hi* work, p. 42. The result of Dr. Wollaston's computations was different. Professor Leslie makes the light of the Moon 150,000 times less than that of the Sun ; it waa for- merly reckoned 100,000 times less. 424. The Moon, though apparently as large as the Sun, is the smallest of all the heavenly bodies that are visible to the naked eye. Her diameter is but 2162 miles ; consequently her surface is 13 times less than that of the Earth, and her bulk 49 times less. It would require 70,000,000 of such bodies to equal the volume of the Sun. The reason why she appears as large as the Sun, when, in truth, she is so much less, is because she is 400 times nearer to us than the Sun. 425. When viewed through a good telescope, the Moon pre- sents a most wonderful and interesting aspect. Besides the large dark spots, which are visible to the naked eye, we perceive extensive valleys, shelving rocks, and long ridges of elevated mountains, projecting their shadows on the plains below. Single mountains occasionally rise to a great height, while circular hol- lows more than three, miles deep, seem excavated in the plains. 422. How is the Moon's orbit situated with respect to the ecliptic ? 423. What ia the inclination of the Moon's axis, and what effect has it on her seasons and atmosphere ? What is the amount of light derived from the Moon as compared with the Suu, and ia there any difference of opinion on this point? 424. What said of the apparent and real diameters of the Moon? Compared with the Earth? The Sun? Why, then, appear as large as he does ? 425. How does she appear through a telescope? 21*2 ASTRONOMY. TELESCOPIC VIEW OF TDK MOON. Specimens of these shadows may be seen in the cut, projecting to the left. Bright points of light, or, in other words, the illuminated tops of mountains, may also be seen near the terminator, in the dark portion. The writer has often watched them, and se-en them en- large more and more, as the Sun arose upon the side of the Moon toward us, and enlightened the sides of her mountains. The shadows are always pro- jected in a direction opposite the Sun, or towards the dark side of the moon ; and as her eastern limb is dark from the change to the full, and her western from the lull to the change, of course the direc- tion of the shadows must be re- versed. Suppose a person stationed at a distance directly over the Andes. Before the Sun arose, he would see the tallest peaks enlightened ; and as he arose, the long shadows of , the mountains would extend to tfie west. At noon, however, little or no shadow would be visible ; but at sunset, they would again be seen stretching away to the eaM. This is precisely the change that is seen to take place with the lunar shadows, except that the time required is a lunar day, equal to about 15 of our days, instead of one of our days of 12 hours. 426. The Moon's mountain scenery bears a striking resem- blance to the towering sublimity and terrific ruggedness of the Alpine regions, or of the Apennines, after which some of her mountains have been named, and of the Cordilleras of our own continent. Huge masses of rock rising precipitously from the plains, lift their peaked summits to an immense height in the air, while shapeless crags hang over their projecting sides, and seem on the eve of being precipitated into the tremendous chasm below. Around the base of these frightful eminences, are strewed numerous loose and unconnected fragments, which time seems to have detached from their parent mass ; and when we examine the rents and ravines which accompany the overhanging cliffs, the beholder expects every moment that they are to be torn from their base, and that the process of destructive separation which he had only contemplated in its effects, is about to be exhibited before him in all its reality. 427. The range of mountains called the Apennines, which traverses a portion of the Moon's disc from northeast to south- west, and of which some parts are visible to the naked eye, rises 426. What said of the Moon's mountain scenery? ficular? 427. Of the Apennines La r THE MOON HER MOTIONS, PHASES, ETC 213 with a precipitous and craggy front from the level of the Mare. Imbrium, or Sea of Showers. In this extensive range are several ridges whose summits have a perpendicular elevation of four miles, and more ; and though they often descend to a much lower level, they present an inaccessible barrier on the northeast, while on the southwest they sink in gentle declivity to the plains. 428. There is one remarkable feature in the Moon's surface which bears no analogy to anything observable on the Earth This is the circular cavities which appear in every part of her disc. Some of these immense caverns are nearly four miles deep, ana forty miles in diameter. They are the most numerous in the southwestern part. As they reflect the Sun's rays more copiously, they render this part of her surface more brilliant than any other. They present to us nearly the same appearance as our Earth might be supposed to present to the Moon if all our great lakes and seas were dried up. 429. The number of remarkable spots on the Moon, whose latitude and longitude have been accurately determined, exceeds 200. The number of seas and lakes, as they were formerly con- sidered, whose length and breadth are known, is between 20 and 30 ; while the number of peaks and mountains, whose perpen- dicular elevation varies from a fourth of a mile to five miles in height, and whose bases are from one to seventy miles in length is not less than one hundred and fifty. Graphical views of these natural appearances, accompanied with minute and familiar descriptions, constitute what is called Selenography, from two Greek words, which mean the same thing in regard to the Moon, as Geography does in regard to the Earth. 430. An idea of some of these scenes may be formed by con- ceiving a plane of about 100 miles in circumference, encircled by a range of mountains, of various forms, three miles in perpen- dicular height, and having a mountain near the center, whose top reaches a mile and a half above the level of the plain. From the top of this central mountain, the whole plain, with all its scenery, would be distinctly visible, and the view would be bounded only by a lofty amphitheatre of mountains, rearing their summits to the sky. 431. The bright spots of the Moon are the mountainous regions ; while the dark spots are the plains, or more level parts of her surface. There may be rivers or small lakes on this 428. What remarkable feature of the Moon's surface noticed ? 429. What numbei c f remarkable spots 1 Of " seas or lakes?" Of mountains? What is Selenography f u. How conceive justly of the lunar scenery? 481. What are the brightest spots o 214 ASTRONOMY. planet ; but it is generally thought, by astronomers of the preset day, that there are no seas or large collections of water, as was formerly supposed. Some of these mountains and deep valley? are visible to the naked eye ; and many more are visible through a telescope of but moderate powers. 432. A telescope which magnifies only 100 times will show a spot on the Moon's surface, whose diameter is 1223 yards ; ana one which magnifies a thousand times, will enable us to perceive any enlightened object on her surface whose dimensions are only 122 yards,' which does not much exceed the dimensions of some of our public edifices, as for instance, the Capitol at Washington. or St. Paul's Cathedral. Some years since, Professor Frauen- hofer, of Munich, announced that he had discovered a lunar edifice, resembling a fortification, together with several lines of road. The celebrated astronomer Schroeter, conjectures the existence of a great city on the east side of the Moon, a little north of 'her equator, an extensive canal in another place, and fields of vegetation ir another. CHAPTER Y. SOLAR AND LUNAR ECLIPSES. 433. OF all the phenomena of the heavens, there are none which engage the attention of mankind more than eclipses of the Sun and Moon ; and to those who are unacquainted with astro* uomy, nothing appears more wonderful than the accuracy with which they can be predicted. In the early ages of antiquity, they were regarded as alarming deviations from the established laws of nature, presaging great public calamities, and other tokens of the divine displeasure. In China, the prediction and observance of eclipses are made a matter of state policy, in order to operate upon the fears of the ignorant, and impose on them a superstitious regard for the occult wisdom of their rulers. In Mexico, the natives fast and afflict them- selves, during eclipses, under an apprehension that the Great Spirit is in deep sufferance. Some of the northern tribes of Indians have imagined that the Moon had been wounded in a quarrel ; and others, that she was about to be swallowed by a huge fish. the Moon's surface? The dark ones? 482. How small objects maybe seen on thi Moon's surface? What announcement by Frauenhofer? Conjecture of Srhroetei ' 483. Subject of Chapter V.? Remark respecting eclipses? How regarded by tin undents ? In China ? Mexico ? By northern Indians ? Anecdote of Columbus ? SOLAR AND LUNAR ECLIPSES. 215 It was by availing himself of these superstitious notions, that Columbus, when ship- wrecked on the island of Jamaica, extricated himself and crew from a most embarrass- ing condition. Being driven to great distress for want of provisions, and the natives refusing him any assistance, when all hope seemed to be cut off, he bethought himself of their superstition in regard to eclipses. Having assembled the principal men of the island, he remonstrated against their inhumanity, as being offensive to the Great Spirit: and told them that a great plague was even then ready to fall upon them, and as a token of it, they would that night see the Moon hide her face in anger, and put on a dreadfully dark and threatening aspect. This artifice had the desired effect; for the eclipse had r,o sooner begun, than the frightened barbarians came running with all kinds of provisions, and throwing themselves at the feet of Columbus, implored his forgiveness. Almagent, vol. /., 55 c. v. 2. 434. An eclipse of the Sun takes place, when the dark body of the Moon, passing directly between the Earth and the Sun, intercepts his light. This can happen only at the instant of new moon, or when the Moon is in conjunction ; for it is only then that she passes between us and the Sun. An eclipse of the Moon takes place when the dark body of the Earth, coming between her and the Sun, intercepts his light, and throws a shadow on the Moon. This can happen only at the time of full moon, or when the Moon is in opposition ; for it is only then that the Earth is between her and the Sun. 435. As every planet belonging to the solar system, both pri- mary and secondary, derives its light from the Sun, it must cast a shadow towards that part of the heavens which is opposite to the Sun. If the Sun and planet were both of the same magni- tude, the form of the shadow cast by the planet, would be that of a cylinder, and of the same diameter as the Sun or planet. CYLINDRICAL SHADOW. Here the Sun and planet are represented as of the same size, and the shadow of the latter is in the form of a cylinder. 436. If the planet were larger than the Sun, the shadow would continually diverge, and grow larger and larger ; but as the Sun is much larger than any of the planets, the shadows which they cast must converge to a point in the form of a cone, the length of which will be proportional to the size and distance of the planet from the Sun. 434. When do sohir eclipses occur? Why only then? Lunar? Why only at full moon? 435. Do all the planets cast shadows? Suppose the Sun and planet were of the, name xizp, what would be the form of their shadows? 436. What if the planet was largest? How as they are smaller than the Sun? How is the length of the shadow modified by the distance of the planet from the Sun ? 216 ASTRONOMY. DIVERGING SHADOW. In this cut, the opaque bofh/ ix the larger, and the shadow projected from it dtve , ,T ^rows more broad as the distance from the planet increases. If the opaque body is smaller than the luminous one, the shadow converged a point. CONVERGING SHADOW. Here the luminous body ia the larger, and the shadow converges to a ^v/int, and ta t the form of a cone. The opaque body being smaller than the luminous one, the length of its shadow will 9 modified by ita distance, as in the following : Here, also, the luminous body is the larger, and both precisely or the pr.rne size as 1 the cut preceding ; but being placed nearer each other, the shadow is shown to be coi siderably shorter. 437. All the planets, both primaries and secondaries, cas shadows in a direction opposite the Sun (see cut on cext page) The form and length of these shadows depend upon the compara- tive magnitude of the Sun and planet, and their distance from each other. If the Sun and a planet were of the same size, the shadow of the planet would be in the form of a cylinder, what- ever its distance. If the planet was larger than the Sun, the shadow would diverge, as we proceed from the placet off into space ; and the nearer the Sun, the more divergent the shadow would be. But as the planets are all much smaller than the Sun, the shadows all converge to a point, and take the form of a cone; and the nearer to the Sun, the shorter their shadows. 437. Why hare the largest and most distant planets the longest shadows? Do any of the primary planets eclipse each other? SOLAR AND LUNAR ECLIPSES 217 SHADOWS OF TE PLAKETS. These principles are partly illus- trated in the adjoining cut. The planets nearest the Sun have com- paratively short shadows, while those more remote extend to a great dis- tance. No primary, however, casts a sliadow long enough to reach the next exterior planet. The magnitude of the Sun is such, that the shadow cast by each of the primary planets always converges to a point before it reaches any other planet; so that not one of the pri- mary planets can eclipse another. The shadow of any planet which is accompanied by Satellites, may, on certain occasions, ec'ipse its satel- lites ; but it is not long enough to eclipse any other body. The shadow of a satellite or Moon, may also, on certain occasions, fall on the primary, and eclipse it. 438. When the Sun is at his greatest distance from the Earth, and the Moon at her least distance, her shadow is sufficiently long to reach the Earth, and extend 19,000 miles beyond. When the Sun is at his least distance from the Earth, and the Moon at her greatest, her shadow will not reach the Earth's sur- face by 20,000 miles. So that when the Sun and Moon are at their mean distances, the cone of the Moon's shadow will termi- nate a little before it reaches the Earth's surface. In the former case, if a conjunction take place when the center of the Moon comes in a direct line between the centers of the Sun and Earth, the dark shadow of the Moon will fall centrally upon the Earth, and cover a circular area of 175 miles in diameter. To all places lying within this dark spot, the Sun will be totally eclipsed, as illustrated by the figure. 439. Eclipses of the Sun must always happen at New Moon, and those of the Moon at Full Moon. The reason of this is, that the Moon can never be between us and the Sun, to eclipse him, except at the time of her change, or New Moon ; and she can never get into the Earth's shadow, to be eclipsed herself, except when she is in opposition to the Sun, and it is Full Moon 440. If the Moon's orbit lay exactly in the plane of the eclip- tic, she would eclipse the Sun at every change, and be eclipsed herself at every full ; but as her orbit departs from the ecliptic over 5 (422), she may pass either above or below the Sun at 438. What is the length of the Moon's shadow when she is nearest the Earth and farthest from the Sun? What when nearest the Sun and farthest from the Earth? What when the Sun and Moon are at their mean distances? 439. At what time of the Mocii k are drawn to represent a view from northern latitude upon the Earth. Hence, by holding the book up south of him, the cuts will generally afford an accurate illustration both of the positions and motions of the bodies represented. 445. The time which elapses be'tween two successive changes of the Moon is called a Lunation, which, at a mean rate, is about If s?v-n? What is the usual number? Can you explain the cause of this variety? 444. What is the direction of a solar eclipse? A lunar? Why this difference? 445. WhAt is a luntttion f What would be the effect if thflow the Sun. If when at C, she will just touch hia lower limb. At C, she will eclipse him a little, and so on to A; at which point, if the change occurs, the eclipse would be central, and probably total. If the Moon was at G, H, I, or J, in her orbit, when the change occurred, she would eclipse the upper or northern limb of the Sun, according to her distance from her node at the time ; but if she was at K, she would pass above the Sun, and would not eclipse him at all. The points C and J will represent the Solar Ecliptic Limits. The mean ecliptic limit for the Sun is 16J$ e on each side of the node ; the mean eclip- tic limit for the Moon is lOJ^ on each side of the node. In the former case, then, there are 83 degrees about each node, making, in all, 66 out of 360, in which eclipses of the Sun may happen ; in the latter case there are 21 about each node, making, in all, 42 . an eclipse? What meant by ecliptic. limit* ? Name the distance of each, respectively, from the node. Illustrate. 447. What is the umbra of the Earth or Moon? Tb< SOLAR AND LUNAR ECLIPSES. 22 J darkest portion is called the umbra, and the partial shadow the UMBKA AND PCXCMRRA CF THE EARTH AND HOOK. >. =&** Penuml>ra is from the Latin pene, almost, and urn-bra, a shadow. In this cut, the Earth's umbra and penumbra will be readily found by the lettering ; while A is the umbra, and B B the penumbra, of the Moon. The latter is more broad than it should be, owing to the nearness of the Sun in the cut, as it never extends to much over half the Earth's diameter. The student will see at once that solar eclipses can be total only to persons "vithiri the umbra; while to all on which the penumbra falls, a portion of the Sun's dine will be obscured. 448. The average length of the Earth's umbra is about 860,000 miles ; and its breadth, at the distance of the Moon, is about 6500 miles, or three times the Moon's diameter. As both the Earth and Moon revolve in elliptical orbits, both the above estimates are subject to variations. The length of th Earth's umbra varies from 842,217 to 871,262 miles ; and its diameter, where the moon passes it, varies from 5235 to 6365 miles. 449. The average length of the Moon's umbra is about 239,000 miles. It varies from 221,148 to 252,638 miles, according to the Moon's distance from the Sun. Its greatest diameter, at the distance of the Earth, is 170 miles ; but the penumbra may cover a space on the Earth's surface 4393 miles in diameter. When the Moon but just touches the limb of the Sun, or the umbra of the Earth, it is called an appulse (see C and J in the cut on the opposite page). 450. A partial eclipse is one in which only part of the Sun or Moon is obscured. A solar eclipse is partial to all places outside the umbra ; but within the umbra, where the whole disc is obscured, the eclipse is said to be total. A central eclipse is one taking place when the Moon is exactly at one of her nodes. If lunar, it is total, as the Earth's umbra is always broad enough, at the Moon's distance, if centrally passed, to obscure her whole disc. But a solar eclipse may be central and not total, as the Moon is not always of sufficient apparent diameter to cover the penumbra f Derivation? Within which are solar eclipses total? 448. The average length of the Earth's shadow ? Breadth at the Moon's distance ? Do they vary ? Why? 4-49. Average length of the Moon's umbra? Does it vary ? Why? Greatest diameter at the Earth's surface? Of penumbra? What is an apputeet 450. A partial eclipse? htotalt A. central f Are all central -.clipses total? Why net? What calltxl then? Why? 222 ASTRONOMY. whole disc of the Sun. In that case, the eclipse would be annular (from annulus, a ring), because the Moon only hides the center of the Sun, and leaves a bright ring unobscured. PKOGKK3S OF A CENTRAL ECLIPSE. Annulnr. Coming on. 451. It has already been shown that the apparent magni- tudes of bodies vary as their distances vary ; and as both the Earth and Moon revolve in elliptical orbits, it follows that the Moon and Sun must both vary in their respective apparent mag- nitudes. Hence some central eclipses of the Sun are total, while others are partial and annular. TOTAL AND ANNULAR ECLIPSES OF THE SUS t Total. At A, the Earth is at her aphelion, and the Sun being at his most distant point, wit) have his least apparent magnitude. At the same time, the Moon is in perigee, and Appear* larger than usual. If, therefore, she pass centrally over the Sun's disc, the eclipse will be total. At B, this order is reversed. The Earth is at her perihelion, and the Moon in apogee; so that the Sun appears larger, and the Moon smaller than usual. If, then, a central eclipse occur under these circumstances, the Moon will not be large enough to eclipse the whole of the Sun, but will leave a ring, apparently around herself, unobscured. Such eclipse will be annular. 452. The greatest possible duration of the annular appearance of a solar eclipse, is 12 minutes and 24 seconds; and the greatest possible time during which the Sun can be totally eclipsed, to any part of the world, is 7 minutes and 58 seconds. The Moon may continue totally eclipsed for one hour and three quarters. 553. As the solar ecliptic's limits are further from the Moon's nodes than the lunar, it results that we have more eclipses of the Sun than of the Moon. There may be seven in all in one 451. Why are 8o:v.e central eclipses total, and others partial and annular? 452. .How long may an annulu/r eclipse continue ? A total eclipse of the Sun ? Of the Moon? 453. Which kind of eclipses is most frequent? Why? The greatest number in a year 7 SOLAR AND LUNAR ECLIPSES. 223 year, viz., five solar and two lunar ; but the most usual number is four. There can never be less than two in a year ; in which case, both must be of the Sun. Eclipses both of the Sun and Moon recur in nearly the same order, and at the same intervals, at the expiration of a cycle of 223 lunations, or 18 years of 365 days and 15 hours. This cycle is called the Period of the Eclipses. At the expiration of this time, the Sun and the Moon's nodes will sustain the same relation to each other as at the beginning, and a new cycle of eclipses begins. 454. In a total eclipse of the Sun, the heavens are shrouded in darkness, the planets and stars become visible, the tempera- ture declines, the animal tribes become agitated, and a general gloom overspreads the landscape. Such were the effects of the great eclipse of 1806. In a lunar eclipse, the Moon begins to lose a portion of her light and grows dim, as she enters the Earth's penumbra, till at length she comes in contact with the umbra, and the real eclipse begins. 455. In order to measure and record the extent of eclipses, the apparent diameters of the Sun and Moon are divided into twelve equal parts, called digits; and in predicting eclipses, astronomers usually state which "limb" of the boiiy is to be eclipsed the southern or northern the time of tJij first con- tact, of the nearest approach of centers, direction, And number of digits eclipsed. FIVE DIGITS ECLIPSED. TWELTK DIGITS. 456. The last annular eclipse visible in the United States, occurred May 26, 1854. The next total eclipse of the Sun will be August 7, 1869. Some of the ancients, and all barbarous nations, formerly regarded eclipses with amazement and fear, as supernatural events, indicating the displeasure of the gods. Co ambus is said How many of each? Least number, and which? Usual number? What ai<\ of the order of eclipses? Time of cycle? 454. Describe the effects of s. total eclipse of the Fun. The process of a lunar eclipse? 455. How are eclipses measured and recorded? 400. AVhen the next annular eclipse visible in this country ? The nr;9,190.435 232,995,860 221.617.045 244,684,375 245.989,960 251,197,100 277.661,440 235.002,450 218,125.700 231,929,960 228.891,670 231.365.945 237.080,005 249,738.280 299.244.965 228,100,700 252.327,505 222.993,975 263,641,815 242,712,270 224,598,905 299,835,010 24595^.7115 272,372,125 255,388,690 1.680 1,684 1,592 1.325 1,511 1,380 1.346 1,193 1,346 2,041 1,403 1,301 1,510 1,522 1,570 1.825 1^421 1,271 1,393 1.366 1,838 1,440 1.557 2,042 1.359 1,581 1,314 1,689 1,492 l,P-28 2,048 1,522 1,773 1,610 Jan. 1. 1801 March 28, 1802 Sept. 1, 1804 March 29, 1807 Dec. 8, 1845 July 1, 1847 Aug. 13. 1847 Oct. 18, 1847 April 25, 1848 April 12, 1849 May 13, 1850 Sept. 13, 1850 Nov. 2. 1850 May 20, 1S51 July 29, 1851 March 17, 1852 April 17, 1852 June 24, 1852 Aug. 22,1852 Sept. 19,1852 Nov. 15, 1852 Nov. 16, 1852 Dec. 15, 1852 April 5, 1853 April 6, 1853 May 5, 1853 Nov. 8. 1853 March 1, 1854 March 1, 1854 July 22, 1854 Sept. 1, 1854 Oct. 26, 1854 Oct. 28, 1854 April 15, 1855 Piazzi . . . Dr. Olbers.. Harding.... Dr. Olbers Hen eke Hencke. . . . Hind Palermo. Bremen. Li lien thai. Bremen. Dresden. DrfePden. London. London. Markvee. Naples. Naples. London. Naples. London. Naples, Naples. Bilk. London. London. Marseilles. Paris. London. London. Naples. Marseilles. Bilk. London. Bilk. London. London. Washington, D. 01 Paris. Paris. Paris. 3. Juno 4. Vesta 5. Astrtea 6. Hebe....... 7. Iris.... 8. Flora 9. Metis 10. Hygeia 11. Porthenope . 12. Clio Hind Graham De Gasparis I)e Gasparis Hind 13. Egeria... 14. Irene 15. Eunomia ... 16 Psvche 17. Thetis 18. Melpomena 19. Fortuna 20. Massilia .... 21. Lutetia 22. Calliope 23. Thalia '24. Themis 25. Phocoea 26. Proserpine.. 27. Kuterpe 28. Bellona.... 29. Amphitrite . 80. Urania 81. Euphrosyne 82. Pomona 33. Polymnia... 84. Circe De Gasparis Hind De Gasparis De Gasparis Luther Hind Hind Chacornnc.. Goldsiiudt.. Hind Hind De Gasparis Ohacornac.. Luther Hind Luther Marth Himl Ferguson . . GoldsmHt Chacornac. . Chacornac . . 475. Appearance of Vesta. 476. Juno's period. Diameter. For what noted ? Dl nietr of Ceres. Of Pallas. 477. Nuinbei of asteroids now known a* per table. 232 ASTKONO-MY TABLE OF THE ASTEROIDS. Continued. No. Names. Distance from ihe Sun in Miles. Periodic Tajs!" T'me of Bv wh- m discovered. Where discovered. 35. Leucothea . . 86. Atalanta 87 Fides 288,216,755 261.126,975 255,981.165 260.270,075 263.091,765 215,379,060 228.032,015 231,219,455 209.364,610 230,886.670 260,568.660 241.296.960 278,641,325 295,150,275 293,180,925 251.844,430 225,901,640 294,330.710 248,224.930 258,811,540 263,965,195 245,428,700 299,942,265 255,971,895 257.714,955 227,203,995 285.377,815 297,430,750 227,654,200 254,437,170 325,996,965 252,117,278 229,421,200 258.652,510 290,924,010 253,662,065 203,783,740 261,841,470 254,435,102 244,645.135 251,1 21^955 302,955,000 253,521,413 262,418,500 232,294,000 215.890,742 263,981,794 257,814.930 232,297.428 225.900.271 252,117,294 1,880 1,665 1,568 1,(56 1,683 1,247 1,358 1,887 1.195 1.384 1.659 1.479 1,786 2,000 1.980 1,577 1.839 1,992 1,543 1,642 1,692 1,517 2,049 1.615 1,632 1,351 1,902 2,024 1,355 1,601 2,322 1,579 1,371 1,641 1,957 1,594 1,148 1,671 1,589 1,509 1,570 2,080 1,597 1,677 1,397 1,271 1,693 1,659 1,382 1,324 1,572 April 19, 1855 Oct. 5, 1855 Oct. 5, 1855 Jan. 12, 1856 Feb. 8, 1856 March 31, 1856 May 23, 1856 Mav 23, 1856 Api-il 15, 1857 May 27, 1857 June 27, 1857 Aug. 16, 1857 Sept. 15, 1857 Sept. 19, 1857 Sept. 19, 1857 Oct. 4, 1857 Jan. 22, 1858 Feb. 4, 1858 April 4, 1858 Sept. 11, 1858 Sept. 11, 1S5S Sept. 9, 1859 Sept. 22,1859 March 24, 1860 Sept. 12, I860 Sept. 15, 1860 Sept 19, 1860 Oct 10, 1860 Feb. 10. 1861 March 2,1861 March 4, 1861 April 9, 1861 April 17,1861 April 20, 1861 April 29,1861 May 5, 1861 May 29, 1861 Aug. 13, 1861 April 7, 1862 Aug. 29, 1862 Sept. 22,1862 Oct. 21, 1862 Nov. 12, 1862 March 15, 1863 Sept. 14, 1S63 May 2, 1864 Sept. 30, 1864 Nov. 27,1864 April 26, 1865 Aug 25, 1865 Sept. 19, 1865 Luther Goldsmidt.. Luther Chacornac. . Chacornac . . Goldsmidt.. Goldsmidt.. Pogson Pogso-p Bilk. Paris. Bilk. Paris. Paris. Paris. Paris. Oxford. Oxford. Paris. Paris. Oxford. Bilk. Paris. Paris. Washington, D. C. Ni sines. Paris. Bilk. Paris. Albany, N. Y. Paris. Bilk. Bilk. Paris. Washington, D. C Paris. Berlin. Naples. Marseilles. Marseilles. Cambridge, Mass. Madras. Bilk. Milan. Paris. Clinton, N. Y. Bilk. Cambridge, Mass. Marseilles. Clinton, N. Y. Copenhagen Clinton, N. Y. Bilk. Ann Arbor, Mich. Oxford. Marseilles. Bilk. Naples. Bilk. Clinton, N. Y. 83. Leda 39. Lsetitia 40. Harmonia .. 41. Daphne 42. Isis 43. Ariadne .... 44. Nysa Goldsmidt.. Goldsmidt. . Pogson Luther Goldsmidt.. Goldsmidt.. Ferguson . . . Laurent Goldsmidt.. Luther Goldsmidr... Searle Goldsmidt.. Luther Luther .... Chacornac. . Ferguson . . . Goldsmidt.. Foster ... De Gasparis Tempel Tempel .... Tuttle Payson Luther Schiaparelli Goldsmidt. Peters . 45. Eugenia 46. Ilestia 47. Aglaia 48 Doris 49. Pales 50. Virginia ... 51. Nemausa. . . . 52. Enropa 53. Calypso 54. Alexandra . . 55. Pandora .. . 56. Melete 57. Mnemosyne 58. Concordia .. 59. Olyrnpia 60. Echo 61. Danae 62. Erato 68. Ansonia 64 Angelina . . . 65. Cybele 66. Maja 67. Aria 68. Leto 69. Hesperia.... 70. Panopspa 11. Feronia 72. Niobe 73. Clytie Tuttle 74. Galatea 75. Euridice 76. Freia 77. Frisrga . . Tempel Peters M. D. Arvert Peters Luther Watson Pogson Tern pel Liither De Gasparis Luther .... Peters 78. Diana. 79. Eurynome.. 80. Sappho 81. Terpsichore. 82. Alcmene ... 83. Beatrix 84. Clio 85 To THE PRIMARY PLANETS JUPITER AND SATURN. 233 CHAPTER Til. PRIMARY PLANETS JUPITER AND SATURN. 47 3. JUPITER is the largest of all the planets belonging to the Bolar system. It may be readily distinguished from the fixed stars, by its peculiar splendor and magnitude ; appearing to the naked eye almost as resplendent as Venus, although it is more than seven times her distance from the Sun. When his right ascension is less than that of the Sun, he is our morning star, and appears in the eastern hemisphere before the Sun risen ; when greater, he is our evening star, and lingers in the western hemisphere after the Sun sets. Nothing can be easier than to trace Jupiter among the con- stellations of the zodiac ; for in whatever constellation he is seen to-day, one year hence he will be seen equally advanced in the next constellation ; two years hence, in the next ; three years hence, in the next, and so on ; being just a year, at a mean rate, in passing over one constellation. The exact mean motion of Jupiter in its orbit, is about one-twelfth of a degree in a day ; Which amounts to only 80" 20' 32* in a year. For 12 years to come, he will, at a mean rate, pass through the constellations of the zodiac, as follows : 1867, Capricornue 1868, Aquarius. 1869, Pisces. 1870, Aries, 1871, Taurus. 1872, Gciini. 1873, Cancer. 1874, Leo. 1875, Virgo. 1876, Libra. 1877, Scorpio. 1878, Sagittarius. 479. Jupiter is the next planet in the solar system above the asteroids, and performs his annual revolution around the Sun in t>early 12 of our years, at the mean distance of 495,000,000 of miles ; moving in his orbit at the rate of 30,000 miles an hour. The exact period of Jupiter's sidereal revolution is 11 years, 10 months, 17 days, 1 1 hours, 21 minutes, 25)3 seconds. His exact mean distance from the Sun is 495,533.837 miles ; consequently, the exact rate of his motion in his orbit, is .29,948 miles per hour 480. He revolves on an axis, which is nearly perpendicular to the plane of his orbit, in 9 hours, 55 minutes, and 50 seconds ; *o that his year contains 10,471 days and nights ; each about o hours long. His form is that of an oblate spheroid, whose polar diameter 478. Comparative size of Jupiter T How distinguished from the fixed stars ? When morning star, Ac. ? Is he easily traced ? 479. His position in the system? His peri- odic time? Distance from the Sun? Rate of motion? 480. Time of diurna. revolu- tion? Potion of axis? Length of his days? Number in his year ? His form Cus %f iiis obJateaess ? Difference of equatorial and polar diameters ? The Earth f '234 ASTIU'NOMY. is to its equatorial, as 16 to 17. He is therefore considerably more flattened at the poles than any of the other planets, except Saturn. This is caused by his rapid rotation on his axis ; for it is an universal law that the equatorial parts of every body, revolving on an axis, will be swollen out, in proportion to the density of the body, and the rapidity of its motion. The difference between the polar and equatorial diameters of Jupiter, exceeds 6000 miles. The difference between the polar and equatorial diameters of the Earth, is only 2(5 miles. Jupiter, even on the most careless view through a good telescope, appears to be oval ; the longer diameter being parallel to the direction of his belts, which are also parallel to the ecliptic. 481. By this rapid whirl on its axis, his equatorial inhabitants are carried around at the rate of 26,554 miles an hour ; which is 1600 miles farther than the equatorial inhabitants of the Earth are carried, by its diurnal motio, in twenty-four hours. The true mean diameter of Jupiter is 88,780 miles ; which is nearly 11 times greater than the Earth's. His volume is, therefore, about thirteen hundred times larger than that of tho Earth. ( For magnitude as compared with that of the Earth, see Map Z) On account of his great distance from the Sun, the degree of light and heat which he receives from it is 27 times less than that received by the Earth. When Jupiter is in conjunction, he rises, sets, and cornes to the meridian with the Sun ; but is never observed to make a transit, or pass over the Sun's disc ; when in opposition, he rises when the Sun sets, sets when the Sun rises, and comes to the meridian at mid- night, which never happens in the case of an interior planet. This proves that Jupiter revolves in an orbit which is evsterior to that of the Earth. 482. As the variety in the*seasons of a planet, and in the length of its days and nights, depends upon the inclination of its axis to the plane of its orbit, and as the axis of Jupiter has little or no inclination, there can be no difference in his seasons, on the same parallels of latitude, nor any variation in the length of his days and nights. It is not to be understood, however, that one uniform season prevails from his equator to his poles ; but that the same parallels of latitude on each side of his equa- tor, uniformly enjoy the same season, whatever season it may be. About his equatorial regions there is perpetual summer j and at his poles everlasting winter ; but yet equal day and equal night at each. This arrangement seems to have been kindly ordered by the beneficent Creator ; for had his axis been inclined to his orbit, like that of the Earth, his polar winters would have been alternately a dreadful night of six years' darkness. 481. Motion at Jupiter's equator? His mean diameter? His volume? Li^ht and heatr Does he ever transit the Sun? What proof that his orbit is exterior to that of th Earth? 48-2. What of the seasons of Jupiter ? What apparent manifestation of Divine Wisdom? THE PRIMARY PLANETS JUPITER AND SATURN. TELESCOPIC TIKW OP JPPITKR. 483. Jupiter, when viewed through a telescope, appears to be surrounded by a number of luminous zones, usually termed Idts, that frequently extend quite around him. These belts are parallel not only to each other, but, in general, to his equa- tor, which is also nearly parallel to the ecliptic. They are subject, however, to considerable variation, both in breath ami number. Sometimes eight have been seen at once ; sometimes only one > but more usually three. Dr. Herschel once perceived his whole disc covered with small belts, though they are more usually confined to within 30 of his equator, that is, to a zone 60 in width. Sometimes these belts continue for months at a time with littlo or no variation, and sometimes a new belt has been seen to form in a few hours. Sometimes they are interrupted in their length ; and at other times, they appear to spread in width, and run into each other, until their breadth exceeds 5000 miles. 484. Bright and dark spots are also frequently to be seen in the belts, which usually disappear with the belts themselves, though not always, for Cassini observed that one occupied the same position more than 40 years. Of the cause of these vari- able appearances, but little is known. They are generally sup- posed to be nothing more than atmospherical phenomena, resulting from, or combined with, the rapid motion of the planet upon its axis. Different opinions have been entertained by astronomers respecting the cause of these belts and spots. By some they have been regarded as clouds, or as openings in the atmosphere of the planet, while others imagine that they are of a more permanent nature, and are the marks of great physical revolutions, which are perpetually agitating and changing the surface of the planet. The first of these opinions sufficiently explains the variations in the form and magnitude of the spots, and the parallelism of the belts. 488. How does Jupiter appear through a telescope? Where are his belts usually seen? Their number? Are they permanent? 484. What else seen upon Jupiter's surface? Are they permanent? Is the cause of these phenomena well understood? What different opinions? 236 ASTRONOMY . The spot first observed by Cassini, in 1665, which has both disappeared and reappeared in the same form and position for the space of 43 years, could not possibly be occasioned by any atmospherical variations, but seems evidently to be connected with the surface ul' the planet. The form of the belt, according to some astronomers, may be accounted for by supposing that the atmosphere reflects more light than the body of the planet, and that the clouds which float in it, being thrown into parallel strata by the rapidity of Its diurnal motion, form regular in-sterstices, through which are seen its opaque body, or any of the permanent spots which may come within the range of the opening. MOONS OF JUPITER. TELESCOPIC VIEWS OF THB MOONS OF JDPITER. 485. Jupiter is attended by four satellites or moons are easily seen with a common spy- glass, appearing like small stars near the primary. (See adjoining cut.) By watching them for a few evenings, they will be seen to change their places, and to occlipy different positions. At times, only one or two may be seen, as the others are either between the observer and the planet, or beyond the primary, or eclipsed by his shadow. 486. The size of these satellites is about the same as our moon, except the second, which is a trifle less. The first is about the distance of our moon ; and the others, re- spectively, about two, three, and five times as far off. They COMPARATIVE DISTANCES OF JUPITER'S MOONS 4th. 3d. 2d. 1st. 481 Their periods of revolution are from 1 day 18 hours to 17 days, according to their distances. This rapid motion is necessary, in order to counterbalance the powerful centripetal force of the planet, and to keep the satellites from falling to his (surface. 4S5. How many moons has Jupiter? How seen? Why not all seen at once? their size? Distances? 487. Periods of Jupiter's satellites? Why so rapid? 436 THE PRIMARY PLANETS JUPITER AND SATURN. 2#? The magnitudes, distances, aud periods of the moons of Jupiter are as follows: Diameter in mile*. Distance. Periodic tiiuen. 1st 2,500 280,000 1 day 13 hours. 2d .. ...2,200 440,000 S " 12 " 3d ...8,500 TOO.OOO T " 14 " 4th 2,890 1,200,000 6 " 16 488. The orbits of Jupiter's moons are all in or rear the plane of his equator ; and as his orbit nearly coincides with the eclip- tic, and his equator with his orbit, it follows that, like our own moon, his satellites revolve near the plane of the ecliptic. On this account, they are sometimes between us and the planet, and sometimes beyond him, and seem to oscillate, like a pendulum, from their greatest elongation on one side to their greatest elon- gation on the other. 489. Their direction is from west to east, or in the direction their primary revolves, both upon his axis and in his orbit. From the fact that their elongations east and west of Jupiter are nearly the same at every revolution, it is concluded that their orbits are but slightly elliptical. They are supposed to revolve on their respective axis, like our own satellite, the moon, once dur- ing every periodic revolution. 490. As these orbits lie near the plane of the ecliptic, they have to pass through his broad shadow when in opposition to the Sun, and be totally eclipsed at every revolution. To this there is but one exception. As the fourth satellite departs about 3 from the plane of Jupiter's orbit, and is quite distant, it some- times passes above or below the shadow, and escapes eclipse. But such escapes are not frequent. These moons are not only often eclipsed, but they often eclipse Jupiter, by throwing their own dark shadows upon his disc. They may be seen like dark round spots traversing it from side to side, causing, wherever that shadow falls, an eclipse of the Sun. Altogether, about forty of these eclipses occur in the sys- tem of Jupiter every month. 491. The immersions and emersions of Jupiter's moons have reference to the phenomena of their being eclipsed. Their entrance inl,o the shadow is the immersion ; and their coming out of it the emersion. 488. How are their orbits situated ? How satellites appear to move? 489. Direction of secondaries? Form of orbits? How ascertained? What motion on axis? 490. What said of eclipses? Of fourth satellite? Of solar eclipses upon Jupiter ? Number of solar and lunar? 491. What are the immeraion^ and emersion* of Jupiter'a noons? Are the immersions and emersions always visible from the Earth ? Why not? Illustrate, 238 ASTRONOMY. ECLIPSES JF JUPITBR'S MOOSS, EJTERSIOXS, ETC. The above is a perpendicular view of the orbits of Jupiter's satellites. His orond hadow is projected in a direction opposite the Sun. At C, the second satellite is suffer- ing an immersion, and will soon be totally eclipsed ; while at D, the first is in the act of emertfion, and will soon appear with its wonted brightness. The other satellites are seen to cast their shadows off into space, and are ready in turn to eclipse the Sun, or cut off a portion of his beams from the face of the primary. If the Earth were at A in the cut, the immersibn, represented at C, would be invisible ; and if at B, the emersion at D could not be seen. So, also, if the Earth were exactly at F, neither could be seen ; as Jupiter and all his attendants would be directly beyond the Sun, and would be hid from ouj view. 492. TiiP system of Jupiter may be regarded as a miniature representation of the solar system, and as furnishing triumphant evidence of the truth of the Copernican theory. It may also be regarded as a great natural dock, keeping absolute time for the whole world ; as the immersions and emersions of his satellites furnish a uniform standard, and, like a vast chronometer hung up in the heavens, enable the mariner to determine his longitude upon the trackless deep. By long and careful observations upon these satellites, astronomers have been able to construct tables, showing the exact time when each immersion and emersion will take place, at Greenwich Observatory, near London. Now suppose the tables fixed the time for a certain satellite to be eclipsed at 12 o'clock at Greenwich, but we find it to occur at :> o'clock, for instance, by our local time : this would show that our time was three hours behind the time at Greenwich ; or, in other words, that we were three hours, or 45, went of Greenwich. If our time was ahead of Greenwich time, it would show that we were eaat of that meridian, to the amount of 15 for every hour of variation. But this method of finding the longitude is less used than the "lunar method" (Art. 407;, on account of the greater difficulty of making the necessary observations. 403. By observations upon the eclipses of Jupiter's moons, as compared with the tables fixing the time of their occurrence, it was discovered that light had a progressive motion, at the rate of about 200,000 miles per second. This discovery may be illustrated by again referring to the preceding cut. In the year 1675, it was observed by Roemer, a Danish astronomer, that when the Earth was nearest to Jupiter, as at E, the eclipses of his satellites took place 8 minutes 13 seconds sooner than the mean time of the tables; but when the earth was farthest from Jupiter, as at F, the eclipses took place 3 minutes and 13 seconds /(tfs-r than the tables predicted, the entire difference being 16 minutes and 26 seconds. This difference of time he ascribed to the progressive motion of light, which he concluded required 16 minutes and 26 seconds lo cross the earth's orbit from E to F. 492. How may the system of Jupiter be regarded ? What use of it made in navigation ? Illustrate method? Is it much used ? 493. What discovery by observing the eclipses of Jupilsr's moons ? Explain the process ? - THE PRIMARY PLANETS JUPITER AND SATURN. 239 Tliis progress may be demonstrated as follows: 16m. 26s.=986s. If the radius of the Earth's orbit be 95,000,000 of miles, the diameter must be twice that, or 190,000,000. Divide 190,000,000 miles by 986 seconds, and we have 192,69T^ miles as the progress of lipht in each second. At this rate, light would pass nearly eight times around the globe at every tick of the clock, or nearly 500 times every minute ! 494. Jupiter, when seen from his nearest satellite, appears a thousand times large?- than our Moon does to us, exhibiting on a scale of inconceivable magnificence, the varying forms of a cres- cent, a half moon, a gibbous phase, and a fall moon, every 42 hours. SATURN". 495. SATUKN is situated between the orbits of Jupiter and Uranus, and is distinctly visible to the naked eye. It may be easily distinguished from the fixed stars by its pale, feeble, and steady light. It resembles the star Fomalhaut, both ' in color and size, differing from it only in the steadiness and uniformity of its light. From the slowness of its motion in its orbit, the pupil throughout the period of his whole life, may trace its apparent course among the stars, without any danger of mis- take. Having once found when it enters a particular constellation, he may easily remem- ber where he is to look for it in any subsequent year; because, at a mean rate, it is just 23y years in passing over a single sign or constellation. Saturn's mean daily motion among the stars is only about 2', the thirtieth part of a degree. 496. The mean distance of Saturn from the Sun is nearly double that of Jupiter, being about 909,000,000 of miles. His diameter is about 73,484 miles ; his volume, therefore, is eleven hundred times greater than the Earth's. Moving in his orbit at tlio rate of 22,000 miles an hour, he requires 29 years to com- plete his circuit around the Sun : but his diurnal rotation on his axis is accomplished in 10J- hours. His year, therefore, is nearly thirty times as long as ours, while his day is shorter by more than one-half. His year contains about 25,150 of its own days, which are equal to 10,759 of our days. 497. The surface of Saturn, like that of Jupiter, is diversified with belts and dark spots. Dr. Herschel sometimes perceived five belts on his surface ; three of which were dark and twc bright. The dark belts have a yellowish tinge, and generally cover a broader zone of the planet than those of Jupiter. To the inhabitants of Saturn, the Sun appears 90 times less than he appears at the Earth; and they receive from him only one ninetieth, part as much light and heat. But 494. How does Jupiter appear from his nearest satellite ? 495. Situation of Saturn flow distinguished V How trac? His rate of motion in the heavens? 496. Distance rom the Sun ? Diameter? Volume? Rate of motion in orbit? Periodic time? Diur nal revolution? Days in his year? 497. Appearance of his surface? Belts* The gun as seen from Saturn? Light and heat of that planet? Estimated strength of the 240 ASTRONOMY. TKLKSCOMC VIEW OF SUTCHN. it is computed that even the ninetieth part of the Sun's light exceeds the illuminating power of 8000 full moons, which would be abundantly sufficient for all the purposes of ' "j. 498. The telescopic appearance of Saturn is unparalleled. It is even more interesting than Jupiter, with all his moons and belts. That which eminently distinguishes this planet from every other in the system, is a magnificent zone or ring, encir- cling it with perpetual light. The adjoining ont is an excel- lent representation of Saturn a.s seen through a telescope. The oblateness of the planet is easily perceptible, and his shadow can be seen upon the rings back of the planet. The shadow of the rings may also be seen running across his disc. The writer has often seen the opening between the body of the planet and the interior ring as distinctly as it appears to the student in the cut. Un- der very powerful telescopes, these rings are found to be again subdivided into an in- dcfiiiite number of concentric circles, one within the other, though this ia considered doubtful by Sir John HerscheL 499. The light of the ring is more brilliant than the planet itself. It turns around its center of motion in the same time that Saturn turns on its axis. When viewed with a good telescope, it is usually found to consist of two concentric rings, divided by a dark band. It has been ascertained, however, that these rings are again subdivided; the thircj division was distinctly seen by Prof. Encke, on the 25th of April, 1837, and also by Mr. Lassel, on the 7th of September, 1843, at his observatory near Liverpool, England. Six different rings were seen at Rome, in Italy, on the night of the 29th of May, 1S38. And more recent observations by Professor Bond, of Cambridge, have led to the conclusion that, in all probability, these wonderful rings are fluid ! It is well known that under the most powerful instruments they seem to be almost indefinitely subdivided. 500. As our view of the rings of Saturn is generally an oblique one, they usually appear elliptical, and never circular. The ellipse seems to contract for about 7 years, till it almost entirely disappears, when it begins to expand again, and con- tinues to enlarge for 7-j- years, when it reaches its maximum of expansion, and again begins to contract. For fifteen years, the part of the rings toward us seems to be thrown up, while for the solar radiance? 498. Telescopic appearance of Saturn? For what distinguished? 499. Comparative light of his rings ? Time of rotation around the planet ? How does it usually appear? What further discoveries? 500. What the general apparent figurf of the rings ? Why elliptical ? What periodic variation of expansion ? Of inclination ! When nearly invisible ? THE PRIMARY PLANETS JUPITER AND SATURN. 24! next fifteen it appears to drop Idow the apparent center of the planet ; and while shifting from one extreme to the other, the rings become almost invisible, appearing only as a faint line of light running from the planet in opposite directions. The rings vary also in their inclination, sometimes dipping to the right, and at others to the left. TELESCOPIC PHASES OF THE RINGS OP SATURN. The above is a good representation of the various inclinations and degrees of expan sion of the rings of Saturn, during his periodic journey of 80 years PERPENDICULAR VIEW OF THE RINGS OF SATURN. 501. The rings of the planet are always directed more or less toward the Earth, and sometimes ex- actly toward us ; so that we never see them perpen- dicularly, but always either exactly edgewise, or ob- liquely, as shown in the last figure. Were either pole of the planet exactly toward us, we should then have a perpendicular view of the rings, as shown in the ad- joining cut. 502. The various phases of Saturn's rings are explained by the facts that his axis remains parallel to itself (see following cut), with an uniform inclination to the plane of his orbit, which is very near the ecliptic ; and as the rings revolve over his equator, and at right angles with his axis, they also remain parallel to themselves. The revolution of the planet about the Earth every 30 years, must therefore bring first one side of the rings to view, and then the other causing all the variations of expansion, position, and inclination which the rings present. 501. How are the rings situated with respect to the Earth? How would they appear ir either pole of Saturn -were toward us? >02. How are the various phases of Saturtr rings accounted for? 242 ASTRONOMY. POINTS IN HIS ORBIT. Here observe, first, that the axis of Saturn, like those of all the other planets, remains permanent, or parattel with iteelf; and as the rings are in the plane of his equator, and at right angles with his axis, they also must remain parallel to themselves, whatever position the planet may occupy in its orbit. This being the case, it is obvious that while the planet is passing from A to E, the Sun will shine upon the under or south, side of the rings ; and while he passes from E to A again, upon the upper or north side ; and as it requires about 30 years for the planet to traverse these two semicircles, it is plain that the alternate day and night on the rings rill be 15 years each. A and E are the equinoctial, and C and G the solstitial points in the orbit of Saturn. At A and E the rings are edgewise toward the San, and also toward the Earth, provided Saturn is in opposition to the Sun. To an observer on the Earth, the rings will seem to expand from A to C, and to contract from C to E. So, also, from E to G, and from G to A. Again : from A to E the front of the rings will appear above the planet's center, and from E to A below it. The rings of Saturn were invisible, as rings, from the 22d of April, 1848, to the 19th of January, 1849. He came to his equinox September 7, 1848 ; from which time to February, 1856, his rings continued to expand. Fiom that time to June. 1S63, they contracted, until ht* reached his other equinox at E, and the rinss became invisible. From June, 1863, to September, 18TO, they will again expand; and from September, 1870, to March, 1877, they will contract, when he will be at the equinox passed September 7, 1848, or 29% years before. The writer has often seen the rings of Saturn in different stages of expansion, and con- traction, and once when they were almost directly edgewise toward the Earth. At that time (January, 1849), they appeared as a bright line of light, as represented at A and E, in the first cut on the preceding page. 503. The dimensions of the rings of Saturn may be stated in round numbers as follows : Miles. Distance from the body of the planet to the first ring 19,000 Width of interior ring 17,000 Space between the interior and exterior rings . . 2,000 Width of exterior ring 10,500 Thickness of the rings 100 508. State the distances and dimensions of his rings, beginning at the body of the planet, and passing outward? What additional statistics from Uerschel? THE PRIMAKV PLANETS JUPITER AND SATURN. 243 In a recent work, entitled " The New Theory of Creation and Deluge," it is predicted v'.nr, at some future time, the fluid rings of Saturn may descend and deluge the planet, at ou.s was deluged in the days of Noah. Sir David Brewster says : " Mr. Otto Struve n-'d Mr. Bond have lately studied with the great Munich telescope at the Observatory of IMkoway, the third ring of Saturn, which Mr. Dassels and Mr. Bond discovered to be hl. These astronomers are of opinion that this fluid ring is not of very recent formation, and that it is not subject to rapid change , and they have come to the extra- oid.Jary conclusion that the inner border of the ring has, since the time of Huygens, ItetT gradually approaching the body of Saturn, and that we may expect, sooner or latr r, perhaps in some dozen of years, to see the rings united with the body of the planet." 504. The rings of Saturn serve us reflectors to reflect the liflht of the Sun upon his disc, as our Moon reflects the light to the Earth. In his nocturnal sky, they must appear like two gorgeous arches of light, bright as the full moon, and spanning the whole heavens like a stupendous rainbow. In the annexed cut, the beholder is supposed to be situated some 30 north of the equator of Baturn, and looking directly south. The ukadow of the planet is seen travelling up the arch as the night advances, wlille a 2iew Moon is shown In the west, and a Full Moon in the east at the eamc lime. 505. The two rings united are nearly 13 times as wide as the diameter of the Moon ; and the nearest is only y^th as far from the planet as the Moon is from us. The two rings united are 27,500 miles wide; which --2160 the moon's diameter=12 T 7_. So 240,000 miles, the Moon's distance + 19,000 the distance of Saturn's interior ring=12}. At the distance of only 19,000 miles, our Moon would appear some forty times as large as she does at her present distance. How magnificent and inconceivably grand, then, must these vast rings appear, with a thousand times the Moon's magnitude, and only one-twelfth part of her distance ! 506. The periodic time of Saturn being nearly thirty years, his motion eastward among the stars must be very slow, amount- ing to only 12 a year, or one sign in 2 years. It will be easy, therefore, having once ascertained his position, to watch his slow progress eastward year after year, as he performs his vast circuit around the heavens. MOONS OF SATURN. 507. Besides the magnificent rings already described, th telescope reveals eight satellites or moons, revolving around Saturn. I3ut these are seen only with good instruments, and under favor- able circumstances. fi04. What purpose do the rings of Saturn serve? How appear in his evening sky? 505. Width of two rings, as compared with Moon ? Distance? Demonstrate both. How would our Mpon appear at the listnnce of -^turn's rings? 5>6. Eastward motion of Saturn? How traced? 507. Moons of Saturn ? How seen ? Best time for obuorvinsc* B.G. 11 244 ASTRONOMY. SATELLITES Of SATUHH. The best time for observ- ing them is when the planet is at his equinoxes, and his rings are nearly invisible. In January, 1849, the author saw five i>f these satellites, as represented in the adjoining cut. The rings appeared only as a line f light extending each way from the planet, and the satellites were in the direction of :he liue, at different distances, as here represented 508. These satellites all revolve eastward with the rings of the planet, in orbits nearly circular, and, with the exception of the eighth, in the plane of the rings. Their mean distances, respectively, irom the planet's center are from 123,000 to 2,366,000 miles ; and their periods from 22 hours to 79 days, according to their distances. The distances and periods of the satellites of Saturn are as follows : Distance In mile*. Periodic time*. 1st 118,000 day 22i hours 2d 152,000 1 u 9 " 8d 188,000 1 tt 21 " 4th 240,000 2 u 17 " Distance in miles. Periodic times. 6th 536,000 4 days 12 honrft 6th 778,000 15 "' 22 " 7th 940,000 22 " .. " 8th 2,268,000 79 " 7 " COMPARATIVE DISTANCES OP THE MOONS OF SATURN. 509. The most distant of these satellites is the largest, sup posed to be about the size of Mars ; and the remainder grow smaller as they are nearer the primary. They are seldom eclipsed, on account of the great inclination of their orbits to the ecliptic, except twice in thirty years, when the rings are edgewise toward the Sun, The eighth satellite, which has been studied more than all the rest, is known to revolve once upon its axis during every periodic revolution ; from which it is inferred that they all revolve on their respective axis in the same manner. Let the line A B represent the plane of the plaaet's orbit, C D his axis, and E F the plane of his rings. The satellite* being in the plane of the rings will revolve around the shadow of the pri- mary, instead of passing through it, and being eclipsed. At the time of his equinoxes, however, when the rings are turned toward the Sun (see A and E, cut, page 242) they must be in the center of the shadow on SYSTEM OF SATDRS KO ECLIPSES. 508. The revolutions? Shape and position of their orbits ? Distances from their prt mary? 509. Comparative size? THE PRIMARY PLANETS JUPITER AND SATURN. 245 the opposite side ; and the moons, revolving in the plane of the rings, must pass through the shadow at every revolution. The eighth, however, may sometimes escape, on account of his departure from the plane of the rings, as shown in the cut. 510. The theory of the satellites of Saturn is less perfect than tfcan that of the satellites of Jupiter. The difficulty of observ- ing their eclipses, and of measuring their elongations from their primary, have prevented astronomers from determining, with their usual precision, their mean distances and revolutions. But of this we are certain : there is no planet in the solar system, whose firmament presents such a variety of splendid and mag- nificent objects as that of Saturn. The various aspects of the seven moons, one rising above the horizon, while another is setting, and a third approaching to the meridian; one entering into an eclipse, and another emerging from one ; one appearing as a crescent, and another with a gibbous phase ; and sometimes the whole of them shining in the same hemisphere, in one bright assemblage I The majestic motion of the rings at one time illuminating the sky with their splendor, and eclipsing the stars ; at another, casting a deep shade over certain regions of the planet, and unveiling to view the wonders of the starry firmament, are scenes worthy of the majesty of the Divine Being to unfold, and of rational creatures to contemplate. Such displays of Wisdom and Omnipotence, lead us to conclude that the numerou? splendid objects connected with this planet, were not created merely to shed their luster on naked recks and barren sands ; but that an immense population of intelligent being; is placed in those regions, to enjoy the bounty, and adore the goodness, of their great Creator. CHAPTER VIII. PRIMARY PLANETS. URANUS AND NEPTUNE. 511. URANUS is the next planet in order from the Sun, beyond or above Saturn. To the naked eye, it appears like a star of only the 6th or 7th magnitude, and of a pale, bluish white ; but it can seldom be seen, except in a very fine, clear night, and in the absence of the Moon. Through a telescope, he exhibits a small, round, uniformly illuminated disc, without rings, belts, 01 discernible spots. His apparent diameter is about 4", from which he never varies much, owing to the smallness of our orbit iii comparison with his own. 510. Is the system of Saturn well understood? Why not? Of what are we sure? What scenes must it present? To what conclusion must these phenomena lead us) 511. Position and appearance of Uranus? Through a telescope ? 246 ASTRONOMY. Sir John Herschel says he is without discernible spots, and yet in his tables he layi down the time of the planet's rotation ("which could only be ascertained by the rotation of spots upon the planet's disc), at 9% hours. This time is probably given on the iuthority of Schroeter, and is marked as doubtful by Dr. Herschel. 512. The motion of Uranus in longitude is still slower than that of Saturn. It moves over but one degree of its orbit m 85 days ; hence he will be seven years in passing over one sign or constellation. His periodic time being 84 years 27 days, his eastward motion can amount to only about 4 17' in a whole vear. To detect this motion requires instruments and close observations. At this date (1866), Uranus has made the entire circuit of the heavens since his discovery in 1781; having passed, in 1865, the point where he was first seen, and being now upon his second known journey around the heavens. It is remarkable that this body was observed as far back as 1690. It was seen three times by Flamstead, once by Bradley, once by Mayer, and eleven times by Lemonnier, who registered it among the stars ; but not one of them suspected it to be a planet. 513. The inequalities in the motions of Jupiter and Saturn, which could not be accounted for from the mutual attractions of these planets, led astronomers to suppose that there existed another planet beyond the orbit of Saturn, by whose action these irregularities were produced. This conjecture was con- firmed March 13th, 1781, when Dr. Herschel discovered the motions of this body, and thus proved it to be a planet. 514. The mean distance of Uranus from the Sun is 1,828,000,000 of miles ; more than twice the mean distance of Saturn. His sidereal revolution is performed in 84 years and 1 month, and his motion in his orbit is 15,600 miles an hour. He is supposed to have a rotation on his axis, in common with the other planets ; but astronomers have not yet been able to obtain any ocular proof of such a motion 515. His diameter is estimated at 36,000 miles ; which would make his volume more than 80 times larger than the Earth's. To his inhabitants, the Sun appears only the ^ T part as large as he does to us ; and of course they receive from him only that small proportion of light and heat. It may be shcwzz, however, that the T | T part of the Sun's light exceeds the illuminating power of 800 full moons. This, added to the light they must receive from their six satellites, will render their days and nights far from cheerless. 512. His motion in longitude ? Periodic time? Angular motion per year? How far has he been traced since his discovery ? When complete his revolution? Was he ever seen previous to !'/! ? By whom ? Why are they not the discoverers, then ? 518. Was his exiitenoe suspected previous to 1781 ? What ground for the suspicion? How proved to be a pi&r.et ? 514. Mean distance? Sidereal revolution? Hourly motion in orbit ? Rotation on axis ? 515, Diameter ? Voiur" "> Light and heat? Use THE PRIMARY PLANETS URANUS AND NEPTUNE. 247 516. Uranus is attended by six moons or satellites, which revolve about him in different periods, and at various distances. Four of them were discovered by Sir William Herschel, and two by his sister, Miss Caroline Herschel. It is possible that others remain yet to be discovered. Most of the satellites revolve from east to west around their primaries; but the satellites of Uranus are an exception to this rule. Their orbits are inclined to the plane of the ecliptic 79, being little less than a right angle ; and their motion in their orbits is retrograde, that is, from east to west. The distance from the planet, and the periodic times of the satellites of Uranus* respectively, are as follows: Dist. in mile*. Periodic time*. Dist. in niilct. Periodic times. D. H. r>. H. 1 120,000 2 1214. 880,000 18 11 2 171,000 4 35 777,000 38 '2 8 258,000 S llU. 1.656,000 107 16 NEPTUNE. 517 This is the most distant of the primary planets, and in some respects one of the most interesting. It is about 35,000 miles in diameter, is situated at the mean distance of 2,862,000,000 miles from the Sun, and revolves around him in 164 years. So remote is this newly-discovered member of the solar system, that for a body to reach it, moving at railroad speed, or 30 miles an hour, would require more than twenty tfwusand yeart ! 518. The circumstances of the discovery of this planet are at once interesting and remarkable. Such is the regularity of the planetary motions, that astronomers are enabled to predict, with great accuracy, their future places in the heavens, and to con- struct tables, exhibiting their positions for ages to come. Soon after the discovery of Uranus, in 1781, his orbit was computed, and a table constructed for determining his future positions in the heavens, but instead of following the prescribed path, or occupying his estimated positions, he was found to be yielding to some mysterious and unaccountable influence, under which he was gradually leaving his computed orbit, and failing to meet conditions of the tables. 516. Number of Moons? By whom discovered? Is it certain that Uranua has s5x latcllites? Why doubtful? 517. Distance and diameter of Neptune? Period? How long to pass from the Sun to it at railroad speed? 518. What remarkable circum- 14; :es respecting its discovery? Perturbation? 248 ASTRONOMY. 519. At first this discrepancy between the observed and the esiimated places of Uranus, was charged upon the tables, and :i new orbit and new tables were computed, which it was thought could not fail to represent the future places of the planet. But these also seemed to be erroneous, as it was soon discovered that the computed and observed places did not agree, and the differ- ence was becoming greater and greater every year. This was an anomaly in the movements of a planetary body. It was not strange that it should be subject to perturbations, from the attrac- tive influence of the large planets Jupiter and Saturn, as these were known to act upon him, as well as upon each other, and the smaller planets, producing perturbations in their orbits, but all this had been taken into the account in constructing the tables, and still the planet deviated from its prescribed path. 520. To charge the discrepancy to the tables, was no longer reasonable, though it was thought perhaps sufficient allowance had not been made, in their computation, for the disturbing influ- ence of Jupiter and Saturn. To determine this question, M. Lc- verrier, of Paris, undertook a thorough discussion of the sub- ject, and soon ascertained that the disturbing influence upon Uranus of all the known planets, was not sufficient to account for the anomalous perturbations already described, and that they were probably caused by some unknown planet, revolving beyond the orbit of Uranus. From the amount and effect of this dis- turbing influence from an unknown source, the distance, magni- tude, and position of the imaginary planet were computed. 521. At this stage of the investigation, Leverrier wrote to his friend, Dr. Galle, of Berlin, requesting him to direct his telescope to that part of the heavens in which his calculations had located the new planet, when lo ! there he lay, a thousand millions of miles beyond the orbit of Uranus, and yet within less than one degree of the place pointed out by Leverrier ! This was on the 1st of September, 1846. 522. While M. Leverrier was engaged in his calculations at Paris, Mr. Adams, a young mathematician of Cambridge, Eng- land, was discussing the same great problem, and had arrived at similar results even before M. Leverrier, though entirely igno- rant of each other's labors or conclusions. This seems to estab- 519. To what attributed at first? What done to correct? What then? 520. What next undertaken, and by whom? What result and conclusion ? 521. What remarkable computation and letter? Result of Dr. Guile's search? 522. Who else investigating the subject at the same time? His conclusions? What fact does this establish? 'Why not Adams the discoverer? THE PRIMARY STARS SATURN AND NEPTU^fc. lish the fact, that the new planet was discovered by calculation, though the failure of Mr. Adams to publish his conclusions, cut off his right to the honor of the discovery. 523. Since the discovery of this planet, it has been ascertained that it was seen as far back as 1795, though supposed to be a fixed star, and catalogued as such ; and that all the irregulari- ties of Uranus, with which astronomers were so much perplexed, are perfectly accounted for by the influence of the new planet. 524. Neptune is attended by but one satellite, s far as is known. It was discovered by Mr. Lassell, of Starfield, near Liverpool, October 12, 1846. It revolves around its primary in 5 days and 21 hours, at a distance of 236,000 miles from the planet's centre. Its orbit is inclined to the plane of the ecliptic 29, and its motion in its orbit is retrograde, like the direction of the satellites of Uranus. CHAPTER IX. COMETSTHEIR NATURE, MOTIONS, ORBITS, &o. 525. COMETS, whether viewed as ephemeral meteors, or as substantial bodies, forming a part of the solar system, are objects of no ordinary interest. When, with uninstructed gaze, we look upwards, to the clear sky of evening, and behold, among the multitudes of heavenly bodies, one, blazing with its long train of light, and rushing onward towards the center of our system, we insensibly shrink back as if in the presence of a supernatural being. But when, with the eye of astronomy, we follow it through its perihelion, and trace it far off, beyond the utmost verge of the solar system, till it is lost in the infinity of space, not to return for centuries, we are deeply impressed with a sense of that power which could create and set in motion such bodies. 526. Comets are distinguished from the other heavenly bodies, by their appearance and motion. The appearance of the planets 528. Has Neptune ever been seen prior to 1846? What supposed to be? Does it account for the perturbation of Uranus? 524. Has Neptune a satellite? When, and by whom discovered? What said of rings? 525. Subject of this chapter? How eoiuets regaried by the uniiistructed ? By the astronomer? 526. How distinguished c?Tfff 250 ASTRONOMY. is globular, and their motiou around the Sun is nearly in the same plane, and from west to east ; but the comets have variety of forms, and their orbits are not confined to any par- ticular part of the heavens ; nor do they observe any one general direction. The orbits of the planets approach nearly to circles, while those of the comets are very elongated ellipses. A wire hoop, for example, will represent the orbit of a planet. If two oppo- site sides of the same hoop be extended, so that it shall be long and narrow it will then represent the orbit of a comet. The Sun is always in one of the foci of the comet's orbit. ORBIT OF A OOMBT. Here it will be seen that the orbit is very eccentric, that the perihelion point is very near the Sun, and the aphelion point very remote. There is, however, a practical difficulty of a peculiar nature which embarrasses the solution of the question as to the form of the cometary orbits. It so happens that the only part of the course of a comet which can ever be visible, is a portion throughout which the ellipse, the parabola, and hyperbola, so closely resemble each other, that no observations can be obtained with sufficient accuracy to enable us to distinguish them. In fact, the observed path of any comet, while visible, may belong either to an ellipse, parabola, or hyperbola. 527. That part which is usually brighter, or more opaque, than the other portions of the comet, is called the nucleus. This is surrounded by an envelope, which has a cloudy, or hairy appear- ance. These two parts constitute the body, and, in many instances, the whole of the comet. Most of them, however, are attended by a long train, called the tail ; though some are with- out this appendage, and as seen by the naked eye, are not easily distinguished from the planets. Others again, have no apparent nucleus, and seem to be only globular masses of vapor. Nothing is known with certainty of the composition of these bodies. The envelope appears to be nothing more than vapor, becoming more luminous and transparent when from other bodies? Form? Orbits? What practical difficulty mentioned? 527. What is the nucleus of a comet? The envelope f The tailt Have all comets these three parts? Do we understand of what they are composed? What evidence of their extreme tenuity ? COMETS THEIR NATURE, MOTIONS, ORBITS, ETC. 25 1 approaching the Sun. As the comets pass between us and the fixed stars, their envelopes and tails are so thin, that stars of very small magnitude may be seen through them. Some comets, hiving no nucleus, are transparent throughout their whole extent. 528. The nucleus of a comet sometimes appears opaque, and It then resembles a planet. Astronomers, however, are not agreed upon this point. Some affirm that the nucleus is always transparent, and that comets are in fact nothing but a mass of vapor, more or less condensed at the center. By others it is main- tained that the nucleus is sometimes solid and opaque. It seems probable, however, that there are three classes of comets, viz. ; 1st. Those which have no nucleus, being transparent throughout their whole extent ; 2d. Those which have a trans- parent nucleus ; and, 3d. Those having a nucleus which is solid and opaque. 529. A comet, when at a distance from the Sun, viewed through a good telescope, has the appearance of a dense vapor surrounding the nucleus, and sometimes flowing far into the regions of space. As it approaches the Sun, its light becomes more brilliant, till it reaches its perihelion, when its light is more dazzling than that of any other celestial body, the Sun excepted. Iii this part of its orbit are seen to the best advantage the phe- nomena of this wonderful body, which has, from remote antiquity, been the specter of alarm and terror. 530. The luminous train of a comet usually follows it, as it approaches the Sun, and goes before it, when the comet recedes from the Sun ; sometimes the tail is considerably curved towards the region to which the comet is tending, and in some instances, it has been observed to form a right angle with a line drawn from the Sun through the center of the comet. The tail of the comet of 1744, formed nearly a quarter of a circle ; that of 1689 was curved like a Turkish sabre. (Map IX., Fig. 73.) Sometimes the same comet has several tails. That of 1744 had, at one time, no less than six, which appeared and disappeared in a few days. (See Map IX., Fig. 74.) The comet of 1823 had, for several days, two tails ; one extending towards the Sun, and the other in the opposite direction. 531. Comets, in passing among and near the planets, are ma- terially drawn aside from their courses, and in some cases have their orbits entirely changed. This is remarkably true in regard 528. What difference of opinion respecting t* e nucleus of comets ? What probable solution? 529. How do they appear when viewed through a telescope at a distance from the Sun? As it approaches him? Where seen to best advantage? 530. Usual Jirection of the trains of cornets? Other positions ? Comet of 1744? Of Ib89? Of $23? 581. Influence of attraction upon cornets? Illustrations? Comet of 1770? 11* 252 ASTRONOMY. to Jupiter, which seems by some strange fatality to be constantly in their way, and to serve as a perpetual stumbling-block to them. " The remarkable comet of 1T70, which was found by Lexell to revolve in a moderat* ellipse, in a period of about five years, actually got entangled among the satellites of Jupiter, and thrown out of its orbit by the attractions of that planet," and 1ms not been heard of since. ffersctiel, p. 310. By this extraordinary rencontre, the motions of Jupiter's satellites suffered not the least perceptible derangement ; a sufficient proof of thj aeriform nature of the comet's mass. 532. It is clear from observation, that comets contain very little matter. For they produce little or no effect on the motion of the planets when passing near those bodies ; it is said that a comet, in 1454, eclipsed the Moon ; so that it must have been very near the Earth ; yet no sensible effect was observed to be produced by this cause, upon the motion of the Earth or the Moon. The observations of philosophers upon comets, Ijave as yet detected nothing of their nature. Tycho Braue and Appian supposed their tails to be produced by the rays of the Sun transmitted through the nucleus, which they supposed to be transparent, and to ope- rate as a lens. Kepler thought they were occasioned by the atmosphere of the comet, driven off by the impulse of the Sun's rays. This opinion, with some modification, was also maintained by Euler. Sir Isaac Newton conjectured that they were a thin vapor, rising from the heated nucleus, as smoke ascends from the Earth; while Dr. Hamilton eupposed them to be streams of electricity. " That the luminous part of a comet," says Sir John Hcrschel, " is something in the nature of a smoke, fog, or cloud, suspended in a transparent atmosphere, is evident from a fact which has been often noticed viz., that the portion of the tail where it comes up to, and surrounds the head, is yet separated from it by an interval less luminous ; as we often see one layer of clouds laid over another with a considerable clear space between them." And again : " It follows that these can only be regarded as great masses of thin vapor, susceptible of being penetrated through their whole substance by the sunbeams." 533. Comets have always been considered by the ignorant and superstitious, as the harbingers of war, pestilence, and famine. Nor has this opinion been, even to this day, confined to the unlearned. It was once universal. And when we examine the dimensions and appearances of some of these bodies, we cease to wonder that they produced universal alarm. According to the testimony of the early writers, a comet which could be sef-n in day- light with the naked eye, made its appearance 43 years before the birth of our Saviour. This date was just after the death of Cajsar, and by the Romans, the comet was believed to be his metamorphosed soul, armed with fire and vengeance. This comet is again men- tioned as appearing in 1106, and then resembling the Sun in brightness, being of H great size, and having an immense tail. In the year 1402, a comet was seen, so brilliant ai to be discerned at noon-day. 534. In 1456, a large comet mads its appearance. It spread a wider terror than was ever known before. The belief was very general, among all classes, that the comet would destroy the Earth, and that the Day of Judgment was at hand ! 532. What said of their i Lysical natures ? Opinion of Tycho Brahe ? Of Kepler and Euler ? Of Newton and Dr. Hamilton 1 Of Sir John Herschel ? 533. How have cornets usually been regarded by ihe ignorant? What remarkable comet mentioned? 534. What comet in 1456 ? Effect of its appearance ? Has it appeared since ? Its period ? COMETS THEIR NATURE, MOTIONS, ORBITS, ETC. 2f3 The same comet appeared again in the years 1531, 1607, 1682, 1758 and 1835. It passed its perihelion in November, 1835, and will re-appear every 75 years thereafter. At the trme of the appearance of this comet, the Turks extended their victorious arms across ^he Hellespont, and seemed destined to overrun all Europe. This added not a little to the general gloom. Under all these impressions, the people seemed totally regard- less of the present, and anxious only for the future. The Romish Church held at this time unbounded sway over the lives, and fortunes, and consciences of men. To prepare the world for its expected doom, Pope Calixtus III. ordered the Ave Maria to be repeated three times a day, instead of two. He ordered the church bells to be rung at noon, which was the origin of that practice, so universal in Christian churches. To the Ave Maria, the prayer was added 41 Lord ! save us from the Devil, the Turk and the Comet ; and once, each day, these three obnoxious personages suffered a regular excommuni- cation. The Pope and clergy exhibiting such fear, it is not a matter of wonder that it became the ruling passion of the multitude. The churches and convents were crow 'ed for con- fession of sins ; and treasures uncounted were poured into the Apostolic chat. ber. The comet, after suffering some months of daily cursing and excommunicati % n, began to show signs of retreat, and soon disappeared from those eyes in which it -und nc favor. Joy and tranquillity soon returned to the faithful subjects of the Pope, bu not sc their money and lands. The people, however, became satisfied that their lives, and the safety of the world, had been cheaply purchased. The Pope, who had achieved so signal a victory over the monster of the sky, had checked the progress of the Turk, and kept, for the present, his Satanic majesty at a safe distance ; while the Church of Rome, retaining her unbounded wealth, was enabled to continue that influence over her follow- ers, which she retains, in part, to this day. 535. The comet of 1680 would have been still more alarming than that of 1456, had not science robbed it of its terrors, and history pointed to the signal failure of its predecessor. This comet was of the largest size, and had a tail whose enormous length was more than ninety-six millions of miles. (Map IX., Fig. 75.) At its greatest distance, it is 13,000,000,000 of miles from the Sun ; and at its nearest approach, only 574,000 miles from his center ;* or about 130,000 miles from his surface. In that * In Brewster's edition of Ferguson, this distance is stated as only 49,000 miles. This is evidently a mistake ; for if the comet approached the Sun's center within 49,000 miles, It would penetrate 390,000 miles below the surface ! Taking Ferguson's own elements for computing the perihelion distance, the result will be 494,460 miles. The mistake may be accounted for, by supposing that the cypher had been omitted in the copy, and the period pointed off one figure farther to the left. Yet, with this alteration, it would be still incor- rect ; because the Earth's mean distance from the Sun, which is the integer of this calcu- lation, is assumed at 82,000,000 of miles. The ratio of the comet's perihelion distance from the Sun, to the Earth's mean distance, as given by M. Pingre, is as 0.00603 to 1. This multiplied into 95,273,869, gives 574,500 miles for the comet's perihelion distance from the Sun's center; from which, if we substract his semi-diameter, 443,840 miles, we shall have 130,660 miles, the distance of the comet from the turface of the Sun. Again, if we divide the Earth's mean distance from the Sun, by the comet's perihelion distance, we shall find that the latter is only l-166th part of the Earth's distance. Now the square of 166 is 27,556 ; and tins expresses the number of times that the Sun appears larger to the comet, in the above situation, than it does to the Earth. Squire makes it 84,596 times larger. According to Newton, the velocity is 830,000 miles per hour. More recent discoveries indicate a velocity of 1,240,108 miles per hour. Incidents repec ting the Turks and Church of Rome ? 585. Comet of 1680 ? Length of Us tail? Aphelion and perihelion distances? Rapidity of its motion when nearest the Sun f What error corrected ? Appearance of the Fun from that point ? Heat of the comet? Indicates what? Fanciful theory of Dr. Whislon, and remarks upon it? 254 ASTRONOMY. part of its orbit which is nearest the Sun, it flies with the amaz- ing swiftness of 1,000,000 miles in an hour, and the Sun, as seen from it, appears 27,000 times larger than it appears to us ; con- sequently, it is then exposed to a heat 27,000 times greater than the solar heat at the Earth. This intensity of heat exceeds, several thousand times, that of red-hot iron, and indeed all the degrees of heat that we are able to produce. A simple mass of vapor, exposed to a thousandth part of such a heat, would be at once dissipated in space a pretty strong indication that, however volatile are the elements of which comets are composed, they aro, nevertheless, capable of enduring an inconceivable intensity of both heat and cold. This ' the comet which, according to the reveries of Dr. Winston and others, deluged the vrr id in the time of Noah. Whiston was the friend and successor of Newton ; but, anxi< us to know more than is revealed, he passed the bounds of sober philosophy, and presumed not only to fix the residence of the damned, but also the nature of their punish- ment. According to this theory, a comet was the awful prison-house in which, as it wheeled from the remotest regions of darkness and cold into the very vicinity of the Sun, hurrying its wretched tenants to the extremes of perishing cold and devouring fire, the Almighty was to dispense the severities of his justice. Such theories may be ingenious, but they have no basis of facts to rest upon. They more properly belong to the chimeras of Astrology, than to the science of Astronomy. 536. When we are told by philosophers of great caution and high reputation, that the fiery train of the comet, just alluded to, extended from the horizon to the zenith ; and that that of 1744 had, at one time, six tails, each 6,000,000 of miles long, long, and that another, which appeared soon after, had one 40,000,000 of miles long, and when we consider also the incon- ceivable velocity with which they speed their flight through the solar system, we may cease to wonder if, in the darker ages, they have been regarded as evil omens. But these idle fantasies are not peculiar to any age or country. Even in our own times, the beautiful comet of 1811, the most splendid one of modern times, was generally considered among the superstitious, as the dread harbinger of the war which was declared in the following spring. It is well known that an indefinite apprehension of a more dreadful catastrophe lately pervaded both continents, in anticipation of Biela'a comet of 1S32. 537. The nucleus of the comeS of 1811, according to observa- tions made near Boston, was 2617 miles in diameter, correspond- ing nearly to the size of the Moon. The brilliancy with which it shone, was equal to one-tenth of that of the Moon. The envelope, or aeriform covering surrounding the nucleus, was 24,000 miles thick, about five hundred times as thick as the atmosphere which encircles the Earth ; making the diameter of comet, including its envelope, 50,617 miles. It had a very 536. Why not strange that these comets were regarded as evil omens ? Are such super- stitions peculiar to any age or country? What illustrations? 537. Size of the cone* of ISll? Its motion at its perihelion ? COMETS THEIR NATURE, MOTIONS, ORBITS, ETC. 255 luminous tail, whose greatest length was onv. hundred millions of mileJ. Map IX., Fig. 76. This comet moved, in its perihelion, with an almost inconceivable velocity fifteen hundred times greater than that of a ball bursting from the mouth of a cannon. 538. According to Regiomontanus, the comet of 1472 moved over an arc of 120 in one day. Brydone observed a comet at Palermo in 1770, which passed through 50 of a great circle in the heavens in 24 hours. Another cornet, which appeared in 1759, passed over 41 in the same time. The conjecture of Dr. Halley, therefore, seems highly probable, that if a body of such a size, having any considerable density, and moving with such a velocity, were to strike our Earth, it would instantly reduce it to chaos, mingling its elements in ruin. The transient effect of a body passing near the Earth, could scarcely amount to any great convulsion, says Dr. Brewster ; but if the Earth were actually to receive a shock from one of these bodies, " having any considerable density," the consequences would indeed be awful. A new direction would be given to its rotary motion, and it would revolve around a new axis. The seas, forsaking their beds, would be hurried, by their centrifugal force, to the new equatorial regions ; islands and continents, the abodes of men and animals, would be covered by the universal rush of the waters to the new equator, and every vestige of human industry and genius would be at once destroyed. But so far as we are as yet acquainted with these singular bodies, they are altogether too light and gasseous to produce any such results by collision. 539. The chances against such an event, however, are so very numerous, that there is no reason to dread its occurrence. The French government, not long since, called the attention of some of her ablest mathematicians and astronomers to the solution of this problem ; that is, to determine upon mathematical principles, how many chances of collision the Earth was exposed to. After a mature examination, they reported " We have found that, of 281,000,000 of chances, there is only one unfavorable there ex- ists but O7ie which can produce a collision between the two bodies." " Admitting, then," say they, u for a moment, that the comets which may strike the Earth with their nucleuses, would annihilate the whole human race; the danger of death to each individual, resulting from the appearance of an unknmcn com there must be 3,529,470 within the orbit of Uranus ! 552. Of 97 comets whose elements have been calculated by astronomers, 24 passed between the Sun and the orbit of Mer- cury: 33 between the orbits of Mercury and Yenus ; 21 between the orbits of Yenus and the Earth ; 15 between the orbits of Ceres and Jupiter. 49 of these comets move from east to west, and 49 in the opposite direction. The total number of distinct comets, whose paths during the visible part of their course had been ascertained, up to the year 1855, was about one hundred and fifty. 553. What regions these bodies visit, when they pass beyond the limits of our view ; upon what errands they come, when they again revisit the central parts of our system ; what is the difference between their physical constitution and that of the Sun and planets ; and what important ends they are destined to accomplish in the economy of the Universe, are inquiries which naturally arise in the mind, but which surpass the limited powers of the human understanding at present to determine. 554. Such is the celestial system with which our Earth was associated at its creation, distinct from the rest of the starry hosts. Whatever may be the comparative antiquity of our globe, and the myriads of radiant bodies which nightly gem the immense vault above us, it is most reasonable to conclude, that the Sun, Earth, and planets differ little in the date of their origin. This, fact, at least, seems to be philosophically certain, that all the bodies which compose our solar system must have been placed at one and the same time in that arrangement, and in those positions in which we now behold them ; because all maintain their present stations, and motions, and distances, by thrir mutual action on each other. Neither could it be where it Phenomenon 60 years before Christ? M. Arago's reasoning and conclusion? 652. Perihelion distances of various comets ? Directions in longitude ? Number whose paths have been ascertained? 553. What inquiries awakened by the visits of cometary bodies? 5;>4. Remarks respecting the date of the solar system? What supposed proof that the whole system was created at once? 262 ASTRONOMY. is, nor move as it docs, nor appear as we see it, unless they were all co-existent. The presence of each is essential to the system the Sun to them, they to the Sun, and all to each other. This fact is a strong indication that their formation was simultaneous. CHAPTER X. OF THE FORCES BY WHICH THE PLANETS ARE RETAINED IN THEIR ORBITS. 555. HAVING described the real and apparent motions of the bodies which compose the solar system, it may be interesting next to show, that these motions, however varied or complex they may seem, all result from one simple principle, or law, tiamely, the LAW OF UNIVERSAL GRAVITATION. By gravitation is meant, that universal law of attraction, by which every particle of matter in the system has a tendency to every other particle. This attraction, or tendency of bodies towards each other, is in proportion to the quantity of matter they contain. The Earth, being immensely large in comparison with all other substances in its vicinity, destroys the effect of this attraction between smaller bodies, by bringing them all to itself. It is said, that Sir Isaac Newtoa, when he was drawing to a close the demonstration of the great truth, that gravity is the caus which keeps the heavenly bodies in their orbits, was so much agitated with the magnitude and importance of the discovery he was about to make, that he was unable to proceed, and desired a friend to finish what the intensity of his feelings did not allow him to do. 556. The attraction of gravitation is reciprocal. All bodies not only attract other bodies, but are themselves attracted, and both according to their respective quantities of matter. The Sun, the largest body in our system, attracts the Earth and all the other pianets, while they in turn attract the Sun. The 555. Subject of this chapter? What is meant by gravitation ? Upon what does the amount of this attraction depend ? Influence of the Earth ? Anecdote of Newton ? f>f>6. Is attraction reciprocal? What illustration cited? Ways in which attraction LAW OF GRAVITATION. 253 Earth, also, attracts the Moon, and she in turn attracts the Earth. A ball, thrown upwards from the Earth, is brought again to its surface ; the Earth's attraction not only counter- balancing that of the ball, but also producing a motion of the ball towards itself. This disposition, or tendency towards the Earth, is manifested in whatever falls, whether it be a pebble from the hand, an apple from a tree, or an avalanche from a mountain. All terrestial bodies, not excepting the waters of the ocean, gravitate towards the center of the Earth, and it is by the same power that animals on all parts of the globe stand with their feet pointing to its center. 557. The power of terrestial gravitation is greatest at the Earth's surface, whence it decreases both upwards and down- wards ; but not both ways in the same proportion. It decreases upwards as the square of the distance from the Earth's center increases ; so that at-a distance from the center equal to twice the semi-diameter of the Earth, the gravitating force would be only one-fourth of what it is at the surface. But below the sur- face, it decreases in the direct ratio of the distance from the center ; so that at a distance of half a semi-diameter from the center, the gravitating force is but half of what it is at the surface. Weight and Gravity, in this case, are synonymous terms. We say a piece of lead weighs a pound, or 16 ounces ; but if by any means it could be raised 4000 miles above the surface of the Earth, which is about the distance of the surface from the center, and consequently equal to two semi-diameters of the Earth above its center, it would weigh only one-fourth of a pound, or four ounces ; and if the same weight could be raised to an elevation of 12,000 miles above the surface, or four semi-diameters above the center of the Earth, it would there weigh only one-sixteenth of a pound, or one ounce. 558. The same body, at the center of the Earth, being equally attracted in every direction, would be without weight ; at 1000 miles from the center it would weigh one-fourth of a pound : at 2000 miles, one-half of a pound ; at 3000 miles, three-fourths of a pound ; and at 4000 miles, or at the surface, one pound. It is a universal law of attraction, that its power decreases as the square of the, distance increases. The converse of this is also true, viz.: The power increases as the square of the distance decreases. Giving to this law the form of a practical rule, it will stand thus : The gravity of bodies above the surface of the Earth decreases in a duplicate ratio (or as the squares of their distances), in semi- diameters of the Earth, from the Earth's center. That is, when manifests itself? 557. Where is the power of terrestrial gravitation greatest? How diminished ? In what ratio as we ascend above the Earth ? As we descend toward its tenter? Are weight and gravity the same ? 558. What would be the weight of a body at the Earth's center? At 100 miles from the center ? At 2000 miles ? At 4000? What nuiversallaw? What rule based upon this law? What illustrations given? What rule 264 ASTRONOMY. the gravity is increasing, multiply the weight by the square tff the distance ; but when the gravity is decreasing, divide, the './eight by the square of the distance. Suppose a body weighs 40 pounds at 2000 miles above the Earth's surface, what would it weigh at the surface, estimating the Earth's semi-diameter at 4000 miles, from th), and it will be found that (865.2564)* : (6S6.979C)-' : : (1)3 : (1.52369)3. 667. State the second law of Kepler? Explain it? UJuuration ? J. The Utird 'aw? What E.G. 12 ASTRONOMY. According to these laws, which are known to prevail throughout the solar system, many of the facts of astronomy are deduced from other facts previously ascertained. They are, therefore, of great importance, and should be studied till they are, at least, thoroughly understood, if not committed to memory. 569. From the foregoing principles, it follows, that the force of gravity, and the centrifugal force, are mutual opposing powers each continually acting against the other. Thus, the weight of bodies on the Earth's equator, is diminished by the centrifugal force of her diurnal rotation, in the proportion of one pound for every 290 pounds : that is, had the Earth no motion on her axis, all bodies on the equator would weigh one two hundred and eighty-ninth part more than they now do. On the contrary, if her diurnal motion were accelerated, the centrifugal force would be proportionally increased, and the weight of bodies at the equator would be in the same ratio diminished. Should the Earth revolve upon its axis with a velocity which would make the day but 84 minutes long, instead of 24 hours, the centrifugal force would coun- terbalance that of gravity, and all bodies at the equator would then be absolutely desti- tute of weight ; and if the centrifugal force were further augmented (the Earth revolving in less than 84 minutes), gravitation would be completely overpowered, and all fluids, and loose substances near the equator would fly off from the surface. 570. The weight of bodies, either upon the Earth, or on any other planet having a motion around its axis, depends jointly upon the mass of the planet, and its diurnal velocity. A body weighing one pound upon the equator of the Earth, would weigh, if removed to the equator of the Sun, 27.91bs.; of Mer- cury, 1.03 Ibs.; of Venus, 0.98 Ibs.; of the Moon, l-6th of a-lb. ; of Mars, J Ib. ; of Jupiter, 2.716 Ibs. ; of Saturn, 1.01 Ibs. CHAPTER XL PROPER MOTION OF THE SUN IN SPACE. 571. THOUGH we are accustomed to speak of the Sun as the fixed center of the Solar System, the idea of his fixedness is cor- rect only so far as his relation to the bodies revolving around him are concerned. As the planets accompanied by their satel- lites revolve around the Sun, so he is found to be moving with all his retinue of worlds, in a vast orbit, around some distant and unknown center. 569. What results from these principles, as respects the weight of bodies on the Earth's surface? How increased or diminished? What illustrations given? 570. Upon what, then, does the weight of bodies upon the planets depend? What illustrations? CTl. IB the Sun a fixed body? What motion in space? Who first advanced this uleaf PROPER MOTION OF THE SUN IN SPACE. 269 This opinion was first advanced, we think, by Sir William Herschel ; but the honor of actually determining this interesting fact, belongs to Struve, who ascertained not only the direction of the Sun and Solar System, but also their velocity. The point of tend- ency is towards the constellation Hercules, Right Ascension 259*, Declination 35*. The velocity of the Sun, Ac., in space, is estimated at about 20,000 miles per hour, or nearly S miles per second ; 572. With this wonderful fact in view, we may no longer con- sider the Sun as fixed and stationary, but rather as a vast and luminous planet, sustaining the same relation to sonic central orb, that the primary planets sustain to him, or that the second- aries sustain to their primaries. Nor is it necessary that the stupendous mechanism of nature should be restricted even to these sublime proportions. The Sun's central body may also have its orbit, and its center of attraction and motion, and so on, till, as Dr. Dick observes, we come to the greftt center of all to the THRONE OF GOD. THE CENTRAL SUN. 573. In 1847, an article appeared in several European jour- nals, announcing the probable discovery by Professor Madler, of Dorpat, of the Sun's central orb ; the inclination of his orbit to the. plant of the. ecliptic ; and his periodic time ! By an extensive and laborious comparison of the quantities and directions of the proper motions of the stars in various parts of the heavens, combined with indications afforded by the paral- laxes hitherto determined, and with the theory of universal gra- vitation, Professor Madler arrived at the conclusion that the Pleiades form the central group of our whole astral or sidereal system, including the Milky Way and all the brighter stars, but exclusive of the more distant nebulas, and of the stars of which those nebulae may be composed. And within this central group itself he has been led to fix on the star Alcyone, as occupying exactly or nearly the position of the center of gravity, and as entitled to be called the central Sun. Assuming Bessel's parallax of the star 61 Cygni, long since remarkable for its larger proper motion, to be correctly determined, Madler proceeds to form a first approximate estimate of the distance of this central body from the planetary or solar system ; and arrives at the provisional conclusion, that Alcyone is about 84,000,000 times as far removed from us, or from our own Sun, as the latter luminary is from us. It would, therefore, according to this estimation, be at least a million times as distant as the new planet, of which the theoretical or deductive discovery has been so great and beautiful a triumph of modern astronomy, and so striking a confirmation of the law of Newton. The same approximate determination of distance conducts to the result, that the light of the cen- tral sun occupies more than five centuries in travelling thence to us. Direction and velocity of the Sun and Solar System ? 572. How, then, should we regard the Sun? What further speculation? Dr. Dick's observation? 573. What great discovery in 1847, and by whom? By what process? What conclusion first reached ? What star afterward designated ? Further description of the progress of the discovery ? What conclusion respecting the passage of light from the :entral Sun to u* f 270 ASTRONOMY 574. The enormous orbit which our own Sun, with the Earth, and the other planets, is thus inferred to be describ- ing about that distant ARC OF THE BUS'S ORBIT cen- -not, indeed, under its o ter- influence alone, but by the combined attractions of all the stars which are nearer to it than we are, and which are estimated to amount to more than 117,000,000 % of masses, each equal to the total mass of our own Solar System is supposed to require upwards of eighteen millions of years for its complete description, at the rate of about eight geographical miles in every second of time. At this rate, the arc of its orbit, over which the Sun has traveled since the creation of the world, amounts to only about ^oVo^h P ar * f n ^ s orbit, or about 7 minutes an arc so small, compared with the whole, as to be hardly distinguishable from a straight line. The plane of this vast orbit of the Sun is judged to have an inclination of about 84 degrees to the ecliptic, or to the plane of the annual orbit of the Earth ; and the longitude of the ascending node of the former orbit on the latter is concluded to be nearly '232 degrees. CHAPTER XII. PRECESSION OF THE EQUINOXES OBLIQUITY OF THE ECLIPTIC. 575. OF all the motions which are going forward in the Solar System, there is none, which it is important to notice, more difficult to comprehend, or to explain, than what is called the PRECESSION OF THE EQUINOXES. The equinoxes, as we have learned, are the two opposite 574. Supposed period of the Sun's revolution ? What portion of his orbit gone over lince the creation of our race? Situation of his orbit with respect to the ecliptic? Lon- gitude of ascending node? 575. Subject of this chapter? What are the equinoxes? PRECESSION OF THE EQUINOXES. 271 points in the Earth's orbit, where it crosses the celestial equator. The first is in Aries; the other, in Libra. By the precession of the equinoxes is meant, that the intersection of the equator with the ecliptic is not always in the same point : in other words, that the Sun, in its apparent annual course, does not cross the equi- noctial, Spring and Autumn, exactly in the same points, but every year a little behind those of the preceding year. 576. This annual falling back of the equinoctial points, is called by astronomers, with reference to the motion of the heavens, the Precession of the Equinoxes; but it would better accord with fact as well as the apprehension of the learner, to call it, as it is, the Recession of the Equinoxes ; for the equinoc- tial points do actually recede upon the ecliptic, at the ra f e of about 50J" of a degree every year. It is the name only, and not the position, of the equinoxes which remains permanent. Wherever the Sun crosses the equinoctial in the spring, there is the vernal equinox ; and wherever he crosses it in the autumn, there is the autumnal equinox \ and these points are constancy PRECKSSIOS OF THB KQCINOXKS. moving to the west. To render this subject familiar, we will suppose two carriage roads, extending quite around the Earth ; one, representing the equator, run- ning due east and west; and the other representing the ecliptic, run- ning nearly in the same direction as the former, yet so as to cross it with a small angle (say of 23%), both at the point where we now stand, for instance, and in the nadir, exactly opposite ; let there also be another road, to represent the prime meri- dian, running north and south, and crossing the first at right angles, in the common point of intersection, as in the annexed figure. Let a carriage now start from this point of intersection, not in the road leading directly east, but along that of the ecliptic, which leaves the former a little to the north, and let a person )>e placed to watch when the carriage comes around again, after having made the circuit of the Earth, and see whether the carriage will cross the equinoctial road again precisely in the same track as when it left the goal. Though the person stood exactly in the former track, he need not fear being run over, for the carriage will cross the road 100 rods west of him, that is 100 rods west of the meridian on which he stood. It is to be observed, that 100 rods on the equator is equal to 50^ seconds of a degree. If the carriage still continue to go around the Earth, it will, on completing its second What meant by their precession? 676. With reference to what Is it a precettionf It it really a precession of the equinoxes ? Where are the equinoxe* spring and fall ? Can you illustrate by the two carriage roads, &c. ? By the other diagram? Does the Sun 372 ASTRONOMY. RECESSION OF TUB EQUINOXES. circuit, cross the equinoctial path 200 rods west of the meridian whence it fltst set out ; on the third circuit, 300 rods west; on the fourth circuit, 400 rods, and so on, continually. After 71% circuits, the point of intersection would be one degree west of its place at the commencement of the route. At this rate it would be easy to determine how many com- plete circuits the carriage must perform before this continual falling back of the inter- secting point would have retreated over every degree of the orbit, until it reached again the point from whence it first departed. The application of this illustration will be mani- fest when we consider, further, that this interesting phenomenon may be explained in another way by the actial. 3 E is the obliquity of the ecliptic. The star C, at the top, represents the pole star, and the curve \ine passing to the right from it, may represent the circular orbit of the north pole of the heavena around the north pole of the ecliptic. 586. The effect of such a motion on the aspect of the heavens, is seen in the apparent approach of some stars and constellations to the celestial pole, and the recession of others. The bright star of the Lesser Bear, which we call the poh star, has not always been, nor will always continue to be, our polar star. At the time of the con- 584. What said of the causa of this recession? 585. what, then, does It consist? What said of the pole of the ecliptic, and the aspects of ti- neavens during this revolu- tion? 685. How ia the effect of this motion manifeu u? How with the Pole star? SUTATION Or TDK KABTH'S AXIS. B PRECESSION OF THE EQUINOXES. 277 struction of the earliest catalogue, this star was 12 from the pole ; it is now only 1 34' from it, and it will approach to within half a degree of it ; after which it will again recede, and slowly give place to others, which will succeed it in its proximity to the pole. The pole, as above considered, Is to be understood, merely, as the vanishing paint of the Earth's axis; or that point in the concave sphere which is afaxtys opposite the terrestial pole, and which consequently must move as that moves. 587. The precession of the stars in respect to the equinoxes, is less apparent the greater their distance from the ecliptic ; for whereas a star in the zodiac will appear to sweep the whole circumference of the heavens in an equinoctial year, a star situ- ated within the polar circle will describe only a very small circle in that period, and by so much the less, as it approaches the pole. The north pole of the Earth being elevated 23 2 7' towards the tropic of Cancer, the circumpolar stars will be suc- cessively at the least distance from it, when their longitude is 3 signs or 90. 588. The position of the north polar star in 1855, was in the 17 of Taurus; when it arrives at the first degree of Cancer, which it will do in about 250 years, it will be at its nearest possible approach to the pole namely, 29' 55". About 2900 years before the commencement of the Christian era, Alpha Dra- conis, the third star of the Dragon's tail, was in the first degree of Cancer, and only 10' from the pole ; consequently it was then the pole star. After the lapse of 11,600 years the star Lyra, the brightest in the northern hemisphere, will occupy the position of a pole star, being then about 5 degrees from the pole ; whereas now its north polar distance is upward of 51. The mean average precession from the creation (4004 B. C.) to the year 1800, is 49'.51465; consequently the equinoctial points have receded since the creation, 2s. 14 8' 27". The longitude of the star Beta Ariette, was in 1820, 81 27' 28" : Jfcton, a famous mathematician of Athens, who flourished 480 years before Christ, says, this star, in his time, was in the vernal equinox. If he is correct, then 81 27' 28", divided by 2260 years, the elapsed time, will give 50%* for the precession. Something, however, must be allowed for the imperfection of the instruments used at that day, and even until the six- teenth century. 589. Since all the stars complete half a revolution about the axis of the ecliptic in about 12,500 years, if the North Star be at its nearest approach to the pole 250 years hence, it will, What, then, is the real pole of the heavens ? 687. Where is the precession of the stars most apparent? Where least? When are the circumpolar stars nearest the tropic of Cancer, and why? 588. Where was the pole star in 1856? When will it be nearest the true pole? How near then? What said of Alpha DraconteT Of Lyrat Mean average recession for 5800 years ? Amount? Longitude of Btta Arietin in 1820? Be- fore Christ 480 years, where ? Average of precession for these 2250 years ? 6S9. What further result of the revolution of the pole of the heavens? What effect? Where, then, 278 ASTRONOMY. 12,500 years afterwards, be at its greatest possible distance from it, or about 47 above it : That is, the star itself will remain immovable in its present position, but the pole of the Earth will then point as much below the pole of the ecliptic, as now it points above. This will have the effect, apparently, of elevating the present polar star to twice its present altitude, or 47. Wherefore, at the expiration of half the equinoctial year, that point of the heavens which is now 1 18' north of the zenith of Hartford, will be the place of the north pole, and all those places which are situated 1 18' north of Hartforl, will then have the present pole of the heavens in their zenith. OBLIQUITY OF THE ECLIPTIC. 590. The inclination of the Earth's axis to the plane of the ecliptic causes the equinoctial to depart 23 28' from the eclip- tic. This angle made by the equinoctial and the ecliptic is called the Obliquity of tfie Ecliptic. OBLIQUITY OF TUB ECLIPTIC. B Let the line A A represent the axis of the Earth, and B B the poles or axis of the eclip- tic. Now if the line A A in- clines toward the plane of the ecliptic, or, in other words, departs from the line B B, to the amount of 28 28', it is obvious that the plane of the equator, or equinoctial, will depart from the ecliptic to the same amount. This depar- ture, shown by the angles C C, constitute the obliquity of the ecliptic. 591. Hitherto, we have considered these great primary circles in the heavens, as never varying their position in space, nor with respect to each other. But it is a remarkable and well-ascer- tained fact, that both are in a state of constant change. Wo have seen that the plane of the Earth's equator is constantly drawn out of place by the unequal attraction of the Sun and Moon acting in different directions upon the unequal masses of matter at the equator and the poles ; whereby the intersection of the equator with the ecliptic is constantly retrograding thus producing the precession of the equinoxes. will the north pole be 12,500 years hence ? 590. What is the Obliquity of Hie Ecliptic t b91. Is this angle always the same? What variation of the equinoctial? PRECESSION OF THE JStJlTlXOXSS. 279 592. The displacement of the ecliptic, on the contrary, is pro- duced chiefly by the action of the planets, particularly of Jupi- ter and Venus, on the P^arth ; by virtue of which the plane of the Earth's orbit is drawn nearer to those of these two planets, and consequently, nearer to the plane of the equinoctial. The tendency of this attraction of the planets, therefore, is to dimi- nish the angle which the plane of the equator makes with that of the ecliptic, bringing the two planes nearer together ; and if the Earth had no motion of rotation, it would, in time, cause the two planes to coincide. But in consequence of the rotary motion of the Earth, the inclination of these planes to each other remains very nearly the same ; its annual diminution being scarcely more than three-fourths of one second of a degree. The obliquity of the ecliptic, at the commencement of the present century was, accord- ing to JSaily, 23 27' 56%', subject to a yearly diminution of 0".4T55. According to Bett- *fl, it was 23 27 r 54".32, with an annual diminution of 0'.46. At this date (1855), it is only about 23* 27' 29'. Consequently, the angle is diminished about 27" in 55 years. This diminution, however, is subject to a slight semi-annual variation, from the same caused which produce the displacement of the plane of the ecliptic, in precession. 593. The attraction of the Sun and Moon, also, unites with that of the planets, at certain seasons, to augment the diminu- tion of the obliquity, and at other times, to lessen it. On this account the obliquity itself is subject to a periodical variation ; for the attractive power of the Moon, which tends to produce a change in the obliquity of the ecliptic, is variable, while the diur- nal motion of the Earth, which tends to prevent the change from taking place, is constant. Hence the Earth, which is so nicely poised on her center, lows a little to the influence of the Moon, and rises again, alternately, like the gentle oscillations of a balance. This curious phenomenon is called Nutation (589). In consequence of the yearly diminution of the obliquity of the ecliptic, the tropics ar* elowly and steadily approaching the equinoctial, at the rate of little more than thivr- fourths of a second every year; so that the Sun does not now come so far north of tl:e equator in summer, nor decline ao far south in winter, by nearly a degree, a it must have done at the Creation. 594. The most obvious effect of this diminution of the obli- quity of the ecliptic, is to equalize the length of our days and nights ; but it has an effect also to change the position of the stars near the tropics. Those which were formerly situated north of the ecliptic, near the summer solstice, are now found to be still farther north, and farther from the plane of the ecliptic. On the contrary, those which, according to the testimony of the . 592. What displacement of the ecliptic, and by what caused ? Effect of these causes ? Amount of change annually? Obliquity of the ecliptic in 1800? In 1 855? 593. Diminution In 55 years? What is Mutation f Its cauuef What effect from this annual diminu- tion of obliquity? 594. What other effect? Will this diminution continue? WliM 280 ASTRONOMY. ancient astronomers, were situated south of the ecliptic, near the summer solstice, have approached this plane, insomuch that some are now either situated within it, or just on the north side of it. Similar changes have taken place with respect to those stars situated near the winter solstice. All the stars, indeed, partici- pated more or less in this motion, but less, in proportion to their proximity to the equinoctial. It is important, however, to observe, that this diminution will not always continue. A time will arrive when this motion, growing less and less, will at length entirely cease, and the obliquity will, apparently, remain constant for a time ; after which it will gra- dually increase again, and continue to diverge by the same yearly increment as it before had diminished. This alternate decrease and increase will constitute an endless oscilla- tion, comprehended between certain fixed limits. Theory has not yet enabled us to determine precisely what these limits are, but it may be demonstrated from the constitu- tion of our globe, that such limits exist, and that they are very restricted, probably not exceeding 2 42'. If we consider the effect of this ever- varying attribute in the system of the universe, it may be affirmed that the plane of the ecliptic never has coincided with the plane of the equator, and never will coincide with it. Such a coincidence, could it happen, would produce upon the Earth perpetual spring. 595. The method used by astronomers to determine the obliquity of the ecliptic is, to take half the difference of the greatest and least meridian altitudes of the Sun. The following table exhibits the mean obliquity of the ecliptic for every ten years during the present century. 1800 1810 1820 1S30 1840 1860 23 23 23 28 23 23 27' 27 27 27 27 27 54".78 60 .21 46 .64 41 .07 86 .50 81 .98 1860 1870 1880 1890 1900 1910 23" 28 23 23 28 23 27' 27 27 27 27 27 2V. 36 22 .79 13 .22 13 .65 09 .08 04 .52 CHAPTER XIII. PHILOSOPHY OF THE TIDES. 596. TIDES are the alternate rising and falling of the waters of the ocean, at regular intervals. Flood tide is when the waters are rising ; and ebb tide, when they are foiling. The highest and lowest points to which they go are called, respectively, high and low tides. The tides ebb and flow twice every twenty-four hours i. e., we have two flood and two ebb tides in that time. cycle of oscillation ? Its probable limits? What conclusion from this oscillation of the ecliptic? 595. By what method do astronomers determine the obliquity of the ecliptic f 696. What a re tides? Flood and ebb tides ? High and low ? How often do they ebb aixl flow ? PHILOSOPHY OF THE TIDES. 281 597. The tides are not uniform, either as to time or amount. They occur about 50 minutes later every day (as we shall explain hereafter), and sometimes rise much higher and sink much lower than the average. These extraordinary high and low tides are called, respectively, spring and neap tides. 598. The cause of the tides is the attraction of the Sun and Moon upon the water of the ocean. But for this foreign influ- ence, as we may call it, the waters having found their proper level, would cease to heave and swell, as they now do, from ocean to ocean, and would remain calm and undisturbed, save by their own inhabitants and the winds of heaven, from age to age. In this figure, the Earth is represented as surrounded by water, in a state of rest or equilibrium, as it would be were it not acted upon by the Sun and Moon. 599. To most minds, it would seem that the natural effect of the Moon's attraction would be to produce a single tide-wave on the side of the Earth toward the Moon. It is easy, there- fore, for students to conceive how the Moon can produce one flood and one ebb tide in twenty four hours. In this cut, the Moon is shown at a distance above the Earth, and ONE TIDE-WAVK. attracting the waters of the ocean, so as to produce a high tide at A. But as the moon makes her apparent westward revolution around the ag j Karth but once a day, the simple rising of a flood tide on the side of the ^J Earth toward the moon, would give give us but one flood and one ebb tide in twenty-four hours ; whereas it is known that we have two of each. " The tides," says Dr. Ilerschel, " are a subject on which many per- sons find a strange difficulty of conception. That the Moon by her attraction, should heap up the waters of the ocean under her, seems to many persons very natural. That the same cause should, at the same time, heap them up on the opposite side of the Earth (viz., at B in the figure), seems to many palpably absurd. Yet nothing is more true." 600. Instead of a single tide-wave upon the waters Two -"DE-WAVES. of the globe, directly under the Moon, it is found that on the side of the Earth directly opposite, there is another high tide ; and that half-way between these two high tides are two low tides. These four tides, viz., two high and two low, traverse the ocean from east to west every day, D ^ which accounts for both a flood and an ebb tide every twelve hours. 591. Are the tides uniform? What variation of time? As to amount? What are these extraordinary high and low tides called? 598. The cavxe of tides? How but for this influence? 599. What most obvious effect of the Moon's attraction? Substance of note? Remark of Dr. Uerschel? 6uO. How many tide-wave* are there on the globe, and how situated? 2S2 ASTRONOMY. In this cut, we have a representation of the tide-wave* as they actually exist, that their height, as compared with the magnitude of the Earth, is vastly too great. It is designedly exaggerated, the better to illustrate the principle under consideration. While the Moon at A attracts the waters of the ocean, and produces a high tide at I'., we see another high tide at C on the opposite side of the globe. At the same time it is low tide at I) and E. 601. The principal cause of the tide-wave on the side of the Earth opposite the Moon is the difference, of the Moon's attrac- tion on different sides of the Earth. If the student well understands the subject of gravitation, he will easily perceive how a difference of attraction, as above described, would tend to produce an elongation of the huge drop of water called the Earth. The diameter of the Earth amounts to about _l_th of the Moon's distance; so that, by the rule (558), the difference in her attraction on the side of the Earth toward her, and the opposite side, would be about yVth. The attraction being stronger at B24. What said of the form of the Earth's orbit? When are we nearest the Pun? Why is it not then the warmest in the United States? 626. What is the amount of the Earth's variation in distance from the Sun? What effect upon the light and heat of the Earth? 626. Subject of this chapter? Mean rate of the Moon's daily delay io rising? 294 ASTRONOMY. takes place, especially about the time of narvest, when the full Moon rises to us for several nights together, only from 18 to 25 minutes later in one day, than on that immediately preceding. From the benefit which her light affords, in lengthening out the day, when the husbandmen are gathering in the fruits of the Earth, the full Moon, under these circumstances, has acquired the name of Harvest Moon. It is believed that this fact was observed by persons engaged in agriculture, at a much earlier period than that in which it was noticed by astronomers. The former ascribed it to the goodness of the Deity; not doubting but that he had so ordered it for their advan- tage. 627. About the equator, the Moon rises throughout the year with nearly the equal intervals of 48f minutes ; and there tin; harvest Moon is unknown. At the polar circles, the autumnal full Moon, from her first to her third quarter, rises as the Sun sets ; and at the poles, where the Sun is absent during one-half of the year, the winter full Moons, from the first to the third quarter, shine constantly without setting. By this, it is not meant that the Moon continues full from her first to her third quar- ter ; but that she never sets to the North Polar regions, when, at this season of the year, she is within 90* of that point in her orbit, where she is at her full. In other words, as the Sun illumines the south pole during one-half of its yearly revolution, so the Moon, being opposite to the Sun at her full, must illumine the opposite pole, during half of her revolution about the Earth. The phenomenon of the Harvest Moon may be thus exem- plified by means of the globe. Rectify the globe to the latitude of the place, put a patch or piece of wafer in the eclip- tic, on the point Aries, and mark every 12* preceding and following that point, to the number often or twelve marks on each side of it; bring the equinoctial point marked by the wafer to the eastern edge of the horizon, and set the index to 12; turn the globe westward till the other marks successively come to the hori/,on, and observe the hours passed over by the index ; the intervals of time between the marks coming to the horizon, will show the diurnal difference of time between the Moon's riding. If these marks be Drought to the western edge of the horizon in the same manner, it will show the diurnal difference between the Moon's setting. From this problem it will also appear, that, when there is the least difference between the times of the Moon's rising, there will be the greatest difference between the times of her setting, and the contrary. The reason why you mark every 12 is, that the Moon gains 12* 11' on the apparent course of the Sun every day, and these marks serve to denote the place of the Moon from day to day. It is true, this process supposes that the Moon revolves in the plant of the ecliptic, which is not the case ; yet her orbit so nearly coincides with the ecliptic (differing only 5 9' from It), that they may, for the convenience of illustration, be con- sidered as coinciding ; that is, we may take the ecliptic for the representative of the Moon's orbit. 628. The different lengths of the lunar night, at different lati- tudes, is owing to the different angles made by the horizon and different parts of the Moon's orbit ; or, in other words, by the What remarkable deviation ? What is the Moon then called, and why ? How anciently was this phenomenon observed? To what attributed? 627. Is the Harvest Moon known at the equator? How at the Polar circles? At the poles? Does she there exhi- bit her usual phases ? Can you illustrate the phenomenon of the Harvest Moon by a globe ? &2S. To what is the different lengths of the lunar nights attributable? THE HARVEST MOON AND HORIZONTAL MOON. 295 Moon's orbit lying sometimes more oblique to the horizon than at others. In the latitude of London, for example, as much of the ecliptic rises atnut Pisces and Aries in two hours as the Moon goes through in six days ; therefore, while the Moon is ic these signs, she differs but two hours in rising for six days together ; that is, one day with another, she rises about 20 minutes later every day than on the preceding. 629. The parts or signs of the ecliptic which rise with the smallest angles, set with the greatest ; and those which rise with the greatest, set with the least. And whenever this angle is least, a greater portion of the ecliptic rises in equal times than when the angle is larger. Therefore, when the Moon is in those signs which rise or set with the smallest angles, she rises or sets with the least difference of time ; but when she is in those signs which rise or set with the greatest angles, she rises or sets with the greatest difference of time. Let the globe, for example, be rectified to the latitude of New York, 40* 42' 40', with Cancer on thii ? Mow niadof 13* 300 ASTRONOMY. the light are more refrangible than others, so that the light is analyzed, or separated into its component parts or elements. Let a ray of light from the Sun be admitted through a hole in the window shutter, A, into a room from which all other light is excluded ; it will form on a screen placed a little distance in front, a circular image, B, of white light. Now interpose near the shutter a ghiss prism, C, and the light, in passing through it, will not only be refracted in the same direction, both when it enters the prism and when it leaves it, but the several rays oi which white light is composed will be separated, and will arrange in regular order on the screen, immediately above the image B, which will disappear. The violet ray, it will be seen, is most refracted, and the red leust; the whole forming on the scale an elongated image of the Sun, called the solar spectrum. Johnston. 644. It is the refraction of the clouds that gives the sky its beautiful colors morning and evening ; and the refracting power of the rain-drops produces the beautiful phenomenon of the rain- bow. ATMOSPHERICAL REFRACTION. 645. The refracting power of the atmosphere produces many curious phenomena. Sometimes ships are seen bottom upwards in the air, single or double. At other times, objects really below the horizon, as ships or islands, seem to rise up, and to come dis- tinctly in view. 646. A very important effect of refraction, as it relates to astronomy, is, that it more or less affects the apparent peaces of all the heavenly bodies. As the light coming from them strikes the atmosphere obliquely, and passes downward through it, it is refracted or bent towward the Earth, or toward a perpendicular. And as we judge of the position of the object by the direction of the ray when it enters the eye, we place objects higher in the heavens than they really are. ATMOSPHERICAL KEFIUCTIOS. Let A, in the cut, repre- sent the Earth ; B, the at- mosphere ; C C, the visible horizon ; and the exterior circle the apparnt con- cave of the heavens. Now, as the light passes from the stars, and strikes the atmosphere, it is seen to curve downward, because it strikes the atmosphere obliquely ; and the air in- creases in density as w approach th Earth. But as the amount of refraction depends not only upon the density, but also upon the obli- quity of the contact, it is seen that the refraction is greatest at the horizon, and gradu- ally diminishes till the object reaches the zenith, when there is nc obliquity, and the refrac- 44. What other effects of refraction? 645. Atmospherical refraction? EffecU on ten es trial objects? i46. Upon apparent places of stars, Ac.? REFRACTION AND TWILIGHT. tion wtoiiy ceases. The dark lines In the cut show the true, and the dotted the apparent positions. In the cut, the depth of the atmosphere, as compared with the globe, is greatly exag- gerated. Even allowing it to be 50 miles deep, it is only J-th of the semi-diameter of the globe, which is equal to only aboutySjth of an inch upon a common 13-inch globe. But it was necesary to exaggerate, in order to illustrate the principle. 647. The amount of displacement of objects in the horizon, by atmospherical refraction, is about 33', or a little more than the greatest apparent diameter of either the Sun or Moon. It follows, therefore, that when we see the lower edge of either apparently resting on the horizon, its whole disc is in reality below it ; and would be entirely concealed by the convexity of the Earth, were it not for refraction. 648. Another effect of refraction is, that the Sun seems to rise about three minutes earlier, and to set about three minutes later, on account of atmospherical refraction, than it otherwise would ; thus adding about six minutes, on an average, to the length of each day. The atmosphere is said to be so dense about the North Pole as to bring the Sun above the horizon some days before he should appear, according to calculation. In 1596, some Dutch navigators, who wintered at Nova Zembla, in latitude 76, found that the Sun began to be visible 17 days before it should have appeared by calculation ; and Kepler computes that the atmospheric refraction must have amounted to 5, or 10 times as much as with us. 649. The twilight of morning and evening is produced partly by refraction, but mainly by reflection. In the morning, when the Sun arrives within 18 of the horizon, his rays pass over our heads into the higher region of the atmosphere, and are thence reflected down to the Earth. The day is then said to be dawn, and the light gradually increases till sunrise. In the evening, this process is reversed, and the twilight lingers till the Sun is 18 below the horizon. There is thus more than an hour of twilight both morning and evening. In the arctic regions, the Sun is never more than 18* below the horizon ; so that the twilight continues during the whole night. 650. In making astronomical observations, for the purposes of navigation, &c., allowance has to be made for refraction, according to the altitude of the object, and the state of the atmosphere. For this pirpose tables are constructed, showing the amount of refraction :or every degree of altitude, from the horizon to the zenith. 647. Amount of displacement of celestial objects by refraction? What follows? $48. Influence of refraction on length of days ? How about the North Pole ? 649. Cause ef tooilight f 650. What allowance for refraction? Tables? 302 ASTRONOMY. CHAPTER XYII. AURORA BOREALIS AND PARALLAX. 651. THE sublime and beautiful phenomena presented by the Aurora Borealis, or northern lights, as they are called, have been in all ages a source of admiration and wonder alike to the pea- sant and the philosopher. In the regions of the north (and indeed in many other places) they are regarded by the ignorant with superstitious dread, as harbingers of evil ; while all agree in placing them among the unexplained wonders of nature. These lights, or meteoric coruscations, are more brilliant in the arctic regions, appear- ing mostly in the winter season and in frosty weather. They commonly appear at twi- light near the horizon, and sometimes continue in that state for several hours without any sensible motion; after which they send forth streams of stronger light, shooting with great velocity up to the zenith, emulating, not unfrequently, the lightning in vivid- ness, and the rainbow in coloring ; and again, silently rising in a compact majestic arch of steady white light, apparently durable and immovable, and yet so evanescent, that while the beholder looks upon it, it is gone. At other times they cover the whole hemisphere with their flickering and fantastic coruscations. On these occasions their motions are amazingly quick, and they astonish the spectator with rapid changes of form. They break out in places where none were seen before, skimming briskly along the heavens ; then they are suddenly extinguished, leaving behind an uniform dusky track, which, again, is brilliantly illuminated in the same manner, and as suddenly left a dull blank. Some nights they assume the appearance of vast columns ; exhibiting on one side tints of the deepest yellow, and on the other, melting away until they become undistinguishable from the surrounding sky. They have generally a strong tremulous motion from end to end, which continues till the whole vanishes. 652. Maupertius relates, that in Lapland, " the sky was sometimes tinged with so deep a red that the constellation Orion looked as though it were dipped in blood, and that the people fancied they saw armies engaged, fiery chariots, and a thousand prodigies." Chnelin relates, that, "in Siberia, on the confines of the icy sea, the spectral forms appear like rushing armies ; and that the hissing, crackling noises of those aerial fireworks so terrify the dogs and the hunters, that they fall prostrate on the ground, and will not move while the raging host is passing.'' Kerguden describes " the night between Iceland and the Ferro Islands, as brilliant as the day" the heavens being on fire with flames of red and white light, changing to columns and arches, and at length confounded in a brilliant chaos of cones, pyramids, radii, sheaves, arrows, and globes of fire. 653. But the evidence of Captain Parry is of more value 651. What said of the Aurora J'orfalist How regarded by the ignorant? Whor* most brilliant? In what weather? Describe? 662. Observations of A Gmelin, and Kerguelen T 653. Observations of Capl. Parry t AURORA BOKEAL1S AND PARALLAX. 303 than that of the earlier travelers, as he examined the phenomena under the most favorable circumstances, during a period of twenty-seven consecutive months, and because his observations are uninfluenced by imagination. He speaks of the shifting figures, the spires and pyramids, the majestic arches, and the sparkling bauds and stars which appeared within the arctic cir- cle, as surpassing his powers of description. They are, indeed, sufficient to enlist the superstitious feelings of any people not fortified by religion and philosophy. 654. The colors of the polar lights are of various tints. The rays or beams are steel grey, yellowish grey, pea green, celandine green, gold yellow, violet blue, purple, sometimes ro>-e red, crim- son red, blood red, greenish red, orange red, and lake red. The arc.hej are sometimes nearly black, passing into violet blue, grey, gold yellow, or white bounded by an edge of yellow. The luster of these lights varies in kind as well as intensity. Sometimes it is pearly, sometimes imperfectly vitreous, sometimes metallic. Its degree of intensity varies from a very faint radiance to a light nearly equaling that of the Moon. 655. Many theories have been proposed to account for this wonderful phenomenon, but there seems to be none which is entirely satisfactory. One of the first conjectures on record attributes it to inflammable vapors ascending from the Earth into the polar atmosphere, and there ignited by electricity. Dr. Halley objects to this hypothesis, that the cause is inadequate to produce the effect. He was of opinion that the poles of the Earth were in some way connected with the aurora ; that the Earth was hollow, having within it a magnetic sphere, and that the magnetic effluvia, in passing from the north to the south, might become visible in the northern hemisphere. 656. That the aurora borealis is, to some extent, a magnetical phenomenon, is thought, even by others, to be pretty clearly established by the following considerations : (1.) It has been observed, that when the aurora appears near the northern horizon in the form of an arch, the middle of it is uot in the direction of the true north, but in that of the mug netic needle at the place of observation ; and that when the arch rises towards the zenith, it constantly crosses the heavens at right angles, not to the true magnetic meridian. 654. What said of the colors, &c., of these polar lights? &$. Is tht-re a satisfactory explanation of these phenomena ? What conjecture? Dr. Halley'a objection ? His owu singular opinion ? 660. What evidences ilmt the Aurora Horcaii* is of origin? 304 ASTRONOMY. (2.) When the beams of the aurora shoot up so as to pass *he zenith, which is sometimes the case, the point of their con- vergence is in the direction of the prolongation of the dipping needle at the place of observation. (3.) It has also been observed, that during the appearance of an active and brilliant aurora, the magnetic needle often becomes restless, varies sometimes several degrees, and does not resume its former position until after several hours. Prom these facts, it has been generally inferred that the aurora is in some way con- nected with the magnetism of the Eartli ; and that the simultaneous appearance tf the meteor, and the disturbance of the needle, are either related as cause and effect, or as the common result of some more general and unknown cause. 657. Dr. Young, in his lectures, is very certain that the phe nomenon in question is intimately connected with electro-mag- netism, and ascribes the light of the aurora to the illuminated agency of electricity upon the magnetical substance. It may be remarked, in support of the electro-magnetic theory, that in magnetism, the agency of electricity is now clearly established, and it can hardly be doubted that the phenomena both of electricity and magnetism are produced by one and the same cause ; inasmuch as magnetism may be induced by electricity, and the electric spark has been drawn from the magnet. 658. Sir John Herschel also attributes the appearance of the aurora to the agency of electricity. This wonderful agency, says he, which we see in intense activity in lightning, and in a feebler and more diffused form traversing the upper regions of the atmosphere in the northern lights, is present, probably, in immense abundance in every form of matter which surrounds us, but becomes sensible, only when disturbed by excitements of peculiar kinds. PARALLAX OF THE HEAVENLY BODIES. 659. Parallax is the difference between the altitude of any celestial object seen from the Earth's surface, and the altitude of the same object seen at the same time from the Earth's cen- ter ; or it is the angle under which the semi-diameter of the Earth would appear, as seen from the object. The true place of a celestial body is that point of the heavens in which it would be seen by an eye placed at the center of the Earth. The apparent place is that point of the heavens where the body is seen from the surface of the Earth. The parallax 657. Dr. Young's opinion? What remark in support of his views? 653. Sir John Herschel's opinion? 659. Parallax? True place of a celestial body? Apparent? When parallax greatest ? Least ? Called what, and why ? What objects the greatest parallax ? AURORA BOREAL1S AND PARALLAX. 305 of a heavenly body is greatest when in the horizon, and is thence called the horizontal parallax. Parallax decreases as the body ascends towards the zenith, at which place it is nothing. The adjoining cut will afford a sufficient illustration. When the observer, standing upon the Earth at A, PARALLAX OF THK PLANXTS. views the object at B, it appears to be at C, when, at the same time, if viewed from the center of the Earth, it would appear to be at D. The parallax is the angle B C D or A B E, which is the difference between the altitude of the object B, when seen from the Earih's surface, and when seen from her center. It is also the angle under which the semi-diameter of the Earth, A E, is seen from the object B. As the object advances from the horizon to the zenith, the parallax is seen gradually to diminish, till at F it has no parallax, or its apparent and true place are the same. This diagram will also show why objects nearest the Earth have the greatest parallax, and those most distant the least; why the Moon, the nearest of all the heavenly bodies, has the greatest parallax ; while the fixed stars, from their immense distance, have no appreciable horizontal parallax the semi-diameter of the Earth, at such a distance, being no more than a point. 660. As the effect of parallax on a heavenly body is to depress it below its true place, it must necessarily affect its right ascen- sion and declination, its latitude and longitude. On this account, the parallax of the Sun and Moon must be added to their apparent altitude, in order to obtain their true altitude. The true altitude of the Sun and Moon, except when in the zenith, is always affected, more or less, both by parallax and refraction, but always in a contrary manner. Hence the mariner, in finding the latitude at sea, always adds the parallax, and subtract* the refraction, to and from the Sun's observed altitude, in order to obtain the true altitude, and thence the latitude. 661. The principles of parallax are of great importance to astronomy, as they enable us to determine the distances of the heavenly bodies from the Earth, the magnitudes of the planets and the dimensions of their orbits. The Sun's horizontal parallax being accurately known, the Earth's distance from the Sun becomes known ; and the Earth's distance from the Sun being known, that of all the planets may be known also, because we know the exact periods of their sidereal revolutions, and, according to the third law of Kepler, the squares of the times of their revolutions are proportional to the cubes of their mean distances. Hence, the first great desideratum in astronomy, where measure and magnitude are concerned, is the determination of the true parallax. At a council of astronomers assembled In London some years since, from the rarjt 660. Effect of parallax? How obtain true altitude? How differ from refraction? Dow then obtain true altitude? 601. Use of parallax? How employed? NoteT 300 ASTRONOMY. learned nations in Europe, the Sun's mean horizontal parallax was settled, as the n..nt of their united observations, at 0' 8'.6776. Now the value of radius, expressed )ike- wise in seconds, is 206i64".8; and this divided by 8".5776, gives 24047 for the distance of the Sun from the the Earth, in semi-diameters of the latter. If we take the equatorial Kemi-diameter of the Earth, as sanctioned by the same tribunal, at (7924-*-2=)89G2 miles, we shall have 24047 x 3962 =95,273,869 miles for the Sun's true distance. A TABLK OF THE SUN'S PARALLAX IM ALTITUDE. Sun's Altit. Swn's Horizontal Parallax. Sun's Altit. Sun's Horizontal Parallax. 8.4 8.5 8.6 8.T 8.8 f 8.4 8.5 8.6 8.7 8.8 8.40 8.50 8.60 8.70 8.80 45 5.94 6.01 6.0S 6.15 6.22 5 8.37 8.47 8.57 8.67 8.77 50 5.40 5.46 5.53 5.59 5.66 10 8.27 8.37 8.47 8.57 8.67 55 4.82 4.89 4.93 4.99 5.05 15 8.11 8.21 8.31 8.40 8.50 60 4.20 4.25 4.30 4.35 4.40 20 7.89 7.99 8.08 8.18 8.27 65 3.55 8.59 3.63 3.6S 3.72 25 7.61 7.70 7.79 7.88 T.98 70 2.87 2.91 2.94 2.98 3.01 30 7.2S 7.36 7.45 7.53 7.62 75 2.17 2.20 2.23 2.25 2.28 35 6.S8 6.96 7.04 7.13 7.21 80 1.46 1.48 1.4.9 1.51 1.53 40 6.44 6.51 6.59 6.66 6.74 - 85 0.73 0.74 0.75 0.76 0.77 45 5.94 6.01 6.08 1 6.15 6.22 90 0.00 0.00 0.00 0.00 0.00 662. The change in the apparent position of the fixed stars, caused by the change of the Earth's place in her revolution around the Sun, is called their annual parallax. So immense is their distance, that the semi-annual variation of 190,000,000 of miles in the Earth's .distance, from all those stars that lie in the plane of her orbit, makes no perceptible difference in their apparent magnitude or brightness. The following cut will illustrate our meaning: Let A represent a fixed star In the plane of the Earth's orbit, B. At C, the Earth is 190,000,000 of miles nearer the star than it will be at D six months afterward ; and yet this semi-annual variation of 190,000,000 miles in the distance of the star is so small a fraction of the whole distance to it, as*neither to increase or diminish its apparent brightness. 663. It is only those stars that are situated near the axis of the Earth's orbit whose parallax can be measured at all, on 663. What meant by Earth's annual parallaxT Effect, of variation of Earth's dis- on the fixed stars? Diagram. 663. What stars have perceptible parallax? AURORA BOREALIS AND PARALLAX. 307 PARALLAX OF TTTB STAI account of its almost imperceptible quantity. So distant are they, that the variation of 190,000,000 miles in the Earth's place c \ / E causes an apparent change of less than 1' in the nearest and most favorably situated fixed star. Let A represent the Earth on the 1st of January, and B a star observed at that time. Of course, its apparent place in the more distant heavens will be at C. But in six months the Earth will be at D, and the star B will appear to be at E. The angle A B D or C B E will constitute the parallactic angle. In the cut, this angle amoucU to about 48, whereas the real parallax of the stars is less than J th of one degree, or og^Q- o-th part of this amount. Lines approaching each other thus slowly would appear parallel ; and the Earth's crbit, if filled with a globe of fire, and viewed from the fixed stars, would appear but a point of light 1' in diameter ! For a splendid diagram illustrative of the annual parallax of the stars, see Map I., of the Atlas. ABERRATION OF LIGHT. 664. In the year 1725, Mr. Molyneux and Dr. Bradley fixed up a very accurate and costly instrument, in order to discover whether the fixed stars had any sensible parallax, while the Earth moved from one extremity of its orbit to the other ; or which is the same, to determine whether the nearest fixed stars are situated at such an immense distance from the Earth, that any star which is seen this night, directly north of us, will, six months hence, when we shall have gone 190,000,000 of miles to the eastward of the place we are now in, be then seen exactly north of us still, without changing its position so much as the thickness of a spider's web. 665. These observations were subsequently repeated, with but little intermission, for twenty years, by the most acute observers in Europe, and with telescopes varying from 12 feet to 36 feet in length. In the mean time, Dr. Bradley had the honor of announcing to the world the very nice discovery made while endeavoring to ascertain the parallax of the fixed stars, that the motion of light, combined with the progressive motion of the Earth in its orbit, causes the heavenly bodies to be seen in a differ- ent position from what they would be, if the eye were at rest. Thus was established the principle of the Aberration of Light. 666. This principle, or law, now that it is ascertained, seems Amount? Diagram, and explanation. 664. What experiment by Molyneux an.i Bradley? With what results ? 6C5. What further observations for the same purpose ? What discovery made while investigating the subject of parallax ? What is the aberra- tion, of light f 6C<>. What remarks upon the principle or law of observation ? How ia 308 ASTRONOMY. not only very plain, but self-evident. For if light be progres- sive, the position of the telescope, in order to receive the ray, must be different from what it would have been if light had been instantaneous, or if the Earth stood still. Hence the place to which the telescope is directed will be different from the true place of the object. The quantity of this aberration is determined by a simple proposition. The Earth describes 59' 8" of her orbit in a day = 3548 '', and a ray of light comes from the Sun to us in 8' 13'' = 493" : now 24 hours or 86400" : 493 : : 3548: 22"; which is the change in the star's place, arising from the cause abore- mexitioned. CHAPTER XYIII. PRACTICAL ASTRONOMY REFLECTION AND REFRAC- TION OF LIGHT. 667. Practical Astronomy has respect to the means employed for the acquisition of astronomical knowledge. It includes the properties of light, the structure and use of instruments, and the processes of mathematical calculation. In the present treatise, nothing further will be attempted than a mere introduction tc practical astronomy. In a work designed for popular use, mathematical demonstrations would be out of place. Still, every student in astronomy should know how telescopes arc made, upon what laws they depend for their power, and how they are used. It is for thu purpose mainly that we add the following chapters on practical astronomy. PROPERTIES OF LIGHT. 668. Light is that invisible ethereal substance by which we are apprised of the existence, forms, and colors of material objects, through the medium of the visual organs. To this sub- tile fluid we are especially indebted for our knowledge of those distant worlds that are the principal subjects of astronomical inquiry. 669. The term light is used in two different senses. . It may signify either light itself, or the degree of light by which we are enabled to see objects distinctly. In this last sense, we put light the quantity oJ aberration determined? 667. Subject of Chapter XVIII.? What U practical astronomy t How far discussed in this treatise? 668. Define lifht,. For what indebted to it? 669. Different senses in which the term is used? What is REFLECTION AND REFRACTION OF LIGHT. 309 iu opposition to darkness. But it should be borne in mind, that darkness is merely the absence of that degree of light which is necessary to human vision ; and when it is dark to us, it may be light to many of the lower animals. Indeed, there is more or less light, even in the darkest night, and in the deepest dungeon. "Those unfortunate individuals," says Dr. Dick, "who have been conQned in the dark- est dungeons, have declared, that though, on their first entrance, no object could be per- ceived, perhaps for a day or two, yet, in the course of time, as the pupils of their eyes exparuied, they could readily perceive rats, mice, and other animals that infested their cells, and likewise the walls of their apartments; which shows that, even in such situa- tions, light is present, and produces a certain degree of influence." 670. Of the nature of the substance we call light, two theo ries have been advanced. The first is, that the whole sphere of the universe is filled with a subtile fluid, which receives from luminous bodies an agitation ; so that, by its continued vibra- tory motion, we are enabled to perceive luminous bodies. This was the opinion of Descartes, Euler, Huygens, and Franklin. The second theory is, that light consists of particles thrown off from luminous bodies, and actually proceeding through space. This is the doctrine of Newton, and of the British philosophers generally. Without attempting to decide, in this place, upon the relative merits of these two hypo- theses, we shall use those terms, for convenience sake, that indicate the actual passage of light from one body to another. 671. Light proceeds from luminous bodies in straight lines, and in all directions. It will not wind its way through a crooked passage, like sound ; neither is it confined to a part of the cir- cumference around it. As the Sun may be seen from every point in the solar system, and far hence into space in every direction, even till he appears but a faint and glimmering star, it is evident that he fills every part of this vast space with his beams. And the same might be said of every star in the firmament. 672. As vision depends not upon the existence of light merely, but requires a certain degree of light to emanate from the object, and to enter the pupil of the eye, it is obvious that if we can, by any means, concentrate the light, so that more may enter the eye, it will improve our perception of visible objects, and even enable us to .see objects otherwise wholly invisible. Some animals have the power of adapting their eyes to the existing degree of light. The cat, horse, Ac., can see day or night ; while the owl, that sees well iu the night, sees poorly in the day-time. 673. Light may be turned out of its course either by reflection dark'iess? Can it be dark and light at the same time? Is there any place without light? Quotation from Dr. Dick? 670. What theories of the nature of light, and by whom supported respectively? Uemark of author? 671. How light proceeds from uminous bodies f Radiations from Sun and stars? 67*2. How improve vision, a IK' %-Ly f Animals ? 673. How is light turned out of ita course ? 310 ASTRONOMY. OP refraction. It is reflected when it falls upon the highly polished surface of metals and other intranspareut substances ; and refracted when it passes through transparent substances of diffe- rent densities, as already illustrated in Chapter XVI. REFRACTION BY GLASS LENSES. 674. A lensis a piece of glass, or other transparent substance, of such a form as to collect or disperse. the rays of light that are passed through it, by refracting them out of a direct course. They are of different forms, and have different powers. In the adjoining cut, we have an edgewise view of six different lenses. A is the plano-conveaSj or half a double con- vex lens ; one side being convex and the other plane. B is a. plano-concave ; one surface being con- cave, and the other plane. C is a double-convex lens, or one that is bounded by two convex surfaces. D is a double-concai)6 lens, or a circular piece of glass hollowed out on both sides. E is a concavo-convfw lens, whose curves differ, but do not meet, if produced. F is a meniscus, or a concavo-convex lens, the curves of whose surfaces meet. 4* 675. A double-convex lens converges parallel rays to a point called the focus ; and the distance of the focus depends upon the degree of cocvbxity. In the first of these cuts, the lens is quite thick, and the focus of the rays is quite near ; but the other being less, convex, the focus is more distant. LENSES OF DIFFERENT FORMS. LIGHT REFRACTED BY LENSES. 676. The distance of the focus of a double-convex glass lens is the radius of the sphere of its convexity. In this cut, it wtil be seen that the parallel rays A are refracted to a focus at C, by the double-convex lens B, the convexity of whose surfaces is just equal to the curve of the circle D. 677. The focal distance of a plano-convex lens is equal to the diameter of the sphere formed by the convex surface produced. DOUBLE CONVEX FOCAL DISTANCE. 674. What is a Una? Draw and describe different kinds. 675. Refracting power of tlouble-conve&tena? Focal distance? Diagram, and illustrate. 67(5. How focal dis- tance governed ? Diagram, and illustrate. 677. What it> the focal distance of REFLECTION AND REFRACTION OF LIGHT. It must be borne in mind, that PLANO-OONCAVE FOCAL DISTANCE,. fight is refracted both when it enters, and when it leaves a double convex lens, and in both instances In the same direction ; and, so far as the distance of the focus is concerned, to the same extent. But when the lens is convex only on one side, half its refracting power is gone, so that the rays are not so soon refracted to a focus. In this case, the focal dis- tance is equal to the diameter of the sphere formed by extending the convex surface of the lens; while with the double-convex lens, the focal distance is only equal to the radius of such sphere. In the cut, the parallel rays A ure refracted to a focus at U, by the plano-concave lens C; and the distance C B is the diameter of the circle D, formed by the convex surface of the lens C produced. RATS DISPERSED BY REFRACTION. \ 678. A doulk-cvn- cace lens disperses pa- rallel rays, as if they diverged from the cen- ter of a circle formed by the convex surface produced. In this cut, the parallel rays A are dispersed by the double- concave lens C, as shown at I! ; and their direction, as thus refracted, is the same as if they proceeded from the point D, which is the center of a circle formed by th concave surface of the lens produced. 679. Common spectacles, opera-glasses, burning-glasses, and refracting telescopes are made by converging light to a focus, by the use of double-convex lenses. The ordinary burning-glass, which may be bought for a few shillings, is i double-convex disk of glass two or three inches in diameter, inclosed in a slight metallic frame, with a han- dle on one side. Old tobacco-smokers some- times carry them in their pockets, to light their pipes with when the Sun shines. In other in- stances, they have been so placed, as to fire a cannon in clear weather, by igniting the prim- ing at 12 o'clock. The adjoining cut represents a large burn- ing-glass converging the rays of the Sun to a focus, and setting combustible substances on fire. Such glasses have been made powerful enough to melt the most refractory substances, as platinum, agate, &c. " A lens three feet in diameter," says Professor Gray, "has been known to melt cornelian in 75 seconds, and a piece of white agate in 30 seconds." BURNING-GLASS. Diagram. 678. Effect of double-convex lens? Amount of diver pitncy of rays? 679. What articles made with double-convex lenses ? Uses? Powet Of burning glasses? 312 ASTRONOMY. REFLECTION OF LIGHT. 680. We have now shown how light may be turned out of its course, and analyzed, dispersed, or converged to a point by refraction. Let us now consider how it may be converged to a focus by reflection. When light falls upon a highly-polished surface, especially of metals, it is reflected or thrown off in a new direction, and the angles of contact and departure are always equal. Let A B represent the polished metallic surface, C the source of light, and the arrows the direction of the ray. Then D would represent the angle of incidence or contact, and E the angle of retlection or departure which angles are seen to be equal. -A. RKFEECTIOJ BY A PLASK MIRROR. RKFLECDON BY A CONCAVE Mir.KOR. 681. A concave mirror re- flects parallel rays back to a focus, the distance of which is equal to half the radius of the sphere formed by the concave surface produced. In this cut, the parallel rays A fall upon the concave mirror B B, and are reflected to the focus C, which is half the radius of the sphere formed by the surface of the mirror produced. If, therefore, it was desirable to construct a concave mirror, having its focus 10 feet distant, it would only be necessary to grind it on the circle of a sphere having a radius of 20 feet. 682. In reflection, a por- tion of the light is absorbed or otherwise lost, so that a reflector of a given diameter will not converge as much light to a focus as a double-convex lens of the same size. In the latter case all the light is trans- mitted. Still, reflectors have been found of such power as to melt iron, and other more difficult substances. We have now considered so much of optics as is necessary to an understanding of the principles upon which telescopes are constructed; and, for further particulars, shai! refer the student to books on Natural Philosophy. 680. What now shown in this chapter? What next? What is reflection, and when does it take place? What law governs it? Diagram. 681. How does a concave mirror reflect parallel rays ! Distance of focus ? Diagram. How would you construct a concave mirror with a 10 feet focus ? 682. Is all the light falling upon a polished urface reflected ? What then ? Closing note ? TELESCOPES REFRACTORS AND REFLECTORS. 313 CHAPTER XIX. TELESCOPES REFRACTORS AND REFLECTORS. 683. A TELESCOPE is an optical instrument employed in view- ing distant objects, especially the heavenly bodies. The terra tti'escope is derived from two Greek words, viz., tele, at a distance, and skopeo, to see. So far as is now known, the ancients had no knowledge of the telescope. Its invention, which occurred in ] 609, is usually attributed to Galileo, a philosopher of Florence, in Italy. The discovery of the principle upon which the refracting telescope is constructed was purely accidental. The children of one Janaen, a spectacle-maker of Middleburgh, in Holland, being at play in their father's shop, happened to plaoe two glasses in such a manner, that in looking through them, at the weathercock of the church, it appeared to be nearer, and much larger than usual. This led their father to fix the glasses upon a board, that they might be ready for observation ; and the news of the discovery was soon conveyed to the learned throughout Europe. Galileo hearing of the phenomenon, sooc discovered the secret, and put the glasses in a tube, instead of on a board ; and thus the first telescope was constructed. 684. The telescope of Galileo was but one inch in diameter, and magnified objects but 30 times. Yet with this simple instrument he discovered the face of the Moon to be full of ine- qualities, like mountains and valleys ; the spots on the Sun ; tho phases of Venus ; the satellites of Jupiter ; and thousands of new stars in all parts of the heavens. Notwithstanding this propitious commencement, so slow was the progress of the telescope towards its present state, that in 1816, Bonnycastle speaks of the 30-fold mag- nifying power of the telescope of Galileo as " nearly the greatest perfection that this icind of telescope is capable of!" 685. If he be the real author of an invention who, from a knowledge of the cause upon which it depends, deduces it from one principle to another, till he arrives at the end proposed, then the whole merit of the invention of the telescope belongs to Galileo. The telescope of Jansen was a rude instrument of mere curiosity, accidentally arranged ; but Galileo was the first who constructed it upon principles of science, and showed the practi- cal uses to which it might be applied. It is said that the original telescope constructed by Galileo is still preserred in the British Museum. A pigmy, indeed, in its way, but the honored progenitor of a race of jianta ! 686. The discovery of the telescope tended greatly to sustain <>S8. Subject of Chapter XIX. ? Telescope ? Derivation ? Ancient or modern ? In- fentor? Incidents of discovery? 684. Galileo's telescope? Discoveries with it? Progress in telescope making? 685. Is Galileo entitled to the honor of inventing the telescope ? Where is bis ? 6S6. Re4ation of discovery to Copernican theory ? EffecWi ASTRONOMY. the Copernican theory, which had just been promulgated, and of which Galileo was an ardent disciple. Like Copernicus, how ever, his doctrines subjected him to severe persecutions, and he was obliged to renounce them. The following is his renunciation, made June 28, 1633 : " I, Galileo, in the seventieth year of my age, on bended knees before your eminences, having before my eyes and touching with my hands the Holy Gospels, I curse and detest the error of the Earth's movement." As he left the court, however, after this forced renunciation, he is said to have stamped upon the Earth, and exclaimed, " It does move, after all?" Ten years after this, he was sent to prison for the same supposed error; and soon, his age advanc- ing, the grave received him from the malice of his persecutors. DIFFERENT KINDS OF TELESCOPES. 681. Telescopes are of two kinds Reflectors and Refractws. .Refracting telescopes are made by refracting the light to a focus with a glass lens (675) ; and reflecting telescopes, by reflecting it to a focus with a concave mirror (681). Besides this general division, there are various kinds both of reflectors and refractors. Telescopes assist vision in various ways first, by enlarging the visual angle under which a distant object is seen, and thus magnifying that object ; and, secondly, by converging to a point more light than could otherwise enter the eye- thus rendering objects distinct or visible that would otherwise be indistinct or invisible. All the light falling upon a six or a twelve inch lens may be converged to a focus, so as to be taken into the human eye through the pupil, which is but one-fourth of an inch in diameter. Our vision is thus made as perfect b; art as if nature had given us ability to enlarge the eye till the pupil was a foot rn diameter. 688. Refracting telescopes may consist of a double-convex lens placed upon a stand, without tube or eye-piece. Indeed, a pair of ordinary spectacles is nothing less than a pair of small telescopes, for aiding impaired vision. REKRACTIKQ TBLKSOOTK WITH A SIHOLB LENS. Here the parallel rays are seen to pass through the lens at A, and to be so converged to a point as to enter the eye of the beholder at B. His eye is thus virtually enlarged to the size of the lens at A. But it would be very difficult to direct such a telescope toward celestial objects, or to get the eye in the focus after it was thus directed. upon Galileo? His renunciation? Death? 687. Kinds of telescopes? Describe, liow assist vision F Illustration, 688. Simplest form of refracting telescope ? TELESCOPES REFRACTORS AND REFLECTORS. 315 689. The Galilean telescope consists of two glasses a doubts- convex next the object, and a double-concave near the eye. The former converges the light till it can be received by a small double-concave, by which the convergency is corrected (502), and the rays rendered parallel again, though in so small a beam as to be capable of entering the eye. GALILBAN TKLE9COPK. Here the light is converged by the lens A, till It can be received by the double-concave lens B, by which the rays are made to become a small parallel beam that can enter the eye at C. This was the form of the telescope constructed by Jansen, and improved by Galileo ; on which account it is called the Galilean telescope. In the cut, the two lenses are represented as fastened to a board, as first exhibited by Jansen. 690. The common astronomical telescope consists of two glasses viz., a large double-convex lens next the object, called the object-glass ; and a small double-convex lens or microscope next the eye, called the eye-piece. For the greater convenience in using, they are both placed in a tube of wood or metal, and mounted in various ways, according to their size, and the pur- poses to which they are devoted. LENSES PLACED IN A TUBE. A !s the object-glass, B the eye-piece, and C the place where the tube, In which the eye- piece is set, slides in and out of the large tube, to adjust the eye-piece to the focal dis- tance. By placing the lenses in a tube, the eye is easily placed hi the focus, and the object-glass directed toward any desired object. 691. The object-glass of a telescope is usually protected, when not in use, by a brass cap that shuts over the end of the instru- ment ; and the eye-pieces, of which there are several, of differ- 6S9. Galilean telescope ? Why called Galilean T 690. How common astronomical telescopes made? Why in tube? 691. How object-glaas protected? What saiJ of eye-pieces' E.G. 14 316 ASTRONOMY. BEFKiCTISQ TELESCOPE XOU8TBD OB A BTAHD. cnt magnifying powers, are so fixed as to screw into a small movable tube in the lower end of the instrument, so as to adjust them respectively, to the fwus, and to the eyes of different observers. Such telescopes usually repre- sent objects in an invert- ed position. The adjoining cut represents the simplest form of a mounted refrac- tor. The object-glass is at A, where the brass cap may be seen cover- ing it B is the small tube into which the eye-piece is screwed, and which is moved in and out by the small screw C. Two eye-pieces may be seen at D one short one, for astronomical observations, and a long one, for land objects. For viewing the Sun, it is necessary to add a screen, made of colored glass. At , a bolt goes into a socket in the top of the stand, in which it turns, allowing the tele- scope to sweep around the hori/.on ; while the joint, connecting the saddle in which the telescope rests with the top of the bolt, allows it to be directed to any point between the horizon and the zenith. But such stands answer only for comparatively small instruments. 692. Refracting telescopes are mounted in various ways. So important is it that they should not shake or vibrate, that, in most observatories, the stand rests upon heavy mason-work in no way connected with the building, so that neither the wind nor the tread of the observer can shake it. They are then fur- nished with a double axis, which allows of motion up and down, or east and west ; and two graduated circles show the precise amount of declination and right ascension. They are often furnished with clockwork, by which the telescope is made to move westward just as fast as the Earth turns eastward ; so that the celestial object being once found, by setting the instrument for its right ascension and declination, or by the aid of the Finder & small telescope attached to the lower end of the large one it may be kept in view by the clockwork for any desirable length of time. A telescope thus fur- nished with right ascension and declination circles is called an Equatorial, or is said to be equatorialfy mounted, because it sweeps east and west in the heavens parallel to the equator. 693. The object-glasses of telescopes are not always made of a single piece of glass. They may be made of two concavo-con- vex glasses, like two watch crystals, with their concave sides 692. How refractors mounted, and why? When equatorial, and why? 698. How object-glassea made ? What a lent T A Barlow lens ? TELESCOPES REFRACTORS AND REFLECTORS. 317 towards each other, or with a thin double concave glass between them. They are thus double, or triple ; but when thus con- structed, the whole is called a lens, as if composed of a single piece. Leuses have also been formed by putting two concavo-convey glasses together, and filling the space between them with some transparent fluid. These are called Barlow lenses, from Prof. Barlow, their inventor. 694. As a prism analyzes the light, and exhibits different colors, so a double convex lens may analyze the light that falls near its circumference, and thus represent the outside of the heavenly bodies as colored. But this defect is remedied by using discs made of different kinds of glass, so as to correct one refraction by another. Refracting telescopes thus corrected are called Ach/romatic telescopes. Achromatic is from the Greek a chroma, which signifies destitute of color. Most refracting telescopes are now so constructed as to be achromatic. 695. It is but recently that any good refracting telescopes have been made in this country. The best have formerly been made in Germany and France ; but a number of very fine instru- ments have been made in this country, most of them by Mr. Henry Fitz, Jan., formerly of New York City. Several very good instruments have also been made by Alvan Clark, Esq., of Boston, and others still by Charles A. Spencer, Esq., of Troy, N. Y. Mr. Fitz died in New York, November 27, 1863. 1. The author was personally well acquainted with Mr. Fitz, and during his life gave favorable descriptions of his instruments in these pages, and did all that he could to make his capabilities known to the American public. He made his first telescope in 1835. In the Winter of 1844 he invented a method of perfecting object-glasses for refract- ing telescopes, making the first one of the bottom of an ordinary tumbler. In the Fall of 1845 he exhibited, at the Fair of the American Institute, an instrument of 6 inches aperture, which, although made of common American material, in the way of flint glass, was a very excellent instrument. Continually progressing in size, he finally succeeded in making instruments of 16 inches aperture, one of which is now in the possession of Mr. Van Diizee, of Buffalo, N. Y. He made two of 13 inches one for the Dudley Observa- tory, at Albany, and the other for an associatien of gentlemen, at Alleghany City, Pa. Of 12 inches aperture, he produced one for the Observatory at Ann Arbor, Michigan, and another for the Vassar Female College. He made for M. L. Rutherford, of New York, at various times, telescopes of 4, 5J, 6^9, and 11 J inches aperture ; the last, an instrument of remarkable defining power, is now mounted in Mr. Rutherford's Observatory, in Eleventh Street, New York City. Mr. Vickers, of Baltimore, has a 10-inch. Several of the size of 8 and 9 inches are scattered over the country. The British Charge d'Af- faires at Montevideo has a 9-inch. Mr. Campbell, of New York, has an 8-inch. Of a large number of 6 inches aperture, one very fine instrument was ordered by the United States Government, for Lieut. Gillies's expedition to Chili; it is still in the Observatory of the Chilian Government At about the same time, he made another of the same size for Mr. Kobert Van Arsdale, of Newark. N. J. Mr. Thomas F. Harrison, Principal of the Public Grammar School in Greenwich Avenue, New York, has another mounted on that building. 2. For a list of telescopes in this country, with the names of their respective makers, focal length, size of object-glasses, &c., see table on subsequent page. 695. What said of the manufacture of telescope*.? "What other Americans have made them ? (What said of Mr. Fitz ? Telescopes ?) 318 ASTRONOMY. BUTHKBFORD'S EQUATOEIAL EEFBACTOB. 696. The above cut represents an equatorial telescope manu- factured by Mr. Henry Fitz, of New York the one used by the author in making most of his observations. Its object- glass is six inches in diameter, and its focal length eight feet. It is perfectly achromatic, and performs all the tests laid down in Dick's Practical Astronomer, as evidence of a good instru- ment, with perfect ease. Under favorable circumstances, it shows the sixth star in the trapezium of Orion, and to show Polaris double is a very easy test indeed. A Finder is seen attached to the lower end of the large instrument. It takes in a larger field of view in the heavens than the latter, and enables the observer to look up objects with facility, and bring them into the field of the larger instrnment. REFRACTING TELESCOPES. 319 THB PHILADELPHIA BEFBACTOB.* C9V. This instrument is located in the Observatory of the High- School of Philadelphia. Its focal length is eight feet, and its aperture six inches the same as the one on the preceding page. It was made by Merz & Mahler, of Munich, and cost $2,200. * We are indebted to the courtesy of Messrs. Harper Brothers, of New York, far copies of several of these cuts from their Monthly Magazine for June, 1856. 697. The Philadolphiu redactor? Sizo? By whom made? Coat? 320 ASTRONOMY. HAMILTON COLLEGE KJUTKACTOR. 698. This instrument has a focal length of sixteen feet, with an object-glass thirteen-and-a-half inches in diameter. Its focal length is therefore about four feet less than is usual in the Mu- nich instruments of the same aperture. The flint and crown glass discs for it were imported from Germany, and the instru- ment was made by Messrs. Spencer & Eaton, of Canastota, N. Y., at a cost of $10,000. It is reported to be a very superior tele- scope, and, in workmanship, is regarded as fully equal to the Munich instruments. 698. Sizo of the Hamilton College telescope? What peculiarity as to length? By whom made? Cost? REFRACTING TELESCOPES. 321 GBEAT EKFBAOTINO T1ELE8COPE AT CINCINNATI, OHIO. 699. The above cut represents one of the best telescopes in the United States. It is located in the observatory on Mount Adams, near Cincinnati, Ohio, and was for several years under the direction of the late Prof. 0. M. Mitchel, by whose instru- mentality it was purchased and mounted. The object-slass is about 12 inches in diameter, with a focal distance of 17 feet It was purchased in Munich, Germany, in 1844, at an expense of nearly ten thousand dollars. 699. Cincinnati refractor where located? By whom purchased ? (Where? When? Cost? Size and focal distance ?) 322 ASTRONOMY. THE EQTTATOBIAL KEFBACTOE AT ALBANY, K. T. 700. This superb instrument is mounted in the Dudley Ob- servatory, at Albany, and is one of the most important instru- ments in America. Its focal length is 15 feet 2 inches. The object-glass, made by the late Henry Fitz, of New York, is 13 inches clear aperture, and the tube is of mahogany, constructed by glueing together strips of about an inch in width. A finder, or small telescope for finding objects, is seen attached to the lower end of the large instrument. 700. Where located? Sixe? By -whom made ? What said of tube ? Finder? REFRACTING TELESCOPES. 323 Tllii UKK.VT EQUATORIAL REFRACTOR AT CAMBRIDGE MA88. Vol. This is probably the best ins iimient in the United States. Its object-glass is 15 inches in diameter, with a focal length of 22 feet 6 inches. It has eighteen different powers, ranging from 103 to 2,000. It was made by Merz & Mahler, of Munich, Ba- varia, and cost $19,842. The cut shows the opening in the revolving dome of the observatory, and the observer iu his chair at the eye-piece. 701. Comparative value? Size? Magnifying powers? By whom made ? Cost of instrument? 321 ASTRONOMV, THM fiEEAl CEAIG TJ6LE8COPE, WAND8WOKTH COMMON, NEAR LONDON. 702. This is the largest refracting telescope ever constructed The object-glass is two feet in diameter, with a focal distance of 76 feet. The tube is of heavy sheet iron, and shaped somewhat like a cigar. It is 13 feet in circumference in the largest place, and weighs about three tons. This telescope is suspended from a brick tower, 65 feet high, 15 feet in diameter, and weighing 220 tons. The top of the tower, from which the telescope is suspended, re- volves ; and by a chain running over pulleys, and a weight and windlass, it is balanced, and raised or lowered. The lower end rests on a small carriage, that runs upon a circi - lar railroad around the tower, at the distance of 52 feet from its center. By these means it is directed to almost any point in the heavens. It is called the " Craig" telescope, in honor of the Rev. Mr. Craig, under whose direction, and at whose expense, it was con- structed. It is located at Wandsworth Common, near London. 702. Describe the Craig telescope. Object glass ? Focal distance ? Counted f Whj called " Craig" telescope ? Where located f Tubef How TRANSIT INSTRUMENTS. 325 A TRANSIT INSTRUMENT. 703. A Transit Instrument is a telescope used for observing the transits of celestial objects across the meridian, for the pur- pose of determining differences of right ascension, or obtaining correct time. They are usually from six to ten feet long, and are mounted upon a horizontal axis, between two abutments of mason-work ; so that the instrument, when horizontal, will point exactly to the south. It will then take objects in the heavens, when they are exactly on the meridian. The Transit Instrument and Mural Circle have been combined in one instrument, called a Meridian Circle, as shown on a sub- sequent page. Let A D in the cut represent the telescope, and E and W the east and west abutments, between which it is placed. On the left is seen, attached to the mason work, a graduated circle; and on the eastern end of the axis of the telescope is seen an arm, w, extending to the circle, as an index. Now, suppose the index n to be at o, in the upper part of the circle, when the telescope is horizontal ; then if the meridian altitude of the object to be taken is 10', the index must be moved 10 from 0, as the degrees on the circle and the altitude of the object will correspond. 703. What Is a transit instrument? Size? How mounted? Describe parts as shown in the cut. How set the instrument for the altitude of a star? What combination Bpokcn of? 326 ASTRONOMY. TKAK81T 1NSTBUMKNT, WASHINGTON, . C. 704. This instrument is located in the National Observatory, at Washington, D. C. It is mounted upon piers of granite, which rest firmly upon a foundation of stone, extending ten feet below the surface of the ground. The object-glass was furnished by Merz & Mahler, and the instrument was constructed by Ertel & Son, Munich. The entire cost was $1,480. 704. Where located? How mounted? By whom mad?? Cost? TRANSIT INSTRUMENTS. 327 MERIDIAN CIRCLE AT ALBANY, N. T. 705. This is a superior transit instrument, with a innral circle attached. It is located in the east wing of the Dudley Observa- tory, at Albany, N. Y., and rests upon piers of Lockport lime- stone, which rest upon a bed of sand and gravel, some ten feet Itelow the floor of the cellar. Taken as a whole, it is probably ihe best transit instrument in the United States. 1. A Mnral Circle is a larjre graduated circle, with a telescope crossing its center. usel for tlu- measurement of the altitudes and zenith distances of the heavenly bodies, at the instant of their crossing the meridian. They are usually fixed upon a horizontal axis, that turns in a socket firmly fixed in a north flhd south wall. The decrees, minutes, and seconds on the circle are read by means of microscopes, and indicate the.allitudo ol the object Th Mural Circle and a transit instrument, as now combined, are called a Meridian Cirvlt. 705. Where located? How mounted? Comparative Import Oirclet Uo? How usuallj mounted ? How combined? "" ance? What Is a Mtmtl 328 ASTRONOMY. 2. The old Mural Circle is now being rapidly superseded by the Meridian Circle in the best observatories. 706. A Comet Seeker is a re- A COMET SEEKER. fracting telescope with a large aperture and short focal distance. As comets cannot be found by their right ascension and declina- tion, but often have to be searched up, by sweeping around the heavens with a telescope, be- fore they became visible to the naked eye, it is important to have telescopes that will cover considerable space that is, of wide aperture and short focal distance. Such a telescope was made by Mr. Fitz for Miss Mitchel, of Newport, R. I. Miss Mitchel is an amateur astronomer, and has the honor of having discovered a num- ber of new comets. 707. An Ast-ronomical Clock is a clock adapted to keep exact sidereal time. Taking the vernal equinox in the heavens as the zero point, and reckoning 24 hours eastward to the same point again, the time reckoning 15 to an hour when an object crosses the meridian, will always represent the right ascension of the object. Hence right ascension is usually given in hours, minutes, and seconds ; or in. time by the astronomical clock, set by the vernal equinox. Professor Mitchel, we believe, made some valuable improvements in astronomical clocks. A very fine instrument of this kind is located in the Dudley Observatory, at Albany, N. Y. REFLECTING TELESCOPES. 70S. The Reflecting Teletcopt is one in which the light is con- verged to a focus by means of a concave metallic reflector or speculum. Like the Refractors, they may be constructed with very little mounting ; though for convenience in use, it is neces- sary to place the reflector in a tube. The student should fully understand the difference between the two kinds of tele- scopes, viz. : refractors and reflectors. In one respect they are alike, as they both con- y>rge the rays of light to a focus; but they do it by widely different processes, as the following pages will show. 706. What is a comet seeker t Why necessary? 707. What is an astronomical clock? 70S. Describe a reflecting telescope. Simplest form ? DIFFERENT KINDS OP TELESCOPES. SIMPLEST FOKM OF A REFLECTING TZiLBSCOPE. 329 In this cut, the light A is een passing from the object on the right, and falling upon t!ie concave surface of the reflector at B, from which it is reflected back to a focus, and enters the eye of the observer at C. This telescope has no eye-piece. 708. The focal distance of a concave reflector is equal to half the radius of the sphere formed by the concave surface pro- duced. Hence to grind a reflector for a focus of 20 feet, it will be necessary to have the curve that of a circle whose radius is 40 feet. rOCAL DISTASfOK Of A OOXCAVK REFLECTOR. Hvre the curve of the speculum B is that of a circle, whose center is ; while the focus of the speculum is at D, which is only hair the distance from B to C. 709. Reflecting telescopes are of several kinds viz., the Gre- pr>ria,n, the Newtonian, the Caascgranian, the Her sc/ielian, &i' The Gregorian Reflector has an aperture in the center of the speculum, and a small concave mirror in the focus of the spcu- mn, which reflects the light back through the aperture to the eye-piece. In this way the observer is enabled to face the object, and to direct the telescope toward it, as if it were a refractor. 70S. Pocai distance? 709, How many kinds of reflectors? Describe the Gregorian. Why called Gregorian? 330 ASTRCNOMY. GRKGORIAX REFLECTOR. Here the light A falls upon the speculum at B, and is reflected back to the small mir- ror C, by which it is thrown out through the aperture in the speculum, to the ejeof the observer at D. The object is supposed to be off on the right, in the direction towards which the instrument is pointed. It is called a Gregorian telescope, after Mr. James Gregory, who first suggested the construction of reflecting telescopes. 7 10. The Newtonian Reflector is so called after Sir Isaac Newton, its inventor. Instead of a concave mirror in the focus of the speculum, he placed a plane mirror there, inclined so as to reflect the light to the side of the tube, where it was received by the observer. NEWTONIAN REFLECTOR. The light from the speculum is here shown falling upon the inclined mirror in the cen- ter, and reflected out to the eye of the observer. 711. The Cassegranian Reflector is so called from M. Casse- grain, its inventor. It resembles the Gregorian, except that the speculum placed in the focus of the reflector is convex instead of concave. The Herschelian Reflector differs from all others, in having no> small reflector whatever ; the light being reflected back to a focus at the top of the telescope, and near the edge of the tube, where the eye-piece is placed, and where the observer sits look- ing into the mirror with his back to the object. HERSCHELIAN TELESCOPE. Here the concave speculum is seen to be inclined a little to the lower side of the tube 90 that the parallel rays A are reflected back to the observer at B, at the de of tha instrument, where the eye-piece is placed. "710. Newtonian reflectors? 711. Cassegranian? Difference? HerschelSan ? Where eye-pi ece f Mow observer sit? 14* DIFFERENT KINDS OF TELESCOPES. 331 712. The first telescope constructed upon this plan was that by Sir William Herschel, in 1182. This was called his 20 feet reflector, and was the instrument with which he made many of his observations upon the double stars. In 1789, he completed bis forty feet reflector, until recently the largest telescope ever constructed. SIR WILLIAM HERSCUEL'S FORTY FEET REFLECTOR. 713. The speculum of this instrument is 4 feet in diameter, 3$ Inches thick, and weighed, before being ground, 2,118 pounds. 712. First Herschelian telescope? What called? Next? 718. Herschel's forty feet txjflector? Size of Speculu-M? Weight? Tube? Length and weighi ? How mounted? 332 ASTRONOMY. The tube is made of sheet iron riveted together, and painted within and without. The length of the tube is 89 feet 4 inches, and its weight 8,260 pounds. It is elevated or lowered by tackles, attached to strong frame-work ; and the observer, who sits in a chair at the upper end of the tube, and looks down into the reflector at the bottom, ia raised and lowered with the instrument. Three persons are necessary X) use this tele- scope one to observe, another to work the tube, and a third to note down the observa- tions. A speaking tube runs from the observer to the house where the assistants are at work. By this telescope, the sixth and seventh satellites of Saturn were discovered ; and it was the chief instrument used by its distinguished owner, in making the observa- tions and discoveries which have immortalized his name, and which have so abundantly enriched and advanced the science of astronomy. LORD ROSSE'S GREAT RKFLECT1NG TELESCOPE. f 14. This is the largest reflecting telescope ever constructed. The speculum, composed of copper and tin, weighed three tons as it came from the mould, and lost about th of an inch in grinding. It is 5 inches thick, and 6 feet in diameter. It was cast on the 13th of April, 1842, and was cooled gradually in an oven for 16 weeks, to prevent its cracking, by a sudden or unequal reduc- tion of the temperature. This speculum has a reflecting surface of 4071 square inches. The tube is made of deal wood, one inch thick, and hooped with iron. Its diameter is seven feet, and its length 56. The entire weight of this telescope is twelve tons. It is mounted between two north and south walls, 24 feet apart, 72 feet long, and 48 feet high. The lower end rests upon an universal hinge. It can be lowered to the horizon, and raised to the zenith, and lowered northward till it takes in the Pole Star. Observer where? Usefulness? 7J4. Lord Rosse's telescope? Weight of speculum? Diameter? Thickness? Cooling? Tube? Entire weight? How mounted? What OBSERVATORIES AND TELESCOPES. 333 OBSERVATORIES AND TELESCOPES IN THE UNITED STATES. OBSERVATORIES. THEIR TELESCOPES. When procured. Name of maker. Focal length. Aperture of object glass. Cost. Yale College, 1830 1836 (1836 11852 1837 1840 1841 1844 1846 1848 1849 || 1850 1851 1852 1846 1854 1853 1857? 1857 1846 1847 j 1850 1 1851 u 1852 Dollond. Lerebours. Holeoinb. A. Clark. Simms. Merz. Lerebours. Merz. u Simms. Fitz. Merz.; Fitz. u u Clark. Fitz. Spencer. Fitz! M U ft. in. 10 IJ _ 10 9 5 6 8 4 8 15 3 17 22 6 9 7 6 7 10 4 8 4 5 7 8 6 17 15 2 16 8 4 7 5 7 8 4 11 6 5 10 9 6 inches. 5 6 reflector. 7 4 ? 9-6 12 15 6-4 4-8 5-6 7-5 9 5 Ti Ml 18 13* 63-10 5 4 5 4 8 9 $1.000 1,000 1,900 6,000 9,437 19,842 1,600 1,050 8,500 1,200 225 1,800 6,000 14,500 10,000? 1.833 900 425 750 1,000 2,220 300 225 1,150 2.200 Wesleyan University. Williams College Hudson, Ohio Philadelphia West Point Washington Cambridge Dartmouth College Erskine . Shelby Columbia (S. C.) College Columbia (Mo ) Friends, Philadelphia Amherst College Michigan University DudleV, Albany, N. Y. Hamifton College J. Jackson, near Philadelphia. . . Mr. Longstreet, Philadelphia S. G. Gummere, Burlington, N. J. E. Vanarsdale, Newark, N. J. . . . . W. S. Van Duzee, Buffalo, N. Y. . W. S. Dickie, Elkton, Ky. D. Mosman, Bangor, Me. ; J. Campbell, New York L. M. Kutherford, New York .... FOBEIGN OBSERVATORIES THEIK LATITUDE AND LONGITUDE. OBSKRVATOKIES. La itu.le. Longitude in Time. Altona. 53 54 52 50 52 83 55 58 53 55 51 51 54 48 38 48 50 41 45 48 82 21 80 51 12 56 40 22 23 57 81 28 42 8 6 50 56 53 4 12 45 12.7 16.7 10.7 51.8 8 53 47.1 13 23.2 47.9 38.2 50.4 45 44 13 29.7 54 6 85.5 N. N. N. N. N. 8. N. N. N. N. N. N. N. N. N. N. N. N. N. N. h 1 1 1 2 1 m. 39 26 58 17 13 50 46 25 12 89 22 46 53 9 1 49 80 5 8. 46.2 35.5 34.9 27.2 23.5 56.0 19.3 54.6 22 43.0 46.8 0.0 0.4 25.4 25.5 21.5 13.5 54.7 48.4 82.6 E. W. E, E. E. E. E. E. W. W. E. E. E. E. E. E. E. E. E. Armagh Berlin Brussels (Jape of Good Hope Copenhagen Dorpat Dublin Edinburgh, Koni^sberg ... Munich. Palermo Paris Turin Vienna 699. Public observatories in this country? Largest telescope ? Table? Privaie observatories names ? Telescopes by whom mostly inde ? What other table ? 334 ASTEONOMr. CHAPTER XX. PROBLEMS AND TABLES. PROBLEM I. TO CONVERT DEGREES, ETC., INTO TIME. RULE t Divide the degrees by 15, for hours ; and multiply the temamder, if any, by 4, for minutes. 2. Divide the odd minutes and seconds in the same manner by 15 for minutes, seconds, &c., and multiply each remainder by 4, for the next lower denomination. EXAMPLE 1. Convert 32 34' 45" into tame. Thus, 32-M5 = 2h. 8' 34 -f-15= 2 16" 45 -^-15= 3 Ans. 32 34' 45 // =2h. 10' 19" EXAMPLE 2. If it is 12 o'clock at this place, what is the time 20 east of us ? Thus fifteen in 20, once, and five over ; the once is 1 hour, and the 5 multiplied by 4, gives 20 minutes ; the time is then 1 hour and 20 minutes past 12. EXAMPLE 3. The longtitude of Hartford is 72 50' west of Greenwich; what time is it at Greenwich when it is 12 o'clock at Hartford ? Ans. 4h. 51m. 20s. EXAMPLE 4. When it is 12 o'clock at Greenwich, what is the time at Hartford ? Ans. 7h. 8m. 40s. PROBLEMS AND TABLES. 335 PROBLEM II. TO CONVERT TIME INTO DEGREES, ETC. RULE. Multiply the hours by 15, and to the product add one- fourth of the minutes, seconds, &c., observing that every minute of time makes , and every second of time {'. EXAMPLE 1. In 2 hours, 10 minutes, and 19 seconds; how many degrees? Tims; 2h. 10m. 19. Add 10 quarters, or \ of the min. 2 30' Add 19 quarters, or { of the sec. 4 45* Ans. 32 34' 45* Ex. 2. When it is 12 o'clock at Hartford, it is 4 hours, 51 minutes, and 20 seconds past noon at Greenwich ; how many degrees is Hartford west of Greenwich ? Thus : 15 times 4 is 60 added to \ of 51, is 72 45", and this increased by i of 20, is 72 50'. Ans. Ex. 3. A Liverpool packet, after sailing several days from New York, finds the time by the Sun 2 hours and 40 minutes later than by the ship's chronometer : how far has the ship pro- gressed on her way ? Ex. 4. A vessel leaves Boston, and having been tossed about in foul weather for some days, finds, that when it is 12 o'clock by the Sun, it is only 11 o'clock and 50 minutes by the watch ; is the vessel east or west of Boston ; and how many degrees ? Ex. 5. The moment of greatest darkness, during the annular eclipse of 1831, took place at New Haven, 10 minutes after 1 o'clock. A gentleman reports that it happened precisely at 1, where he observed it ; and another that it was 5 minutes after 1 where he saw it ; Query. How far east or west were these gentlemen from each other, and how many degrees from New Haven ? 336 ASTRONOMY. PROBLEM III. ON THE MERI THE EVENING OF ANY GIVEN DAY. RULE. Look for the given day of the month, at the bottom of the maps, and all the stars having the same degree of right ascension will be on the meridian at that time. EXAMPLE 1. What stars will be on the meridian at 9 o'clock, the 19th of January? Solution. On Map III. I find that the principal stars stand- ing over against the 19th of January, are Rigel and Capella. Ex. 2. What stars are on the meridian the 20th of Decem- ber ? Ans. Menkar and Algol. PROBLEM IV. ANY STAR BEING GIVEN, TO FIND WHEN IT CULMINATES. RULE. Find the star's right ascension in the table, or by the map (on the equinoctial), and the day of the month at the top or bottom of the map will be the day on which it culminates at 9 o'clock. EXAMPLE 1. At what time is the bright star Sirius on the meridian ? Solution. I find by the table, and by the map, that the right ascension of Sirius is 6 hours and about 38 minutes ; and the time corresponding to this, at the bottom of the map is the llth of February. Ex. 2. At what time is Alpheratz, in the head of Andromeda, on the meridian ? Ans. The 9th of November. PROBLEMS AND TABLES. 337 PROBLEM V. THE RIGHT ASCENSION AND DECLINATION OF A PLANET BEING GIVEN, TO FIND ITS PLACE ON THE MAP. RULE. Find the right ascension and declination of the planet 011 the map, and that will be its place for the given day. EXAMPLE 1. Venus's right ascension on the 1st of January, 1833, was 21 hours, 30 minutes, and her declination 16f south ; required her situation on the map ? Solution. On the right hand of the Plate II. I count off 16f from the equinoctial, on the marginal scale south, and from that point, 30 minutes to the left or just half the distance between the XXI. and XXII. meridian of right ascension, and find that Venus, that day, is within two degrees of Delta Capricorni, near the constellation Aquarius, in the zodiac. . Ex. 2. Mars* right ascension on the 13th of March, 1833, is 5 hours, 1 minute, and his declination 24i north ; required his situation on the map ? Solution. I find the fifth hour line or meridian of right ascen- sion on Plate III.., and counting upward from the equinoctial 24t, I find that Mars is between the horns of Taurus, and about 5 S. \V. of Beta Auriga?. Ex. 3. Required the position of Jupiter and Saturn on the 13th of February and the 25th of May? PROBLEM VI. TO FIND AT WHAT MOMENT ANY STAR WILL PASS THE MERIDIAN ON A GIVEN DAY. RULE. Subtract the right ascension of the Sun from the star's right ascension, found in the tables : observing to add 24 hours to the star's right ascension, if less than the Sun's, and the difference will show how many hours the star culminates after the Sun. 338 ASTEOXOMT. EXAMPLE 1. At what time will Procyon pass the meridian on the 24th of February ? Solution. R. A. of Procyon, 7h. 30m. 33s. + 24h. 31 30' 83* R. A. of Sun, 24th Feb. 22 29 1 Ans. ~9 I 32~ That is 1m. 32s. past 9 o'clock in the evening. Ex. 2. At what time will Denebola pass the meridian on the first of April ? Solution. R. A. of Denebola is llh. 40' 32 ff R. A. of Sun, April 1, 41 25 Ans. 10 59 7 That is, at 59 minutes, 7 seconds, past 10 in the evening. Ex. 3. At what time on the first day of each month, from January to July, will Alcyone, or the Pleiades, pass the meri- dian ? Ex. 4. At what time will the Dog-Star, or Sirius, culminato on the first day of January, February, and March ? Ex. 5. How much earlier will Spica Virginis pass the meri dian on the 4th of July, than on the 15th of May ? Ans. 3 hours, 25 minutes. PROBLEM VII. TO FIND THE SUN'S LONGITUDE OB PLACE IN THE ECLIPTIC, ON ANT GIVEN DAY. RULE. On the lower scale, at the bottom of the Planisphere (Map VIII.) look for the given day of the month ; then the sign and degree corresponding to it on the scale immediately above it will show the Sun's place in the ecliptic. EXAMPLE 1. Required the Sun's longitude, or place in the ecliptic, the 16th of September. Solution. Over the given day of the month, September 16th, stands 5 signs and 23 degrees, nearly, which is the Sun's place in the ecliptic at noon on that day ; that is, the Sun is about 23 degrees in the sign Virgo. PROBLEMS AND TABLES. 339 N.B.- If th 5 signs be multiplied by 80, and the 28 degrees be idded to it, it will glre Uie longitude in degrees, 173. Ex. 2. Required the Sun's place in the ecliptic at noon, on the 10th of March. PROBLEM VIII. GIVEN THE SUN'S LONGITUDE, OR PLACE IN THE ECLIPTIC, TO FIND HIS RIGHT ASCENSION AND DECLINATION. RULE. Find the Sun's place in the ecliptic (the curved lice which runs through the body of the planisphere), and with a pair of compasses take the nearest distance between it and the nearest meridian, or hour circle, which being applied to the gra- duated scales at the top or bottom of the planisphere (measur- ing from the same hour circle), will show the Sun's right ascen- sion. Then take the shortest distance between the Sun's place in the ecliptic and the nearest part of the equinoctial, and apply it to either the eiist or west marginal scales, and it will give the Sun's declination. EXAMPLE 1. The Sun's longitude, September 16th, 1833, is 5 signs, 23 degrees, nearly ; required his right ascension, and declination. Solution. The distance between the Sun's place in the eclip- tic and the nearest hour circle being taken in the compasses, and applied to either the top or bottom graduated scales, shows the right ascension to be about 11 hours 35 minutes ; and the dis- tance between the Sun's place in the ecliptic, and the nearest part of the equinoctial, being applied to either the east or west marginal scales, shows the declination to be about 2 45', which Is to be called north, because the Sun is to the northward of the equinoctial ; hence the Sun's right ascension, on the given day, at noon, is about 11 hours 35 minutes, and his declination 2 45' N. Ex. 2. The Sun's longitude, March 10th, 1833, is 11 signs, 19 degrees, nearly ; required his right ascension and decline tion ? Ans. R. A. 23h. 21m. Deci. 4 11' nearly. PROBLEM IX. TO FIND THE RIGHT ASCENSION OF THE MERIDIAN AT ANY filVEN TIME. RILE. Find the Sun's place in the ecliptic by Problem IX., and his right ascension by Problem X., to the eastward of 240 ASTROXOUT. which count off the given time from noon, and it will show the right ascension of the meridian, or mid-heaven. EXAMPLE 1. Required the right ascension of the meridian 9 hours, 25 minutes past noon, September 16th, 1833 ? Solution. By Problems IX. and X., the Sun's right ascen- sion at noon of the given day, is 1 1 hours 35 minutes ; to the eastward of which, 9 hours and 25 minutes (the given time) being counted off, shows the right ascension of the meridian to be about 21 hours. Ex. 2. Required the right ascension of the meridian at 6 hours past noon, March 10th, 1833? Solution, By Problems IX. and X., the Sun's right ascension at noon of the given day, is 23 hours and 21 minutes ; to tli* eastward of which, the given time, 6 hours, being counted off, shows the right ascension of the meridian to be about 5 hours, 21 minutes. REMARK. In this example, it may be necessary to observe, that where the eastern, or left-hand extremity of the planisphere leaves off, the western, or right-hand extremity begins ; therefore, in counting off the given time on the top or bottom graduated scales, the reckoning is to be transferred from the left, and completed on the right, as if the two outside edges of the planisphere were joined together. PROBLEM X. TO FIND WHAT STARS WILL BE ON OR NEAR THE MERIDIAN, AT ANY GIVEN TIME. RULE. Find the right ascension of the meridian by Problem XI., over which lay a ruler, and draw a pencil line along its edge from the top to the bottom of the planisphere, and it will show all the stars that are on or near the meridian. EXAMPLE 1. Required what stars will be on or near the meridian at 9 hours, 25 minutes past noon, Sept. 16th, 1833 ? Solution. The right ascension of the meridian by Problem XI. is 21 hours : this hour circle, or the line which passes up and down through the planisphere, shows that no star will be directly on the meridian at the given time ; but that Alderamin will be a little to the east, and Deneb Cygni a little to the west of it ; also Zeta Cygni, and Gamma and Alpha in the Little Horse, very near it on the east. PROBLEM XI. TO FIND THE EARTH'S MEAN DISTANCE FROM THE SUN. RULE. As the Sun's horizontal parallax is to radius, so Is the semi-diameter of the Earth to its distance from the Sun. PROBLEMS AND TABLES. 341 By Logarithms. As tangent of the Sun's horizontal parallax is to radius, so is the Earth's semi-diameter to her mean distance from the Sun. 8'.5776 : 206264-.S : :39G2: 95,273,869 miles. By Logarithms. As tangent of the Sun's horizontal parallax, 8* .5776= 5.6189407 Is to radius, or 90% =10-0000000 So is the Earth's semi-diameter, 3962= 8.5979143 To the Earth's distance, 95,273,869= 7.9789733 PROBLEM XII. TO FIND THE DISTANCE OF ANY PLANET FROM THE SUN, THAT OF THE EARTH BEIXG KNOWN. RULE. Divide the square of the planet's sidereal revolution round the Sun, by the square of the Earth's sidereal revolution, and multiply the cube root of the quotient by the Earth's mean distance from the Sun. By Logarithms. Prom twice the logarithm of the planet's sidereal revolution, subtract twice the logarithm of the Earth's sidereal revolution, and to one-third of the remainder, add the logarithm of the Earth's mean distance from the Sun. KXAMPLR. Required Mercury's mean distance from the Sun, that of the Earth being 95,'J73,869 miles. Mercury's sidereal revolution is 87.969258 daya, or* 7600543" .89 12 : the Earth's sidereal revolution is 365.256374417 days, or 31558151-.5 7600543.9 81558151'.5 7600543.9 995916962096952.25 by which divide 5776S267575S27.21 and the quotient will he 0.052005106713292, the cube root of which is 0.8870977, and this multiplied by 94,881,891, gives 36,727,607 miles, for Mercury's distance from the Sun. Tliis problem may be performed by logarithms in as many minute* as the former method requires hours. Mercury's Sid. Rev. 7600543'.9 lng.=6.SS08447 2 18.7616394 Earth's Sid. Rev. 8155S151". log.=7.4991302x 2 14.90^2(504 H ) 2.7634-190 1 .SS7809T Add log. of the Earth's mean distance, 7.97S9738 Mercury's distance, 36,880,422. Ans. 7.5667S35 If the pupil have not already learned the use of logarithms, this problem will satisfy him of their unspeakable advantage over all other modes of computation. Hy reviewing the above calculation, he will perceive that instead of multyplying 31558151'.5 by itself, be need only multiply its logarithms by two I and instead of extracting the cube root of 088005106718293, he need only divide its logarithm by three! and instead of multiply- ing 0.8870977, by 95,273,869, he need only add their logarithms together. He need not think himself a dull scholar, if by the former method he come to the true result Injlvt Hours ; nor remarkably quick, if by the latter he come to it in Jive mimutet. PROBLEM XIII. TO FIND THE HOURLY MOTION OF A PLANET IN ITS ORBIT. RULE. Multiply the planet's mean distance from the Sun by 34:2 ASTRONOMY. 6.2831853, and divide the product by the time of the planet's sidereal revolution, expressed in hours, and the decimals of an hour. By Logarithms. Add 0.1981*199 to the logarithm of the planet's mean distance from the Sun, and from the sum subtract the logarithm of the planet's revolution expressed in hours. EXAMPLE. Required the Earth's hourly motion in its orbit. Log. of Earth's distance=7.9780738 + 0.7981799= 8.7771587 Subtract log. of Earth's revolution 8.9428090 Gires Earth's horary motion, 68,288 miles, 4.88434#- PROBLEM XIV. TO FIND THE HOURLY MOTION OF A PLANET ON ITS AXIS. RULE. Multiply the diameter of the given planet by 3.14159, and divide the product by the period of its diurnal rotation. By Logarithms. Add 4.0534524 to the logarithm of the planet's diameter, and from the sum subtract the logarithm of its diurnal rotation, expressed in seconds. Earth's diameter, 7924 log. = Add log. of 8600' + log. of 8.14159 = Subtract log. diurnal rotation, 23h. 56' 4".09 = Ana. 1040.09 miles = PROBLEM XV. TO FIND THE RELATIVE MAGNITUDE OF THE PLANETS. RULE. Divide the cube of the diameter of the larger planet by the cube of the diameter of the less. By Logarithms. From three times the logarithm of the larger, subtract three times the logarithm of the less. EXAMPLE. How much does the size of the Earth exceed that of the Moon ? Earth's diameter, 7912 log. 8.8982863 x 3= 11.6948589 Moon's diameter, 2160 log. 3.3848376 x 8= 10.0030128 The Earth exceeds the Moon, 49.1865 times. Ans. 1.6918461 In this example, 7912 miles is assumed as the mean between the Earth's equatorial and polar diameter : the former being 7924, and the latter 7898 miles. PROBLEM XVI. TO FIND THE PROPORTION OF SOLAR LIGHT AND HEAT AT EACH OF THE PLANETS. RULE. Divide the square of the planet's greater distance from the Sun, by the square of the less. Or, subtract twice the logarithm of the greater distance from twice the logarithm of the less. PROBLEMS AND TABLES. 343 EXAMPLE. How much greater is the Sun's light and heat at Mercury, than at the Earth ? Log. of Earth's distance " of Mercury's Ana. 6.6736 times greater: 7.9789733x2=15.9579476 7.5667959 x 2=15.1835918 0.8243558 PROBLEM XVII. TO FIND THE CIRCUMFERENCE OF THE PLANETS. RULE. Multiply the diameter of the planet by 3.14159, or, add the logarithm of the planet's diameter to 0.4971499. PROBLEM XVIII. TO FIND THE CIRCUMFERENCE OF THE PLANETARY ORBITS. RULE. Multiply the planet's mean distance from the Sun by 6.2831853 ; or, to the logarithm of the planet's mean distance, add 0.7981799, and the sum will be the logarithm of the answer. PROBLEM XIX. TO FIND IN WHAT TIME ANY OF THE PLANETS WOULD FALL TO THE SUN, IF LEFT TO THE FORCE OF GRAVITATION ALONE. KULE. Multiply the time of the planet's sidereal revolution by 0.176776 ; the result will be the answer. By Logarithms. From the logarithm of the planet's sidereal revolution, subtract 0.7525750, and the remainder will be the logarithm of the answer, in the same denomination as the side- real revolution. Required the times, respectively, in which the several planeta would fall to the Sun oy the force 01 gravity. Planets would fall to the Sun. Days. H. M. S. Logarithms. Mercury, Venus, Earth, Mars, Jupiter, Saturn, Herschel, Moon to the Earth, 15 13 13 16 89 17 19 22 64 13 83 55 121 10 36 8 265 21 83 85 1901 23 24 4 5424 16 52 1 4 19 54 57 6.1282686 6.5355424 6.7465357 7.020881 T 7.8206849 8.2157186 8.6708897 5.6204459 THE END. EXPLANATIONS AND PROBLEMS ADAPTED VO WHITALL'S PLANISPHERE. TO BE USED IN CONNECTION WITH THE CELESTIAL ATLAS. NOTE. This is a movable Planisphere, invented and copy- righted by Henry Whitall, and for sale by the publishers of 13 nr- ritt's GEOGRAPHY OF THE HEAVENS, exhibiting the stars that are ris- ing, setting, on the meridian, or their position in the firmament, as seen in the United States every minute, for HUNDREDS OF YEARS. The right ascension and declination of the sun, moon, stars, and planets ; the equation of time (sun fast or slow) ; harvest-moon ; sun and moon running high and low; the milky way, as it changes its course for every hour ; change of seasons,