UNIVERSITY OF CALIFORNIA. FROM THE LIBRARY OF WILLIAM M. PIERSON. GIFT OF MRS. PIERSON AND L. H. PIERSON. No. He telleth the number of the Stars, and calleth them all by their names. TUB GEOGRAPHY OF THE HEAVENS, CLASS-BOOK OF ASTL'OffOHT ACCOMPANIED BT A CELESTIAL ATLAS. 4. ELIJAH H. BURRITT, A.M. ^' ENLARGED, REVISED, AND ILLUSTRATED, BY H. MATTISON, A. M. AND REVISED EDITION, CORRECTED IN 1873. NEW YORK. SHELDON & COMPANY, / lettered according to Act of Congress, in the year 18W, 39 1*. J. nUNTINGTON, O O'.erk's Office of the District Court of the United StateB for ttr Southern District of New York. terxd according to Act of Congress, in the year 1873, by SHELDON & CO., the Office of the Libraries of Congress, at Ww R E F A C E . THE rapid progress of the science of astronomy, for the ion: 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 bas 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 Smyths Cycle of Celestial Oljeds, will be found especially 7366 IV PREFACE. valuable to all institutions having an equatorial telescope Indeed, they greatly enhance the value of the work for ill classes of students. 4. Several small constellations that were delineated on ihf maps, but were not described in former editions of the book, have been described, and their history given in the preseni edition. 5. The page of the book has been greatly enlarged, lor tht 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, adopting it, in this respect also, t< the wants of both teacher and student. 6. Still further to illustrate the second part of the work, the 5rst map of the atlas has been re-drawn and re-engraved, so as to illustrate mare and belter 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, Nebula;, 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 mapg, bow matter, and numerous illustrations, making it the most per- lect and complete text-book of astronomy ever offered to th American public. H. MM Yorl;. J'liv isdti. REVISED IN 1878. LNDEX TO THE CONSTELLATIONS. Andromeda ftnuuous . Anser et Velpecula A.ries . 18 . 118 .121 . 28 Argo Navis ...... 62 Aquiia, ....... 118 Aquarius . . . . . . 181 Auriga . ..... 49 Bootes ....... 84 Oauielopardahw ..... 51 Oancer ....... 64 Janes Venatici ..... 83 Canis Major ...... 59 Canis Minor ...... 56 Capricornus ...... 12T Cassiopeia ...... 22 Centau rui ...... 88 Cepheus ...... 25 Cetus . ..... 82 Columba ...... 46 Coma Berenices ..... 11 Corvua ....... 78 Corona Australia ..... 118 Corona BoreaH* .... 94 Orater . .... 71 Cyguus ....... 124 Delphinu ....... 122 Draco ....... 110 KridaLUB ...... 47 Kquuleus ...... 18i Gemini . . . . . . .53 Gloria Fred erica . . 134 . . 108 HMt Hydra ....... 71 Lacerta ...,.., 184 Leo ,66 Leo Minor 68 Lupus (The Wolf) .... 90 Lepus (The Hare) ... 4t Libra :, Lynx 52 Lyra 112 Monoceros ...... 59 Musca 82 Nocta 83 Ophiuchus . ... 107 Orion .41 Pegasus . . ... 129 Perseus 85 Pisces 20 Pisces Australia .... 13d Sagittarius . . .116 Sagitta . 121 Scutum Sobieski 116 Scorpio 100 Sceptrum Brandenburgium ... 49 Serpentarius vel Ophiuchus . . 107 Serpens 98 Sextans TO Taurus 88 Taurus Poniatowski . . . . 115 Telescopium Herschellii . . 53 Triangulae . . . . .31 Ursa Major .... .78 Ursa Minor .... *> Virgo .... .81 CONTENTS. PART I. -THE CONSTELLATIONS. ' iGV Dfc il'TER I. Constellations on the meridian in November, . . 18 II. " " " December, .... S III. ' " " Januarj, .... 38 " IV. " * " February, .... 63 " V. " " " March, .... 62 " VI. " " April, . . .66 " VII. ' " " May, . . .73 " V1U. " " June, .... 84 " IX. " " " July, . 10(1 " X. " " " August, . ,110 " XL " " " September, .... 122 ** XII. " " " October, .... 129 " XIII. Variable and Double Stars Clusters and Nebula 135 " 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 1 1 . - T II E SOLAR SYSTEM. Oa heavens? Poles of the heavens? Equate! '.? the Earth? Equator of '.he heavens, or Equ toctial? 7. Rational horizon? Scnai Me 01 apparent ? CHICLES OF THE SPHERE. 11 nsibie 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. ft a person standing on a plain, this circle is but a few miles in diameter. If the ey b9 elevated five feet, the radius of the sensible horizon will be less than two miles and three |iiarters; if the eye be elevated six feet, it will be just three miles. The observer being always in the centre of the sensible homon, it will move as he moves, and enlarge W contract, as his station U elevated or depressed. 8. The Poles of 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 P)i?ne Vertical is that which passes through the east and west points of the horizon. 9. 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 axi^s 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* 45'. At the beginning of 1836, it was only 23* 27' 38", showing an annual diminution of about half a second, or 46" .70 in a hundred years. A time will arrive, however, when this angle, having reached its minimum, will again inciease 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 i i 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 to the same point again in the following order : Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpio, Sagittarius, Capri 8. Poles of the horizon? Vertical circles? Prime Vertical? 9. Ecliptic? Equi oxes? Hew is the Ecliptic situated with respect to the Equinoctial? Obliquity if ftcP.pticf Ii this angle permanent? 10. How is the Ecliptic divided? Where coin- Bu-iiced, and how reckoned? Name sigi 3 in order? How does the Sun pi oceed tliVyjgl 1* 12 ASTRONOMY. cornus, Aquarius, Pisces. The Sun, commencing at the first degree of Aries, about the 21st of March, passes, at a meak rate, through one sign every month. 11. The Zodiac is a zone or girdle, about 1 6 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, rin/,e they are never seen beyond 8 either north or south of the ecliptic. 12. Parallels of Latitude are small circles imagined to bo 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 23J C ocrth 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 tbe 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 28c* ; but, as we have seen, the obliquity o* the ecliptic is continually changing; therefore the position of the tropics must make correspondent change. 14. The Colures are two great circles which pass through th* 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, and is thence called the Solstitial Colure. The Sun is in the equinoctial points the 21st of March and the 28d of September. H f m the solstitial points the 22d of June and the 22d of December. 15. The Polar Circles are two small circles, each about 66 11. What la th* Zodiac? 12. Parallels of latitude? Of declination? 18. Th| tropics? Cancer? Capricorn? What do these circles mark in the celestial sphere. Oa v *> terrestrial ? 14. The Colures? Where situated ? When is the gun at th qof hoetia* y>,':its? The *<>lstici:il? 16. What are the Pola Circles? CIRCLES OP THE SPHERE. 13 the equator, being always at the same distance from the poles that the tTopics are from the equator. The northern is called the Arctic circle, and the southern the Antarctic circle. 1 6. Meridians are imaginary great circles drawn through th* poles of the world, cutting the equator and the equinoctial at light angles. Every place on 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 beavens, 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 ffoiir Circles. In measuring distances and determining positions on the Earth, the equator and some 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 passe? through the first point of Aries, called the equinoctial colure. 17. Latitude on the Earth, is distance north or south rf the tquator, 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 pome fixed meridian, measured on the equator. Longitude in the Heavens, is distance east from the first poinl of Aries, measured on the ecliptic. 18. Declination is the distance of a heavenly body either north w 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 eor- 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 360. It is easy to convert ripht 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, whicn 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 win pass the meridian first which has the least right ascension. 19. In consequence of the Earth's motion eastward in ita orbit, the stars seem tc have a motion westward, besides their apparent diurnal motion caused by the Earth's revolution on ita axis ; so that they rise and set sooner every succeeding day by about four minutes, than they d ; d on the preceding. This if 18. Meridians? How many? What other name? How measure distances on Lie *rth? tn the heavens? 17. What is latitude on the earth? In the heavens! Longitude on the earth? In the heavens? 13. Declination? Right ascension Why describe by D. and R. A.? Extent of latitude? Declination! Longitude and R A ? How convert R. A. into time? Which of two bodies given will first pass the merl Jiaij? 19 What a >pareut motion of gtars? 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 constet 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 westorr. horizon, and are seen no more, until, having passed through tho *ower 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, p 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 J.'u-uary, February, and March; the third, those visible in April, May, and June ; and the fourth, those visible in July, August, f,nd September ; with the excep- tion, however, of the constellation vvlii'?!: lie beyond the 50th degree of north and south decl ; ;~_t''on, of which, indeed, those around the North Pole are alwiys, and those around the South Pole, never visible to us. 21. These constellations are represented on the sixth and seventh maps, called circumpc/lar maps, which are an exact con- tinuation of the others, and if joined to them at their correspond- ing degrees of right ascension and decimation, 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 Rig/it Ascension, or Hour Circles. The scale at the top and bottom of the first four maps, and in the circumference of <.he circumpolar maps, indicates the daily progress of the stars in right ascension, and fsbows on what day of the month any star will be on the meridian at 9 o'clock in th evening UO. What sail of maps? First? Next six? 21. Sixth and seventh f Scale Describe lines? S'ale indicates whatf CLASSIFICATION OF STARS, NEBLUE, 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 aouth, 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 Hiaps he mist suppose himself to face the pole, and to hold them in such 4 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 ,ion the principal stars are marked iu the order of their right ascension. That point of projection for the maps which would exhibit eacli 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 OP STARS, NEBUL-E, &o. 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 f3, Beta; the next, 7, Gamma, &c., till the Greet 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, 8, &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 th celestial globes, the Greek alphabet is here introduced for the use of those who ar unacquainted with it. The capitals are seldom used for designating the stars, but are here given for the sake of regularity. 22. How use the firsi four maps of the hearens? Circumpolar. What exception! What point of projection chosen, and why? 28 Classification or designation o, fctirs? By whom invented, and when? 16 ASTRONOMY. THE GREEK ALPHABET. A a Alpha N v Nu B ft Beta 3 Xi F y Gamrr.a O o Omicron A 6 Delta n TT Pi E f Epsilon P p Rho Z C Zeta 2 f Sigma H 17 Eta T r Tan 6 Theta Y v Upel.^on J i Iota 4> Phi K K Kappa X % Qhi A A Lambda * ^ Psi II ^t Mil 2 u Omega 24 As a further aid in finding particular stars, and especial Ij In determining their number, and detecting changes, should anj occur, catalogues of the stars have been constructed, one of which is over two thousand years old. Several of the principa. stars have specific names, like the planets, as Sirius, Aldebaran t Regulus, &c. 25. The stars are still furrier distinguished, as single, double, triple, multiple, binary, variable, w *?, and 'nebulous. A single star is one that appeals as a unit under the most powerful telescopes. Uoubk,, tri^c^ and. multiple stars, are those that appear single to the naked b/ v but by the aid of telescopes are found to consist of two Oi More stars. Binary stars are double stars revolving around ei.'h 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 cluster of stars is an assemblage or group, thrown promiscuously together, like the Pleiades and Hyades 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. Resolvabk Nebula:, 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 ditln fni?hed? Single ptars? Double, Ac.? Binary? What other name? Variable stars what other name and why? Newstars? Nebulous? 26. What are clusters? Ntbu l*j? Resolvable Nebulae? Irresolvable ? Annula* ? Planetary? CLASSIFICATION OF STARS, NEBULA, ETC. I 1 ) is ycL been thus resolved. Annular Nebula are those that have the form of an annulus or ring. Planetary Nebula are those 1 1 tut resemble planets in form, and in the sharpness of iheir out- line Stellar Nebula are those with a star in the centre, the same as nebulous stars, already described (25). A nsre detailed account of the double stars, clusters and. nebulas, will be given after he student has become somewhat familiar with the constellations. 27. We may now imagine the pupil ready to begin the study jf 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 th 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 tne 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-ise 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 passes. Thus in Georgia, for instance, the starting point should be those stars which are utuated in this meridian near the 83d degree of north dedication, 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 equinox at the first point of Aries, not only because it is the meridian from which the distances of till the heavenly bodies are measured ; but especially because the student will thus be enabled to observe and compare th? 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 cf the other planets. 27. Whfct first important in commenc'ng study of the heavens? What star would eem best starting point? Why? Whj not the best? What point preferable, an| why? Illustration from map. 28. With what stars might we begin F What raerilui -hosea bj the author? Why? PART I. THE CONSTELLATIONS CHAPTER I. CONSTELLATIONS ON THE MERIDIAN IN NOVEMBEH ANDROMEDA. MAP II.* 29. IF we look directly overhead at 10 o'clock, on the 1 ti, af November, we shall see the constellation celebrated in fable by the name of ANDROMEDA. It is represented on the- map by thy 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 66 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 Merach, Mu, and Nu. 31. If a straight line, connecting Almaacklwith Merach, bt * As the eastward motion of the earth in her orbit causes thel sun to pass eastward *iiT.ually around the heavens, and the constellations to rise earliarand earlier (19), the t iauent will find it necessary to proceed eastward around the heavens, in studying t Constellations. And as ttte right hand of the map is west, and tHe Keft hand east, begin with the equinoctial colure, map II., and proceed to the left\in the *rder in whicJi thf constellations successively arise. 99. What constellation? Maps, and why? (Note.) How Andromeda represented Boundaries? Situation? Kiglit ascension ana declination? 30. Number of stars Magnitude? Altnaack? Merach? "Girdle?" 31. Situation ot Delta ? Magnitude How otherwise known? Alplierati? Substanc't of note (tine ANDROMEDA. 19 produced south-westerly, 8 farther, it will reach 4 o (<5) Ddta, a star of the 3d magnitude in the left breast. This star may bo otherwise known by its forming a line, N. and S., with two smaller ones on either side of it ; or, by its constituting, with two others, a very small triangle, S. of it. Nearly in a line with Almaack, Meraeh and Delta, but rnrv ing a little to the N. 7 farther, is a lone star of the 2d magni- tude, in the head, called Alpheratz (a}. This is the N.E. ?oi nor of the great " Square of Peirasus," to be liereafter described. It will be well to have the positie- - vpheratz well fixed in the mind, becatUi it ib >jt one minute west of the great equinoctial colure, or first meridian of the heavens, anJ forms nearly a right line with Algenib, in the wing of Pegasus, 14 ri. of it, ac1 with IK-ta in Cassiopeia, 30 N. of it. If a line, connecting these three stars, be produced, it will terminate in the pole. These three guides, in connection with the North Polar Star, >oint out to astronomers the position of that great circle in the heavens from which the right ascension of all the heavenly bodies is measured. MYTHOLOGICAL HISTORY- 32. The story of Andromeda, from which this constellation derives its name, is as follows: She.' was daughter of Cepheus, King of Kthiopia, by Cassiopeia. She was promised in marriage to Phineus, her uncle, when Neptune drowned the kingdom, and sent a sen monster to ravag. the country, to appease the resentment which his favorite nymphs bore against Cassiopeia, because she had boasted herself fairer than Juno and the Nereides. The oracle of Jupiter Ammon was consulted, and nothing could pacify the anger of Neptune unless the beautiful Andromeda should be exposed to the sea monster. She was accordingly chained to a rock for this purpose, near Joppa (now Jaffa, in Syria), am' at the moment the monster was going to devour her, Perseus, who was then return- ing through the air from the conquest of the Gorgons, saw her, and was captivated by her beauty. "Chained to a rock she stood ; young Perseus stay'd llli rapid flight, to woo the beauteous maid." He promised to deliver her and destroy the monster if Cepheus would give her to him in marriage. Cepheus consented, and Perseus instantly changed the sea monster into a rock, by showing him Medusa's head, which was still reeking in his hand. The enraged Phineus opposed their nuptials, and a violent battle ensued, in which he, also, was turned into a stone, by the petrifying influence of the Gorgon's head. The morals, maxims, and historical events of the ancients, were usually communicated in fable or allegory. The fable of Andromeda and the sea monster might mean that she was courted by some monster of a st/a-captain, who attempted to carry her away, but R-as prevented by another more gallant and successful rival. TELESCOPIC OBJECTS. 33. Under the head of Telescopic Objects, will be included clusters and nebulre thai ure visible to the naked eye, as well as the principal objects of interest that are strictly telescopic. In describing the location of these objects, It. A. will denote Jtigfit A seen* tion ; and Dec., Declination. The initials N. and S. will indicate whether tb? declination is North or South of the equinoctial. In describing the location of the telescopic object, the R. A. will be given intnn, iriz.,in hours, ntinutes, and seconds, instead of degrees, minutes, and seconds; c"ch hour answering to 15. The hour circles are Hstinctly drawn on all the maps, ir.e f r*l being 15 east of the equinoctial colure (Map 11.), and so on eastward to the same pc it ag.-.in. The hours will be seen marked just under the equinoctial, which is mnrkec' into degrees, each of which answers to four minutes of time. The student will soon i^_C it much more convenient to reckon II. A. by hours, on the maps, than by degrees, ic. 32. HiSTom. What may it have meant? 88. What included among Telescopic Objects ? What meant by R. A. ? Dec. ? N. and 8.? How R. A. laid down? How on map? What mode of describing components of doiifclr stars? Of a Andromeda? Of discrepancies between R. A. given, ;md locu- tion of stars on the ^ ?ps? How is R. A. given in locating objects* \Vliy? Ho are hourt marked on the maps? The minutes? 20 ASTRONOMY 84. In consequence of the perpetual recession of the equinoxes westward, the R. A of objects is constantly increased by about 50" per year. It is vain, therefore, to attempt tc give II. A. for the time when a bookioill be U8*d ; or to construct maps that wiJ! Bl.ow objects in their true place, for different years to come. The necessary allowance amst be made in all cases ; so that tne R. A. for one epoch is about as good as another. The R. A. here given is from Smyth's Celestial Cycle, epoch Jan. 1, 1S40. Maps shoul.) be re-engraved every fifty years, but for all shorter periods allowance can be made by the student. As the maps accompanying this work were drawn and engraved iu ISSf, their present R. A. (1S64) is about IT' or 4m. of time east of their places c,n the maps. 86 The order in which the telescopic objects will be arranged is first the double stars ; tecondly, clusters ; and lastly the nebulas. The double stars will be classed according to their order in the respective constellations ; i.e., a first, 3 next, &c. ThuSj as the argest objects are first named, the student can begin with those jasiest found, ani ,/e.juiring the least telescopic power; and proceed from the easier to those more diffi jult. The same plan is generally pursued with the clusters and nebulae. TELESCOPIC OBJECTS IN ANDROMEDA. 1. a A>*ROMKD.S (Alpheratz) A star with a minute companion, R. A. Oh. Om. 03s. . Dec., N. 2c' 12' 05". A. 1, bright white ; B. 11, purplish. On the map it is went of the equinoctial, the map having been engraved some twenty years; but the equinox having constantly receded westward, had passed Alpheratz before 1840, some 8'. Similar dis- crepancies between the R. A. given and the location of different stars on the map, are due to the same cause. 2. /? ANDROMEDA; (Merach) A bright star with a distant telescopic companion, R. A. In. 00m. 47s. ; Dec., N. 84 46' 08". A. 2, fine yellow ; B. 12, pale blue, with several small stars in the field. 3. y ANDROMEDA (Alnninek~)A SPLENDID DOUBLE STAR on the right foot, R. A. Ih. 54m. 06s ; Dec. N. 41 83' OC". A. 3}<$, orange color ; B. 5M, emerald green. Found by a line from fi to /?, and about twice as far beyond. (Map VIII., Pig. 1.) 4. ( ] ANDROMKIU& A bright star on the right breast, with a distant telescopic com- panion, R. A. Oh. 80m. 47s. ; Dec., N. 29 59' 01". A. 8, c range ; B. 1 1 }$, dusky ; with the small stars in the southern part of the field. 5. K ANDROMEDA A wide, but delicate TRIPLE ST-iR, in the northern hand ; midway between (3 Pegasi and a Cassiopeia ; or about IS" from each ; R. A. 23h. 82m. 83s ; Dec., N 43 27' 0". A. 5, brilliant white; B. 14, dusky; C. 12, ash-co!ored. C. AN ELONGATED NEBULA on the lady's right foot, R. A,2h. 12rn. 35s. ; Dec., N.41" 8C". It was discovered by Miss Caroline Herschell, in 17S8. Sir William Ilerschell described it as having " a black division or chink in the middle." He regarded it as a flat ring of enormous dimensions, seen very obliquely. Captain Smyth says: "In my telescope it is certainly brighter at the edges than along the central part." See map VIII., Fig. 21. 7. About 2 from Nu at the north-western extremity of the girdle, R. A. 00* 34m. 05s., N. Dec., 40 23' 06", is .1, remarkable nebula of very minute stars, and the only one of the kind which is ever visible to the naked eye. It resembles two cones of light, joined at their base, about ?i in length, and ^ in breadth. It was known as far back as A.D. 905, is of an oval shape, and is described by Smyth as " an overpowering nebula, with a companion about 25' in the south vertical." Sir "William Herschell considered this the nearest of all the grea't nebula;, and yet so remote thai it would require 6,000 years for UffM to pass from it to our system, though flying at the rate of 190,000 miles per second I Fig. 22, map VIIL, is a representation of this object. PISCES (THE FISHES), MAP V. 36. This constellation is now the first in Older of the twelve constellations of the Zodiac, and is usually represented by two (ishes tied a considerable distance apart, at the extremities of a lon undulating cord, or ribbon. It occupies a large triangular spaci S4. What said of tt i change of R. A of objects? Canse? Epoch of R. A. giveu li book? Of that marked on maps ? Allowance to be n.ade in finding objects by maps S5. Order in which objects are presented? Advantage of this arrangement? 1'RLKSCOPic OBJECTS. What doubls stars? a? /3? >? What clusters cr uebui* Shown on map, or not? W Pisces? Where situated? What D( w called ? PISCES. 2) in the heavens, and its outline at first is somewhat difficult to b traced. In consequence of the annual precession of the stars, the constellation Piscea has nov PISCIUM A close double star in the space between the two fishes, about half-way between ^ Andromeda and (j 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. Oii 1m. 63s. ; Dec. N. 10 14' 06". A. 6, silvery white ; B. 13k-, pale blue. 5. A FAINT NEBULA in the eye of the western Fish, about 10* south-half-east oC Mar- fcab, near y Piscium; R. A. 23h. 06m. 86s. ; Dec. 8 89' 7" : 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 hor left hand the branch 41. HL"TORY? Greek account? OviJ's and others? Sentiment or moral f Zodiac? Astrology? Tn J >'SOOPio OBJECTS. Double stars Clusters? Nebulae? Sliowa on mtp, or notf 4?. Cassiopeia? How represented Head? vPASSlOPEIA. > of a palm tree. Her head and body arc seen in the Milky Way HIT. foot rests upon the Arctic Circle, upon which her chair is placed She is surrounded by the chief personages of her roya 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. 13. This constellation is situated 26 N. of Andromeda, and tnidwuy 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 ia 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 should be remembered that the apparem 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 arc of the 3d magnitude, and so situated 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, brillhnt 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. 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. Shedir, 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 glance. 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. 46. It is generally supposed that the North Polar Star, so sailed, 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 48. Situation? How seen? Jl. A. and Dec.? When ou meridian? 44. Number o! Stara? Magnitudes? Figure? Character of this constellation ? 46. Caph? How 8ltut Caph? 48. PoU Is tt the tree pole? What variat onf How pole star situated with reference to 84 ASTRONOMY. appellation of the North Polar Star ; but it is, in reality, mor* than a degree and a half distant from it, and revolves aboit 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 ibove, and once below the pole ; and twice at its greatest elonga- lon E and W. The Polar Star not being exactly in tne N. pole of the heavens, but one degree ana ft., m&yutes on that side of it which is towards Caph, the position of the latter becomes 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 fro:n the pole, and exactly opposite another remarkable star in the square of the Great Pear, on the other side of the pole. [Se# Megree,] It also serves to mark a spot lu the starry heavens, rendered memorable as being the place of a lost star. Two nun* dred and fifty yeara ago, a bright star shone 5' N. N. E. of Caph, where now is a uark void ! On the 8th of November, 1572, Tycho Brahe and Cornelius Gemma saw a star in th 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, this great brilliancy diminished, until tho 15th of March, 1578, when, without moving from its place, it became utterly extinct. Its ojlor, 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 b> visible at such a distance. It waa 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. Rev. Professor Vince, one of the most learned and pious astronomers of the age, ha* 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 thua 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, whd will con- tinue to rise higher and higher in their enjoyments, and go on to contemplate system after system through the 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, continue! 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 difiereut 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 mam er we know nothing, but the fact if Incontrovertible; it is foretold by revelation; it is inscribed in the heavens; it is fsil through the earth. Such is the awful and daily text ; what then ought to be the Csnmit? The great and good Beza, falling in with the superstition of his age, attempted to prov* Jiat this was a ccmet, or the same luminous appearance which conducted the raagi, or rise men of the East, into Palestine, at the birth of our Saviour, and that it now appeared t> announce his second coming. Papl t i ? What other important fact in relation to the position of Caph? What remark- able fact stated? By whom attested? Describe phenomenon? Mrs, SomervlUe'f remark? Other astronomers'? Professor Vince's remarks? The author's? la Place's ? Dr. Good 'a ? Bew'a T CEPIIEUS. 2ft HISTORY. Oasstjpeiu was. the wife of Ccpheus, King of Ethiopia, and mother of Andromeda. 8h< was a 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 'nsult, who sent a frightful monster to ravage her coast, as a punishment for her inso- lence. 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 he? exposed to the fury of this monster. She was thus left, and the monster a proached , imt 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." Evaders Ovid. TELESCOPIC OBJECTS. 1. a CASSIOPK* (Shedir} A bright star, with a companion in the bosom of the figure , R. A Oh. 81m 29s.; Dec. 65 89 05". A 8, pale rose tint; B 10}$, small blue. S-u,tb and llerschell note Shedir as variable. 2. fi CASSIOPEJS (Cup1i)\ bright star on the left side, with a minute companion ; R. A. Oh. Om. 42s.; Dec. N. 53 1C' 03'. A 2}$, whitish; B 11>$, dusky. Look directly opposite Megris, in the great dipper, through the pole star, and about as far beyond. 3. y CASSIOPE^E A bright star with a distant companion on the right side of the figure ; R. A. Oh. 47m. 05s. ; Dec. N. 59 50 08". A 8, brilliant white; B 18, blue. Mary small gtars in the field. 4. 7? CASSIOPE*> A BISAKY STAR, about- 4 from a towards Polaris; R. A. Oh. 89m. 27s., Dec. N. 56 57' 09". A. 4, pale white ; B. 7%, purple. Estimated period 700 years. 5. /u CASSIOPK. A coarse TRIPLE STAR in the right elbow ; R. A. Oh. 57m. 23s, ; Dec. N, 'M OS' 01". A 5^ , deep yel\ow ; B 14, pale blue ; C 11, bluish. Several small stars in the field. 6. a CASSIOPK*: A beautiful double star in the left elbow; R. A. 23h. 50m. 55s. ; Dec. N. 54 51' OS". A 6, flushed white; B 8, smalt blue; the colors clear and distinct. 7. A coarse QUADRUPLE STAR, just south of Cepheus* right hand ; or about 27 south- outh-west of Polaris, on a line drawn over y Cephei. R. A. 23h. 17m. 45s. ; Dec. N. 64' 24' 03". A 5, pale yellow ; B 9, yellowish ; C 11, and D, 13, both blue. 8. A LARGE ASP STRAGGLING CLUSTER, between the footstool of Cassiopeia and the head of Oepheus; R. A. Oh. 18m. 10s. ; Dec. N. 70 30' 08'. A line from y Cassiopese, % the dU tance to y Cephei, will fall upon this object. A coarse double star in the field. 9. A R.CH, BUT SOMEWHAT STRAGGLING CLUSTER; R. A. Oh. 24iu. 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. 84m. 15s.; Dec. N. eia f as if for favor and defence of the queen. " Cepheus illumes The neighboring heavens ; still faithful to his queen, With thirty-five faint luminaries mark'd." This constellation is about 26" N. W. of Cassiopeia, near the 2d coil of Draco, and is on /ne meridian at 8 o'clock the 8d of November; but it will linger near it for many days kSXe Cassiopeia, it may be seen at a.l hours of the night, when the sky is clear, for to us it nevi.-r sets. l?y reference to the lines on the map, which all meet in the pole, it will be evident that a t'tar, near the pole, moves over a much less space in one hour, than one at the equi- no :tial ; and generally, the nearer the pole, the narrower the space, and the slower h motion. The stars that are so near the pole may be better described by their polar distance, tl>.:-:n by their declination. By polar distance is meant, the distance from the pole, anJ w what the declination wants of 90. 48. In this constellation there are 35 stars visible to the naked eye ; of these, there glitters on the left shoulder, a star of the 3d magnitude, called Alderamin, which with two others of the same brightness, 8 and 12 apart, form a slightly curved line towards the N. E. The last,. whose letter name is Gamma, is in the right knee, 19 N. of Oaph, in 'Cassiopeia. The middle one in the line is Alphirk, in the girdle. This star is one-third of the distance from Alderamin to the pole, and nearly in the same right line. It cannot be too well understood that the bearings, or direction of one star fron. another, as given in this treatise, are strictly applicable only when the latter one is on, or near the meridian. The bearings given, in many cases, are not the least approxima- tions to what appears to be their relative position; and in some, if relied upon, wiil lead to errors. For example : It is said in the preceding paragraph, that Gamma, in Cepheus, bears 19 N. of Caph in Cassiopeia. This is true, when Caph is on the meridian, but at this very moment, while the author is writing this line, Gamma appears to be 19 due west of Caph; and six months hence, will appear to be the same distance east of it. The reason is obvioue ; the circle which Cepheus appears to describe about the polo, is within that of Cassiopeia, and consequently when on the east side of the pole, will be within, or between Cassiopeia and the pole that is, treat of Cassiopeia. And for the same reason, when Cepheus is on the west side of the pole, it is between that and Cassio- peia, or east of it. Let it also be remembered, that in speaking of the pole, which we shall have frequent occasion to do, in the course of this work, the North Polar Star or any imaginary point very near it, is always meant; and not, as some will vaguely apprehend, a point in iht horizon, directly N. of us. The true pole of the heavens is always elevated just as many degrees above our horizon, as we are north of the Equator. If we live in 42 N. latitude, the N. pole will be 42 above our horizon. (See North Polar Star.) 49. There are also two smaller stars about 9 E. of Aldera- ,nin and Alphirk, with which they form a square ; Aldorarair being the upper, and Alphirk the lower one on the W. 8 apart la the centre of this square there is a bright dot, or semi-visible htar. The head of Cepheus is in the Milky-Way, and may be known 46. Number of stars visible? Principal stars? Situation? 49. WJ-.at oth'- star* and iituation ? Situation of the heaa, and how known ? Distance of this Asteriais frc the pole et ar ? CEPHEUS. 27 *>? three stars of the 4th magnitude in the crown, which form a small acute triangle, about 9 to the right of Alderamin. The mean polar distance of the constellation is 25, while that c-f Alderamin is 28 10'. The right ascension of the forme^ is 338 ; consequently, it is 22 E. of the equinoctial colure. The student will understand that nght ascension is reckoned on the equinoctial, fwai .he fi.-st point of Aries, E., quite round to the same point again, which is 860. Now, #S* measured from the same point, will reach the same point again, within 22; which in the difference between 860 and 838*. This rule will apply to any other case. HISTORY. This constellation immortalizes the name of the king of Kthiopia. The name of hie queen was Cassiopeia. They were the parents of Andromeda, who was betrothed to Perseus. Cepheus was one of the Argonauts who accompanied Jason on his perilous expedition in quest of the golden fleece. Newton supposes that it was owing to this circumstance that he was placed in the heavens ; and that not only this, but all the ancient constellations, relate to the Argonautic expedition, or to persons some way con- r.ected with it. Thus, he observes, that as Musieus, one of the Argonauts, was the first Greek who made a celestial sphere, he would naturally delineate on it thos- figures which .lad some reference to the expedition. Accordingly, we have on our globes to this day the Golden Rum, the ensign of the sJiip in which Phryxus fled to Colchis, the scene o the Argonautic achievements. We have also the Bull with brazen hoofs, tamed by Jason ; the Ttcinn, Castor and Pollux, two sailors, with their mother Leilti, in the ford of a Swan, and Argo, the ship itself; the watchful Dragon, Hydra, with the Cup ot Medea, and a raven upon its carcase, as an einolem of death ; also Chiron, the Master of Jason, with his Attar and Sacrifice; Hercules, the Argonaut, with his club, his dart and vulture, with the dragon, crab, and lion which he slew; and Orpheus, one of the company, with his harp. All these, says Newton, refer to the Argonauts. Again ; we have Orion, the son of Neptune, or, as some say, the grandson of Minos with his dogs, and hare, and river, and scorpion. We have the story of Perseus in tin- constellation of that name, as well as in Cassiopeia, Cepheus, Andromeda, and Cetu3*, that of Calisto and her son Areas, in Ursa Major; that of Icarius, and his daughter Erigone, in Bootes and Virgo, fjrsa Minor relates to one of the nurses of Jupiter. Auriga, to Erichtonius ; Ophinchus, to Phorbas ; Sagittarius, to Crolus, the son of ont of the Muses ; Capricorn, to Pan, and Aquarius to Ganymede. We hav-e also Ariadne'f crmon, Bellerophon's horse, Neptune's dolphin, Ga-nymede's eagle, Jupiter's goat, with her&jrfs, the asses of Bacchus, the fishes of Venus and Cupid, with their parent, the southern fish. These, according to Deltoton, comprise the Grecian constellations men tioned by the poet Araf.us ; and all relate, as Newton supposes, remotely or immediately to the Argonauts. It may be remarked, however, that while none of these figures refer to any transactions of a later date than the Argonautic expedition, yet the great disagreement which appears in the mythological account of them, proves that their invention must have been 07 greater antiquity than that event, and that these constellations were received for sonia time among the Greeks, before their poets referred to them in describing the particular y of that memorable expedition. TELESCOPIC OBJECTS. 1. a CEPHKI (AU(eramin)- A FINK STAR, with a distant companien on the left should;* of Cepheus; R. A., 21h. 15m.; Dec., 61* 54'. It is about half way between Polaris and Deneb, and 8 south-west from /JCephei. A 8, white; B 10, p<*le blue, with a companion '" '.be same magnitude and color. 2. /L CKPHEI (Alpkirk) A DOUBLE STAR on the left side of the girdle of Cepheus, two vhirdu of the distance from Polaris to Alderamin. A 8, white ; B 8, blue, with a very Tin-He double star preceding. 8 y CBPHRI (Er Rai, A DOUBLK STA* in the knee of Cepheus, with a distant telescoj tc r^nvar.ion on the preceding parallel. A 8, yellow; B 14, dusky. R. A., 28h. 89m. 47. AN IRREGULAR CLUSTER between the head of Cephcus and the chain of Andromeda; R, A., 28h. 17m. 10s.; Dec., N. 60 48' 1". It is about one-third of the distance from 3 Cassiopese to a Cephei ; and may be seen on Map VI., near the sceptre of Cephcuc for a telescopic view, see Map VI1L, Fig. 24. CHAPTER II. CONSTELLATIONS ON THE MERIDIAN It DECEMBER. ARIES (THE BAM). MAP II. 50. TWENTY-TWO centuries ago, as Ilipparchns informs as, 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 eas*. *f Pisces, and is midway between the Triangles and the Fly on the N. and the head of Oetus on the S. It contains 66 stars, pf which, one is of the 2d, one of the 8d, and two of tbe 4th magnitudes. " Kirst, from the east, the Ram conducts the year; Whom Ptolemy with ticice wne 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 8d magnitude, situated ii. the right horn, is called Alpha Arietis, or simply Ariettts; the other, which is of the 3d magnitude, lying near the left horn, is called Sheratan, and maf >e known by another star of the 4th magnitude, in the ear, 1 ty S. of it, called M^artkim^ Which is \kefir8t star in this constellation. Arietis and Sheratan, are one instance out of many, where stars of more than ordinary kMrUibtuess are seen together in pairs, as in the Twins, the Little Dog, &c., the brightest Mar being commonly on the east. * See "Precession of the Equinoxes," page 270. Constellations in this chapter? Aries 22 centuries apof Now; and wby n-itshocJ ? Arietis and Slurataa ? ARIES. 5J9 51 . The position of Arietis 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 01 harbor on the earth. See Part II., page 206. Arietis comes to the meridian about 12 minutes after Shent ian, on the 5th December, near where the sun does in midsum- mer. Arietis, also, is nearly on the same meridian with Ahnaack, 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, neaily 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 hottom, and having filled it witli water, suffered the same to distill, drop by drop, into another vessel set beneath to receive it, beginning at the moment when some \:tar rose, and continuing till it rose the next following night, when It would have performed one complete revolution in the heavens. The water railing 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 as 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, correspond;* g to the 12 months of the year commencing at the vernal equinox. Each of these , irtions served as the visible ^presentative or sign of the month it appeared in. AT those stars in the Zodiac which were observed to rise while tne first vessel was fill- ing, were constellated and included in the first sign, and called Ar-if*, an animal held in great esteem by the shepherds of Chaldea. All those stars in the Zodiac which rose while the second vessel was filling, were coi stellated and included in the second sign, which, for a similar reason, was denominated Taurwt ; and all those stars which were observed to rise while the third vessel was filling, were constellated in the third sifs, and called Gemini, in allusion to the twin seanon of the flocks. Thus each sign of 30 in the Zodiac, received a distinctive appellation, according to ths 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 30* oehind. The sign Aries, therefore, included all the stars embraced in the first 80 of th< Zodiac, and no more. The sign Taurus, in like manner, included all those stars embraced M Position of Arietis? Importance to mariners? When come to meiidian? When. And ~iHda and Cassioi>eia then ? Perseus ? Taurus, Auriga, Orion, Pervsus *nd Sw*t What /. other st;irs in Aries? Ancient method of dividing the Zod *c? Nuuiea c* 30 ASTKONOMt fa the next 80' of the Zodiac, or thoso between 80* ami 60% and so of the real. Of UMOC who imag.ne that the twelve constel aliens of the Zodiac refir to the twelve triUx) of Israel, i-Jtne ascribe Aries to the tribe of Suneou, and others, to Gad. HISTORY. Aceovcling to fable, this is the ram which bore the golden fleece, and carried Phryxus and his 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 with giddiness, and she fell from his back into that part of the sea which was afterwards called Hellespont, in commemoration of the dreadful prent. Phryxus arrived safe at Colchis, but was soon murdered by his own father-in-law 2Etes, who envied him his golden treasure. This gave rise to the celebrated Argonautii 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 Mfe, was afterwards changed into a cloud, as a reward for her parental soliritude ; 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, Is 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 temp] 3 supposed by some to have been dedicated to Isis, the female deity of the Egyptians, w.'.o believed that the ris- ing of the Nile was occasioned by the tears which she continual'/ shed for the loss of her brother Osiris, who was murdered by Typhon. Others s-ippcje this edifice was erected for astronomical purposes, from the circumstance that t^jo Zodiacs were discovered, drawn upon the ceiling, on opposite sides. On both t! <.:'. Zodiacs the equinoctial points are in Leo, and not in Aries ; from which it has btuc concluded, by those who pertina- ciously endeavor to array the arguments of science r.gainst 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 9720 years ago, or 4000 years before the inspired account of the creation. The infidel writers in France and Germany make it 10,000 years before. But we may " set to our seal," that whatever is true in fact and coi - -e^tin 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 ChampoUion has put this question for ever at rest ; and M. Latronne, & most learned antiquary, has very satisfactorily demonstrated that these Egyptian Zodiacs are merely the horoscopes of distinguished personages, or the precise situation of the heavenly bodied in the Zodiac at their nativity. The idea that such was their pur- pose and origin, >lrst suggested itself to this gentleman on finding, in the box of a mummy, a similar Zodiac, with such inscriptions and characters as determined it to be the horo- scope of the deceased person. Of all the discoveries of the antiquary among the relics of ancient Greece, the ruins o. Palmyra, the gigantic pyramids of Egypt, the temples of their gods, or the sepulchres of heir kings, scarcely one so aroused and riveted the curiosity of the learned, as did the liscovery of Champollion the younger, which deciphers the hieroglyphics of ancient The potency of this invaluable discovery has already been signally manifested in set- ting a formidable cont jversy between the champions of infidelity and those who main- tain the Bible account f the creation. It has been shown that the constellation Pisces, since the days of Hipparchus, has come, by reason of the annual precession, to t ocupy the same apparent place in the heavens that Aries did two thousand years ago. The Christian astronomer and the infidel are perfectly agreed as to the fact, and the amount of this yearly gain in the apparent motion of the stars. They both believe, and both can demonstrate, that the fixed stars have gone forward in the Zodiac about 50" of a degree In every revolution of the heavens since the creation ; eo that were the world to light upon any authentic inscription or record of past ages, which should give the true posi- tion or longitude of any particular star at thai time, it would be easy to fix an unques- tionable date to such a record. Accordingly, when the famous " Egyptian Zodiacs," which were sculptured on the walls of the temple at Dendera, were brought away tn ti$, flushed; C 11, dusky. A beautiful trio. 6. A QUADRUPLK STAR half way between a and y under the right horn; R. A. Ih. 50m. 43s.; Dec. N. 20 10' 07". A 6, t^paz yellow; U 15, deep blue; C 10, lilac; D, pale blue An exquisite object. 7. A ROUND NEBULA near y Arietis, and just east of it; R. A. Ih. 50m. 84s.; Dec. N 18 18' 06". It is large and pale, and lies among some small stars, some of which form t curve across \he south part of the field. TRIANGUL^E (THE TRIANGLES). MAP II. 52. The Triangles are situated between the head of Aries on the north, and the feet of Andromeda on the south. R. A. 2h.; Dec, N. 30. They contain two stars of the 4th magni- tude, and two of the 5th ; with several smaller. A line from Bheratan in Aries, to Almaack, will pass through the ludda Trianguh, about midway between them. TsL8COPh,' OBJKCTS? What a Arietis? Other double stars? Triple? Any clusters? Nebulae? t2. Situation of the Triangles ? Number and size of stars ? How find tbeir lucid* F 3* ASTRONOMY. HISTORY. The upper or Northern Triangle is one of the ancient 48 asterisma ; and Hcvcliui too* three other stars between it and the head o* Aries, to form Triangulum minu. Th latter figure, however, is discontinued, though shown on the map. TCLESCCPIO OBJECTS. 1 a TRIASOOLI A bright FOURTH MAGNITUDK STAR, with a Telescopic companion ; E. A Jh.43m. 5Ss.; Dec. N. 28* 47' OS'. A b^, yellow; B 11, lilac. t. e TRIANGDLI A MOST DELICATK DODBUS STAR; R. A. Ih. 58m. 3Sa.: Dec. N. 3S* 8C OB' k 5^, bright yellow; B 15, dusky. 8. A large and distin :t but faint PALB WHITB NEBULA, between the Triangles and & bead of the Northern Fish; R. A. Ih. 24ra. 51s.; Dec. N. 29 61' 08". A bright st&r tittle north-west, and five others more remote in the east. MUSOA (THE FLY). MAP II. t>3. This very small constellation lies directly between tho back of Aries on the south, and the head of Medusa on the north. It has one star of the 2d, two of the 4th, 'and two of the 5th magnitudes. An unimportant asterism, and not always mentioned in the catalogues, though shown on the map. TELESCOPIC OBJECTS. 1. A FINK DOUBLBSTAR over the back of Aries, nearly midway between the Pleiades ano ft Andromedaj; It. A. 2h. 31m. 20s. ; Dec. N. 26" 22 02*. A 6, pale topaz; B 9, light blae, An easy object. 2. a Muse.* H COARSE QDADRUPLK STAR, in the body of the figure, and forming ita jucida ; R. A. 2h. 40m. 34s. ; Dec. N. 26 85' 09'. A 3, white ; B 18, deep blue ; C 11, lurid; D 9, pale grey. Both these objects are usually classed as belonging to Aries. OETUS (TUB WHALE). MAP II. 54. As the whale is the chief monster of the deep, and the largest of the aquatic race, so is it the largest constellation in the heavens. It occupies a space of 50 in length, E. and W., with a mean breadth of 20 from N. to S. It is situated below Aries and the Triangles, with a mean declination of 1 2 S. It ts represented as making its way to the E., with its body below, ind its head elevated above the equinoctial ; and is six weeks in massing the meridian. Its tail comes to the meridian on the 10th )f November, and its head leaves it on the 22d of December. 55. This constellation contains 97 stars ; two of the 2d mag- nitude, ten of the 3d, and nine of the 4th. The head of Cetua HISTORY. Which ancient? Who formed the other ? Now recognized, or not? TELESCOPIC OBJECTS? Double stars ? Nebula? 68. Situ?.ion of Musca? Stars? Relative importance? Is it always recognised at jotistrllation ? 54. Cetus? Comparative sizt? Situation? How represented! 90. Ntuubei of stars Magnitudes ? How may the beaJ of O.hw be known ? Brighteil CETUS. 33 be readily distinguished, abcr.t 20 S. B.of Aries, by means of five remarkable stars, 4 and 5 apart, and so situated as to form a regular pentagon. The brightest of these is Menkar, of the 2d magnitude, in the nose of the Whale. It occupies the S. E. angle of the figure. It is 3 N. of the equinoctial, and 15 E. of El Rischa in the bight of the cord between the Two Fishes. It is directly 37 S. of Algol, and nearly in the same direction from the Fly. It makes an equilateral triangle wiUi Arietis and the Pleiades, being distant from each about 23 S., and may otherwise be known by a star of the 3d magnitude in the mouth, 3 W. of it, called Gamma, placed in the south mid- dle angle of the pentagon. 56. NU is a star of the 4th magnitude, 4 N. W. of G imma, and these two constitute the S. W. side of the pentagon : n the head of the Whale, and the N. E. side of a similar oblong Qguro in the neck. Three degrees S. S. W. of (j arnma, is another star of the 3d magnitude in the lower jaw, marked Delta, constituting the E. side of the oblong pentagon ; and 6 S. W. of this, is a noted star in the neck of the Whale, called Mira, or the "wonderful star of 1596," which forms the S. E. side. This variable star was first noticed as such by Fabricius, on the 13th of August, 1596. It changes from a star of the 2d magnitude so an to become invisible once in 234 days, or about 7 times in 6 years. Herschel makes its period 331 days, 10 hours, and 19 minutes ; while Hevelius assures us that it once disappeared for 4 years so that its true period, perhaps, has not been satisfactorily deter- mined. The whole number of stars ascertained to be variable amounts to only 15; while tho?- which are suspected to be variable, amount to 87. 57. Mira is 7 S. S. E. of El Rischa, in the bend or knot 01 the ribbon which connects the Two Fishes. Ten degrees S. of Mira, are 4 small stars, in the breast and paws, about 3 apart which form a square, the brightest being on the E. Ten degree? S. W. of Mira is a star of the 3d magnitude, in the heart called Baten Kaitos. which makes a scalene triangle with two other stars of the same magnitude 7 and 10 W. of it ; also, *n equilateral triangle with Mira and the easternmost one in the square. /*ar? Position! Name? 56. Size and Position of Nu ? Delta? Mira? Position! Peculiarity? When, and by whom first noticed? Period and extent of variability i Whole number of variable stara? 57. Baten Kaitos? Position with regard to Mirt < fa "tiMcr stars ? 34 ASTRONOMY. A great number of geometrical figures may be formed from the stars in this, and I* most of the other constellatit n, merely by reference to the maps; but it is better that the student should exercise his own ingem Jty in this way with reference to the stari themselves, for when once he has constructed a group into any letter or figure of his own invention, he never will forget it. The teacher should therefore require his class to commit to writing the result of then wn observations upon the relative position, magnitude and figures of the principal starn in each constellation. One evening's exercise in this way will disclose to the student a surprising multitude of crosses, squares, triangles, arcs and letters, by which he will b better able to identify and remember them, than by any instructions that could be given. For example : Mira and Baten in the Whale, about 10 apart, make up the S. E. 01 shorter side of an irregular square, with El Rischa in the node of the ribbon, and another itar in the Whale as far to the right of Baten, as El Rischa is above Mira. Again, There are three stars of equal magnitude, forming a straight line W. of Baten ; from which, to the middle star is 10, thence to the W. one 12j ; and 8 or 9 S. of this line, fu a triangular direction, is a bright star of the second magnitude in the coil of the tail, cjil.'cd Diphda. l/i a southerly direction, 25 below Diphda, is Alpha in the head of the Phenix, and about the same distance S. W. is Fomalhaut, in the mouth of the Southern Fish, forming together a large triangle, with Diphda in the vertex or top of it. That fine cluster of small stars S. of the little square in the WhaJe, constitutes a part of a new constellation called the Ch/ymical Furnace. The two stars N. E., and the three to the southward of the little square, are in the river Eridawus. HISTORY. This constellation is of very early antiquity: though most writers consider it the famous sea-monster sent by Neptune to devour Andromeda because her m^'her Cassio- peia had boasted herself fairer than Juno or the Sea Nymphs ; but slain ^,y Perseus ana placed among the stars in honor of his achievement. "The winged hero now descends, now soars, And at his pleasure the vast monster gores. Deep in his back, swift stooping from above, His crooked sabre to the hilt he drove." It is quite certain, however, that this constellation had a place in the heavens long prior to the time of Perseus. When the equinoctial sun in Aries, which is right over the head of Cetus, opened the year, it was denominated the Preserver, or Deliverer, by the jdolaters of the East. On this account, according to Pausanius, the sun was worshipped, at Eleusis, under the name of the Preserver or /Saviour. " With gills pulmonic breathes the enormous whale, And spouts aquatic columns to the gale; Sports on the shining wave at noontide hours, And shifting rainbows crest the rising showers." Darwin, TELESCOPIC OBJECTS. 1. CETI A DOUBLE STAR ; R. A. Oh. 35m. 84s. ; Dec. S. 18 51' 9'. A 2^, yellow ; B 13, pale blue. 2. y Qe.ti A OJ OSB DOUBLE STAR in the Whale's mouth ; R. A. 2h. 85m. Ols. ; Dec. N. 2 88' 6". 4 3, pale yellow ; B 7, lucid blue ; the colors finely contrasted. 8. v A DorBf.s STAB in the Whale's eye ; >' R. A. 2h. 27m. 29s. ; Dec. N.4" JHY 5'. A 4J$, pale yellow ; B 15, blue. 4. A LONG NARROW KEEP; v, of a pale, milky tint ; R. A. Oh. 39m. 45s. ; Dec. S. 2* 10' 1". It is situated in the space south of the tail of Cetus, neai a line drawn from a Andromeda to /3 Ceti. Discovered by Miss Herschel, in 1788. 5. A PLANETARY NEBULA ; R. A. 2h. 19m. 25s. ; Dec. S. 1 51' 6" : in the middle of thi Whale's neck. 6. A BRIGHT ROUND NEBULA ; R. A. lh. 28m. 20s. ; Dec. S. 7 41' 8". Registered ly 8ta W. Herschel, 17&5. It is just above the Whale's back. .Antiquity? Its original name? When, and why? What worship la Sequence ? Tujsuoono OBJBCTS. Beta? Ga.nma? Nu? Nebulr PERSEUS, ET CAPUT MEDUSAE. 35 f . A ROUND STELLAR NBBDLA, near J in the Whale's lower jaw, and about 2J$* from > : - MI a line towards , or south by west. A very distant object, classed by Sir W. u 10 times as distant as stars of the first magnitude. PERSEUS, ET CAPUT MEDUSAE. MAP III. AND IV. 58. PERSEUS is represented with a sword in ois right bard, the head of Medusa in his left, and wings at his fuet. It i* situated directly N. of the Pleiades and the Fly, between Andromeda on the W. and Auriga on the E. Its mean decli- nation is 46 N. It is on the meridian the 24th of December. It contains, including the head of Medusa, 59 stars, two of which are of the 2d magnitude, and four of the 3d. According to Eudosia, it contains, including the head of Medusa, 67 stirs Perseus next, Brandishes high in heaven his sword of flame, And holds triumphant the dire Gorgon's head, Flashing with fiery snakes ! the stars he counts Are sifKty-sffoen ; and two of these he boasts, Nobly refulgent in the second rank One in his vest, one in Medusa's head." 59. THE HEAD OF MEDUSA is not a separate constellation, out forms a part of Perseus. It is represented as the trunkless Dead of a frightful Gorgon, crowned with coiling snakes, instead of hair, which the victor Perseus holds in his hand. There are, in all, about a dozen stars in the head of Medusa ; three of the 4th magnitude, and one, varying alternately from the 2d to the 4th magnitude. This remarkable star is called Algol. It is situated 12 E. of Almaack, in the foot of Andromeda, and may be known by means of three stars of the 4th magnitude, lying a few degrees S. W. of it, and forming a small triangle. It is on the meridian the 21st of December ; but as it continues above the horizon 18 hours out of 24, it may be seen every evening from September to May. It varies from the 2d to the 4th magnitude in about 3 hours, and" back again in the same time ; after which it remains steadily brilliant for 2| days, when the same changes recur. The periodical variation of Algol was determined in 1783, by John Goodricke, of York (JSng.), to be 2 days, 20 hours, 43 minutes, and 56 seconds. Dr. Herschel attributes th variable appearance of Algol to spots upon its surface, and thinks it lias a motion on Iti axis similar to that of the Sim. He also observes, of variable stars generally :--" Tin rotary motion of the stars upon their axis is a capital feature in their resemblaacc ti the sun. It appears to me now, that we cannot refuse to admit such a motion, and tL*4 todeed it may be as evidently proved as the diurnal motion of the earth. Dark spots, 58. Perseus? How represented ? When on the meridian? Number of sta.ro? Else* &. Head of Medusa? How represented? Number of stars? What remarkable out Situation? Variableness and period? When and by whom determined? ' eue of variability f Lalando ? 2* 36 ASTRONOMY. or large portions of the surface ess luminous than the rest, turned alternately In certalii directions either toward, or ft cm us, will account for all the phenomena of periodica, changes in the lustre of the stars, so satisfactorily, that we certainly need not look out for any other cause." It is said that the famous astronomer Lnlande, who died at Paris In 180T, was wont t remain whole nights, in his old age, upon the Pont Neuf> to exhibit to the curious ih rariations in the brilliancy of the sUr Algol. 60. Nine degrees E. by N. from Algol, is the bright star Alge- nib, of the 2d magnitude, in the side of Perseus, which with Al tnaack, makes a perfect right angle at Algol, with the open part towards Cassiopeia. By means of this strikingly perfect igure, the three stars last mentioned may always be recognized without the possibility of mistaking them. Algenib may otherwise be readily distinguished by its being the brightest and middle one of a number of stars lying four and five degrees apart, in a large semicircular form, curving towards Ursa Major. Algenib comes to the meridian on the 21st December, 15 minutes after Algol, at which time the latter is almost directly overhead. When these two stars are on the meridian, that beautiful cluster, the Pleiades, is about half an hour E. ot it; and in short, the most brilliant portion of the starry heavens is then visible in the eastern hemisphere. The glories of the scene are unspeakably magnificent; and the student who fixes his eye upon those lofty mansions of being, cannot fail to covet a knowledge of their order and relations, and to "reverence Him who made the Seven Stars and Orion." 61. The Milky Way around Perseus is very vivid, being undoubt- edly a rich stratum of fixed stars, presenting the most wondei 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 88 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 tui 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 mortality. 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 *cales, and their very looks had the powor of turning into stones all those on whoi-i they fixed their eyes. To equip Perseus for this perilous enterprise, Pluto, the god of the infernal regions, tent him his helmet, which had the power of rendering the wearer invisib e. Minerva, the goddess of wisdom, furnished him with her buckler, which was as resplendent as * jjolished mirror ; and he received from Mercury wings f u r his feet, and a dagger madt 60. Algenih? Howknown? When on the meridian? Where, then, are the Plaiadea Vhat the general aspect of the heavens? 61. Milky Way around Perseus? Obserra lion of Kohler? HISTORY. Who waa Perseus ? What fate at birth, Ac. f PERSEUS, ET CAPUT MEDUSJB. 37 T diamonds finis equipped, he mounted into the air, conducted by Minerra, and cam* opan the monsters who, with the watchful snakes about their heads, were all asleep. Ho 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 invisible, and the vengeful pursuit of the Gorgons 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." P?.reua then made his way through the air, with Medusa's head yt retting in hi* &s.<1, and from the blood which dropped from it as he flew, sprang all those iimumerabU ijrjrjats 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 go'-y 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 WM 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 HNE DOUBLE STAR ; R. A. 3h. 12m. 55s. ; Dec. N. 49 17' 2'. A 2J$, bril- liant lilac ; B 9, cinereous. This is Algenib, in the hero's left side. 2. (3 PKRSKI, or Algol; R. A. 2h. 57m. 46s. ; Dec. N. 41* 20'. A variable DOUBLE STAR. A 2 to 4, whitish ; 1511, purple. The former varies in brightness periodically, from the 2d to the 4th magnitude, and back again to the 2d magnitude, period being 2d. 20h. 48m. D6s. ; an object of great interest. 3. y PKRSKI A WIDE UNEQUAL DOUBLE STAR in the hero's left shoulder; R. A. 2h. 53m. 14s.; Dec. N. 52" 52' 4". A 4, flushed white ; B 14, clear blue. 4. d PERSEI A BRIGHT STAR with a companion in the hero's hip; R. A., 3h. 81m. 83s.; Dec., N. 47* 16' 2". About 3 south-west of a Persei. A 3), white ; B 11, pale blue. 5. f PERSEI A NEAT DOUBLE STAR in the right knee ; R. A. 3h. 47m. 08s. ; Dec. N. 39* 32' 4". A 3>$, pale white ; B 9, lilac ; a fine delicate object. 6. | PfcRSKi A DELICATE QUADRUPLE STAR ; R. A. 3h. 44m. 05s. ; Dec. N. 81 24 2" A 3>$. flushed white; B 10, smalt bl^e; C 12, ash-c.-lored ; D 11, blue. It is situated 'n the r.'ght foot, and is designated by Smyth as "an elegant group." 7. T) PERSKI A FINE DOUBLE STAR in the head of the figure; R. A. 2h. 89m. 04s.; Dec. N. 55" 13' 5". A 5, orange ; B SJ, smalt blue ; the colors in fine contrast. 8. A GORGEOUS CLUSTER in the sword handle of Perseus ; R. A. 2h. 08m. 58s. ; Dec. N 66* 24' 4". It may be seen with the naked eye, and when seen through a good telescope is one of the most magnificen* 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. 3h. 04m. Ols.; Dec. N. 46* 37' 9'. Smyth says "it has a gathering spot about 4' in diameter, where the star-dust glows among minute points of light." Uerschel says, " the large stars are arranged in liues like interwoven letters, 10. An ELONGATED NEBULA ; R. A. 2h. 30m. 25s.; Deo. N. 88* 21' 3" ; supposed, to be vast ring, seen obliquely. Map VIII., Fig. 26. 11. A pretty compressed OVAL GROUP OF STARS, in the left knee of Perseus, nearly mid way between A and fi; R. A. 3h. 58m. 11s.; Dec. N. 49* 04' 05". A well-marked object, surrounded by a curve of larger stars, somewhat in the form of the letter D. Ma,p VIIL- Vig. 27. TviKscortc OB/HCTS. Alpha? Beta? Gamma? Delta Eptllan? ZeUf Zt< Nebula? Which shown on the map ? 38 ASTRONOMY, CHAPTER 111. CONSTELLATIONS ON THE HERMAN N JANUARY. TAURUS (THE BULL). MAP III. 62 TAURUS is represented in an attitude of rage, as if abonl 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 cannot 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 BO conspicuously Bituated, that tne most inexperienced can easily trace them out. 63. Taurus is now the sec.ond 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 ot 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 HYADKS. The firsi is now on the shoulder, and the latter in the face of the Buh. The names of the Pleiades are Alcione, Merope, Maia, >Jlectra, 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 18 stars; and Rheita affirms that he counted 200 stars in this small cluster. For its appearance through an ordinury tele scope, see Map YIIL, Fig. 28. The most ancient authors, such as Homer, Attalus, and Geminus, counted only sia fleiades; but Simonides, Varro, Pliny, Aratus, Hipparchus, and Ptolemy, i . Kon thea 62. How is Tairus represented? How much of him seen? What constellations most br'U'ttnt' 63. In wbat sign is Taurus ? What constellation? How 4000 /ears ago? What next led the year? What now? At what time does Taurus set with, the sun? How situated? 04. How many visible stars in Tauius? Clusters? How situated? Names of the Pleiades? Wl.at said of Merope? Hew many of the Pleiaac; visible U the nuked eye? Dr. Hook and Rheita? AncieU authu-s? T A u iirs. 39 iu numcer; and it was asserted, that the seventh had been seen before the born- ing of Troy ; 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, nkeeiv pieein, 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, ?Ayi (Lat the stars were relied upon, in the first ages of nautical enterprise, to guide the rud* tafwwering names." 69. Aldebaran is of Arabic origin, and takes its name frora two words which signify, " He went before, or led the way" alluding to that period in the history of astronomy when thia 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 Sam hath doubled ten degrees, And join'd seven more, then rise the Hyades." A line 15j B. N. E. of Aldebaran will point out a bright star of the 2d magnitude in ths extremity of the northern horn, marked Beta or El 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 S", in a southerly direction. This star forms a right angle with Aldebaran and Beta. Beta and Zeta, then, in the button of tha horns, are in a line nearly north and south, 8 apart, with the brightest on the north That V3ry bright star 17}$ N. of Beta, is Capetta, in the constellation Auriga. 67. What other name have the Pleiades, and why ? Citation from Job ? Syrian name f 18. Where are the Hyades situated? How known? Where the most brilliant start Name? Ar ? they shown or the map? 69. Origin and import of the name Aldebaran t Wben does it come to the meridian at 9 o'clock p.m. ? Where is Beta? In w'uat othei coastr'.ation? Zeta, and its distance? How situated with reference to AKebarar. aarding to the Grecian mythology, this is ;h : animal which bore Europa over tin teas to that country which derived from her its name. She was the daughter cf Ageaor Mid princess of Phoenicia. She was so beautiful that Jupiter became enamoured of he" *nd assuming the shape of a snow-white bull, he mingled with the herds !>f Agenoi while Europa, with her female attendants, were gathering flowers in the meadows Kuropa caressed the b"autilul animal, and at last had the emu-age 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. |r me suppose she lived about 1552 years before the Christian Era. It i.s probable, however, 11, ai 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 ChaU leans. Both the Egyptians and Persians worshipped a deity under this figure, by the ziame of Apis ; and Belzoni is said to have found an embalmed bull iu one of the i.otubli tepulchres near Thebes. In t>e Hebrew Zodiac, Taurus is ascribed to Joseph. Tlu. Pleiades, according to fable, were tlie seven daughters of Atlas and the nyrapr Pleione, who were turned into stars, with their sisters the Hyades, on account of theii amiable virtues and mutual affection. Thus we everywhere find that the ancients, with all their barbarism and idolatry, enttrfained the bel'"^' tl.>, unblemished virtue and a meritorious life would meet th tauphire blue. Map VIII. Fig. 3. .'{. y OKIONIS (Btitatrix)^.. A. 5h. 16ra. 33s.; Doc. N. 6 12 . A FINB STAB, with a ffunute d ! slant companion. A 2, pale yellow ; B 15, grey. 4. t) ORIONIS (Mintttkti) A coarse DOCBLK STAR in the girdle of the figure; R. A. 6h tfm 50s. ; Dec. S. 0" 25' 4'. A 2, while ; B 7, pale violet. 5. f OI.TOMS (Alnilum] in the centre of his belt; K. A. 5h. 2Sm. 06s.; Dec. S. 1 J 18 6' 4 2%, white and nehulous ; B. 10, pale blue.. i. C OKIOXIS (Alnitit/i) the last or lowest in the belt; R. A. 5h.82ra. 41s.; Dec. S. 2 09* k line TRIPLE STAR. A 8, topaz yellow ; B 6^, light purple; and C 10, gray. 7. A minute DOUBI STAR and cluster, in Orion's left hand; R. A. 5h. 59m. 25s. ; Dec. K. 18 : 58' . A 7fc, B S>$, boih lucid white. 8. Another DOUBLK STAR in a cluster, in the left shoulder; R. A. 6h. 03m. 85s. ; Dej. N. B' 28' 9". A 9>j and B 10, both pale yellow. A tolerably rich cluster, with numerous stragglers. 9. A PLANET \Y NEBCLA, of a bluish white tint, on the nape of Orion's neck small, pale, bnt quite distinct. U. A. 5h. 33m. 21s. ; Dec. N. 9 00' 2'. 10. Two stars " in a WISPY NEBULA," just above the left hip; R. A. 5h. 3Sm. 33s.; Dec. N. 0" 00 7'. A 8% and B. 9, bolh while. A singular mass, belween two small stars, about equi-distant, in a blankish part of the heavens. 11. The GRKAT NKBULA OF ORION The most conspicuous nebula in all the heavens. It is situated in the sword of Orion, helow the middle star of the belt ; K. A. 5h. 27m. 25s.; "Dec. S. 5 80'. For its position in the constollalion see Map VIII., Fig. 31. It may be seeii 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. 82.) 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-iucb refractor. These stars constitute the Tntpeziinn of O/'ion. The region around this nebula is rich in stars, as shown on Map VIII., Fig. 33. LEPUS (THE IIABE). MAP III. 71 This constellation is situated directly south of Orion, and comet to the meridian at the same time ; namely, on the 24th of January. It has a mean declination 18 S., and contains 19 bmall 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. Zela, 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. TELESCOPIC OBJECTS. Alpha ? Beta? Gamma? Delta, Ac.! What double sUisf Nebnlw? Point out on the map ? 77. Location of Lepus? Number and magnitude of stars? How may it be distin- guished? 73. Size and situation of Zeta? Other principal stars? How marital or we map? 46 ASTRONOMY. 79. Alpha, otherwise called Arneb, and Beta form the N. W. end of the trapezium, and are about 3 apart. Gamma and Delta form the S. E. end, and are about 2 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 Hare. HISTORY. This constellation is situated about 18 west of the Great Dog, which, from the motion of thf earth, seems to be pursuing it, as the Greyhounds do the Bear, round the Circuit of the skies It was one of those animals which Orion is said to have delighted in hunt- ing, and which, for this reason, was made into a constellation and placed near him among the stars. TELESCOPIC OBJECTS. 1. a LEPCRIS (Arneb) A distant DOUBLE STAR ; R. A. Sh. 25m. 40s. ; Dec. S. 17 56' 05'. A 33$, pale yellow ; B 9^, grey. 2. tf LKPORIS (Nihal) A STAR with a distant telescopic companion ; R. A. 5h. 21ra. 23s.; Dec. S. 20* 58' 05". A 4, deep yellow ; B 11, blue. 3. y LKPORIS A wide TRIPLE STAR in a barren field ; R. A. 5h. 37m. 48s. ; Dec. S. 22' 80' 02". /* *,- light yellow ; B 6%, pale green ; C 13, dusky. 4. L LEPORIS A delicate DOUBLE 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 a reddish distant star nearly north. 5. A" LKPORIS A close DOUBLE STAH, at the root oSthe left ear ; R. A. 5h. 5m. 51s. ; Dec. 8. 13" 08'. 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, nearry 3' in diameter, of a globular form, and extremly rich." An imaginary Jine run from Betelguese before a Leporis, and oree 8, will hit this object about 4 south-west of the latter. COLUMRA (NOAH'S DOVE). MAP III. 80. This constellation is situated about 16 S. of thu Hare, 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 eaoternmost 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 Naos, in the ship, a large equi- lateral triangle. 79. What other name teas Alpha; and with Beta what does it form? What furthel iescription ? HISTORY. Why was Lepus placed in the heavens? TKLKSCOPIC OBJKCTS. Alpha? Beta? Gamma? Iota? Kappa? Nebula? SO. Situatirn of Columba? Number and size of stars? The two brightest, and situ* Won ? How find Phaet ? What figure does it help to form ? With what other s*ar ? ERIDANUS. 47 HISTORY. This constellation is so called in commemoration of the dove wli ch Noah " sect fbrtli to see if the waters were abated from off the face of the ground," after the ark bad rested on mount Ararat. " And the dove came in to him in the evening, and lo, in her tocttth ros ao olive leaf plucked off. 1 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 (TIIE RIVER PO). MAP HI. 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 8d and 4th magnitudes, arching up in a jemi-circular form, a-id marking i\\Q Jirst bend of the northern stream. About 8 below these, or 19 W. of Itijrel, is a bright star of the 2d magnitude, in the second bend of the northern stream, marked Gamma. This star culminates 18 minutes after the Pleiades, and one hour and a quarter before Rigel. Passing Gamma, and a smaller star west o' 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 Jiied, which is thought by some to be considerably nearer the earth than Sirius. Theemim, in the southern stream, id a star of the 8d magnitude, about 17' S. W. of the square in Lepus, and may be k-..own by means of a smaller star 1 above it. Achtr* nar is a brilliant star of the 1st magnitude, in the extremity of the southern stream; bi-t t'iving58 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 ire of the 3d Many of these cannot be pointed out by verbal desciiptiou ; they must be traced from the map. HISTORT Origin of this constellation ? SI. What said of Eridanus? Length? How divided? 82. Trace the Northern "treani? Gamma? Theemim? Acht-ruar? S3. WhoU- number of stars in Kridanu** 48 ASTRONOMY, 84 In the upper part of the Northern stream, near the feet of Taurus, nay be seen a modern, but now discarded constella tion, of which Captain Smyth says: "Abbe Hell (who also placed HerschePs Telescope among the celestials) has squeezed in his Harpa Georgii, to compliment a sovereign of those realms ; Having filched from Eridauus about thirty or forty stars, some df the 4th magnitude, for the purpose. HISTORY. Kridauus is the name of a celebrated river in Cisalpine Gaul, also called Padus.. It* modern name is Po. Virgil calls it the king of rivers. The Latin poets have rendered '.t memorable from ts connection with the fable of Phaeton, who, being a son of Phoabus And Clymene, became a favorite of Venus, who intrusted him with the care of one of her temples. This favor of the goddess made him vain, and he sought of his father a public and incontestable sign of his tenderness, that should convince the world of his origin. Phoebus, after some hesitation, made oath that he would grant him whatever be required, anJ QO 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, Rash 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 fo r ce Turns stars and planots ir. a diff( 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 stern the rapid po'e?" Phoebus represented the dangers to which he would be exposed in vain. He under- took the afirial journey, and the explicit directions of his father were . forgotten. .No .ooner had Phaeton received the reins than he betrayed his ignorance of the mannet of guiding the chariot. The flying coursers became sensible of the confusion of theii 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 rivei Eridanus. His body, consumed with fire, was found by the nymphs of the place, who h /nored him with a decent burial, and inscribed this epitaph upon his tomb: "Hij situs est Phaeton, currun auriga pnterni: Queue id non tenuit, maynis tameii. ea-ciiJit ausis." His sisters mourned his unhappy end, and were changed 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 ahed turned to amber, with whic^ the Phreniciang and Carthaginians carried oc 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 iried up the Wood of the Ethiopians, and turned their skins black; and to have pre- faced sterility and barrenness over the greater part of Libya. "At once from life and from the chariot diiven, Th' ambitious boy fell thunderstruck from heaven." ******* 8-1, What discarded constellation mentioned? Is it on the map? Remark ef Catt Broyt.if r. Named after what? Modern name? Fable of Phaeton? Its evidea* AURIGA. 49 "The breathless 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." Die fable of Phaeton evidently alludes to some extraordinary heats whkl w-sn txoerienced in a very remote period, and of which only this confused tradition tin* ascended to later times. TELESCOPIC OBJECTS. 1. ERIDANI A bright star with a distant telescopic companion, on the shin bjre of Orion ; R. A. 4h. 59m. 59s. ; Dec. S. 5 17' 9". A 3, topaz yellow; B 12, pale blue. FLi* tai is just above Rigel, in the direction of the Hyades. 2. y EJUDANI A star with a distant companion ; R. A. 8h. 50m. 84s. ; Dec. S. 18* 58'. A e.^, yellow ; B 1C pale grey. 3. A MILK WHITE NKBCLA ; R. A. 8h. 33m. 02s. ; Dec. S. 19" 04' 8*. Pale, distinct, round, and bright in the centre. 4. A PLANETARY NEBULA ; R. A. 4h. 06m. 50s. ; Dec. S. 18 09' 1'. About 4% from v in the direction of Rigel. A splendid though not very conspicuous object, of a greyish white color. Map VI II., Fig. 84, represents it in its best aspects, highly magniued, with four telescopic stars in the field, two of which point exactly towards the nebula. SCEPTRUM BRANDENBURGIUM (SOEPTKE OF BRANDENBURG). MAP III. 85. This is a slender constellation, situated between the two stf earns of the Uiver Po. It was constructed by Kirch, in 1 68. 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 sjuth; 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 hei 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 eliminates at the same hour of the night. Both of these con- stellations are on the meridian at 9 o'clock on the 24th of TKL^WPIC OBJECTS. Beta? Gamma? Nebula? Point out on the map. 95. Describe the Sceptre of Brandenburgh ? Situation? When and by whom constf. tPd* Is it recognized by astronomers? Number at d magnitude of stars? 86. How Auriga represented? Situation? When on the meridian? 50 ASTRONOMY. January, and 1 hour and 40 minutes east of it on the ^st Oi January. 81. 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. Capdla is the principal star in this con- stellation, and is one of the most brilliant in the heavens. It lakes its name from Capella, the goat, which hangs upon the left shoulder. It is situated in the west shoulder of Auriga, 24 K of Algol, and 28 N. E. of the Pleiades. It may be known b) 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 Nath, 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, 7& E. of Capella, ami culminates the next minute after Betelguese, 37% S. of it. Th"ta^ 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, lalf 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 io!ure. " See next the Goatherd with his kids ; he shines With seventy stars, deducting only four, Of which Capella never sets to us. Ani 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 Erirn- honius, the fourth king of Athens, and son of Vulcan and Minerva, who awarded him a t.la-ie among the constellations on account of his many useful inventions. He was of ;\ monstrous shape. He is said to have invented chariots, and to have excelled all r ther* li the management of horses. In allusion to this, Virgil has the following lines " Primus Erichthonius CUITUS et quatuor ausus Jungere equos, rapidisque rotis insistere victor." Georgic. Lib. Hi p. 113. "Bold Erichthonius was the first whojoin'd Pour horses for the rapid race design'd, And o'er the dusty whet-Is presiding sat." 9T. Number of stars visible? Magnitude and situation of Capella? How \tnv* Menkalina ? Delta compared wixh Theta? HMTORY. The first supposition ? Seci.r.tl? Third? Opinion of Jaraieson 9 CAMELOPARlMuOo. 51 Other writers say that Bootes invented the chariot, and that Auriga was the son o 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 foi ihe goat and her kids, it has been supposed that they refer to Amalthaea 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 foi Iheir being placed in the arms of Auriga, and the inference is unavoidable, thai aaythology is at fault on this point. Jamiesca is of opinion that Auriga is a mere type or scientific symbol of the beaut ifm Vftble of Phaeton, because he was the attendant of Phojbus at that remote period when la irus opened the year. TELESCOPIC OBJECTS. 1. a AURIGA (Capella)\ fine star with two distant companions, on the right shoulder- blade of Auriga ; R. A. 5h. 04m. 53s. ; Dec. N. 46" 49' 07'. A 1, bright white ; B 12, pal blue ; C 9, grey. 2. ft AURIGJE (Menkttlina)A. bright star in the left shoulder, with a distant corn- panion ; R. A. 5h. 47m. 48s. ; Dec. N. 44' 55' 3'. A '2, yellow; B 10J in the head of Auriga R. A. 4h. 19ra. 23s. ; Dec. N. 5' 88 8' A 7J$, white ; B 8JS, sapphire blue. 2. Another close DOUBLE STAR, between the hind feet; R. A. 4h. 27m. 18s. ; Die. N. 58' 09'. A 53S, yellow ; B. 7j$, pale blue. 8, A very delicate DOUBLK STAR in the animal's hind hoof; R. A. 4h. 44m. 28s, ; Dec. N J8 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. 46ra. 19s. Dec. N. 79 01' 8". A 5^, light yellow ; B 9, pale blue. 5. A bright PLANETARY NEBULA, of a bluish white tint, about 60* in diameter, in tin lind flank of the animal, R. A. 4h. 53in. 29s. Dec. N. 60 23' 5". A curious body, in i ich tield of small stars. CHAPTER IV. CONSTELLATIONS ON THE MERIDIAN IN FEBRUARY. TLJE LYNX. MAPS III. AND VJ. 40. THIS constellation, like that of the Oaraelopard, exhibits ru very interesting features by which it can be distinguished. It contains only a moderate number of inferior stars, scattered over a large space K 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 3 N. of Menkalina, in the E. shoulder of Auriga. The other two principal stars are in the brush of the tail, 3i- 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 dose DOCBLE STAR, in the nose of the Lynx ; R. A. 6h. 07m. 51s. ; Dec. N. 59' 25 8" About 30 from the Pole star, on a line toward Sirius. A 6, and B 7J<&, both white. At elegant bat difficult object. 2. A i.?se DOUBLE STAR in the eye of the Lynx, between Dubhi and Capella ; R. A. Sh SSm. 57s. ; Dec. N. 59 37' 6". A 5>$, golden yellow ; B 7, purple. A delicate and preitj c-bject. 8. A coarse TRIPLE STAR on the animal's lower jaw; R. A. 6h. 12ra. 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 fon> paws of Leo Minor; R. A. 9h. 14m. 82s. Dec. N 85 11' 9'. It is pale white, sparkling in the centre. TELESCOPIC OBJECTS. Alpha? What other double stars? Nebula" 90. Describe the Lynx? Situation ? 91 . Numb:r and size of its stars f Where li tt rgest situated? The othei two principal --tars? TLKrop.c OHJBOTS. What double stars'! Triple? Nebula GEMINI. 63 TELESCOPIUM HERSCHELLII (IIERSOHEL'S TELESCOPS). MAP III. 92. About midway between the body of the Lynx and Gemini, may be seen the rude figure of a refracting Telescope, with it* 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 ued on the map more as a matter of history than to perpetuate it as a constellation. GEMINI (THE TWINS). MAP 111. 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 thr feeble lustre of ths 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 arrived at the eastern limit of a constellation, the western part of it may bo 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 tbe sun on any day, it is plain that the one uppo>ile 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 mouths hence, rise at sun-setting, and set at sun-rising. For example: the sun is in the centre of Gemini about theCth of July, and must rise and set with it on that day; consequently, six months from that lime, or about the 4th of January, it will rise in the east, just when the sun is setting in tho west, and will come to the meridian at midnight; being then exactly opposite the sun. And as the stars gain upon the sun at the rate of two hours every month, it follows tluif the cectre of this constellation will, on "the 17th of February, come to the meridian throe hours earlier, or at 9 o'clock in the evening. The sun is in the vernal equinox about the 21st of March, from whence it advance! 92. What said of Herschers Telescope? Why perpetuated on the map? 93. How i* Wtt-.ini represented? Its order in the signs, &c.? Situation? 94 How with respect ... t'y Ecliptic? What result from this fact? What remarks respecting the sun int} 54 ASTRONOMY. through one sfgn or constellation every succeeding month thereafter, and tl.at Korwtfcllation is one month in advance of the iyn of t\iat uarae: wherefore, re KHCCS in March, Aries in April, Tairus in May, and Gemini in June, Ac., beginning Witt Bach constellation at the 2ist, or 22d of the month. 05. Gemini contains 85 stars, including two of the 2d, three yf the 3d, and six of the 4th magnitudes. It is readily recog rized by means of the two principal stars, Castor and Pollux, of the 1st and 2d magnitudes, in the heads of the Twins, about 4 J- apart, There being only 11 minutes' difference in the transit of these two stars over the meri- dian, tL3y may both be considered as culminating at 9 o'clock about the 24th of Febru- ury. 6'z*w, in the- head of Castor, is a star of the 1st magnitude, 4J^ N. W. of Pol- ux, and is the northernmost and the brightest of the two. Pollux is a star of the 2d magnitude, in the head <>f I'ollux, and is 4^ S. E. of Castor. This is one of the stars from which the moon's distance is calculated in the Nautical Almanac. - " Of the famed Ledean pair, One most illustrious star adorns their sign, And of the second order shine twin lights." 96. The relative magnitude or brightness of these stars has undergone considerable changes at different periods ; whence it has been conjectured by various astronomers that Pollux must vary from the 1st to the 3d magnitude. But Herschel, who observed these stars for a period of 25 years, ascribes the varia- tion to Castor, which he found to consist of two stars, very close together, the less revolving about the larger once in 342 years and two months. Bradley and Maskelyne found that the line joining the two stars which form Castor was, at all times of the year, parallel to the line joining Castor and PoUuz ; and that both of the former move around a common centre between them, in orbita aosr'y circu- '.ar, as two balls attached to a rod would do, if suspended by a string aiTLsed to tne cen- tre of gravity between them. "These men," says Dr. Bowditch, "were endowed with a sharpness of vision, and a power of penetrating into space, almost unexampled in the history of usivoiiomy." 97. About 20 S. W. of Castor and Pollux, and in a line nearly parallel with them, is a row of stars 3 or 4 apart, chiefly of the 3d and 4th magnitudes, which distinguish the feet of the Twins. The brightest of these is AUiena, in Pollux's upper foot ; the next small star S. of it, is in his other foot ; the two upper stars in the line next above Gamma, mark Cas- tor's feet. This row of feet is nearly two-thirds of the distance from Pollux to Betelguese in Orion, and a line connecting them will pass through Alhena, the principal star in the feet. About two thirds of the distance from the two in the head to those in the feet, and nearly P**V!aiWil& them, there is another row of three stars about 6 apart, which mark Hut apart, which nees. 98. Nmber of stars in Gemini? Magnitudes? How recognize this constellation t What Liid of the culmination of Castor, arid of Pollux ? %. Are they variable ? Wha 4id B.-adley and Maskelyne ascertain? Remark of Bowdilch? 97. What (.-onatituti Gtemini ? Alhena ? How s tuated ? What mark the kneeat PS. There are, hi this constellation, two other rcnuirfe ' blu parallel rows, lying at right angles with the former ; one, lead ing from the head to the foot of Castor, the brightest star being in the middle, and iu the knee : the other, leading from the head to the foot of Pollux, the brightest star, called Wasat, being in the body, and Zeta, next below it, in the knee. Wasat is in the ecliptic, and very near the center of the constellation. The two stwa. Mu and Tejat, in the northern foot, are also very near the ecliptic; Tejat is a small stai of between the 4th and 5th magnitudes, 2" W. of Mu, and deserves to be noticed because It marks th spot of the summer solstice, in the tropic of Cancer, just where the sun is on the longest day of the year, and is, moreover, the dividing limit between the torrid and the N. temperate zone. Propus, also in the ecliptic, 2%* W. of Tejat, is a star of only the 5th magnitude, but rendered memorable as being the star which served for many years to determine thu position of the planet Herschel, after its first discovery. HISTORY. Castor and Pollux were twin brothers, sons of Jupiter, by Leda, the wife of Tyndarus. king of Sparta. The manner of their birth was very singular. They were educated at Pallena, and afterwards embarked with Jason in the celebrated contest for the golden fleece, at Colchis; on which occasion they behaved with 'unparalleled courage and bravery. , Pollux distinguished himself by his achievements in arms and personal prowess, and Castor in equestrian exercises and the management of horses ; whence they are represented, in the temples of Greece, on white horses, armed with spears, riding side by side, their heads crowned with a -petafts, on whose top glitters a star. Among the ancients, and especially among the Rouans, there prevailed a superstition that Castor and Pollux often appeared at the head of their armies, and led on their troops to riattle and to victory. u Castor and Pollux, first In martial force, One bold on foot, nnd one renown'd for horse. Pair Leda's twins in time to stars decreed, One fought on foot, one curb'd the fiery steed." VfoffU. ** Castor alert to tame the foaming steed, And Pollux strong to deal the manly deed." Martial. The brothers cleared the Hellespont and the neighboring seas from pirates after then return from Colchis; from whicl: circumstance they have ever since been regarded as the friends and protectors of navigation. In the Argonautic expedition during a violent storm, it is said two flames of fire were seen to play around their heads, and immediately the tempest ceased, and the sea was calm. From this circumstance; the sailors inferred, that whenever both fires appeared in the sky, it would be fair weather; but when only >ne appeared, there would be storms. St. Paul, after being wrecked on the island of Melita, embarked for Rome "in a ship whose sign was Castor and Pollux;" so formed, no doubt, in accordance with the popu- lar belief that these divinities presided over the science and safety of navigation. They were initiated into the sacred mysteries of Cabiri, and into those of Ceres at Eleusis. They were invited to a feast at which Lynceus and Idas were going to celebrate their nuptials with Phoebe and Telaria, the daughters of Leucippus, brother to Tymlnrus. They became enamored of the daughters, who were about to be married, and resolved to supplant their rivals: a battle ensued, in which Castor killed Lynceus, and was himself killed by Idas. Pollux revenged the death of his brother by killing Idas ; but being him- self immortal and most tenderly attached to his deceased brother, he was unwilling to survive him; he therefore entreated Jupiter to restore him to life, or to be deprived him- self of immortality ; wherefore, Jupiter permitted Castor, who had been slain, tc shar the immortality of Pollux; and consequently as long as the one was upr.n earth, so long was the other detained in the infernal regions, and they alternately lived and died evcrj lay. Japiter also further rewarded their fraternal attachment by changing them joti 98. What other remarkable rows of stars in Gemini ? Situation of Wasat f Of Propu* t OBT. Myth of the parentage of Gemini? Their achievements? Roman supcrrti That of sailors ? Allusion of St. Paul ? Story of the fatai wedding ? 56 ASTRONOMY. Into a constellation under the rwnie of Gemini, Tioins, which, it id strangely pretended Qerer appear together, but when one rises the other sets, and so on, alternately. " By turns they visit this ethereal sky, And live alternate, and alternate die." Homer. " Pollux, offering his alternate life, Could free his brother, and could daily go By turns aloft, by turns descend below." Virgil. Oasto/ and Pollux were worshiped both by the Greeks and Romans, who sacrificed tfiite 'ambs upon their altars. In the Hebrew Zodiac, the constellation of the Twiu, lefera la the tribe of Benjamin. TELESCOPIC OBJECTS. 1. a GEMINORUM (Castor) A neat DOUBLE STAR ; K. A. 7h. 24m. 28s. ; Dec. N. 82 14' I A 8. bright white; B 8J3, pale white; with a third star of the llth magnitude about 72 distant. A Binary System, with a probable period of 232 years. A beautiful object, an easily found. Map VIII., Fig. 4. , 2. /? GKMINORUM -A QUADRUPLE STAR in the eye of Pollux, R. A. 7h. 85m. 81s.; Dec \ N. 28 25' 4". A 2, orange tinge; B 12, ash-colored ; C 11, pale violet, with anothei minute companion visible with tne best instruments. 8. y GEMIXORUM (Alheiui) A coarse TRIPLE STAR, in the right foot of Pollux: R. A 6h. 28m. 2Ss. ; Dec. N. 16 31' S". ; A 3, brilliant white; B 13, and C 12, both pale plum color. It is on a line from Rigel to Geminorum, and nearest the former. 4. (J GKMIXORUM (Wasaf) A DOUBLB STAR on the right hip of Pollux; R. A. 7h. 10m. S4s. ; Dec. N. 22' 16' 3". A 833, pale white; B 9, purple. 5. E GEMINORCM (Jfcluctft) A star with a distant companion, on Castor's right kneu , R. A. Ch. 34m. 05s. ; Dec. N. 25 16' 9". A3, white ; B 9^, cerulean blue. 6. GEMIXORUM A coarse TRIPLK STAR on the right knee of Pollux ; R. A. 6h. 54m. 37s. ; Dec. N. 20 47' 9". A 4, pale topaz ; 15 8, violet ; C 13, grey. 7. A CLUSTER, near the right foot of Castor ; R. A. 5h. 59m. Old. ; Dec. N. 24 21' 8'. A gorgeous field of stars from the Uth to the iGth magnitudes. 8. A CLUSTER in the calf of Pollux's right leg; R. A. 6h. 45m. 56s. ; Dec. N. 18 10' 5" A faint angular group of extremely small stars, in a rich region, but seen with difficulty. See Map VIII., Fig. 35. 9. A COMPRESSED CLUSTER under the left shoulder of Pollux, one-third the distance from (3 Geminorum, to /? Canis Minoris; R. A. 7h. 28ra. 57s. ; Dec. N. 21 55' 7". A faint object about 12 in diameter, with a small star near the centre. Map VIII., Fig. 36. CANIS MINOR (THE LITTLE DOG), MAP III. 99. This small constellation is situated about 5 N. of the equi- noctial, and midway between Canis Major and the Twins. It contains 14 stars, of which two are very brilliant. The brightest star is called Procyon. It is oi* the 1st magnitude, and is about 4 S. E. of the nsxt brightest, marked Go?nelza, which is of the 3d magnitude. These two stars resemble the two in the h >ad of the Twins. Procyon, in the Little Dog, is 23 S. of Pollux ui Gemini, and Gomelza is about the same distance S. of Castor. 100. A great number of geometrical figures may be formed of the principal stars in the vicinity of the Little Dog. Fcr example : Procyou is 23 S. of Pollux, and 26 E. of Betel TRLESCVPIC OBJECTS. Alpha? Beta? Gamma? Delta, Ac 1 .? Clusters? WLJcii *hown on the map? 99. Where is Canis Minor situated? Number of stars? Name of brightest? Mag iJtude? Next brightest? What do these two resemble f 100. What said of geouia rical figures t Of the name Procyonl Its import? \\ CANIS MINOR. 57 nir before it. For this reason, it was called J'roct/on, from two Greek words which rtg-iit'y (Ante Canitt) " before the dog." HISTORY. The Little Dog, according to Greek fable, is one of Orion's hounds. Some suppose U refers to the Egyptian god Anubis, which was represented with a dog's head ; others to Diana, the goddess of hunting ; and others, that it is the faithful dog Msera, which belonged to Icarus, and discovered to his daughter Erigone the place of his burial Others, again, say it is one of Acteeon's hounds that devoured their master, after IMau\ had transformed him into a stag, to prevent, as she said, his betraying her. " This said, the man began to disappear By slow degrees, and ended in a deer. Transforiu'd at length, he flies away in haste, And wonders why he flies so fast But as by chance, within a neighb'ring brook, He saw his branching horns, and alter'd look, Wretched Acteon ! in a doleful tone He tried to speak, but only gave a groan ; And as he wept, within the watery glass, He saw the big round drops, with silent pace, Run trickling down a savage, hairy face. What should he do ? or seek his old abodes, Or herd among the deer, and skulk in woods? As he thus ponders, he behind him spies His opening hounds, and now he hears their cries. From shouting men, and horns, and dogs he flies. When now tlie fleetest of the pack that press'd Close at his heels, and sprung before the rest, Had fastened on him, straight another pair Hung on his wounded side, and held him there, Till all the pack came up, and every hound Tore the sad huntsman groveling on the ground." It is not difficult to deduce the moral of this fable. The selfishness and caprice of l.un,an friendship furnish daily illustrations of it. While the good man, the philanthro- pist, or the public benefactor, is in affluent circumstances, and, with a heart to devise, has the power to minister blessings to his numerous beneficiaries, his virtues are the general theme ; but when adverse storms have changed the ability, though they could not shake the will of their benefactor, he is straightway pursued, like Actaeon, by his own hounds ; and, like Acteeon, he is " torn to the ground" by the fangs that fed upon hii bounty. It is most probable, however, that the Egyptians were the inventors of this con- itsllation , and as it always rises a little before the Dog Star, which, at a particulai leason, they so much dreaded, it is properly represented as a little watchful cre> tan- giving notice like a faithful sentinel of the other's approach. TELESCOPIC OBJECTS. 1. a OASIS MINORIS (Procyori) A bright star in the loins of th Jog with a dlstan f npamon , R. A. 7h. 30m. 55s ; Dec. N. 5 87' 8'. A 1 J$, yellowish white ; B 8, orange int. faeveral small stars in the field. HISTOHY.- What is the Little Dog supposed to represent? Fable of Aciawn K Fl .T.oral ? Who probably invented this constellation ? To represent whatV TKII-^COPIC OBJECTS. Alpha? Beta? Double star? Triple? 58 \STRONOMY. . CANIS MINURIS (Oomelza)^ wide TRIPLK STAR in theneck; R. A 7n. ISm. 24a Dec. N. 8 86' 4". A 3, white ; B J2, orange ; C 10, flushed the last coar&ely tfsuble with one of the same magnitude. Other stars in the field. 8. A close DOUBLE STAR, in a fine vicinity in the loins ; R. A. 7h. 31m. 87s ; Dec. N. 5* 16 7'. A 7, white ; B 8, ash-colored, with a minute blue star 2' distant. 4. A WIDK TRIPLS STAR, fi S. E. of Procyon ; R. A. 7h. 50m. 03a. ; Dc. N. 2" 88' 8'. A t, pile white ; B 8, bluish ; C 9, blue. MONOCEROS (THE UNIOOEN). MAP III. 101. This is a modern constellation, made out of the unformed stars of the ancients that lay scattered over a large space of the heavens between the two Dogs. It extends a considerable distance on each side of the equinoctial, and its centre is on the same meridian with Procyon. 102. It contains 31 small stars, of which the seven principal ones are of only the 4th magnitude. Three of these are situ- ated in the head, 3 or 4 apart, forming a straight line N. E. and S. W. about 9 E. of Betelguese in Orion's shoulder, and about the same distance S. of Albena in the foot of the twins. The remaining stars in this constellation are scattered over a large space, and being very small, are unworthy of particular notice. HISTORY. The Monoceros is a species of the Unicorn or Rhinoceros. It is about the size of a horse, with one white horn growing out of the middle of its forehead. It is said to exist in the wilds of Ethiopia, and to be very formidable. Naturalists say that, when pursued by the hunters, it precipitates itself from the tops of the highest rocks, and pitches upon its horn, which sustains the whole force of its fall, so that it receives no damage thereby. Sparmann informs us, that the figure of the unicorn, described by some of the ancients, has been found delineated on the surface of a rock in Caffraria; and thence conjectures that such an animal, instead of being 'atoiioits, as some suppose, did once actually exist in Africa. Lobo affirms that he has seen it. The rhinoceros, which is akin to it, is found in Bengal, Siam, Cochin China, part of China Proper, and the isles of Java and Sumatra. TELESCOPIC OBJECTS. 1. A most delicate DOUBLE STAR ( /), in the Unicorn's eye; R. A. 6h. 26m. 06s. ; Dec. N. 7 41' 05". A 6, yellowish white : B 16, dusky. A difficult object. 2. A neat DOUBLE STAR (&), in the nostril, 7% east of fietelffuese; R. A. 6h. 15m. 17s.; Dec. N. 4 40' 01". A 5%, golden yellow ; B 8, lilac. 8. A fine TRIPLE STAR in the right fore-leg; R. A. 6h. 21m. 04s.; Dec. S. 6 56 01". A 6.^, white ; B 7, and C 8, both pale white. A ray shot from the Bull's eye througa Bella- trix, and rather more than as far again, will pick it up. Supposed by Herschel to be it 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 TRIPLE STAR, in a magnificent stellar field, between the Unicorn's ears* R. A. 61-. 32m. 10s. ; Dec. N. 10 02' 02". One-third the distance from Procyon to .dW* A 6, gretvish ; B 9^, pale grey ; C 15, blue. A fine object. 101. Character and situation of Monoceros? Extentf 102. Number and si*e of tU tars ? How three of the largest situated? HifrivPY . What said of the animal itself? Is it not wholly fabulous ? TKLESCOPIC OBJBCTri. Double stars V Triple ? Any shown on the iasf CANI8 MAJOR UANIS MAJOR (THE GREAT DOG). MAP III. 103. This interesting constellation is situated southward and eastward of Orion, and is universally known by the brilliance of its prkcipal star, Sirius, which is apparently the largest and brightest in the heavens. It glows m 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 8 minutes and 18 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 32 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 8 years and 82 days after it bad 3eased to be. If the nearest 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 nis 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 in 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 2o 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. Tki Virgil : " Turn steriles exurere Sirius agros ; Ardebant herb, et victum segea gra 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." 108. Situation of Canis Major? How known? Supposed distance of Siriiw? Dlus trated by the speed of a cannos ball ? Of light ? 104. How was Sirius regarded by Ji ancients? Uss made of it by the Thebans? The Egyptians? 105. Practice of Uii Roiuane ? 60 ASTRONOMY. 106. Accordingly, to that season of the year wheu Sirius rose with the sun and seemed to blend its own influence with the beat of that luminary, the ancients gave the name of Dog-days, (Dies canicular is.) At that remote period the Dog-days com- menced on the 4th of August, or four days after the summer solstice, and lasted forty days, or until the 14th of September. At present the dog-days begin on the 3d of July, and continue to the llth of August, being one day less than the ancients reckoned. 107. Hence, it is plain that the Dog-days of the moderns have no reference whatever to the rising of Sirius, or any other star, because the lime of their rising is perpetually accelerated by the precession of the equinoxes : they have reference then only to the summer solstice, which never changes its position in respect to the seasons. The time of Sirius' rising varies with the latitude of the place, and in the same latitude, is sensibly changed after a course of years, on account of the precession of the equinoxes. This enables us to determine with approximate accuracy, the dates of many events of antiquity, which cannot be well determined by other records. We do not know, for .nstance, in what precise period of the world Hesiod flourished. Yet he tells us in his Opera et I>ies^ lib. ii. v. 1S5, that Arcturus in his time rose heliacally, GO days after the winter solstice, which then was in the 9th degree of Aquarius, or 89 beyond its present position. Now 39 : 50 3* =2794 years since the time of Hesiod, which corresponds very nearly with history. 108. When a star rose at sun-setting, or set at sun-rising, it was called the Achronical rising or setting. Wheu a planet or star appeared above the horizon just before the sun, in the morn- ing, it was called the Heliacal rising of the star ; and when it sunk below the horizon immediately after the sun, in the evening, it was called the Heliacal setting. According to Ptolemy, stars of the first magnitu-l^ are seen rising and setting when th< sun is 1 below the horizon ; stars of the 2u magnitude require the sun's depression i# be 13 ; stars of the 3d magnitude, 14' , and so on, allowing one degree for each magni- tude. The rising and setting of the stars Described in this way, since this mode of description often occurs in Hesiod, Virgil, Columella, Ovid, Pliny, &c., are called po^i>:cU rising and setting. They served to mark the times of religious ceremonies, the seasons allotted to the several departments of husbandry, and the overflowing of the Nile. 109. The student may be perplexed to understand how the Dog Star, which he seldom sees till mid- winter, should be asso- ciated with the most fervid heat of summer. This is explained by considering that this star, in summer, is over our heads in the daytime, and in the lower hemisphere at night. As " thick the floor of heaven is inlaid with patines of bright gold,' ; by day, 106. Origin of the phrase Dog-dayaJ When did they Deghi in the time of Virgil? At ffhat time now? 107. What inference from these facts? What variation in the Urn* of Sirius' rising ? What calculat MI by knowing the time when Sirius rose, at any pe. iod t 10S. What are the Achronitial and Heliacal rUing or setting of a star or planet? Br mark of Ptolemy in regard to rising and setting of the stars? 109. Hew is fl thv Hirius a winter star, is associated with Uie heat of summer ? CAMS MAJOR. 6} as by night ; but on account of the superior splendor of the sun, we cauuot see them. 110 Sirius is situated nearly S. of Alhena, iu the feet of tha Twins, and about as far S. of the equinoctial as Alhena is N. of it. It is about 10 E. of the Hare, and 26 S. of Betel guese in Orion, with which it forms a large equilateral triangle. It also forms a similar triangle with Phaet in the Dove, and Naos in the Ship, These two triangles being joined at their vertex in Sirius. present the figure of an enormous X called by some, the EGYPTIAN X. Sirius is also pointed out by the direc- tion of the Three Stars in the belt of Orion, Its distance from them is about 23. It conies to the meridian at 9 o'clock on the llth of February. 111. Mirzam, in the foot of the Dog, is a star of the 2d mag- nitude, 5 W. of Sirius. A little above, and 4 or 5 to the left, there are three stars of the 3d and 4th magnitudes, forming a triangular figure somewhat resembling a dog's head. The brightest of them, on the left, is called Muliphen. It entirely disappeared in 1670, and was not seen again for more than 20 years. Since that time it has maintained a steady lustre. 112. Wesen is a star of between the 2d and 3d magnitudes, in the back, 11 S. S. E. of Sirius, with which, and Mirzam in the paw, it makes an elongated triangle. The two hinder feet are marked by Naos and Lambda, stars of the 3d and 4th magnitudes, situated about 3 apart, and 12 directly S. of the fore foot. This constellation contains 31 visible stars, including one of the 1st magnitude, four of the 2d, and two of the 3d ; ill of which are easily traced out by the aid of the map HISTORY. Manillas, a Latin poet who flourished in the Augustan age, wrote an admirable ioem % > Ive books, upon the fixed sta' J , in which he thus speaks of this constellation : " All others he excels ; no fairer light Ascends the skies, none sets so clear and bright." *M.: ETDOSIA b*t describes it "Next shines the Dog with sixty- four distinct; Famed for pre-eminence in envied song, Theme of Homeric and Virgilian lays ; His fierce mouth flames with dreaded Sirius: Three of his stars retire with feeble beanvj." A :co HY to some mythologists, this constellation represents ons of Orion's honnda, itich xit. \ Uced in the sky, near this celebrated huntsman. Others say U received iu c.dhen ? 112. Wesen ? What other stars ? Whole number* HrgroiiY. -U.-A xassical description of Canis Major? What different accounts of iu 62 ASTRONOMT. nn.inalh of his s)ciea. Cephalus, it is aaid, attempted to prove this by running hta against a fox, which, at that time, was thought to be the fleetest of all aiimals. Aftc* they had run together a long time, without either of them obtaining the victory, it ii aid that Jupiter was so much gratified at the fieetness of the dog, that he assigned him a place in the heavens. Rut the name and form of this constellation are, no doubt, derived from the Egyp- tians, who carefully watched its rising, and by it judged of the swelling of the Nile, which they ca.ied Sir's, and, in their hieroglyphical manner cf writing, since it WAS, aw it were, the sentinel and watch of the year, represented it under the figure of a dog They observed that when Sirius became visible in the east, just before the morning dawt>, the overflowing of the Nile immediately followed. Thus it warned then:., like a faithful dog, to escape from the region of the inundation. TELESCOPIC OBJECTS. 1, o CAMS MAJOIJIS A brilliant star, with a distant companion ; It. A. (?h. SSin 06s. ktec. S. 16 8$, very pale. Oth :r small stars in the Sold, A line from Betelguese through tfirius intercepts it 12" below the latter star. 8. CANIS MAJORIS (Acthara) A star with a distant companion in the belly ; It. A 6h. 52m. 20s. Dec. S. 28 45' 5". A 2 J<, pale orange : B 7, violet. Found by running line from the middle of Orion's belt through (3 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. 18 29' 2". Tole- rably compressed; stars of the 8th to llth magnitudes, of which the four principal form the letter Y. 5. A CLUSTKR between Sirius and Monoceros ; R. A. 7h. 10m. 85s. ; Dec. S. 15 21' * Stars principally of the 10th magnitude. Discovered by Miss ilerschel in 1785- CHAPTER V. CONSTELLATIONS ON THE MERIDIAN IN MARCH AKGO NAVIS (THE SHIP AKOO). MAP III. 113. THIS constellation occupies a large space in the southern nemisphere, though but a small part of it can be seen in tho 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 JVaos, 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- TRLBSCOPIC OBJECTS. Alpha ? Delta? Epsilon? "What clusters? 118. Size and situation of Argo Navis? How kn^wn? 114. How toad J?*i, :t! <*here situate:! Uow high when on the meridian? ARGO NAVIS 63 era horizon, It coines to the meridian on the 3d of March, about half an hour after Procyon, and continues visible but a tew 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 sonth era 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 Sirius, and comes to the meridian 17 minutes after it'; but hav- iug about 53 of S. declination, it cannot bo seen in the Northern States. The same is true of Miaplacidux, a star of the 1st matrm- tude in the oars of the ship, about 25 E of Canopus, and 6P S. of Alphard, in the heart of Hydra. An observer in the northern hemisphere, can see the stars as many degrees south of the equinoctial in the southern hemisphere, as his own latitude lacks of 90, and D : more. 116. Markeb, is a star of the 4th magnitude, in the prow of the ship, and may be seen from this latitude 1 6 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. 117. This constellation contains 64 stars, of which two ar> ol the 1st magnitude, four of the 2d, and nine of the 3d. Moh( cf these are too low down to be seen in the United States. HISTORV. 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 perilouj expedition of recovering the golden fleece. The derivation of the word Argo has been 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 Grecians, commonly called Argives. Diodorus derives the word from dpyb:, which signifies ftwift. Ptolemy says, but not truly, that Hercules built the ship, and called it Argo, after a son o. 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 ship 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 Mi :rva, which had the power of giving oracles to the Argonauts. This ship was the ftm, 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 thj 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 yean 115. Size and situation of Gamma? Name the principal star in this constellation 1 Its magnitude? Is it ever seen in the U.S.? What said of Miaplacidus? Remark in fine print? 116. Whai said of Markeb? How known? 117. Number of stars if. Argo Na vis? Magnitudes? HtSTOkY. Design of th'.s constellation? Import of the term Argo? Size and 3tra, lure of the ship? What myth respecting this ship? What remark refljrectOfc ftta Isaac Newton? Dr. Brya t'e opinion? 64 ASTRONOMY. Wtore the destruction of Troy, and 43 years after the death of 3olon.on. Di Bryunf Dowevor, rejects the history of the Argonautic expedition as a mere fiction of the Greeks, aud supposes that this group of stars, which the poets denominate Argo Navis, refers to Noah's ark aud the deluge, and that the fable of the Argonautic expedition is founded on r:i *ain Egyptian traditions that related to the preservation of Noah and his familj t-annj the flood. TELESCOPIC OBJECTS. ,, ABGO NAVIS A star with a distant companion; R. A. Sh. 00m. 448.; Dec. 8 2^ 80' 8'. A 3^, pa'e yellow ; B 10, greyish. Other small stars in the field. 2. A SMALL GALAXY CLUSTER ; R. A. 7h. 87m. 44s ; Dec. S. 28* 29' 1'. a A neat DOUBLE STAR over the ship's stern ; R. A. 7h. ?8m. 08s. ; Dec. S. 14 18 8". t 1, silvery white; B ?}$, pale white. 4 A close DOUBLK STAR over the Argo's stern ; R. A. 7h 40m. 27s. ; Dec. 8. 11 48' 8' A 7^, pale yellow ; B 9, light blue. 5. A bright PLANETARY NEBULA ; R. A. 7h. 34m. 40s. ; Dec. S. 17" 50' 2". A fine object, pale bluiili white, and may be identified by several small stars in its vicinity. See Map \:il., Fig. 81. CANCER (THE UKAB,. MAP 11J 118. Cancer is now the fifth constellation and fourth sign oi the Zodiac. It is situated in the ecliptic, between Leo on tle 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 Acubens. 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 Capelhi through Pollux, will point out Acubens, 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, inarKS 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 'lih magnitude, 8 or 4 apart, which mark the head of Hydra. The rest of this constellation i* delineated on Map IV. TELESCOPIC OBJECTS. Iota? What cluster? Double stars? Nebula? Point cat c<- t.'ie nap? 118. Place of Cancci- in the Zodiac? In other respects? Number and size of is Btars? 119. Beta? How known? 120. Acubens? How found? 121. 8itufi f>f l>eltaf Remarks respecting Hydra? Respecting the sigu Cancer? CANCER. (J3 The Beginning of the sign Canctr (not the constellation; is called the Tropic of Can, ./*, and when the sun arrives at this 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 itointi^e ; from two Latin -.vo.ds signifying the .sn's standing xtill. The distance from the first point of Cancer to the equinoctial, which, at present, is 23 '27V, is called the obliquity vf IM <'/ij.'liC: It is a remarkable and well ascertained fact, that this is continually growing 'ess and less. The tropics are slowly and steadily approaching the equinoctial, at the 'at? of rtbout half a second evtry year; so that 'he sun does not now come so fai north f the quator in summer, nor d'-ciine so far south in winter, as it must have done at the r.^atiua, by nearly a degree. HISTORY. in t?ie Zodiacs of Esne an.l Dendera, and in most cf the astrological remains of Fgjpi, ft Searahwus, or Beetle, '.s used as the symbol of this sign; but in Sir William Jones' Oriental Zodiac, and in some others found in India, we meet with the pruru of a crab As t'.ie Hindoos, in all probability, derive 1 their knowledge of the stars "from the Chal- deans, it is sup- 'sed that the figure of the crab, in this place, is more ancient than thj He'Mle. In some e? item representations of this sign, two animals, like asses, are foun.l in this divisirn of t e Zodiac; and as the Chaldaie name for the ass may be translated muddi- <-#, it is supposed to allude to the discoloring of the Nile, which river was rising when th'j sun elite -ed Cancer. The Greeks, in copying this sign, have placed two asses as the appropriate symbol of it, which st.il remain. They explain their reason, however, foi adopting this figure, by saying that these are the animals *hat 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 S'empreuite du pavilion d' Issachar que Jacob assimile a Pane." Mytholog sts give different accounts of the origin of this constellation. The prevai'. 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 loy 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 DOCBLK STAR, under the Crab's mouth; R. A. Sh. 85m. f6s. ; Dec. L IS" 44' 04". A 4M, straw color; B 15 blue, only seen by glimpses. 2. CANCRI A star with a distant companion, on the Crab's body; It. A. Sh. 31m. 16s.; Dec. N. 20 06' 02". A 6>$, and B 7, both pale white; and a third star in the field of nearly the same magnitude. 3. C CANCRI A fine TRIPLE STAR, just below the after claws of the Crab; R. A. Sh. 08m. 02s.; Dec N. IS' 07 05". A 6, yellow; B 7, orange tinge; C 7 %, yellowish. Supposed to be a Ternary system. 4. Aboi t, 7 northeasterly from Teg'nine, is a nebulous cluster of very minute stars, in the 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 ->ach. 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 south em Anelli. Bj some of the Orientalists, this cluster was denominated Pr<.exepe, .he Mange)', a contrivance which their fancy filled up for the accommodation of the AftfUi or A weft ; and it is so called by modern astroncn.crs. The appearance of Ibis group to the unassisted eye, is not unlike the nucleus of a comet, and it was repeat- edly mistaken for the comet of 132, which, in the month of Novvmber passed in it* neighborhood. ]\i a p VIII., Fig. 88. 5. A P-CH BUT LOOSE CLUSTER in the Crab's southern claw, where a line from Kiga through Procyon, into the east-northeast, will find it about 5 north of f in the Hya Jrs , R. A. Sh. 42m. 2Gs. ; Dec. N 12' 23' 06". Stars mostly of the 9th and 10th rnagniudea. See Map VIII., Fig. 30. HMTO ..What other figures for Cancer? Egyptian? Hindoo? Greek? Oriuin i: Uiie cor Dilation ? TEUMCOPIC OBJ KCTS. Delta? Eiailon? Ze'jiP WbM Clusters ? Point out on the Mar 66 ASTRONOMY CHAPTER VI. CONSTELLATIONS ON THE MERIDIAN IN APRIL LEO (THE LIOX). MAP IV. 122 LEO is one of the most brilliant constellations in the 4t inter hemisphere, and contains an unusual number of very bright stars. It is situated next E. of Cancer, and directly S. /f Leo Minor and the Great Bear. The Hindoo astronomer, Varaha, says, " Certainly the southern solstice was once in he middle of Asleha (Leo) ; the northern in the first degree of DJumixhta" (Aquarius), Since that time, the solstitial, as well as the equinoctial points, have gone backward on he ecliptic 75. This divided by 50%", gives 5373 years; which carry us back to tho year of the world 464. Sir W. Jones says, that Varaha lived when the solstices were in the first degrees of Cancer and Capricorn ; or about 400 years before the Christian era. 1 23. Leo is the fifth sign, and the sixth constellation of the Zodiac. The mean right ascension of this extensive group is 150, or 10 hours. Its center is therefore on the meridian the sixth of April. Its western outline, however, comes to the meridian on the 18th of March, while its eastern limit does not reach it before the 3d of May. This constellation contains 95 visible stars, of which one is of the 1st magnitude, one of the 2d, six of the 3d, and fifteen of ',he 4th. " One splendid star of highest dignity, One of the second class the Lion boasts, And justly figures the fierce summer's rage." 124. The principal star in this constellation is of the 1st mag- nitude, situated in the breast of the animal, and named Regulus, from the illustrious Roman consul of that name. It is situated almost exactly in the ecliptic, and may be readily distinguished on account of its superior brilliancy. It is the largest and lowest of a group of five or six bright stars which form a figure somewhat resembling a sickle, in the neck and shoulder of the Lion There is a little star of the 5th mag- nitude, about 2 S. of it, and one of the 3d magnitude 5 N. of it, which will serve to point it out. Great use is made of Regulus by nautical cien, for determining their longitude at sea. its latitude, or distance from the ecliptic, is less than %; Hit its declination, or lis &' re from the. equine (Mai, is nearly 18 N. ; so that its meridian altitude will be ju*t 122. Describe Leo. Its situation ? What remarkab e statement of Varaha ? Cal ;ula ti.ns upon it? 123. Position of Leo in the Zodiac ? When on the meridian ? Numbe and size of its stars ? 124. Its principal star? Situation? How distinguished? Wba'. life oiade of Regulus ? When on the meridian, where are Castor and Pollux ? LEO. 69 cqtul to that or the sun on the 19th of August. Its right ascension is very nc'.irly 150*. It therefore culminates about 9 o'clock on the 6th of April. When Regulus is on the meridian, Castor and Pollux are seen about 40 N. W. of it, ivrid the two stars in the Little Dog are about the same distance in a S. W. direction; with which, and the two former, it makes a large isosceles triangle whose vertex is at Regulus. 125. The next considerable star is 5 N. of Regulus, marked Eta, situated in the collar ; it is of between the 3d and 4th magnitudes, and with Regulus constitutes the handle of the sickle. Those three or four stars of the 3d magnitude, N. and W. of Eta, arching round with the neck of the animal, describe the blade. 126. Al Gieba is a bright star of the 2d magnitude, situated in the shoulder, 4 in a N. E. direction from Eta, and may be easily distinguished by its being the brightest and middle one of the three stars lying in a semicircular form curving toward the west; and it is the first in the blade of the sickle. 127. AdJiafera is a star of the 3d magnitude, situated in the neck, 4 JS T . of Al Gieba, and may be known by a very minute star just below it. This is the second star in the blade of the sickle. 128. Ras al Asad, situated before the ear, is a star of the 3d or 4th magnitude, 6 W. of Adhafera, and is the third in the blade of the sickle. The next star, Epsilon, of the same magni- tude, situated in the head, is 2 S. W. of Ras al Asad, and a little within the curve of the sickle. About midway between these, and a little to the E., is a very small star hardly visible to the naked eye. 129. Lambda, situated in the mouth, is a star of the 4th magnitude, 3-J S. W. of Epsilon, and the last in the sickle's point. Kappa, situated in the nose, is another star of the same magnitude, and about as far from Lambda as Epsilon. Epsilon and Kappa are about 4 apart, and form the longest side of a triangle, whose vertex is in Kappa. 130. Zozma, situated in the back of the Lion, is a star of the 3d magnitude 18 N. E. of Regulus, and midway between it and Coma Berenices, a fine cluster of small stars, 18 N. E. of Zozma 131. Thtta, situated in the thigh, is another star of the 3d magnitude, 5 directly S. of Zozma, and so nearly on the same meridian that it culminates but one minute after it. This star 126. Next principal star size and position? 126. Al Gieba? How known! 127. Aihafera? 128. Ras a Asad? Epsilon? 129. Situation and size of Lambda! Of Ktppa? 180. Of Zo/ma. 181. Of Theta? What triangle? What other atari mentioued? B8 ASTRONOMY. makes a right-angled triangle with Zozina on the N. and Dcna- bola on the E., the right angle being at Theta. Nearly in a straight line with Zozma and Theta, nnd 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 tl.e brush of the tail, 10 S. E. of Zozina, and may be distinguished by its great brilliancy. It s 5 W. of the equinoctial col are, and comes to the meridian 1 hour and 41 minutes after Regnltt*, 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 Phatl, in the square of Ursa Major, bears 39 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 w'n.h Phad that it culminates only four minutes before it. Denebola is 85V 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 Rhombus, 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 micron, of the 3d and 4th magnitudes, situated in the foreclaws, and about 8 apart. There are a number of other stars of the 3d and 4th magmv,oJ la 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 Nemsea. 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 hero with the Lion was his first labor, they have placed Leo as Qttjtrtt 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 Nemtean Lion, because Leo was already a zodiacal sign. In hieroglyphic*! 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 annoyed bj lions durfng the heat of summer, as they at that season left the desert, and haunted th< banks of the Nile, which had then reached its greatest elevation, n was therefore natural for their astronomers to place the Lion where 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 everj year by the Egyptians, took place when the sun was in this sign. They therefore pa '4 more attention to it, it is to be presumed, than to any other. This was the pric.'ipoi reason, Mr. Green supposes, why Leo stands first in the zodiacs of Dendera. in the Hebrew Zodiac, Leo is assigned to Judah, on whose standard, according to -i traditions, a Lion is painted. This is clearly intimated in numerous passages of tl c Hebrew writings: Ex. "Judah is a Lion's whelp; he stooped down, he couch rd as 4 132. Size and position of Denebola? How known? When does it come to the inert dian as compared with Regulus? What sail of its meridian altitude? When on th meridian where is Regulus seen ? Phad? What triangle? How is Detebolo situate^ with respect to Arcturus and Spica Virginia ? To Cor Caroli ? What other large figures HISTOHT. Greek fable? Egyptian? Hebrew Zodiacs? Scripture allusions to tb U&nt LEO MINOR. (5 Llou, and as an Old l.ion ; who shall rouse him up?" Gen. xlix. 9. "The Lion of ttt l/lbo of Judah hath prevailed." Kev. v. 5. TELESCOPIC OBJECTS 1. a LKOXIS (Kegulux) A bright star with a distant companion ; R. A. 9h. Khn. 5ls. [> )C . N. 12 44' OS". A t, flushed white ; B S%, pale purple. 2. 3 L)Nis (L>fnehvld)A flue star with a distant companion; R. A. llh. 40m. 54s.; J.-c N 15 28' 0". A 2)4, bluish; B 8, dull red. 3. y LEosrs(Al Giebzna) A co?rse TRIPLE STAR; R. A. llh. 05m. 85s. ; Dec. N. 21 24' I*. A 3, i) Ue yellow ; B 13, blu;; 3 9, violet. 5. e LKOXIS 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, pule grey. C i LEOXIJ--A BIXAKY STAK iu the tlank, 7 S. W. of Denebola (Fon map;; R. A. llh. 15oi. 85s. ; Dec. N. 11 24' 8". It forms a neat scalene triangle with /J and $. A 4, pale yellow ; B 7X- l! ? h .t- llue ; a beautiful object. T. (J. LL^.S (Has Al Asef(>rc Ihc us* 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, Alkes, of the 4th mag' ni tude, 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, t>~ S. and K. of it. Alkes is common both to Hydra and the Cup. Beta, im the S., is in Hydra, and Gamma, on the N. E., is near the middle of the Cup. A line drawn from Zozma, through Thetft 186. Describe Hydra? Its situation ? Number and magnitude of its stars? 137. Po uitif n and magnitude of Alphard ? How pointed out? 139. How b the head of Hydra distinguished? 189. What said of Alkes? Of Beta and Gamma? Uow U BU. bud! 72 AJ tvONGMY. Leonis, ud continued 38^ directly S. will reach Beta ; it ii therefore on the same meridian, and will culminate at the sauw time on the 23d of April. 140. The Cup itself (called also the Crater], may be easil) Distinguished by means of six stars of the 4th magnitude, form- ing a beautiful crescent, or semicircle , opening to the W. The WMter of tbis group is about 15 below the equinoctial, au.d 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 moon is absent, that no other description is necessary to point then.. out. Its center comes to the meridian about two hours after Alphard, on the same evening ; and consequently, it culminatos at 9 o'clock, one mouth 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 Galaxy' 1 * refulgjnt sea; Nearly a fourth of the encirci ng curve Which girds the ecliptic, his \ast folds involve; Yet ten the number ot his stars diffused O'er the long track of his enormous spires ; {'biff beams his heart, sure of the second rank, But emulous to gain the first." Eudonia. 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 pads* the meridian about midnight, when the sun is in Pisces, was called the, lluime of tti.< Lions, Leo being the domicil 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 one represented the oblique course of the stars, while the Hydra, or Great Snake, in the southern hemisphere, symbolized tin- moon's course ; hence the Nodes are called tJte Dragon's head and tail to tki* day, The hydra was a terrible monster, which, according to mythologies, infested tht neighborhood of the lake Lerna, in the Peloponnesus. It had a hundred heads, accord- ing to Diodorous; fifty, according to Sitnonides; and nine, according to the more com nionly received opinion of Apollodorus, Hyginus, and others. As soon as one of their )eads was cut off, two immediately grtw up if the wound was not stopped by tire " Art thon proportion'd to the hydra's length, Who by his wounds received augmented strength? He raised a hundred hissing heads in air, When one I lopp'd, up sprang a dreadful pair." To destroy this dreadful monster, was one of the labcrs of Hercules, and this he eaaily 'jflTtcted with the assistance of lolaus, who applied a burning iron to the woundb us i>on as one head was cut off. While Hercules was destroying the hydra, Juno, jealo'45 of i.'s glory, sent a sea-crab to bite hrs foot. This new enemy was soon despatched ; AD! 140. HOT* is the Cup distinguished? Is it easily fomd ? 141. What id said of ttu Ateut of Hydr-i east and west? History of Ifydr-t ' URSA MAJOR. 73 Juno was unable to succeed in her attempts to lessen the fame of Hercules. The coa ^ueror dipped his arrows in the gall of the llydra, which ever after rendered the wound" inflicted with them incurable and mortal. This fable of the many-headed hydra may be under.tooi to mean nothing more than that the marshes of Lerna were infested with a multitude of serpents, which ueeincd to multiply as fast as they were destroyed TELESCOPIC OBJECTS. 1. a GKATKRIS A star with two very distant companions in the base of the cup; II. A i1>h, 62m. OOs ; Dec. S. 17 26' 9". A. 4, orange tint ; B 8, intense blood color ; C 9, p:Jc Hue 2. y CRATERIS A close DOUBLE STAR, in the center of the cup; R. A. llh. 16m. f4s. ; Dec. S. 18' 48 3"; A 4, bright white; B 14, grey , with a stur of the ilth inagnitsdo fol- lowing, or a line with A. B. 25' distant. 3. d CRATERIS A star with a very distant companion, on the cup, midway between Alphard and Spica, but a little south of the line joining them; R. A. llh. llm. 21s.; 2>.:c. S. 13 54' 8". A 3J<$, pale orange ; B 11, pale blue other small stars in the field. 4. a HYDR.E (Cor tfydrce)A. bright star in the heart of Hydra with a distant com- panion ; R. A, lh. 19m. 44s. ; Dec. S. 7 58' 1". A 2, orange tint; B 10, pale green. 5. 6 HYDR^E A star with a distant companion in the head of Hydra; R. A. 8h. 29m. 14s. ; Dec. N. 6" 15' 5". A 4, light topaz; B 9, livid-several other stars in the field. 6. e HYDROS A double star in the head ; R. A. 8h. 38m. 18s. ; Dec. N. 7 00' 2'. A 4, pale yellow ; B 8%, purple. 7. A PLANETARY NEBULA in the middle of the body; R. A. lOh. ITm. Ola.; Dec. 8. IT* 60' '; greyish white. CHAPTER VII. CONSTELLATIONS ON THE 'MERIDIAN IN MAY. URSA 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 uician navigators, seem to have been equally struck,with its peculiar outlines. And if Is scraewhat 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 " Great Bear," 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 il is colled "Charles' Wain," or wagon, from its fancied resem- TKLBSCOPIO OPJBCTS. Alpha? Gamma P Delta? Alpha Hydras? Delta Hydra i I'ta Hy Jro.. ? Wha t Nebula ? \4'2. Describe Ursa Major? What remarkable fact as to its name? 148. How dip- tipguishcd? What other names for the Dipper? What remark in small type? 74 A&TROKOMY. 'jlaiue' to a wagon drawn by three horses in a line. Others call tfc 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 tha shepherds, for the resemblance is certainly in favor of the Dipper ; the four stars in the square forming the bow', and the other three the handle. J44 When the Dipper is on the meridian, above the pole, the bottom lies toward us, with the handle on the right. Benctuai,ch is a bright star of the 2d magnitude, and is the first in 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 of 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 horizontaj line east and v/eat, 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 4 S. W. of Megrez is Phad, the first star in that part of the bottom which is next tlie handle. The stars in this cluster are so well known, and maybe 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 othtr 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, arc. 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 28J 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 poles? Describe Banetnasch? Mizar ? How known? 146. Alioth? Megrez? Rert.arH respecting? Phad? Remark in small print? 148. Merak anrt Duhhe? Constitute u,it? Remark respecting the names, positions and distances of the stem in UTS Major? Why should these distances be well understood? UU.SA MAJOR. 75 emo nbered , as they wi'l be frequently adverted to. The distance of Dubht, or the Pointer neaiest to the noith pole, is '2$ if*. The distance between the two upper star* iu ihe Dioper is 10; between the two lower ones is 8; the distance from the brim to tne bottom next the handle, is 4)6 ; between Megrez and Alioth, is 5V$ ; between Alcth and Mizar, 4%; and between Mizar and Bent-tnasch, 7". The reason why it is important to have these distances clearly settled in the mind U^ that these stars, being always in view, and more familiar than any other, the studtai ^ill never fail to have a standard measure before him, which the eye can easily make jdo 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- .\octial colure, 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 Phad, 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 amidit one 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 twic the dark, both by land and by sea." TELESCOPIC OBJECTS. 1. tt URSA MAJORM (Dubhe, one of the pointers) A fine star with a distant compa Dion ; 11. A. lOh. 53m. 48s. ; Dec. N. 62 36' 8". A 1 %, yellow ; B 8, yellow. 2. (3 UKSA MAJORS (Merak)A bright star with a distant companion ; R. A. lOh. 52m. W; Dec. N. 57 14' 2". A 2, greenish while ; B 11, paie grey other stars in field. 8. y URSA MAJORIS (F7iad)A star with a distant companion ; R. A. llh. 45m. 23s. j I>ec. N. 54' 35 1". A 2, topaz yellow ; B 9, ashy paieuess, with a fine group of stors is the field. '4. (5 URSA MAJORis(J/n; R. A. 12h. 07m. 28s.; Dec. N. 57 55' 3". A 3, pale yellow; B9, ash coloreu, with o'.her stars in field. . C URSA MAJOHIS (Mizar.) A splendid double star in the middle of the tail ; R. A tfh. Km. 2&s.; Dec. N. 55 45' 8". A 8, brilliant white; B 5, pale emerald. Alcor an other stars in the field. Map VIII. Fig. 7. TELESCOPIC OBJECTS. Alpha? Beta? Gamma? Delta? Zeta f Bra? lota? W l.a'. nt-bula? Which shown on the map? COMA BERENICES. 77 A. 1J URSA MAJORIS (BenrtnascKyK DOUBLE STAR in the tip of the tail; R. A. 18h.41m i,4s. ; Dec. N. 50 06' 5". A 23$, brilliant white ; B 9, dusky. 7. i URSA MAJORIS (Al Kaphrah)b. DOUBLE STAR in the right fo -e paw ; R. A. 8h. 48m, Us. ; Dec. N. 48 39' 9". A 8J$, topaz yellow ; B 13, purple. Sir J. Uerschel supposed A might be a satellite, shining only by reflection. 8. v URSA MAJORIS A delicate DOUBLE STAR in the left aind loot, just above < I ElAcola; R. A. 11 h. 09m. 49s.- Dec. N. 30 58' 0'. A 4, orange tint : B 12, cornelian blue; a close but elegant object. 9. A beautiful PLANETARY NEBULA, just south of /?; R. A. lOh. 2Src;. 45s.; Dec. N. M ' 5(0' 4". A small, well denned object, bluish white, and brightens towards the center. 10. A BRIGHT NEBULA in the right fore leg; R. A. 9h. 10m. 54s.; Dec. N. 51 40' 5". Of a pale creamy whiteness, with several bright stars in the northern part of the field, Nebula large, elliptical and nucleated. 11. A bright-class ROUND NEBULA above the Bear's ear; R. A. 9h. 34m. 32s. ; Dec. N. 78' 01' 2". Several stars in field, of 9th to 12th magnitude. 12. A FINE OVAL NEBULA in the ear ; R. A. 9h. 42m. 10s. ; Dec. N. 69 51' 8'. 13. A LARGE MILK-WHITE NEBULA on the body, about 1" south of ft or Merak ; R. A. lib. 02m. 02s. ; Dec. N. 56" 31' S". 14. A LARGE PLANETARY NEBULA on the flank, with several stars in the field, one of which is pretty close ; R. A. llh. 05m. 24s. ; Dec. N. 55 52' 9" About 2 to the S. E. of ft, and just south of a line from /3 to y ; a singular object, circular, uniform, and seem ingly of the size of Jupiter. W. llerschel assigned this object to the 9SOth order of di tance. Map VIII., Fig. 42. 15. A BRIGHT-CLASS NKBULA in a poor field, behind the left hind leg, one-third the dis- tance from (} towards Denebola; R. A. llh. 58m. 51s.; Dec. N. 48 57' 8". Of A lucid white, various and elongated. Map VIII., Fig. 43. 16. A LARGE WHITE NKBULA near the haunches ; R. A. 12h. lira. 04s. ; Dec. N. 48 11' 1'. A voble-sized oval, with a bright nucleus, the lateral edges better defined than the ends Foind by running a diagonal line across the square, from a through >-, and about 7fc beyond, into the S. E. COMA BERENICES (BERENICE'S HAIR). MAP IV. 152. This is a beautiful cluster of small stars, situated about 5 E. of the equinoctial colure, and midway between Cor Caroli on the northeast, and Denebola on the southwest. If a straight line be drawn from Benetnasch through Cor Caroli, and pro- duced to Denebola, it will pass through it. 153. The principal stars are of between the 4th and 5th mag- nitudes. According 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 one star in this group, entitled to that rank, and this ia situated about 7 S. EL of the main cluster. Although it is not easy to mistake this group for any other in the same region of th hies, yet the stars which compose it are all so small as to be rarely distinguished in UM full presence of the moon. The confused lustre of this assemblage of small stars soraa- what resembles that of the Milky Way. 15 Describe Coma Berenices ? How find it* 168. Its principal *tars. th*ir oarobc, ic.f What remark in fine print? 78 ASTRONOMY. 154. The whole number of stars in this coast ellation is 43 ; its ineau right ascension is 185. It consequently IB on th meridian the 13th of May. "Now behold The glittering maze of Berenice's JJitir; forty the stars ; but such as seein to kiss Thejtowing tresse* with a lambent fln, Four to the telescepo alone are seen." Berenice * as n f royal descent, and a lady of great beauty, who married Ptolemy Sottf, tr Ifverfe'es, one or tne kings of Egypt, her own brother, whom she loved with much linderr.es'i When he was going on a danp-ious expedition against the Assyrians, she vowed to dedicate her hair to the goddess of beauty, if he returned in safety. Some time after tre 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 ld:>&3fl mentioned, and what calcu'ations, &o. ? CANES VENATICI. TELESCOPIC OBJECTS. I. a VIBGINIS (Spica) A. splendid star with a minute companion B. A. 18h. 16m. 4T *c, 8. J0 19' 5". A 1, brilliant flushed white; B 10, bluish tinge. 8. 3 VIBGINIS (Za-rijan)A bright star with a small companion : 11. A. lib. 42m 22s Dec. N. 2 40' 0'. A 33^, pale yellow B 11, light blue. 8. y VihGiNis A fine BINARY STAR in the Virgin's right side ; R. A. 12h. 33m. 38s. ; DsC 3. 0* M' 3". A 4, silvery white ; B 4, pale yellow. A Binary System with a period of abc.it J57 years. Map. VIII. Fig. 8. 4. (5 VIHGINIS A star with a distant companion, _n the left side, about 17 north- nor ,h Wfflt of Spica, and nearly midway between y and e Virginia ; It. A. 12h. 47m. 83s.; Doc N. 4* 1C' 1". A 3%, golden yellow ; B 10%, reddish ; several small stars in the field. 5. VIRGINIS ( Yendemiatriae) A star with a minute distant companion, on the uppei e> rwnity of the Virgin's left wing ; R. A. 12h. 54m. 13s. ; Dec. 1 1 49' 03". A ajg, bright fellow ; 15 15, intense blue. This last color on so small an object is very striking. 6. A TRiPi^; STAR in the lower part of the southern wing, 7 northwest of Spica ; R. A, 18h. Olm. 40s. ; Dec. S. 4 41' 0'. A 4 fc, pale white ; B 9, violet ; C 10, dusky. 7. A LARGK, BUT RATHER PALE NEBULA, between Virgo's left wing and Leo's tail; R. A. 12h. 06u. Ols. ; Dec. N. 15 47' 02". About 6& from f3 Leonis, towards Arcturus, on the outskirts of a vast region of Nebula in the Virgin's wing. It is elongated in the direction of two telescop{c stars. 8. A LONG PALB-WHITE NEBULA, among telescopic stars, on the upper part of the Vir- gin's left wing ; K. A. 12h. 07m. 37s. ; Dec. N. 14 02' OS". Situated one-third of the way from 8 Leonis to Virginis, on the border of the vast nebulous region in Virgo. A curious object in the shape of a weaver's shuttle. 9. > LUCID WHITK 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 NEBULA in the center of Virgo's left wing ; R. A. 12h. 85m. 88s. ; Dec. N. 12 26' Or. It is 5 west of Vendemiatrix, toward Regulus, in a wonderful nebulous region. Map VIII., Fig. 46, shows it on the right, with two other nebula}, and several stars in the figure. II. 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 te*escopic stars. Map. VIII., Fig. 47. 12. A WONDERFUL NEBULOUS REGION, about 2J$ from north to south, and 8 from east to west, is found on the left wing. It includes several of the objects described. For a drawing of this remarkable field, see Map VIIL, Fig. 48. CANES VENATICI (THE GREYHOUNDS). MAP IV. 166. This modern constellation, embracing two in one, was made by Hevelius out of the unformed stars of the ancients which were scattered between Bootes on the east, and Ursa Major on the west, and between the handle of the Dipper on th<3 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 tl leash by which they are fastened together. The northern one is calle I Astenon, and the southern one, Chara. TELESCOPIC OBJECTS. Alpha? Beta? Gamma? . Delta? Epsilon? What triple tin I Nebula? Point out, on the map. 166. Situation of Canes Venatici ? By whom formed ? How represented ? flic bounds? 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 merilian, Cor Caroli is 17V direct y S. of Alioth, the third star in Ui handle of the Dipper, and is so nearly on the same meridian that it culminates only ens minute and a half after 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 first 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 Arcturua 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 DOUBLB STAR near Chara's mouth ; R. A. 12h. 08m. 06s. ; Dec. N. 41 83' 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 6 Leonis. Map VIII., Fig. 10. 2. A MAGNIFICEHT CLUSTER, between the southern Hound and the knee of Bootes ; R. A. 13h. 34m. 46s. A splendid group, supposed to contain not less than 1,000 stars. Map VIII., Fig. 49. 3. A PAIR OF LUCID WHITE NEBULAE, near the ear of the northern Hound ; R. A. 18h. 23ui. 06s. ; Dec. N. 48" 01' 07'. 4. A LARGE BRIGHT NEBULA, 2 J$ north by west of Cor Caroli ; R. A. 12h. 43m. 22s. ; Deo. N. 41 59' 07*. A fino pale-white object, compressed toward the center, and with seveial small stars in the field. CHAPTER VIII. CONSTELLATIONS ON THE MERIDIAN IN JUNK BOOTES (THE BEAR DRIVER). MAP IV. 168. THE B EAR-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 ea/JiEV :' For we are also his offspring." These words are the beginning of the 5th line of the " Phenomena " of Aratus, a celebrated Greek poem written ir. the reign of Ptolemy Philadelphus, two thousand one hundred years ago, and afterward translated into Latin verse by Cicero. Aratus was a poet of St. Paul's own country. The apostle borrows again from the same poet, both in his Epistle to the Galatians, and to Titus. The subject of the poem was grand and interesting : hence we find it referred to in the writings of St. Clement, St. Jerome, St. Chrysostom, CBcumenius, and others. As this poem describes the nature and motions of the stars, and the origin of the constellations, and is, moreover, one of the oldest compositions extant upon this interesting subject, the author has taken some pains to procure a Polyglot copy from Germany, together with the Antronomicon of Manilius, and some other works of similar antiquity, that nothing should be wanting on his part which could impart an interest to the study of the constellations, or illustrate the frequent allusions to them which we meet with in the Scriptures. Dr. Doddridge says of the above quotation, that " these words are well known to t found in Aratus, a poet of Paul's own country, who lived almost 800 years before tne apostle's time ; and that the same words, with the alteration of only one letter, ar< iaedian, and it becomes hallowed by " the divinity that stirred within him." Tertii. Kn remarks, that " in quoting this, the apostle hath sanctified the poet's sentiment. 1 ' TELESCOPIC OBJECTS. 1. a Boons (Arcturus) A DOUBLKSTAR; R. A. 14h. 08m. 22s.; Dec. N. 20 00' 9". A 1, eddish yellow; B 11, lilac. 2. /? BOOTIS (Nekfair) A star with a distant companion in the head of the figure ; R. A- 14h. 65m. 55s. ; Dec. N. 41 01' 5". A 3, golden yellow : B 11, pale grey. 3. (5 Boons A star with a distant companion in the left shoulder ; R. A . 15h. 09m. 03s.; Dec. N. S3 54' 9". A 3^, pale yellow ; B Sfc, light blue. 4. e BOOTIS (Mirac) A DOUBLE STAR in the left hip; R. A. 14h. 38ra. OOs.; Dec. N. 27* 45' 1". A 3, pale orange ; B 7, sea green. A lovely object colors distinct, and strongly contrasted. 5. C Boons A close DOUBLE STAR on the left leg ; R. A. 14h. 33m. 31s. ; Dec. N. 14 e 25' 1*. A 3%, bright white; B 43'8. This success rendering them insolent, they insulted the Lapithie, a people of Thessaly; and because, when attacked, they fled with great rapidity, it was supposed that they were half horses and half men ; men on horses being at that period a very uncommon *ight, and the two appearing, especially at a distance, to constitute but one animal. S the Spanish cavalry at first seemed to the astonished Mexicans, who imagined the horse -.nd his rider, like the Centaurs of the ancients, to be some monstrous animal of a ter- rible form. The Centaurs, in reality, were a tribe of Lapithie, who residen near Mount Pelioa, auH 3rt invented the art of breaking horses, as intimated by Virgil. " The Lapithae to chariots add the state Of bits and bridles ; taught the steed to bound To turn the ring, and trace the mazy ground: To stop, to fly, the rules of war to know* To obey the rider, and to dare the foe." Centaurus is so low down in the south that it would be of no service to describe It* tel* .Kopic objects. 173. HowisCentaurosrepreiented? Its situation ? Number o* stars, *3.f 1T9. Theta iota, Mu, Nu, Ac.? What was Centaurus? Different opinions! 90 ASTRONOMY. LUPUS (THE WOLF). MAPS V. AND VII. 180. This constellation is situated next east of the Centaur and south of Libra ; and is so low down in the southern herni- si here, that only a few stars in the group are visible to us. 11 nntains twenty-foui stars, including three of the 3d magnitude, and as many of the 4th ; the brightest of which, when on the meridian may be seen in a clear evening, just above the southern horizon. Their particular situation however, will be better traced out by reference to the map than by written directions. The most favorable time for observing this constellation IP toward the latter end of June. HISTORY. This constellation, according to fable, is Lycaon, king of Arcadia, who lived about 8600 years ago, and was changed into a wolf by Jupiter, because he offered human victims on the altars of the god Pan. Some attribute this metamorphosis to another cause. The sins of mankind, as they relate, had become so enormous, that Jupiter visited the earth to punish its wickedness and impiety. He came to Arcadia, where he was announced as a god, and the people began to pay proper adoration to his divinity. Lycaon, however, who used to sacrifice all strangers to his wanton cruelty, laughed at the pious prayers of his subjects, and to try the divinity of the god, served up human flesh on his table. This impiety so offended Jupiter, that he immediately destroyed the house of Lycaon. and changed him into a wolf. " Of these he murders one ; he boils the flesh, And lays the mangled morsels in a dish ; Some part he roasts ; then serves it up so drass'd, And bids me welcome to his human feast. Moved with disdain, the table I o'erturned, And with avenging flames the palace burn'd. The tyrant in a fright for shelter ga-ns The neighboring fields, and scours along the plains: Howling he fled, and fain he would have spoke, But human voice his brutal tongue forsook. His mantle, now his hide, w'th rugged hairs, Cleaves to his back : a farnish'd face he bears His arms descend, his shoulders sink away To multiply his legs for chase of prey; He grows a wolf." Ovid. Met. B. i. TELESCOPIC OBJECTS. 1. a LCPI A star with a distant companion, in the tail of Lupus > it. A. 5h. *Am 40s. ; Dec. S. 17 56' 5". A 8J$, pale yellow ; B 9%, grey. To find, draw a line from e tbe central star of Orion's belt, through 6 and its nebulous patch on the sword, as lew down, and Sirius, and you meet a Lupi. 2. /3 Lu?i A DOUBLE STAR; R. A. 5h. 21m. 28s. ; Dec. S. 20* 53 5". A "4, deep yel- .ow; B 11, blue. 8. y LUPI A wide TRIPLE STAR in a barren field ; R. A. 5h. 87m. 4Ss. ; Dec. K' 80' 2" A 4, light yellow ; B 6^, pale green ; C 18, dusky. A line from 6 Orioms th"-ous:l the second cluster, and carried 16 beyond, falls upon it. 4. A bright STKLLAR NEBULA, of a milky white tinge ; R. A. 5h. ITm 50s. Dec. S. **' & 9*. A fine object blazing towards the centre. Situation of Lupus Number and magnitude of Us stars ? Best time to observe . What was Lupus originally? Why changed and by whom? Describe 1 hi that poet ? TRLKSCOPIC OBJECTS. -Alpha? Bet?.? Gamma? Wha- NebuK? LIBRA. 91 LIBRA (THE SCALES). MAP IV. AND V. 181. This is the seventh sign, and eighth constellation, fions the vernal equinox, and is situated in the Zodiac, next east of Virgo. The sun enters this sign, at the autumnal equinox, on the 23! of September ; but does not reach the constellation before tl.c- 2Hh cf October. When the sun enters the sign Libra, tho days 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 and Libra, and the tropics in Cancer and Capricorn, it must be remembered that the #ign* 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 fiemini and Sagittarius; each constellation having g one forward one sign in t/ie ecfiptic. About 22 centuries ago, the constellation Libra coincided with the aign 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 sign Sagittarius, and so on. While Aries is now advanced 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 nagnitude, 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 tho square, are situated about 7 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. Zubeneschaniitli, in the Southern Scale, about 21 E. of Spica, and S E. of Lambda Virginis, is a star of the 2d magnitude, and is situated very near the ecliptic, about 42 j E. of Die autumnal equinox. The distance from this star down to Theta Centauri ia about 23% with which, and Spica Virginis, ie forms a large triangle, on the right. Zubenflgeniabi, the uppermost star in the Northern Scale, is also of the 2d magnitude, 93^ above Zubeneschamali, toward the northeast, and it comes to the meridian about twenty-six minutes after it, on the 23d of June. Zubenelgemabi is the northernmost of the four bright stars in this figure, and is exactly opposite the lower one, which is 11* south of it. ZubenhakraM ia a star of the 8d magnitude in the Northern Scale, 7 S. E. of Zubenel- gemabi, and nearly opposite to Zubeneschamali, at the distance of 11" on the east. These two make the diagonal of the square east and west. Iota is a star of the 4th magnitude, and constitutes the souf ernmost corner of tht square. It is about 6 S. E. of Zubeneschamali, and 11 S. of Zuuenelgemabi, with which It forms the other diagonal north and south. Zebenelffubi is a star of the 3d magnitude, situated below the Southern Scale, st tbo 181. Order an 1 situation of Libra? What circumstance suggesting a balance? Wha Mnarks respecting the distinction between the signs and the constellations ? 18$. Nun* tr of stars in Libra? Its mean declination? Right ascension? When on the mert an? llow 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 situate J 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 Laabda 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 rep. t sent;d 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 cf this asterism, and of the probability of its having ueen originally fabricated by the astronomical sons of Misraim. In some few zodiacs, Astrtc-i, or the virgin who holrls the balance in her hand as an emblem of equal justice, is not drawn. Such are the /.od'acs of Esne and Dendera. Humboldt is of opinion, that although the Romans introduced 'his constellation into their zodiac in the reign of Julius Caesar, still it might have been used by the Egyptians and other nations of very remote antiquity. It is generally supposed that tjie 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 th^ 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 Nil-tnnt-ter, 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 infiitturinj Vte water* in ike hollow of kin kand.lsa.. xl. 12. The ancient husbandmen, according to Virgil, were wont to regard this sign as indi tating the proper time for sowing their winter grain : " But when Astrasa's balance, hung on high, Betwixt the nights and days divides the sky, Then j-oke your oxen, sow your winter grain, Till cold December conies 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 LIBRAE A wide DOUBLE STAR; R. A. 14h. 42m. 02s.; Dec. S. 15 22' 8". A 8, pal* yellow; B 6, light grey. Carry a line from Arcturus to Spica; and from thence a rect- angular one about 22 to the eastward. 2. fi LIBRAE A loose DOUBLE STAR; R, A. 15h. OSm. 24s.; Dec. S. 8 47' 4". A 2%, pah emerald ; B 12, light blue. 3. LIBRAE A fine TRIPLE STAR, between Libra and ihe right leg of Ophiuchus, 16 from Antares, towards Serpentis; R. A. 15h. 55m. 85s.; Dec. S. 10 55' 6". A 4j, origin white ; B 5, pale yellow; 714, grey. Map VIII., Fig. 11. 4. A CLOSE CLUSTER, over the beam of the Scales ; R. A. 15h. 10m. 26s. ; Dec N.241'JJ\ A superb object, with a bright central blaze, and outlines in al? directions. Map IX , Fig. 51. Appears nebulous through small instruments. 5. A LARGE COMPRESSED CLUSTER of minute stars ; R. A. 15h. OSm. 06s. ; Dec. S. 20' 556' 1 faint and. pale. HISTORY. Who was Virgo, Ac. ? Rei lark of Maurice? What genera* supposition What other explanations ? CJOJSOOMC OBJECTS. Alpha? Beta? What triple star? Map? Clustet 9 and Map I ERPENS 93 SERPENS (THE SERPENT). 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 ?ocond is Hydras, 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 Scrpens 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 come to that constel- lation. "The Serpens Ophiuchi 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 hidea." 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 below those in the bead, 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 2J, and the upper one, marked Delia, about 5 from it. The direction of this line is N. N. W. and S. S. E 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 Scalea, nbost ft dozen stars may be counted, of which five or six are conspicuous. For the remainder of this constellation, the student is referred to Serpentariua "Vast as the starry Serpent, that on high Tracks the clear ether, and divides tlie sky, And southward winding from the Northern Wain. Shoots to remoter spheres its glittering train." Statiuc. HISTORY. The Hivites, of the Old Testament, were worshipers of the Serpent, and were called Vphiles. The idolatry of these Ophites was extremely ancient, and was connected with 188. How many serpents among the constellations? Describe each. Which her* referred to? Is it fully described ? 1S4 What stars mark the body and head ? 185. Name the principal star. Where situated and how known ? iliSTORT What said of the Hivites? Tradition respecting Ophiuchus? Supposed 8 aripture reference ? 94 ASTRONOMY. Sabeism, or the worship of t>>e host of heaven. The heresy of the Optntes, mentioned by Mosheim, in his Ecclesiastical H 'story, originated, perhaps, in the admission into thl Christian church of some remnant of the ancient and popular sect of Sabeists, who adored the celestial Serpent. According tc ancient tradition, Ophiuchus is the celebrated physiriian^sculapius, 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 qritics imagine that this constellation is alluded to in the following passage of the book of Job : " By his spirit He hath garnished the Heavens ; his hand hath formed the crooked eer- pent." Mr. Green supposes, however, that the inspired writer here refers to Drsco because it is a more obvious constellation, being nearer the pole where the constellation, 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 SERPKNTIS (Unuk) A star with a minute companion on the heart of the Serpent; R. A. 15h. 36m. 23s. ; Dec. N. 6 55' 9'. A 2^, pale yellow ; B 15, fine blue. An extremely delicate object. 2. /? SERPENTIS A delicate DOUBLE STAR in the Serpent's under jaw ; R. A. 15h. 88m. 48s. ; Dec. N. 15 55' 7'. A 8%, and B 10, both pale blue. 3. (5 SBBPENTIS An elegant DOUBLE STAR in the bend of the neck ; R. A. 15h. 27m. 10a. ; Dec. N. 11 04' 7". A 8, bright white ; B 5, bluish white. A fine object, about 5" N. W. of Unak. 4. 7) SERPENTIS A star with a minute companion iu the Serpent's body, nearly midway between 7? Ophiuchi and a Aquilze; R. A. 18h. 18m. 02s. ; Dec. S. 2 56' 0. A 4, golden yellow; B 13, pale lilac. A delicate and difficult object. 5. v SEKPENTIS A wide DOUBLE STAR in the middle of the Serpent, 4" northeast of rj ; R. A. 17h. Urn. 49s.; Dec. S. 12 40' 7"- A 4}$, pale sea-green; B 9, lilac, with a third star in the field. 6. A delicate DOUBLE STAR R. A. 15h. llm. 08s. ; Dec. N. 2 22' 6'. A 5 )<&, pale yell-ow light grey. Look 9"* southwest of a Serpentis, 24 southeast of Arcturus. CORONA BOREALIS (THE NORTHERN OEOWN). 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 Bootea 3n the west, and Hercules on the east. This asterism was known to the Hebrews by the name of Ataroth, and by this name 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. Alphacca, Arcturus, aul Seginus, form nearly an isosceles triangle, the vertex of which is at Arcturus. TKI.IMCOPIC OBJECTS. Alpha? Beta? Delta? Eta? Nu? Ac. 186. How inay Corona Borealis be known? Where situated? Its Hebrew nanrcj 87. Describe AJphacca? How distinguished ? What triangle " CORONA B'JREALIS. 95 188. This constellation contains twenty-one stars, of which :mly six or eight are conspicuous ; and most of these are not larger thar the 3d magnitude. Its mean declination is SO 1 " north, and its mean right ascension 235; its center is therefore i 7 , the meridian about the last of June, and the first of July. "And, near to ffel^e, 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. Thla 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. Theseua, king of Athens (1236 B. C.), 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 trie 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, he 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* Astronomicon, 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 CCRON^E BOREALIS (Alphacco) A bright star with a distant companion; R. A Iftb ?7m. 54s. ; Dec. N. 27 15 2". A 2, brilliant white ; B 8, pale violet. 2 >' CORONA BOREALIS A most difficult BINARY STAR, 2% from Alphacca; R. A. 15h. 3.MU Ols. ; Dec. N. 26 48' 4"; with a distant companion. A 6, flushed white; B, uncer- tain; C 10, pale lilac. 8. C CORONJE BOREALIS A fine DOUBLE STAR, 10 north and a little easterly froui Alphacca; R. A 15h. 33ni. 21s. ; Dec. N. 37' 09' 6". A 5, bluish white; B 6, smalt blue A beauti- ul iji-et. 4 H CORON.* BOREALIS A BINARY STAR, midway between the Northern Crown and the . JL :f Bootes ; R. A. 15h. 16m. 36s. ; Dec. N. 30 52' 2'. A north-northwest ray from Q J route, through 13, and half as far again, will hit it. A 6, white; B G>$, golden yelSow, 138. How many stars in this constellation? Their magnitudes? Meaii declinattol bod right ascension ? HISTOHY. Story respecting Theseus and Ariadne? TELESCOPIC OEJKOTS. Alpha? Gamma? Zeta? Eta? 96 ASTRONOMY. Sir John Herschel considered this the most remarkable binary star known, and the ealj ne that had completed a whole revolution since its disco veiy. Estimated period J$S years URSA MINOR (THE LKSSEH BEAR). MAP VI. 189. This constellation, though not remarkable in its appear StaC'3, and containing but few conspicuous stars, is, nevertheless, jus'ly 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 polo, appear to revolve about it, very slovvly. and in circles so small as never to descend below the horizon. Hence Ursa Minor wil 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. 190. In all ages of the world, this constellation has been more universally observed, and more carefully noticed than any other, or 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 Cynosyrt ; by the Romans, Cynosura, and by other nations, Alruccabah. In most modern treatises it bears the name of Po- laris, or Alpha Polaris. 191 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- peise, which lies at the distance of 32 011 one side, and Megrez, which lies at the same distance on the other, will pass through the polar star. Of the Pole Star Capt. Smyth observes : At present it is only 1 83' from the polar point, ind by its northerly precession in declination will gradually approach to within 26' 30* 3f it. This proximity to the actual pole will occur in A. D. 2095, but will not recur foi 12,860 years. The period of the revolution of the celestial equinoctial pole about the pole cf the ecliptic, is nearly 26,000 years ; the north celestial pole, therefore, will be *bout 13,000 years ; hence, nearly 49' from the present polar star. 180. Frr what is Ursa Minor distinguish' d ? What *aid of its situation and change 01 os'tionV 190. What said of the notice taken of it? Position of its princ'pal star! l.tfi Greek and Latin names, Ac.? 191 Describe Polafis? How found? tteraar'w o 4 Capt. Smyth respecting f CltSA MINOR 9? 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 ol 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 on-;.e when below the pole. 193. Ileuce, it is evident that the surveyor who regulates his jompass 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 below 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 on -oite ;he 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 now travel one degree toward the north, he would see one degree below the star, and hi would think it had risen one degree. And since we always see the whole of the upper hemisphere at one view, when there it. 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 nru ner, 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 tte t'juator is ahcays 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, 192. What popular error? 198. When is the pole star a safe guide for the surveyoi cr mariner? What allowances should be made by each? 194. What said of finding Oe latitude by observations upon the pole star? What general rule stated P Wl*a' rrrn* ommitted ? ASTRONOMV. and as adopted by teachers generally, is to tell the scholar that the mrth pole nsnj aigher and higher, as he travels farther and farther toward it. In other words, what- ever number of degrees he advances toward the north pole, so many degrees will ;t risa ftbore his horizon. This is not only an jobvious error in principle, but it misleads the a;prebension of the pupil. It is not that the pole is el&cated, but that our liorizon. it deprewed as we advance toward the north. The same objection lies against the artifi- cial globe ; for it ought to be so fixed that the horizon might be raised or depressed, and ire po'.s remain in its own invariable position. 195. Ursa Minor contains twenty-four stars, including three f the 3d magnitude and four of the 4th. The seven principal stars are so situated as to form a figure very much resembling that in 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 to 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 8 from Kochab. The two brighest of these are situated in the breast and shoulder of the animal, about 8 apart, and are called the Guards or Pointei s 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 la clear. 197. 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 Cyiwswre; by us, the POLAR STAR." HISTORY. Its prevailing opinion is that Ursa Major and Ursa Minor are the nymph Calisto au-i her sea Areas, and that they were transformed into bears by the enraged and imperi ui funo, and afterward translated to heaven by the favor of Jupiter, lest they migb'. ft .destroyed by the huntsmen. The Ohinese claim that the emperor Hong-ti, the grandson of Noah, first discovered 195. Numbar of stars in Ursa Minor ? Their magnitudes? How situated ? 196. De- cribe Polaris, Kochab, and the Guards or Pointers? 197. Are all the sturs distinctly risible ? Direction ? What triangle ? HISTORY. What prevailing opinion, or myth? Chinae c'aira ? Phenicians? Greeks URSA MINOR. 99 the polar star, and applied it to purposes of navigation. It is certain that it was used for this purpose in a very remote period of antiquity. From various passages in iha ancients, it is manifest that the Phenieians steered l>y Cynosura, or the Lessor Bear; Thereas, the mariners of Greece, and some other nations, steered by the Greater I) jar, called Helice, or Helix. Lncan, Latin poet, who flourished ahout the time of the birth of our Savicar. Iks? B'lveits 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." ROWK'S Translation, B. HI. The following extracts from other poets contain allusions to the san.e fact: " Phenicia, spurning Asia's bounding strand, By the bright Pole star's steady radiance led, Bade to the winds her daring sails expand, And fearless plough'd old Ocean's stormy bed." MAURICE'S Elegy on Sir W. "Ye radiant signs, who, from the ethereal plain 8i>y a dragon. '2. And finally, he brought up to the earth the three-headed dog Cerberus, th? guar- iiau of the entrance to the infernal regions. Acconling-to Dupuis, the twelve labors of Hercules are only a figurative representation )f the annual course of the sun through the twelve signs of the Zodiac ; Hercules being put for the sun, inasmuch as it is the powerful planet which animates and imparts fecundity to the universe, and whose divinity has been honored, in every quarter, by temples and altars, and consecrated in the religious strains of all nations. Thus Virgil, in the eighth book of his JSneid, records the deeds of Hercules, and He.- brates his praise : "The lay records the labors, and the praise, And all the immortal acts of Hercules. First, how the mighty babe, when swath'd in bands, The serpents strangled with his infant hands; Then, as in years and matchless force he grew, The (Echalian walls and Trojan^ver threw, Besides a thousand hazards they relate, Procured by Juno's and Eurystheus' hate. Thy hands, unconquer'd hero, could subdue The cloud-born Centaur, and the monster crewt Nor thy resistless arm the bull withstood ; Nor he, the roaring terror of the wood. The triple porter of the Stygian seat With lolling tongue lay fawning at thy feel, And, seized with fear, forgot the mangled meat. The infernal waters trembled at thy sight: Thee, god, no face of danger could affright; Nor huge Typhaeus, nor the unnumber'd snake, Increased with hissing heads, in Lerna's lake." Besides these arduous labors which the jealousy of Eurystheus in jsvieed upon him, n> also achieved others of his own accord, equally celebrated. Before he delivered hirnsell up to the king of Mycenae he accompanied the Argonauts to Colchis. He assisted the gods in their wars against the giants, and it was through him alone that Jupiter obtained the victory. He conquered Laomedon and pillaged Troy. At three different times he experienced fits of insanity. In the second, he slew the brother of his beloved lole; in the third he attempted to carry away the sacred tripod from Apollo's temple at Delphi, for which the oracle told him he mu3t be soki as a slave. He was sold accordingly to Omphale, queen of Lydia, who restored him to liberty, and married him. After this he returned to Peloponnesus, and re-established on the throne of Sparta his friend Tyndarus, who had been expelled by Hippocoon. He became enamored of Dejanira, whom, after having overcome all his rivals, he married ; but wa? obliged to leave his father-in-law's kingdom, because he had inadvertently killed a man ! th a blow of his fist. He retired to the court of Ceyx, king of Trachina, and in his way was stopped by the streams of the Evenug, where he slew the Centaur Nessus, for presuming to offer indignity to his beloved Dejanira. The Centaur, on expiring, gave to Dejanira the celebrated tunic which afterward caused the death of Hercules. "This tunic," said the expiring monster, " has the virtue to recall a husband from unlawful l-vre." Dejanira, fearing lest Hercules should relapse again into love for the beautiful lole, gave him the fatal tunic, which was so infected with the poison of the Lcrnseaa exploits ? Origin and character of the twelve labors ? What are these labors supposed to represent? What quotation from Virgil ? Story of the death of Herculeaf Ovid" 106 ASTRONOMY. Hydra, that he had no sooner i: vested himself with it, than it began tr penetrate hit bones, and to boil througn all his veins. He attempted to pull it off, but it waa too Uta " As the red iron hisses in the flood, So boils the venom in his curdling blood. Now with the greedy flame his entrails glow, And livid sweats down all his body flo'* The crackling nerves, burnt up, are burst in twain, The lurking venom melts his swimming brain." As the distemper was incurable, he implored the protection of Jupiter, gave hia bow and arrows to Philoctetes, and erected a large burning pile on the top of Mount Q5ta. He spread o^ ine pile the skin of the Nemaean lion, and laid himself down upon it, as on x ">ed, leaning his head upon his club. Philoctetes set fire to the pile, and the hero saw tinsel, on a sndden, surrounded by the most appalling flames; yet he did not betray iny marks of fear or astonishment. Jupiter saw him from heaven, and told the sur- rounding gods, who would have drenched the pile with tears, while they entreated tl >t he would raise to the skies the immortal part of a hero who had cleared the earth frtm BO many monsters and tyrants ; and thus the thunderer spake: '' Be all yoiir fears forborne : The (Etean fires do thou, great hero, scorn. Who vanquish'd all things shall subdue the flame That part alone of gross maternal frame Fire s'hall devour ; while what from me he drew Shall live immortal, and its force subdue : That, when he's dead, I'll raise to realms above , May all the powers the righteous act approve." Ovid's Met. lib. ix. Accordingly, after the mortal part of Hercules was consumed, as the ancient poeU gay, he was carried up to heaven in a chariot drawn by four horses. 41 Quern pater omnipotens inter cava nubila raptum, Quadrijugo curru radiantibus intulit astris." " Almighty Jove Ir. his swift car his honor'd offspring drove; High o'er the hollow clouds the coursers fly, And lodge the hero in the starry sky." Ovid's Met. lib. ix. v. 271. TELESCOPIC OBJECTS. 1. a HERCULIS (Rec. N. 46 47' 0". About 4 east by north from T. It is large, round, and of a Iuel4 pa.e blue hue. A 6th magnitude star near it somewhat eclipses its brightness SERPENTARIUS. VEL OPHIUOHUS (TUB SERPENT BEARER).- MAP V. 206. THE SERPENT-B RARER is also called JEsculapius, or the e;od of medicine. He is represented as a man with a venerable beard, having both hands clenched in the folds of a prodigious serpent, which is writhing in his grasp. The constellation occupies a considerable space in the mid- heaven, directly south of Hercules, and west of Taurus Ponia- towski. Its center is very nearly over the equator, opposite to Orion, and comes to the meridian the 26th of July. It contains seventy-four stars, including one of the 2d magnitude, five of the 3d, and ten of the 4th. 207 The principal star in Serpentarius is called Has Alkagut. It is of the 2d magnitude, and situated in the head, about 5 E. S. E. of Ras Algethi, in the head of Hercules. Ras Alhague is nearly 13 N. of the equinoctial, while Rho, in the southern foot, is about 25 south of the equinoctial. These two stars serve to point out the extent of the constellation from north to south. Ras Alhague comes to the meridian on the 28th of July, about 21 minutes after Ras Algethi. About 10 S. W. of Ras Alhague are two small stars of the 4th magnitude, scarcely more than a degree apart. They distinguish the left or west shoulder. The northern one is marked Iota and the other Kappa. Elaven or twelve degrees S. S. E. of Ras Aihague are two other stars of the 8d magni- tude, in the east shoulder, and about 2* apart. The upper one is called Chtiel), and the lower one Gamma. These stars in the head and shoulders of Serpentarius, form a 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? Situatijn aaJ txtent? Number and size of its principal st;irs? 207. Name of its principal ?ta-f Magnitude and situation? Rho, and its situation? Use of these two slurs'? What sait' of Iota and Kappa? Of Chelcb and Gamma? 203. What remarkable cluster? F. 108 ASTRONOMY. lower star in the vertex of the Y. The lettor name of thm star is k. There is something remarkable in its central position. It is situated almost exactly fn the mid-heavens, being nearly equidistant from the poles, and midway between the ver- nal and autumnal equinoxes. It is, however, about one and a third degrees nearer th* sortli than the south pole, and about two degrees nearer the autumnai than the vera-J o^uinox, being about two degrees west of the solstitial colure. Directly south of the V, at the distance of about 12, are two very small stars, aboul \" apart, situated in the right hand, where it grasps the serpent. About half-way ix.t-.reen, and nearly in a line with, the two in the hand and the two in the shoulder, i; another star of the 3d magnitude, marked Zeta, situated in the So pent, opposite the right elbow. It may be known by means of a minute star just under it. Marsic, in the left arm, is a star of the 4th magnitude, about 10 S. W. of lola an ! Kappa. About 7* farther in the same direction are two stars of the 3d magnitude, situ- ited in the hand, and a little more than a degree apart. The upper one of the two, which is about 16 N. of G raffias 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 Serpentarius. The left arm of S jrpentariua 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. and 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 3 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 12* 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 3d 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 :r.ups. " 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 t<-n 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 Chm- tian era. Homer mentions it. It is thus referred to in the Astronomicon of Mauiiiua - " Next, Ophiuchus strides the mighty snake, Untwists his winding folds, and smooths his back, Extends his bulk, and o'er ti-.-. 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." 55aculapius was the son of Apollo, by Coronis, and was educated by Chiron the Ceu taur in the art of medicine, in which he became so skilful, that he was considered th Inventor and god of medicine. At the birth of JKsculapius, the inspire'! daughter at Chiron uttered, "in sounding verso " this prophetic strain. "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 stirs icnthofit? "What of Marsic? Of Yed and Epsilon ? How trace the left arm ? HISTORY. Antiquity of this constellation? Proof? Who was JEsculapius? Account of hi* great skill? Ilia metamorphosis i Remarkable fact respectin Socrates and I'lato* SERPENTAKJUS. 109 He accompanied (be Argonauts to Colchis, in the capacity of physician. Fie is said to Have restored many to ale, insomuch that Pluto complained to Jupiter, that his dark dominion was in danger of being depopulated by his art. jfisculapius was worshiped at Kpidaurus, a city of Peloponnesus, and hence he is styled by Milton " the god in Epidaurus." Being sent for to Home in the Unit of a plague, he assumed the form of a serpent and accompanied the ambassadors, but though thus changed, he was Jiscuiapius still, in serpente deux the deity in a serpent and under that form he continued to be worshiped at Rome. The cock and the serpeni were sacred to him, especially the latter. The ancient physicians used them in tneir prescriptions, Cue of the last acts of Socrates, who is accounted the wisest and best man of Pagan sntiqiu;;?, was to offer a cock to ^Esculapius. He and Plato were both idolaters; they "palnmed, and advised others to conform, to the religion of their country ; to gross Ic'iatry and absurd superstition. If the wisest and most learned were so blind, what sust the foolish and ignorant have been ? TELESCOPIC OBJECTS. I a OpHiucin ! Ras Alhague) A bright star with a minute companion, in Ine head ol the figure; K. A. :i\\. 27m. 30s.; Dec. N. 12 40' OS". A 2, sapphire; B 9, pale grey. A coarse triplet of snnll stars near them. 2. 6 OPKIUCIII (Yed) A star with a distant companion, in the right hand ; R. A. IGh. 05m. 58s. ; Dec. S. 3 16' v7*. A 3, deep yellow ; B 10, pale lilac ; a third minute star in the field. 3. i] OPHIDCHI A brilliant star with a distant companion, on the left knee ; on the margin of the milky way ; R..A. 17h. Olm. 13s. ; Dec N. 15 81' 03'. A 2fc, pale yellow ; B 13, blue. 4. T OPHIUCHI A close BINARY STAR on the teft hand, 15* northeast of the bright star V, just described, towards Altair ; R. A. 17h. 54m. 22s. ; Dec. S. S' 10' 04". A 5, and B 6. both pale white; 10, light blue; two other stars in the field. Out of place on the map, or R. A. wrong in the tables, as given above. 5. A TRIPLE or rather MULTIPLE STAR, between the left foot of Ophiuchus, and the root of die tail of Scorpio ; R. A. 17h. 05m. 29s. ; Dec. S. 26 e 21' 05'. It is about 10 due east of \ntares. A 4.^, ruddy; B 6%, pale yellow; C 7^, greyish. The latter is double, a minute companion appearing at a distance, though not seen through ordinary instruments For relative position, &c., see Map VIII., Fig. 14. 6. A fine GLOBULAR CLUSTKR, between the right hip and elbow ; R. A. 16h. 38m 56s. ; Dec. S. 1 40' 03*. A rich cluster, condensed towards the center, with many straggling outlayers. About 8' from c Ophiuchi, towards ft. 1. A RICH CLUSTER of compressed stars, in the right hip; R. A. 16ti. 48m. 45s. ; Dec. S. 3 51' 03". About 8 east of e Ophiuchi ; or half-way between fi Libras, and a Aquilas. A oeautiful round cluster, and may be seen with a telescope three feet in length, 8. AROUND CLUSTER on the left leg; R. A. ITh. 09m. 42s.; Dec. S. 18" 2t/' 07'. It lici about 3 southeast of , and rather more than % the distance on a line from Antares U: Altair. A fine object myriads of stars clustering to a blaze in the center. 9. A LARGE GLOBULAR CLUSTER in the left arm; R. A. 17h. 29m. 13s.; Deo. S 3* 09' 01'. It lies 1G south of Ras Alhague, or about half way from Soorpii to t Aquilae. 6V south- &y-west of y Ophiuchi. A fine object, of a lucid white, and may be seen with small instru- ments. Several stars in the field. Map IX., Fig. 55. OBJTCTS. Alpha? Delta? Eta? What multip' ? star? Point ou 3* <* What clusters ? T"?hich shown on ths map ? 110 ASTRONOMY. CHAPTER X. CONSTELLATIONS ON THE MERIDIAN IN ADGUtfT, DRACO (THE DRAGON).- -MAP VL 209. THIS constellation, which compasses a large circuit in ms polar regions by its ample folds and contortions, contains many stars which may be easily traced. From the head of the mon- ster, which is under the foot of Hercules, there i? a complete coil tending eastwardly, about 17 N, of Lyra ; thence he winds down northerly about 14 to the second coil, where he reaches almost to the girdle of Cepheus; thcu he loops down somewhat in the shape of the letter U, and makes a third coil about 15 below the first. From the third coil he holds a westerly course for about 13, then goes directly down, passing between the head of the Lesser and the tail of the Greater Bear. 210. Draco contains eighty stars, including two of the 2d magnitude, three of the 3d, and sixteen of the 4th. " The Dragon next, winds like a mighty stream : Within its ample folds are eighty stars, Four of the second order. Far lie waves His ample spires, involving either Scar." The head of the Dragon is readily distinguished by means of four stars, 3, 4, and 5 apart, so situated as to form an irregu- lar square ; the two upper ones being the brightest, and both of the 2d magnitude. The right-hand upper one, called Etanin, has been rendered very noted in modern astronomy from its connection with the discovery of a new law in physical science, called the Aberration of Light. The letter name of this star is Gamma, or Gamma Draconis ; and by this appellation \t is most frequently called. The other bright star, about 4 from it on the left, it Rastaben* 211. About 4 W. of Rastaben, a small star may, with close attention, be discerned in the nose of the Dragon, which, with the irregular square before mentioned, makes a figure somewhat resembling an Italic V, with the point toward the west, and the open part toward the east. The small star in the nose, is called Er Raids. 209 Describe Draco its situation and extent. 210. Number and size of its princi- pal stars? How may the head of Draco be distinguished? What said of Etanin? Its letter name? What of Rastaben? 211. Of Er Rakis ? Further of Rastaben? 01 ttanin? Of Chromium 1 OfOmicron? How may the second coil be recognised ? Wha/ :t 7-cta? Of Eta, Theta, and Asich ? Of Thuban, Kappa, and Giansar ? UK AGO. Ill The two small stars 5 r; 6 S. of Rastaben are in the left foot of Hercules. Rastaben is on the meridian nearly at the same moment with Ras Alhague. Etanir^ 40 N. of it, is on the meridian about the 4tn of August, at the same time with the thre western stars in the face of Taurus PoniatOTvakii, or the V. It is situated less than 2* west o ' the solstitial colure, and is jyaotly in the zenith of London. Its favorable position haa lei English astronomers to wuch its appearance, for long periods, with the most exact and unwearied scrutiny. Of the four stars forming the irregular square in the head, the lower and right-hand one % 53$ N. of Etanin. It is called Grwiiiiwm, and is of the 8d magnitude. A few degree* I, of the square, may be seen, with a little care, eight stars of the 5th magnitude, and onuild a city where he should see a heifer stop in the grass, and to call th* country Bceotia. He saw the heifer according to the oracle, and as he wished to rendei thanks to the god by a sacrifice, he sent his companions to fetch water from the neighbor- ing grove. The waters were sacred to Mars, and guarded by a most terrific dragon, who devoured all the messengers. Cadmus, tired of their seeming delay, went to the place, and saw the monster still feeding on their flesh. Cadmus, beholding such a scene, boldly resolved to avenge, or *o share their fate. Ho 'Jierefore attacked the monster with slings and arrows, and, with the assistance ti Minerva, slew him. He then plucked out his teeth, and sowed them, at the coirraami >1 Pallas, iu a plain, when they suddenly sprung up into armed men. Entertaining worse apprehension from the direful offspring than he .had done from lk Iragon himself, he was about to fly, when they fell upon each other, and were all slain in >ne promiscuous carnage, except five, who assisted Cadmus to build the city of Bceotia. TELESCOPIC OBJECTS. I. a DRACONIS (Thubari) A star with a distant companion in the fifth coil of Draco ; R A. 14h. 00m. 03s. ; Dec. N. 65" 08' 04". A 83i, pule yellow ; B 8, dusky ; two other stars in '1 e field. Upwards of 4,6tJO years ago, this was the pole-star of the Chaldeans. 3. DRACONIS (Rcusbiben) A star with a very distant companion, in the eye of Draco; R. A. ITh. 26m. 48s. ; Dec. N. 52 25' 02". A 2, yellow ; B 10, bluish ; other stars in field. 3. }' DRACONIS (Etanin) A star with a telescopic companion, in the crown of Draco; R. A. 17h. 52m. 53s. ; Dec. N. 51 30' 06". A 2, orange tint; B 12, pale lilac. A third star in the field making a neat triangle with A and B. Etanin is celebrated as the star by viewing which, Bradly discovered the aberration of light in 1725. It is a zenith-star at the Greenwich observatory. 4. 6 DRACONIS A bright star with a distant companion, in the second flexure ; R. A. 19h. 12m. 30s. ; Dec. N. 67" 22' 08". A 3, deep yellow ; B 9^, pale red ; other small stars in the field. 5. e DRACONIS A fine double star between the second and third flexures; R. A. 19h. 48m. 41s. ; Dec. N. 69 51' 6". A 5J$, light yellow; B S, blue ; a third star just nortb if a. 6. r) DRACONIS A star with a companion, between the third and fourth flexures; R. A 16h. 21rn. 48s. ; Dec. N. 61 52' 04". A 3, deep yellow ; B 11, pale grey. 7. fj. DRACONIS A very neat BINARY SYSTEM, on the tip of the Dragon's tongue ; R. A 17h. 02m. 02s.; Dec. N. 54 41' 02". A 4, and B 4}, both white. Resembles Castor, though the components are nearer equal. Period, about 600 years. 8. A TRIPLE STAR in the first flexure; R. A. ISh. 21m. 36s.; Dec. N. 58 42' 05". A 5, pale white; B 8)6, light blue; C 7, ruddy. A difficult object about midway between y and <$. 9. A beautiful TRIPLE STAR in the nose of Draco, on a line from y over ft, and near twice as much further ; R. A. 16h. 32m. 28s. ; Dec. N. 53 14' 09*. A 6, pale yellow ; B 6%, 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 23' 0". Faint at the edges, with four stars in the field ; one quite near it. II. A PLANETARY NEBULA, between the second and third coil, on a line from Polaris to y Draconis: R. A. ITh. 58m. 38s.; Dec. 66 88' 01". A remarkably bright and pale blue Dlyect, with several telescopic stars in the field. Map IX., Fig. 56. It ia situated exactly to, the 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 TKLKSCOPIO OBJECTS. Alpha ? Beta? Gamma? Delta? Epsilon? Eta? Iful Trii/le stars ? Nebulae ? 218. How is Lyra distinguished? Where lituated? Number and site -tf iits pra&t .tol stars ? LYRA. Hi L-iist, and Hercules on the west ; and when on the meridian, \x 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 Dura, for the- brightness of her stars, More than their number, eminent ; thrice seven She counts, and one of these illuminates The heavens far around, blazing imperial In the ./?/'*< order." 214 This star " blazing imperial in the first order" is called rvo-tf, and sometimes Wega ; but more frequently, Lyra, after the name of the constellation. There is no possibility of mistaking this star for any other, [t is situated 14| S. E. of Eltauin, arid about 30 N. N. E. of Ras Alhague and Ras Algethi. It may be certainly known bv means of two small, yet conspicuous stars, of the 5th magnitude, situated about 2 apart, on the east of it, and 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 Zetti. About 2 S. E. of Zeta, and in a line with Lyra, is a star of the 4th magnitude, marked Delta, in the middle of the Harp; and 4 or 5 S. of Delta, are two stars of the 3d magnitude, about 2 apart, in the garland of the Harp, forming another triangle, whose vertex is in Delta. The star on the east is marked Gamma ; that on the west, Btta, If a line be drawn from Etanin through Lyra, and produced 6 farther, it will reach Beta. This is a variable star, changing from the 3d to nearly the 5th magnitude in the spacj of a week ; it is supposed to have spots on its surface, and to turn on its axis, liko our sun. Gamma, comes to the meridian 21 minutes after Lyra, and precisely at the same moment with Epsiion, in the tail of the Eagle, 17V S. of it. The remarkable brightness of a Lyra has attracted the admi- ration of astronomers in all ages. Manilius, who wrote in the age of Augustus, thus alludes to it : vbore looking behind till he had come to the extremest borders of their dark cominjr na 214. Names o f the most brilliant star? How certainly known? Where are leta, Delta, Gamma, and Beta? What peculiarity about B-U ? In a Lyr f 114 ASTRONOMY. The cond'.tion was accepted, and Orpheus was already in eight of the uppei eglous ol he air, when he forgot, and turned back to look At his lonj.-lost Eurydice. He saw her Out she instantly vanished from his sight. He attempted again to follow her, but wai refused admission. From this time, Orpheus separated himself from the society of mankind, which M offended the Thracian women, it is said, that they tore his body to pieces, and threw hih head into the Hebrus, still articulating the words Eurydice ! Eurydice ! as it was carried down the stream into the ^igean sea. Orpheus was one of the Argonauts, of which cele- brated expedition he wrote a poetical account, which is still extant. After his death, he received divine honors, and his lyre became one of the constellations. This fable, or allegory, designed merely to represent the power of music in the hand.- >f the great roaster of the science, is similarly described by three cf the most renowned Lath i>oets. Vl"gil, in the fourth book of his Georgics, thus describes the etfect of tl /r* >- " E'en to the dark dominions of the night He took his way, through forests void of lipht, And dared amid the trembling ghosts to sing, And stood before the inexorable king. The infernal troops like passing shadows glide, And listening, crowd the sweet musician's side ; Men, matrons, children, and the unmarried maid, The mighty hero's more majestic shade, And youth, on funeral piles before their parents laid. E'en from the depths of hell the dauui'd advance ; The infernal mansions, nodding, seem to dance ; The gaping three-mouth'd dog forgets to snan ; The furies hearken, and their snakes uncurl ; Ixion seems no more his pain to feel, But leans attentive on his standing wheel. All dangers past, at length the lovely bride In safety goes, with her melodious guide." Pythagoras and his followers represent Apollo playing upon a harp of seven strings, l*y which is meant (as appears from Pliny, b. ii. c. 2'2, Macrobius i. c. 1U, and Censoriiis c. ii.), the sun in conjunction with the seven planets ; for they made him the leader of that septenary chorus, and the moderator of nature, and thought that by his attractive force lie acted upon the planets in the harrncnical ratio of their distances. The doctrine of celestial harmony, bj which was. meant the music of the spheres, was common to all the nations of the East To this divine music Euripides beautifully alludes : "Thee 1 invoke, thou self-created Being, who gave birth to Nature, and whom light and darkness, and the whole train of globes encircle with eternal music. 1 ' So a.s<- fc'iakspeare : " Look, how the floor of heaven . Is thick inlaid, with patiues of bright gold ; There's not the smallest orb which thou behold'st, But in his motion like an angel sings, Still quiring to the young-eyed cherubim : Such harmony is in immortal souls ; But, while this muddy vesture of decay Doth grossly close it in, we cannot hear it." The lyre was a famous stringed instrument, much used among the ancients, said to have been invented by Mercury about the year of the world 2,000 ; though some ascribe the invention to Jubal. (Genesis iv. 21.) It is universally allowed, that the lyre was the first instrument of the string kind ever used in Greece. The diiferent lyres," at various periods of time, had from four to eighteen strings each. The modern lyre is the Welsh harp. The lyre, among painters, is an attribute of Apollo and the Muses. All poetry, it has been conjectured, was in its orjgin lyric; that i', adapted to recita 'if n or song, with the accompaniment of music, and distinguished by the utmost boldness of thought and expression ; being at first employed in celebrating the praises of gods and heroes. Lesbos was the principal seat of the Lyric Muse; and Terpander, a native of this inland, who flourished about 660 years B. 0., is one of the earliest of the Lyric poets hose nam we find on record. Sappho, whose misfortunes have united with hir taleuta \*. *6nder he. name memorable, was born at Mitylene, the chief city of Lesbos. She was HISTORY. Story of Orpheus and Eurydice ? Design ct this myth ? Celebrated U/ whjtf poets ? Origin of the Lyre, and c.' Lyre poetry ? AVhat said if IMndar? r A *^ TAURUS PON reckoned a tenth muse, and placed without controversy at the head of the female writer? in Greece. But Findar, a native of Thebes, who flourished about 500 years B. 0,, It styled the prince of lyric poets. To him his fellow-citizens erected a mor.ameiit ; and ?hec the Lacedemonians ravaged Boeotia, and burnt- the capital, the following words $, fain) vellow ; D 9, light lilac. /3 is regarded as variable. 3. y LYR>K A lustrous star 7 southeast of Vega, with a minute distant companion R. A. ISh. 52m. 57s,; Dec. N. 82 28' 05". A 3, bright yellow; B 11, blue; other tele- scopic stars in the field. 4. e LYR.E A splendid MULTIPLE STAR, only 1J^ northeast of Vega; R. A. ISh. 8Pm. 02s. ; Dec. N. 39 30' 03". Map VIII., Fig. 16. With small instruments it appears simply double ; but with better instruments each of the components are found to be double, and binary systems. Between the twin systems are three minute stars. The components of the two systems are described as A 5, yellow; B 6%, ruddy; C 5, and D 5}, both white. A, B r.re the lowest, or northern pair. These two twin systems are in motion around a common center of gravity, as well as the respective components around each other. The period of the individual systems is estimated at about 2,OUO years; while 1,000,000 of years are supposed to be requisite for a revolution round the common center of both ! 5. C LYR.*:- -A fine DOUBLE STAR about 2 south of e ; R. A. ISh. 39m. 15s. ; Dec. N. 37' 26' 05". A 5, topaz ; B 5^, greenish. 6. 77 LYR. A neat DOUBLE STAR 6 east of Vega; R. A. 19h. OSin ISs. ; Dec. N. 88 52 05". A 5, sky blue ; B 9, violet tint. A fine object for a moderate telescope. 7. v LYRA: A QUADRUPLE STAR in the cross-piece of the Lyre ; R. A. ISh. 43m. 48s. ; Dec. N. 32 3S 0". A 9, pale yellow; B 13, bluish; C 11, pale blue; D 15, blue; three other stars 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 ; R. A. 19h. lOrn. 19s. ; Dec. N. 29 54' 02\ About 5V southeast of Lyra}, towards ft Cygni, and 3% from the latter. Map IX., Fig. 57. 9. An ANNULAR NEBDLA between ,3 and y\ R. A. ISh. 47m. 37s.; Dec. N. 82* 50' 01". A wonderful object, in the form cf an elliptical ring. Supposed by Herschel to b 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 Ophiu- 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 pcntarius, article 206. TKLBbOOPic OBJECTS. Alpha ? Beta? Gamma? Epsilon? Point tint on the map Zeta? Eta? Nu? What cluster? Point out on the mip. What aebula. and whew ound on the map ? 16. Describe Taurus Poniatowskii. Where situated? 116 ASTRONOMY. TELESCOPIC OBJECTS. 1. A aeat .JOUBLE STAR in the space between the Polish Btll, and the Eagle's wing, 8 east of a Ophiuchi, in a line towards Altair ; R. A . 17h. 08m. 17s. ; Dec. N. 11 L9 08* A 8, straw-color; B 8Jg, sapphire blue. 2. A fine PLANETARY NEBULA, in a rich vicinity, in the shoulder; R. A. ISh, 04m. 2!s. Dec. N. 6* 49' 02". A small but bright object, regarded by Prof. Struve as one of the mop carious in the heavens. Many telescopic stars in the field. SCUTUM SOBIESKI (SOBIESKI'S SHIELD). MAP V. 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 DOITBLB STAR IV northeast of fj. Sagittarii ; R. A. ISh. 07m. 87s.; Dec. S. 19" 55' 05'. A SJ$, and BIO, both grey. 2. A neat DOUBLE STAR, in a long and straggling assemblage below the Shield ; R. \, 18h. 10m. 36s. ; Dec. S. 17 1V 07". A 9, and B 1 1. both bluish. It is 4 from // Sagittarii, in a very rich vicinity ; several splendid fields lying only about 1" south of it'. 8. A BEAUTIFUL CLUSTER below the base of the Shield; R. A. ISh. OSm. 49s.; Dec. S. IS' 27' 05". A line from a Aquilae, southwest over "k Antinoi, and continued as far again, will reach this object. 4. A SCATTERED BUT LARGE CLUSTER, north-half-east from IJL Sagittarii 7; R. A. ISh. 09ra. 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-SHOE NEBULA just below the Shield ; R. A. ISh. 1 1m. 28s. ; Dec. S. 16 .15' OS". It lias been compared to a Greek 2. 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 255,000 stars in a space 10 long, and 2V wide; many of which were 2,300 times as far off as Sirius ! SAGITTARIUS (THE ARCHER). MAP V. 217. This is the ninth sign and the tenth constellation of th< 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 cons' d* 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. TKLESCOPIC OBJECTS. What double star ? What nebula ? 21(J. 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 &nd constellation?? When does tho son pate i.iis #v f The tovustf-Uation J Its extent? Namter and size of its nan? SAGITTARIUS. 117 218. 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 Mi Iky- Way. This little figure is so conspicuous that it cannot easily be mistaken. It is situated about 33 E. of Antares, and comes .0 tlrj 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 4>6, and th tMSternmost one in the bowl of the Dipper, are all of the 4th magnitude. The star in the end of the handle, is marked Ldmbdn, and is placed in the how 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 riii 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 In 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 pro '.need about farther to the west, : .t will point out Delta, and produced about 3' from Del'.a, it will point out Gninmn ; stars )f the 3d magnitude, in the a: row. 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 same meridian with Etanin, in the head of Draco, that it culminates 01113- two minutes after it. A few other conspicuous stars in this constellation, forming a variety of geometiical figures, may be easily traced from the map. HISTORY. This constellation, it is said, commemorates the famous Centaur Chiron, son of Philyra and Saturn, who changed himself into a horse, to elude the jealous inquiries of his wife Rhea. Chiron 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 ^Esculapius physic, Apollo music, and Her cules astronomy ; and was tutor to Achilles, Jason, and ^Eneas. According to Ovid, he was slain by Hercules, at the river Evenus, for offering indignity to his newly inarrieJ bride. " Thou monster double shap'd, my right set free- Swift as his words, the fatal arrow flew; 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 tha Lernaean Hydra, rendered the wound incurable, even by the father of raedicinf himself, and he beg^s d Jupiter to deprive him of immortality, if thus he might escape bis excruciating pain3. Jupiter granted his request, and translated him to a plrtC* among the constellations. u Midst golden stars he stands refulgent now, And thrusts the Scorpion with his bended bow." This is the Grecian account of Sagittarius; but as this constellation appears on th odiacs of Egypt, Dendera, Esne, and India, it seems conclusive that the Greek* 318. How distinguished? Where is Lambda? How known? Where are Mu, Delta, rid Gamma ? HISTORY. What does Sagittarius commemorate ? Story of Chiron ? "What naij \>f !* antiquity of this constellation 118 ASTUONOMl. only borrowed the figure, while they invented the j tble. This is known to be trre witt respect to very many of the ancient constellations. Hence the jargoc of the coufiiclinv accounts which have descended to us. TELESCOPIC OBJECTS. 1. fJ. SAGITTARII A MCLTIPLE STAR in the north end of the Archer's bow; R. A. ISh. aim. 11s. ; Dec. S. 21" 05' 07" About 25* east-northeast of Antares. A 8^, pale yellow; U 16, blue ; C 933, and D 10, both reddish. 2. a SAGITTAKII A star with a distant companion in the Archer's right shoulder; R. A. ISh. 45m. 20s. ; Dec. S. 26 29' 03'. A 3, ruddy ; B 9 J$, ash-colored. 8 A very delicate TRIPLE STAR, between the heads of Sagittarius and Capricorn, about 85 3 south-by-west of Altair, and 10 west of >3 Capricorni; R. A. 19h. 31m. 83s.; Dec. S 16 39' 02". A 5}$, yellow ; 13 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; It. A. ISh. 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. ISh. 22m. 14s. ; Dec. S. 19 10' 02". The most prominent are a pair of 8th magni- tude stars. It is about 5" northeast of fj. Sagittarii. 6. A FINE GLOBULAR CLUSTER between the head and bow, near the solsticial colure; R. A. ISh. 26m. 26s. ; Dec. S. 24 01' 04". A fine group, compressed towards the center, with several single stars in the field. Map IX., Fig. 60. CORONA AUSTRALIS (THE SOUTHERN CROWN). MAP V. 219. This is a small and unimportant constellation near tbo 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 ANTINOUS (THE EAGLE AND ANTINOTJS). 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 stars, 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 TELESCOPIC OBJECTS. Mu? Sigma? What triple star? What clusters? Which thown on the map? Point it out. 219.- Describe Corona Australia. Its principal stars ? History and Telescopic Objects! <20. Situation of Aquila and Antinous? Number and siae of its principal stars* 221 Altair how known ? Stars each side of it? Use of Altair in navigation? What 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 art 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 )f 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 ia nearly 8-J- 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 be in- ning of June. Ovid alludes to the rising of this constellation ; or, more probably, to that of the piin- o. pal star, Altair : " Now view the skies, f 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." Eudofda. 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 down 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 Delta, 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 and 6 apart, extending southerly, but curving a little to the west, which mark the youth Antinous. The northern wing of the Eagle is not distinguished by any conspicuous stars. Zeta and Epsilon, 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 tracel 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. Kia is remarkable for its changeable appearance. Its greatest brightness continue! out 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 Btaf of the 8d magnitude. From these phenomena, it is inferred that it not only has spots on its surface, Ifke om run, but that it also turns on its axis. Similar phenomena are observable in Algol, Beta, in the Hare, Delta, ia Cepaecd, &nd in the Whale, and many others. Aquila the next, Divides the ether with her ardent wing: Beneath the Sican nor far from POETIC EAGLK." poetic quotation ? Where are Tarazed and Delta ? Zeta and Epsilon f Theta ? Kta Far wh'U remr.rkable ? 120 ASTRONOMY, HISTORY. Aquikt, or tht Eagle, is a constellation usually joined with Antinous. Aquila in 3Uf posed to have been Merops, a king of the island of Cos, in the Archipelago, and the hut- hand of Clymene, the mother of IMiaHon ; this monarch having been transformed inU> an eagle, and placed among the constellations. Some have imagined that Aquila was th eagle whose form Jupiter assumed when he carried away Ganymede; others, that it -{presents the eagle which brought nectar to Jupiter while he lay concealed in the cave a' } ett, to avoid the fury of his father, Saturn. Some of the ancient poets say, that thic t l l-.e eagle which furnished Jupiter with weapons in his 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 lie, a bird, supplies The heaven with sacred bolts, and arms one skies." Maniliu? IVIiat nt-Kul.i? SAGJTTA ANSER ET VULPECULA. l*2j it lies 10' due r.oith-of A Antinoi, a 3d magnitude slur, ami 13* west of ft A\\u\se. Tht brul .test; object of its immediate neighborhood. 7. A WIDE DOUBLE STAR about 4 west-by-south of A Antinoi, between the foot and Sobieski's Shield ; K. A. ISh. 4im. 07s. ; Dec. S. 6 05' 08'. A 7, orange tint; B 9, ceru van blue. Many telescopic stars in the field. S. A SPLENDID CLUSTER close to the southeast of the last described object R A. 1'JU *2m. 32s. ; Dec. S. 6 27' 02". It is between the left foot and Sobieski's Shield. A g<>r- geous object " somewhat resembling a (light of wild ducks in shape," has an Sth magni- tude star in the middle, and two larger east of it; probably all three between us and tha cluster. Map IX., Fig. 61. 9. A LOOSE CLUSTER between the lower wing and the leg of Antinous, and 13 southwest 5f Altair, on a line from Vega through e Aquilae ; R. A. 19h. 08m. 36s. ; Dec. S. 1 11' 09' A splashy group of stars from the 9th to the 12th magnitudes, on the easterti margin of the Galaxy. 10. A STELLAR NEBULA on the Eagle's back, about 5* west of Altair; R. A. 19h. 28m. 55s. ; Dec. N. 8* 54' Of. A minute object in the Milky- Way ; and in the most powerful telescopes, fan-shaped. SAG ITT A (THE AEROW.) MAP V. 222. SAGITTA is a small but old constellation between the Fox and Goose on the north, and the Eagle on the south. Its two principal stars are of the 4th magnitude, and lie nearly east and west, about 4 apart. The next two largest stars are of the 5th magnitude. TELESCOPIC OBJECTS. 1. SAGITT* A star with a distant companion about 8* north-northwest of Altair, ft- a line towards Vega; R. A. 19h. SOrn. 03s. ; Dec. N. 16 06' 5". A 6, pale white; B 8, light blue. 2. C SAGITT.S A neat DOUBLE STAR just above the Arrow, 9" south by east from /? Cygni, and 10" north of Altair; R. A. 19h. 41m. 53s.; Dec. N. 18 44' 8". A 5, silvery white ; B 9, blue. 3. & SAGITT* A TRIPLE STAR near the head of the Arrow, about half-way from ft Cygni to a Delphini ; R. A. 20h. 02m. 53s. ; Dec. N. 20 26' 6*. A 7, pale topaz ; B 9, grey C 8, pearly yellow. 4. A RICH COMPRESSED CLUSTER on the shaft of the arrow, 10 northeast of Altair R. A. 19h. 46m. 86s. ; Dec. N. 18 22' 1". Telescopic stars around it. ANSER ET VULPECULA (TUB FOX AND GOOSE). MAP 'v . 223. This is a modern constellation, situated between the Swan on the north, and the Arrow or the Dolphin and Eagle on the south. It is composed of some thirty stars, the largest of is of the 3d magnitude. TELESCOPIC OBJECTS. 1. A stir with a distant companion on the nose of Reynard, and neck of the ' south of ft Cygni ; R. A. 19h. 22m. 08s. ; Dec. N. 24' 20' ?'. 222. Describe Sagitta its principal stars. T&uttconc OBJECTS. Epsilon ? Zeta? What triple star? OlostorV MB. Dewrribe the Pox and Goo*;. Its component stars ? 122 ASTRONOMY. 2. A WIDK DOUBLE STAR, 11%" north of Altair, between the Fox &,nd the Arrow, in ttu sastern edge of the Galaxy; R. A. 19h. 46m. 20s. ; Dec. N. 19 55' 5'. A and B both 7 and both white. 3. A LARGE STRAGGLING CLUSTER on the neck of the Goose, and about S c from /^ Cygni; R. A I9h. 2()m. 80s. ; Dec. N. 24 49' 8". Two 7th magnitude stars in the west. The clustei Las the form of a Greek Q. 4. The celebrated DUMB-BELL NKBULA, on tt e Fox's breast, about 7* southeast of Cygni, and aearly half-way between it and the Dolphin; R. A. 19h. 52m. 39s. ; Dec. N. 22* 17' \' (Map IX., Fig. 62.) This magnificent and singular object is in a crowded vicinity, wh?.*t ftrtlri aft^r field is very rich. CHAPTER XL CONSTEM,ATIONS ON THE MERIDIAN IN SEPTEMBER DELPHINUS (THE DOLPHIN). MAP V. 224. THIS beautiful little cluster of stars is situated 13 U or 14 N. E. of the Eagle. It consists of eighteen stars, including four of the 3d magnitude, but none larger. It is easily distin- guished from all others, by means of the four principal stars in the head, which are so arranged as to form the figure of a dia- mond, pointing N. E. and S. W. To many, this cluster is known by the name of Job's Coffin; but from whom, or from what fancy, it first obtained this appellation, is not known. 225. There is another star of the 3d magnitude, situated in the body of the Dolphin, about 3 S. W. of the Diamond, and marked Epsilon. The other four are marked Alpha, Bai, Gamma, Delta. Between these are several smaller stars, tou small to be seen in presence of the moon. The mean declination of the Dolphin is about 15 N. It coniCvS to the meridian the same moment with Deneb Cygni, and fibout 50 minutes after Altair, on the 16th of September. ' Thee I behold, majestic Ci/gnus, On the marge dancing of the heavenly sea, Arion's friend ; eighteen thy stars appear One telescopic." 1*1 CnCO?:c OBJECTS. What double stars ? Cluster? Nebula? Point out on the map. 224. Constellations in this chapter? Delphinus? Number and size of stars? Hon J'itt.iguished ? What other name has this constellation? 225. Where are Epsilon 41pha, Beta, Gamma and Delta ? Mean declination, fcc. UBLI'IUNUS. 123 HISTORY. The DclpLiu, according to some mythologists, was made a constellation by Nepturu (wcause oae of these beautiful fishes hud persuaded the goddess Amphi trite, who had mad a vow of perpetual celibacy, to become the wife of that deity; but others maintain, that I is the dolphin which preserved the famous lyric poet and musician Arion, who was a sative of Lesbos, an island in the Archipelago. He went to Italy with Periandrr, tyrant of Corinth, where he obtained immense rlche* \>y his profession. Wishing tc revisit his native country, the sailors of the ship in whijh c-e embarked resolved to murder him, and get possession of nis wealth. Seeing them nuuovable in their resolution, Arion begged p rmission to play a tune upon his lute >efore lie should be put to death. The melody of the instrument attracted a number of lolphins around the ship; he immediately precipitated himself into the sea; when one jf them, it is asserted, carried him safe on his back to Ta^nurus, a promontory of Laco- nia, ia Peloponnesus ; when he hastened to the court of Periander, who ordered all the sailors to be crucified at their return. " But (past belief), a dolphin's arched back Preserved Arion from his destined wrack; Secure he sits, and with harmonious strains Requites his bearer for his friendly pains." When the famous poet Hesiod was murdered in Naupacturu, a city of JJtolia, in Greece, and his body thrown into the sea, some dolphins, it is said, brought back the floating corpse to the shore, which was immediately recognized by his friends; and the assassins being afterwards discovered by the dogs of the departed bard, were put to death by immersion in the same sea. Taras, said by some to have been the founder of Tarentum, now Taivnto, in the south of Italy, was saved from shipwreck by a dolphin ; and the inhabitants of that city pre- served the memory of this extraordinary event on their coin. The natural shape of the dolphin, however, is not incurvated, so that one might ride upon its back, as the poets imagined, but almost straight. When it is first taken from the water, it exhibits a variety of exquisitely beautiful but evanescent tints of color, that pass in succession over its body until it dies. They are an extremely swift-swimming 6sh, and are capable of living a long time out of water ; in fact, they seem to delight to gambol, and leap out of their native element. " Upon the swelling waves th dolphins show Their bending backs ; then swiftly darting go, And in a thousand wreaths their bodies show." TELESCOPIC OBJECTS. 1. a DELPHINI A bright star with a distant telescopic companion; R. A. 20h. 82m , 12s. ; Dec. N. 15* 21' or. A 8fc, pale white ; B 13, blue. 2. J3 DKLPHINI A delicate TKIPLK STAR on the Dolphin's body, 1 J$" south-by-west of <1, In a line with Cygni and y Lyraj; II. A. 20h. 30m. 08s.; Dec. N. 14 02' 06'. A 4, greenish tinge ; B 15, and C 12, both dfsky. 3. y DKLPHINI A beautiful DOUBLE STAR in the head, 2 east of a; R. A. 20h. 89m. 15s.; Dec. N. 15" 88' 02* A 4, yellow; B 7, light emerald, with a third star about 2" distant. 4. A delicate QUADRUPLE STAR, near e in the tail ; R. A. 20h. 28m. 35s.; Dec. N. 10 43' 6". A 7)6, and B S, both white; C 16, blue ; D 9, yellowish ; several other small stars a the field. Map VIII., Fig. 17. 5. A SMALL BRIGHT CLUSTER, in the Dolphin's tail, 3}$ south of f ; R. A. 20h. 26m. 2ls. ; Dec. N. 6' 58' 02". Just east of a 9th magnitude star a coarse telescopic pair at a Kstance, and several minute stars in the field. 6. A small PLAKKTARY NEBULA, betwen the pectoral fin and the arrow head, 6* north- ; : IK west ol' a, and exactly on a line towards Vega Lyrse ; R. A. 20b. 15m. 1J*. ; Dec. N .9" UlT. It is in a coarse cluster, in the center of which are fou. orrepiV-iAiis ttarsu HISTORY. Accounts of the origin of Delphinus? What said of Hesiod f Of Taras if ")! the natural shape, &:. ? TKLKSWPIC OBJBCTS. Ai;>na? Beta? Gamma? What quadruple star? Potnl u1 *\ the map. What clus-,i:r I 1 N'ibulii? 124 ASTRONOMY. (JYGNUS (THE SWAN). MAP V. 226. This remarkable constellation is situated in the Mukj Way, directly E. of Lyra, and nearly on the same meridian with the Dolphin. It is represented on outspread wings, flying dowa 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 Dctie.b Cygni, in the body of the Swan, is a jtar 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. 8ud?r is a star of the 3d magnitude, 6* S. W. of Deneb, situated exactly in the tross, or where the upright piece intersects the cross piece, and is about 20 E. of Lyra. tielta, the principal star in the west wing, or arm of Die cross, is situated N. W. of Sad'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. G-ienah is a star of the 8d 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'i 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", there are two other stars of the 8d 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, iind 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. Ilerschel, "the stars in UK ft'.ilky-Way seem to be clustering into two separate divisions ; each division containing more than one hundred and sixty-ftpe thousand 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 AHair, 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 folkwing beautiful lines says there are one hundred and seven. u Thee, silver Swan, who, silent, can o'erpass? A hundred with seven ra.liant stars compose Thy gracef U form : amid the lucid stream W$. Situation of Cygnus? How represented? Figure made by its principal staif Its position? 227. Which is the brightest of its stars? Describe Sad'r, Delta, Gienah, Albireo. Remark of Dr. Herschel? 2?s. Number of stars in Cygnus ? Variable stt\rs ? What arn they supposed to indicate T CYGNUS. 125 Of the fair Milky- Way distinguished : one Adorns the second order, where she cuts The 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." Eudosia, b. tv. Astronomers 1 ave discovered three variable stars in the Swan. Chi, s tuattvi in th< neck, between Beta and Sad'r, was first observed to vary its brightness in 1686. Its perl- odical changes of light are now ascertained to be completed in 405 days. Sad'r is als changeable. Its greatest luster is somewhat less than that of a star af the 8d magnitude, and it gradually diminishes till it reaches that of the 6th. Its changes are far from bein| 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 Anthelme. 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 rather brighter than at first. After several changes, it disappeared in March, 1672 and has rot been observed since. These lemarkable facts seem to indicate, that there is a brilliant planetary system in 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. Otberi suppose it is the swan into which Jupiter transformed himself when he deceived Lfda, wife 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. " 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 of 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 relatire of Phatton, who deeply lamented the untimely fate of that youth, aid the melancholy end o/ hi* staters, 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; And 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 down, 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 ; _ AH Cycnus now into a swan was turned." Ovid's Jfot. h. in HmoKT. Various accounts? Story of Cycnus and Achilles ? Ovid's account t Wlf gilS remarks respecting the Swan ? 126 ASTRONOMY. VlrgL, also, th3 10th book of his JSncid, alludes to the same fable: ** For Cycnus loved unhappy 1'haeton, And sung his loss in poplar groves alone Beneath the sister shades to soothe his grief; Ueaven heard his song, and hasteu'd his relief And changed to snowy plumes his hoary hair, A^d wing'd his flight to sing aloft in air." Of all the feathered race, there is no bird, perhaps, which makes so keautful at \ najestic an appearance as the, swan. Almost every poet of eminence has taken notice of it. The swan has, probably, 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 f.ho approach of death. " She, like the swan Expiring, dies in melody." jRfchilus. " So on the silver stream, when death is nigh, The mournful swan sings its own elegy." Ovid's Tristla. TELESCOPIC OBJECTS. 1. a CfGN! (Dtneb) A bright star on the b-ick of the Swan, with a telescopic com- panion ; 11. A. 20h. 35m. 57s. ; Dec. N. 44 42' 07". A 1, brilliant white ; B 12}$, pale blue. 2. p GYOKI (Albir(o)A. bright DOUBLE STAR on the bill of the figure ; R. A. 19h. 24m. 16s. ; Dec. N. 27" 37' 07". About 13V south-southeast of Vega. A 3, topaz yellow; B 7, sapphire blue ; the colors in brilliant contrast. A line object, and the first double star ever seen by the present editor. 3. (5 CYGNI A most delicate DOUBLK STAR in the middle of the left wing, 14" west of a Cygni ; R. A. 19h. 39m. 58s. ; Dec. N. 44" 44' 06". A 3>$, pale yellow ; B 9, sea green. Another beautiful object. 4. thof l3 Cepliei, and east-northeast of Deneb; R. A. 21h. 26m. 29s.; Dec. N. 4T IS 9 f . TKL-SJCOPIC OBJECTS.- Alpha ? Beta* Delta? Zeta? Lambda? Mu? What celo* ferated binary star? Remarks -especting? Period? Point out on the map. WU* other double star ? Quadruple? What clusters ? Nebula? CAf RICORNUS. 12* 13. A raBY SIKGCLAR NEBDLA on the tip of the northern wing, about 5J$* noith o .1; R, A. 19h. 40oa. 85s.; Dec. N. 50*07' 6'.. Seen to be nebulous nly with good instra jnents. Several telescopic stars in the field. The Herschels considered this as a coo naeting link between planetary nebula and nebulous stars. CAPRICORNUS (THE GOAT).- MAP V. 229. This is the tenth sign, and eleventh constellation, in tie 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 tbe 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 daya 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 mi inight 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 sign Capricorn, known to the ancients by the name of the " Tower of Gad," are probaWy 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 Tjrjhon came upon them, and compelled them all to assume a different shape, in order to escape nis fury. Oid relates " How Typhon, from the conquer'd skies, pursued Their routed godheads to the seven-mouth'd Hood : 229. Position of Capricornus ? When does the sun enter it ? What said of his plae and motion at that time? Of the winter solstice? 280. Number of stars in Capri- corn? Their magnitudes? How recognize the figure ? What said of Giedi? Ancteff< name of this sign ? ASTRONOMY. Forced every god (his fury to escape), Some beastly form to take, or earthly shap?, Jove (sings the bard) was changed into a ram Prom whence the horns of Libyan Anmon BacchiiA a goat ; Apollo was a crow ; Phoebe a cat ; the wife of Jove a cow, Whose hue was whiter than the falling snow ; Mercury to a nasty ibis turned While Venus from a fish protection craves, And once more plunges in her native waves." Oj this occasion it is further related that Bacchus, or Pan, led the way atid plutgt4 'Into the Nile, and that the part of his body which was under the water assumed the forro >f a rish, and the other part that of a goat; and that to preserve the memory of this fn lie, Jupiter made him into a constellation, in his metamorphosed shape. borne 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 ainon^ lh constellations, and gave one of her horns to the nymphs 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 tilings. The word Amalthea, when used figuratively, has also the same meaning. The real sense of tnis fable, divested of poetical embellishment, appears to be thisj that in Crete, some say in Libya, there was a small territory shaped very much like . bullock's horn, and exceedingly fertile, which the king presented to his daughter Amal- ..hea, 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 all things; and he was often, ronsidered as the great principle of vegetable and anrr.al life. He resided chiefly in Arcadia, in woods and the most rugged mountains. As Pan usually terrified the inhabi- ants 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 : M 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 looks. She is represented as an old woman, and was worshiped with great solemnity *t Rome. Her festivals, which were called I'ulilia, were celebrated on the 20th of April, ?he day on which Uomulus laid the foundations of the city. TELESCOPIC OBJECTS. 1. a CAPRICOXSI A QUINTUPLE STAR in the right horn ; R. A. 20h. 09m. 10 ; Dec. S. 18* 02' r. A 3, pale yellow; B (or a 1) 4, yellow; C 16, blue; D 9, ash-colored ; E 9J$, !rc t rge. Few telescopes will reveal all these components. 2. ft CAPRICORNM A wide PAIR OF STARS in the right horn, 2 %' south-half-east of a', B. A. 20h. 12m. Ols. ; Dec. S. 15 16' 9'. A 8J$, orange yellow; B 7, sky blue. Othei Email 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.) 8. A GLOBULAR CLUSTER between Aquarius and the neck of Capricorn, 9 due fast of a Cipricorni, about }$ from a Cth magnitude star; It. A. 20h. 44m. 89s. ; Dec. S. 18* Of f*. Slanj 6:irs in the field, two of which are close to the cluster, or the east. Map CL fig. 63. 1IU5TORY. Who was Capriconras ? What proof cited What further? What othet myth ? Meaning of this fable ? What g*id of Pales? TELESCOPIC OBJECTS. Alpha 1 Beta? Point out on the map ? What clusters? Where jhown on the map ? PEGASUS 125 4. A ttne PALK WHITK CLUSTER, aDout 20* west-northwest of FoniAlhiut; R A. 2t!i Rlru 16s. ; Dec. S. 28 52 4'- A bright object, with straggling streams of stars, and but "liers In the field. Seen with small instruments. Map IX., Pig. 64. CHAPTER XII. CON'STEI.LATION? OX THE MERIDIAN IN OCTOBER, PEGASUS (THE FI.YIXG HOUSE). MAP II. 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 come to the meridian about the 23d of October, and are 13 apart. The northern one, which is the brightest of three triangular stars in the martingale, is of the 2d magnitude, and is called Scheat. Its declination is 26%. Markab, 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 16J$ 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 l v odies are measured. 2SI. What constellations In thl chapter! Describe Pegasus, its size, position, *c. 232. Do we see the whole of the figure 1 How is it distinguished? What said of Scheat and Markab? Of Alpheratz and Algenib? 233. Remark respecting Algenib, Alph*. ratz and Caph ? What sometimes called, and why? They form what? Remarks 130 ASTRONOMY It I? an arc of the equinoctial :olure which passes through the vernal equinox, anc which the sun crosses about the 21st of March. It is, in astronomy, what the men liar; of Greenwich is in geography. If the sun, or a planet, or a star, be said to have so manj degrees of right ascension, it means that the sun or planet has ascended so many degieet from this prime meridian. Unif, sometimes called Enir, is a star of the 8d magnitude in the nose of Pegasus, nbout 20 W. S. VV. 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 Zeta. The loose cluster directly 8. ot thj 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 tL/OG *re 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 CKl}yj], Pege) of the ocean. According to Ovid, he fixed hia residence on Mount Helicon, where, by striking the earth with his foot, he raised the fabled fountain called Hippocrene. He became the favorite of *he Muses ; and being tamed by Neptune or Minerva, he was given to Bcllerophon, son of Glaucus, king of Ephyre, to aid him in conquering the Chimaera, a hideous monster that continually vom- ited flames. This monster had three heads, that of a lion, a goat, and a dragon. The 'ore parts of its body were those of a lion, the middle those of a goat, and the hin ler those of the dragon. It lived in Lycia, of which the top, on account of its desolate wil- derness, "ras the resort of lions, the middle, which 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 (M PEGASI (Algcnib)\ 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 18, pale blue. 4. e PEGASI (Enif) A star with two distant companions, in the nose of the figure ; R. A. 21h. 36m. 19s. ; Dec. N. 9 03' 07". A 2J, yellow ; B 14, blue ; C 9, violet; and a 9th magnitude star of a viokt tinge, at a distance east. 5. (, PEGASI A star with a minute companion in the middle of the neck ; R. A. 22h. 8dm. 29s.; Dec. N. 9 59' 9". A line from Alpheratz over M?rkab, and carried 7 8 further, wilJ reach (,. A 8, light yellow ; B 18, dusky ; with other stars in the field. 6. A DOUBLE STAR between the head of Pegasus and the hind .egs of the Pox ; or about 10 J$ 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. reepectine 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, Ac. ? How he came among th ftara ? TKMCOPIC OBJECTS. Alpha ? Beta? Gamma? Epsilon? Zeta? What double Btarf What duster ? Point out on the map. What nebula? AQUARIUS. 13 J t. A OLOBTTLAR CLUSTER between the mouths of Pegasus and Equleus, about 4" north. srst of e ; R. A. 21h. 22tn. 18s. ; Dec. N. 11* 27' 4". Map IX., Pig. 65. It is laid down 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 ELONGA TED NEBULA in the animal's mane, about 3 due south of Markab : R. A. J2L 6m. 58s. ; Dec. N. 11 27' 9'. A very faint and difficult object. EQULEUS, VEL EQUI SECTIO (THE LITTLE HORSE, OK TITS HORSE'S HEAD). MAP II, 234 This Asterism, or small cluster of stars, is situated about t W. of Enif, 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. Tnese four stars are situated 10 or 12 S. E. of the diamond in the Dolphin's head. Both of these clusters are noticeable on account of their figure rather than their brilliancy. HISTORY. This constellation is supposed to be the brother of Pegasus, named Celerte, given by Mer- cury to Castor, who was so celebrated for his skill in the management of horses; other* 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 Celeris 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, /3, <5, e and A. ft is rather a star with a companion ; R. A. 21h. 14m. 57s. ; Dec. N. 6' 07' 9*. The othe/ 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 roan pouring out water from an urn. It is situated in the Zodiac, immediately S. of the equinoctial, and bounded by the Littk 284. Situation of Eqiileus? When on the meridian? Number of itari, and hew ito Unguished? What further description 1 HISTORY. What suppositions respecting the origin of Eqvileus? TELESCOPIC OBJECTS. What double stars? How found? 'ft. How is Aquarius represented? I Is boundaries? 132 ASTRONOMY. Ilorse, Pegasus, and the Western Fish on the, 1 N., the Whale M 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 min. 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 MeliJc, t a star of the 8d magnitude, in the E. shoulder, and the principal one in this constellation. 10 S. W. of El Melik, is aiiother 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 Lctmlxla. ScJieat, of the 3d magnitude, lying below the knee, is situated 8%* S. of Lambda; and 4 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 both these constellations, and is one of those from which the lunar distance is computed for Ascertaining the longitude at sea. It culminates at 9 o'clock on the 22d of October. Fomalhaut, Deneb Kaitos, and Alpha in tue head of the Phoenix, make a large triangle, whose vertex is in Deneb Kaitos. Those two stars of the fourth magnitude, situated 4 J 8. 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, MI the urn, in a southeasterly direction toward the tail of Cetus, from which the cascade suddenly bends off near S<-heat, in an opposite course, and finally disappears in 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 Tliessaly, 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 disafpearance of Aquarius caused the Wile to rise, by the sinking of his urn in the water In the Zodiac of the Hebrsws Aquarius represents the tribe of Reuben. ts order in the signs and constellations? Number and size of its stars? 287 How Jistinguish the northeast limit? What said of El Me 4k? Of Sad es Saud? Of Ancha Lambda, Scheat, &c. HISTOKT. Story of Ganj mode, and Jupiter? What other myth? Idea of the , reddish ; a fourth star at a distance. A very difficult object; claimed by Borne for Andromeda, but usually classed as belonging to the Lizard. HISTORY. Supposed origin of this constellation? TELESCOPIC OBJECTS. Alpha ? Where situated ? 239. Describe Lacerta. Where situated ? 240. What other small constellation nearV By whom inserted, when and why? Of what does it consist? To represent what? Is if recognized by astronomers ? TKLKSCUPIC OBJKCTS. What double stars in Lacerta? What triple star? Quadruple Cluster V Any of them shown on the map? VAR'ABLE AM) DOUDLC STARS. 185 ft. A QUADRUPLE STAR, the western one of the three forming the triangle at the end of the tail ; H. A. 22h. 29m. 46s. ; Dec. N. 38 48 5". About 2i> northwest of Alpheratz \ and B 6%, both white ; C 11, greenish ; D 10, blue. 6. A LARGE LOOSE CLUSTER in th > Lizard's mouth ; R. A. *,,.h. OSm. 59s. ; Dec. N. 49" C* P. Stars from the 9th to the 14th magnitudes. A line carried from Polaris throug'i th tiara of Cepheus, and 8 beyond, strikes it. CHAPTER XIII. VARIABLE AND DOUBLE STARS CLUSTERS AND NEBULAE. 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, us Delta in the Great Bear ; others, like Beta in the Whale, to De increasing in brilliancy. 242. Some stars have all at once blazed forth with great splen- dor, and, afier 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 mag iUude suddenly appeared in the right foot of Ophiuchus. It presented, like the fc ur, ill the phenomena of a prodigious flame, being, at first, of a dazzling white, the:, of a reddish yellow, and, lastly, of a leaden paleness ; in which its light expired. These .asVinces prove that the etars are subject to great physical revolutions. (Page yO) 243. A great number of stars have been observed whose lifrJt 3eems to undergo a regular periodic increase and diminution. 241. What said of the periodical variations of the stars ? 242. What other remarks )le vhenomenon? What instances cited? What do these instances jrov;? 24/1. Wh' 136 ASTRONOMY They are properly called Variable Stars. One in the IVhdk ha a period of 344 days ..id is remarkable for the magnitude of it t variations. From oeing a star of the seco d magnitude, it becomes so dim as to be seen with difficulty <-nrough powerful telescopes. Some are remarkable for the sh. tness of the pe;i/>d of their variation. Algol has a perioc 1 of bet een two and three days ; Delta Cephei, of 5^- days ; Beta L\ ce, of 6 2-5 iays ; and Mu Antinoi, of 7 days. The regular succession of these variations precludes th, supposition of ;n a tual destruction of the stars; neither can the variations be supposed to arise from a change of distance; for, as the stars invaria hl y retaia their apparent places, it would be neces- sary to suppose that they approach to, and recede from fhe earth in straight lines, which is very improbable. The most probable supposition is, that the stars revolve, like the sun and planets, about an axis. "Such a motion, "sa^s 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, eiiher toward or from us, will account for all the phenomena of periodical changes in the uster of th stars, so satisfactorily, that we certainly need not look for any other cause.' 1 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 . B Here the observer on the left sees a large and small star at A, apparently near toge- tl-er the lowest star being much the smallest. But instead of their being situated aa tney appear to be, with respect to each other, the true position of the smaller star may 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 oth ir, 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 .'- 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- arc these unsteady stars called ? What specimens referred to, and their periods ? What does this regular succession, Ac., prove? What theory did Dr. Herschel adopt respect- ing the variable stars? 244. What said of double stars? Are they always really neaf ucb. othor? Illustrate on blackboard. Remark of Dr. Herschel? 245. Are thej STARS OPTICALLY' DOl'BLE. 137 cate a revolutior about each other snul about a common urutr In this case they are said to form a Ihtuiry system performing to each oth7>icl by its. train of planets, and their satellites, closely shrouded from our view by the jrlendor of their respective suns, and crowded into a space bearing hardly a greater pr //ortion to the enormous interval which separates them, than the distances of the sateii /tes of v.ur planets from their primaries bear to their distances from the sun itself. 247. The examination of double stars was first under/aken by the late Sir William Herschel, with a view to the question of parallax. His attention was, however, soon arrested by the new and unexpected phenomena which these bodies pj.euented. Sir William observed of them, in all, 2400. Sir James South and Hersch A have given catalogue of 3SO in the Transactions of the Royal Society for 1S'24, and f ' u;h added 45S tn 1820. Sir John Herschel, in addition to the above, published an accoui.' of 1000, befo/c he left England for the Cape of Good Hope, where he went to push his dijjcveries in the southern hemisphere. Processor Strnve, with the great Dorpat telescop/., has given a rviuiloirue of 3,063 of the most remarkable of these stars. Hie ol ject of these catalogues is not merely to fix the place of the star w'i'.iiu such limits u* will erable us easily to discover it at any future time, but also to reco . 1 a description *?r really near each other? What motion ? What do these constitute ? Is it certain .hat stars are ever thus in motion around a common center? 240. W^iat remarkable nstance ci'ed? Its annual angular motion? Period? What other '<;nary systems 1 Are these pkinctdry systems like our own ? 247. Who first undertook Die ex?.minatioa ->; '/ie \louble stars, and with what view? What number did he ob?me? Wha*. catiw 138 ASTRONOMY. of the appearance, position, an r l mutual distances of the individual stars comjoain;.' th i system, in order that subsequent observers may have the means of detecting their con nected motions, or any changes which they may exhibit. Professor Struv j has also taker notice of 52 triple stars, among which No. 11 of the Unicorn, Zeto. of Cancer, And Zi of the Balance, appear to be ternary systems in motion. Quadruple and quintuple stars 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 iomei.a. COLOR OF THE STARS. 248. Many of the double stars exhibit the curious and beau- tiful phenomenon of contrasted colors, or complimentary tints. In guch 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 less 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 AUniaack, in Andromeda both fine double stars. If, however, the colored star be much the less bright of the two, it will not materially affect the other. Thus, for instance, Eta Oassiopeise exhibits the beautiful combination of a large white star, and a imall one of a nch ruddy purple. 249. It is not easy to conceive what variety of illumination two suns a red and a green, or a yellow and a blue one must afford to a planet revolving about either ; and what charming contrasts and grateful vicissitudes a red and a green day, for ifisr:'.,nee, alternating with a white one and with darkness might arise from the presence or absence of one or the other, or both, ftbcve the horizon. Insulated stars of a red color, almost as deep as that of blood, occur in many partg of thfc heavens, but no green or blue star (of any decided hue) has, we believe, ever beer noticed, unassociated with a companion brighter than itself. CLUSTERS OF STARS. 250. When we cast our eyes over the concave surface of the heavens in a clear night, we do not fail to observe that there are, here and there, groups of stars which seem to be compressed together more densely than those in the neighboring parts ; forming bright patches or clusters. ognes? Their object? What triple stars? Ternary systems ? Quadruple stars, &i 'i 348. What said of the colors of the stars? What law of optics referred tr f What illw- 'rations ? 249, What remarks respecting red and green suns, &c. ? Of insulated star; Of a red color f 25<. W>at said of clusters * What s{ ecimen referred to ? Pleiades- NEBULAE. 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. Rheita 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 diffused, and consisting of much larger stars. In Cancer there is a nebuloas cluster of very minute stars, called Prasept^ or the Beehive, which is sufficiently luminous to be seen by the naked eye, in the absence of the moon, arid 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 start over the gone- 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 fl. 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 ths heavens exhibit to our view, this fills 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 ia from them, we fall as far short of adequate language to express our ideas of such immen- uity, as we 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* uess which we see in a clear evening, when the moon is absent. It is also a recent and well-accredited doctrine of astronomy, its Nebuhe? Sir Wm. Herschel's conjecture? 256. What is the Via Lactea? Its Sroek name? What said of its magnificence and grandeur? 257. What said of th ftch'.JVements of astronomy <( Its doctrine respecting the structure of the uciverj,) Of the sun, and ita relation to the fixed stars? 142 ASTRONOMY. that all the stars in the universe are arranged into clusters, 3i groups, which are called NEBULAE or STARRY SYSTEMS, each )f which consists of myriads of stars. The fixed star which we call OOR SCN, belongs, it is said, to that extensive nebula, tt* Milky -Way ; and although apparently at such an inmeasurable distance from its feL'ows 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 start, 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 Heta and Sad'r, in Cygni, the stars seem to be clustering in two divisions ; each division ronta 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 thousand stars, large enough to be distinctly count id ; and he suspected twice as many more, which, for want of sufficient light in his telescope, he saw only now and then. 2f>9. It appears from numerous observations, that various changes are taking place among the nebulae that several nebu- loe 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. Mere than two thousand five hundred nebulae have already been observed; and, if oaiih if them contains as many stars as the Milky- Way, several hundreds of millions of stars must exist, even within ihiit portion of the heavens which lies open to our cbser- ration. " what a confluence of ethereal fires. Prom urns unnuml.'cr'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 5158. Number and economy of the stars Dr. Herschel's statements? What number passed the field of his instrument in a quarter of an hour? In lirty-one minutes? In space apparently only a yard in breadth ? 259. What changes cbserved in the nebu-- ITB! What do they indicate? Number of nebulae? Estimated number of stars? *W When is the Via Lactea seen to the best advantage? Direction when Lyra is on th ORIGIN OF THE CONSTELLATIONS 143 the months of July, August, September, and October, Whet 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 for n, treadtn and appearance are various, indifferent parts of its course. In some ^.ac^s it is dense and luminous ; in others, it is scattered and faint. Its breadth is often aot more than five degrees ; though sometimes it is ten or fifteen degrees, and even tJrenty. In some places it assumes a Double path, but for the most part it is single. It may be traced in the heavens, beginning near the head of Cepheus, about 80 from ll-.e north pole, through the constellations Cassiopeia, Perseus, Auriga, and part of Orion 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, sis it passes over the Zodiac again into the northern 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. Tb; 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'a path, and that its present luminous appearance is the track which its scattered beama (eft visible in the heavens. The ancient poets, aad 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 thione 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 below, And mortals, by the name of Milky, know ; The groundwork is of stars, through which the road Lies open to the Thunderer's abode." Mi'ton 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 XV. ORIGIN OF THE CONSTELLATIONS. 2fil. THE science of astronomy was cultivated by the imme- diate descendants of Adam. JOSEPHUS informs us that the sona )f SRTH employed themselves in the study of astronomy ; and iliiit they wrote their observations upon two pillars, one of brick meridian? Its form, breadth, Ac.? How traced .n the heaven?? Notion of tbc Pagau Of the poets ? What citations? 2t?1. How e.-irly wns astronomy cultivated! 144 ASTRONOMY. am the other of stone,* in order to preserve them against the destruction which ADAM had foretold should come upoii the earth. He also relates, that Abraham argued the unity and power of God, from the orderly jourse of things both at se i and land, in their times and seasons, and from his observa- tions upon the motions and influences of the sun, mooa and stars ; and that he read 1( c- lures in astronomy and arithmetic to the Egyptians, of which they understood nothing till Abraham brought these sciences fromChaldea to Egypt; from whence they passe i tn 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 antediluvUna, that Providence found it necessary to prolong man's day?, 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 la, therefore, very probable that the Chaldeans and Egyptians were the original {sventors of .astronomy ; but at what period of the world they marked out the heavens tato constellations, remains in uncertainty. La Place fixes the date thirteen or fourteei hundred years before the Christian era, since it was about this period that Eudoxuscon- s.ructed the first celestial sphere upon which the constellations were delineated. Sir Is-xac 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 tha memorable enterprise. It should be remarked, however, that while none of the ancien constellations refer to transactions of a later date, yet we have various accounts of then 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 >f stone to remain in Syria in his ow time." i Vince's Complete System of Astronomy, Vol. ii p. 244. Whit proof? What said of Abraham? 262. What further proof? What reason assigned for the longevity of the antediluvians ? 263. What discovery by Calisthenes ; What conclusion from this discoverj ? La Place's date of the origin of the conste'la ttccs? Sir Isaac Newton's opinion? Remark? 264. What researches, and wha results? ORIGIN OF THE CONSTELLATION* 145 their achievements in the arts, and whatever in thci: history was nost 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 bcason ; 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 the 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? 26G. Of Cancer and Leo 267. O Virgo ami Libra? '203 O p Scorpio and Capricorn? 146 ASTRONOMY. 269 Aqiarius, or the Water Bearer, is represented by tht Sgure of a man pouring out water from ai. urn, an emblem of the dreary and uncomfortable season of winter. The last of the zodiacal constellations was Pisces, or a coupta of fishes, tied back to back, representing the fishing season. The severity of winter is over ; the flocks do not afford suste< unco, 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 comes 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 their place as had a more special referefce to their own history. The Romans also pursued the same course with regard to t/i6*r history; and henci tho 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 Schillcrius, 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 i new order of constellations, by converting the firmament into a CCELUM HKRALDICDM, 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 heroes of antiquity should continue to enjoy their fianced honors in the sky, as to se^ 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 atd model i aan\es which we meet with in modern catalogues. 272 Astronomers divide the heavens into three parts, called \he Northern and Southern Hemispheres, and the Zodiac. In the 269. Of Aquarius and Pisces? Course of the Greeks and Romans, In displacing cor s illations? 270. What other re-form attempted f What particular instances cited Bede? Schi'Uirius? Weigelius? How are these innovations regarded by astronomers ill. Numbei if the old constellations 1 How others added? 272. How de autrono ORIGIN OF THE CONSTELLATIONS. 147 northern hemisphere, astronomers usually reckon thirty- four cou- stellations, in the Zodiac twelve, and in the southern hemisphere forty-seven ; making in all ninety-three. Besides these, there ire a few of inferior note, recently formed, which are not cou xidercd sufficiently important to be particularly described. 273. About the year 1G03, 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 ire 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 bea vens, as to any particular house in a populous c ; ty, by its street anl number. Before this practice was adopted, it was customary to denote the stars by referring them to their respective fifttutlioti* in t/tejigure of the constellation to which they severally belonged, as the head, the arm, the foot, &c. It is hardly necessary to remark that these figures, which are all very curiously depicted upon artificial globes aill i 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 ny particular star, or cluster of stars; though these clusters very rarely, if ever, represent the real figures of the objects whose names they bear. Add yet it is somewhat remarkable that the name of "Great Hear," for instance, should have been given to the very xnme 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 nntions, also, between whom there exists no evidence of any intercourse, we find the Zodiac divided into the same number of constel- lations, 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 no 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 PLEIADKS, or loose the bands of ORIOH? Canst thou bring forth MAZZA ROTH in his season, or canst thou guide ARCTORUS with his sons?" Here, too, are consecrated th \ lyre of Orpheus and the ship of the Argonauts; and, in '.he sa.ne firmament, glitter the Mariner's Compass and the Telescope of Herschel. uiers div'Je the constellations? Number in each division? Total? What ethers. 878. John Bayor's invention? Utility of it? How before it was adopted? Wfcat remnrl respecting the figures on reaps and globes, and their use? What remarkkNe facM tted? 2'4. Historical use of the constellations? Illustrations? .G. H8 ASTRONOMY. CHAPTER X71. ffUMBER, DISTANCE AND ECONOMY t;F TEE STARS. 215. THE first conjecture in relation to the distance of the Sxed 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 telesqppe, the heavens become quite another spectacle not only to the understanding but to the senses. N 7 ew worlds burst upon the sight, and old ones expana to a thousand times their former dimensions. Several of those little stars whick 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 sifted by day and night, summer and winter. Beyond these are other suns, giving light and life to other systems, not a thousand, 01 two thousand merely, but multiplied without end, and ranged all around us, at iminensi distances from each other, attended by ten thousand times ten thousand worlds, all in rapid 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 mansionr, which the Supreme Being has created for the accommodation of his worshipers ; and that he may n^w be at work in regions more distant than geometry ever measured, erf at- .rgwonls 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 lize, not inferior to our sun, and that they shine, not by reflected ruys, bi>t 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 m< jusl 8timate? What said of tbe heavens when seen through a telescope? 276. What computation as to the number of stars invisible to the naked eye, but visible through M<;scoj.ef I* this probably the whole universe? Remark of Chalmers T '277 Wl.a' NUMBER, DISTANCE, AND EC NOMY OB THE STAllS. 149 vith 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 arid night. These vast globes of light, then, could never have been designed merely to ilivrjifj the voids of infinite space, nor to shed a few glimmering rays on our far distant woiil, fcT the amusement of a few astronomers, who, but for the most powerful telescopes, had acvr seen the ten thousandth part of them. We may therefore rationally conclude, thai wherever the All-wise Creator has exerted his creative power, there also he has placed ijteiligent 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 tha 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. In 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 this 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 ita apparent position at all, the qwmtity of the change will bear some proportion to the distance gone over; that is, the rearer the star, the greater the angle; and the more renn'te the star, the lew the angle. It is to be observed, that the angle thus fourrt, if called the star's Annual ParalUiw. 279. But it is found by the most eminent astronomers of tho age, and the most perfect instruments ever made, that the paral- lax of the nearest stars does net 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 gl'obe 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 othei inference ? 278. What effort to determine the distances of the stars? What results What necessary in estimating the distances of the stars? What measure taken? De icribe the process of determining the distance of the star? by parallax. 2<9. Wha the parallax of the stars found to be, and what follows as a consequence? Whl 150 our sun, with its whole retinue of planetary worlds, would oecupj a space scarcely exceeding the thickness of a spider's web.* If the nearest of the fixed stars are placed at such inconceivable distances in tho regions of space, with what line shall we measure the distance of those which are a thou- sand or a million of times as much farther from them, as these are from us ? 280. If the annual parallax of a star were accurately known, It would be easy to compute its distance by the following rule : As the sine of the star's parallax : Is to radius, or ninety degrees : : ISo is the earth's distance from the sun : To the star's distance from the sun. if we allow the annual parallax of the nearest star to be 1", the calculation will be, As 0.000004848 i:i(i8 = \at. Sine of 1". Is to 1.0000000000000 = Nat. Sine of 90. So is 91, 43 1,072 = Earth's distance from the sun To 18,859,01 l,981,469 = Star's distance from the sun. In this calculation we havo supposed the earth to be placed at the mean distance of 23,112 of its own semi-diameters, or 91,4 t ?1,072 miles from the sun, which makes the star's distance nearly twenty trillions of miles. Tlie parallax of Sinus being j'g", iti distance must be 6j{ times this amount, or more than 130 millions of million* of mile*. The old determination of the sun's parallax (8"577i5), which made the sun's mean dis- tance about 5)5 millions of miles, made the distance of a star having the parallax of I'' very nearly '20 trillions of miles (19,65!,6'27,6S3,449); or 800,00") millions of miles farther off than the present determination. A parallax of 1" is equivalent to a distance of about 200,300 times the mean distance of the sun. The following table contains the names of the twelve stars the parallaxes of which have been approximately ascertained : Name. Parallax. Name. ParaHay,. Name. Parallax. 0".18S (KM 27 0".067 0".046 a Centauri 61 Cygni 21258 Lalande 17415 Oultzen (/MUST 0".5tf3S 0"/2709 0".24T 1930 Groombridgc 70 Ophiiichi a Lyrse Birius 0".226 0".16 0".I55 0".150 i Ursse Major. Arcturus Polaris Capella * A just idea of the import of this term, will impart a force and sublimity to an expres- ion of St. James, which no power of words could improve. It is said, clnpter i. verso 17, of Him from whom cometh down every good and perfect gift, that there is " oyn ev, 7ia/>a/i/lay?/ ?/ T/JOTT^S an '0 the earth; and should any of them be now destroyed, they would continue to be percep- tible for a trillion of ages to come. Dr. Hersrhel informs us, that the glass which he used would separate stars at 497 time.' the distance of Sirius. 284. It is one of the wonders of creation, that any phenomena of bodies at such an immense distance from us should be pcrce|> tible by human sight ; but it is a part of the Divine Maker'* 281. Former supposed relative distance of the most brilliant stars ? Present op-imsa nd on what founded? 232. What computation as to the light of Sirius? What con- clusion as to the distance of other stars ? How, then, would he appear if as near as on : mn? What conclusion as to the magnitude of the stars? 288. Distance of the sixtfc magnitude stars? How measured by the flight of the earth ? Of light? What forth estimate by Dr. Uerschel? 2S4. What remark respecting our knowledge of the start 152 ASTRONOMY, plan, that although they do not act physically upon us, yet tlie} should so far be objects of our perception, as to expand our ideas of the vastness of the universe, and of the stupendous extent and operations of his omnipotence. "With these facts before us," says an eminent astronomer and divine, " it is most rea- sonable to conclude, that those expressions in the Mosaic history of Creation, which re-late to the creation of the fixed stars, are not to be understood as referring to the titnj when they were brought into existence, as if they had been created about the same tini W'th our earth ; but as s'mply declaring the fact, that, at whatever period in duration they were created, they derived tlieir existence from Qod" 285. "That the stars here mentioned" (Gen. i, 16), says a distinguished commentator, "were the planets of our system, and not the xed stars, seems a just inference from the fact, that after mentioning them, Moses immediately subjoins, ' And Kiohira set them in the firmament of the heaven to give light upon the earth, and to rule over the day and over the night ;' evidently alluding to Yenus and Jupiter, which are alternately our morning and evening stars, and which ' give light upon the earth,' far surpassing in brilliancy any of the fixed stars." However vast the universe now appears, however numerous the worlds which may ;;xist within its boundless range, the language of Scripture, and Scripture alone, is sufti- lieiitly comprehensive and sublime to express all the emotions which naturally arise in the mind when contemplating its structure. This shows not only the harmony which subsists between the discoveries of the Revelation and the discoveries of Science, but also forms, by itself, a strong presumptive evidence, that the records of the Bible aro. authentic and divine. 286. We have hitherto described the stars as being immov- able and at rest ; but from a series of observations on double stars, Dr. Herschel found that a great many of them have changed their situations with regard to each other ; that some perform revolutions about others, at known and regular periods, and that the motion of some is direct, while that of others is retrograde ; and that many of them have dark spots upon their surface, and turn on their axes, like the sun. 281. A remarkable change appears to be gradually taking place in the relative distances of the stars from each other iu the constellation Hercules. The stars in this region appear to be spreading farther and farther apart, while those in the oppo- site point of the heavens seem to close nearer and nearer together, in the same manner as when walking through a forest, the trees toward which we advance appear to be constantly separating while the distance between those which we leave behind is gn dually contracting. by sight? How %rc we to understand Mcses as to the time of the creation of the stara 2SS. What meant by the "stars" mentioned Gen. i., 16? What proof? Remark respo-Tfr Ing the Scriptures? 2R6. How lave the stars been described hitherto? What is th fact? 9-ST. What exan pie cited ? What astonishing conclusion? NUMBER, DISTANCE, AND ECONOMY OF THE STAHS. 5-3 Prom this appearance it is concluded, that the sun, with all its retinue of piano ^rj worlds, is moving through the regions of the universe, toward some distant center of nrnund some wide circumference at the rate of near thirty thousand miles an hour; and that it is therefore highly probable, if not absolutely certain, that we shall never GO. ipy that portion of absolute KJMC*, through which we are at this moment passing, dt infl ull the succeeding ages- of eternity. 288. The direction of the Sun's motion is towards the constel* lation of Hercules ; R. A. 259 ; Dec. 35. This velocity in space is estimated at 8 miles per second, or 28,000 miles per hour. His period is about 18,200,000 years ; and the ire of his orbit, over which he has traveled since the creation of the world, amounts to only about ^^th part of his orbit, or about 7 minutes an arc so small, compared with the whole, as to be hardly distinguishable from a straight line. "With this wonderful fact in view, we may no longer consider the sun AS fixed and sta- tionary, but rather as a vast and luminous planet, sustaining the same relation to some central orb that the primary planets sustain to him, or that the secondaries 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 itd orbit, and its center of attraction and motion, and so on, till, as Dr. Dick observes, we come to the great center of all to the THRONE OK GOD! Professor Madler, of Dorpat, in Hussia, has recently announced as a discovery that t'ie star Alcyone, one of the seven stars, is the center around which the sun and solar ystein are revolving. 289. Dr. Dick, the author of the CHRISTIAN PHILOSOPHER, endeavors to convey some idea of the boundless extent of the universe, by the following sublime illustration : "Suppose that one of the highest order of intelligences is endowed with a power of rapid motion superior to that of light, and with a corresponding degree of intellectual energy ; that he has been flying without intermission, from one province of crea- tion to another, for six thousand years, and will continue the same rapid course for a thousand million years to come, it is highly probable, if not absolutely certain, that, at the end of this vast tour, he would have advanced no farther than the ' sub- urbs of creation,' and that all the magnificent systems of mate- rial and intellectual beings he had surveyed, during his rapid (light, and for such a length of ages, bear no more proportion to ihe whole empire of Omnipotence, than the smallest grain of sand does to all the particles of matter contained in ten thousand worlds." Were a seraph, in prosecuting the tour of creation in the manner now stated, ercr to arrive at a limit beyond which no farther displays of the Divinity could be perceived, th thought would overwhelm his faculties with unutterable emotions ; he would feel that h had now, in some measure, comprehended all the plans and operations of Omnipotence^ ,iml ti.at no farther manifestation of the Divine glory remained to be explored. But w? in*} rest aodured that this can never happen in the case of any created intelligence. 28S The direction and velocity of the sun ? Period? Arc of orbit passe* c ver sincj ..nation? How, then, should we consider the sun? View of the universe? Discovers of Professor Madler ? 28. Dr. Dick'a illustrations ? 154 ASTRONOMY 290. There is, moreover, an argument derivable from th laws of the physical world, that seems to strengthen, I had almost said, to confirm, this idea of the Infinity of the material universe. It is this If the number of stars be finite, and occupy only a part of space, the outward stars would be con- tinually attracted to those within, and in time would unite io one. But if the number be infinite, and they occupy an infinite i.pace, all parts would be nearly in equilibrio, and consequently j.ach fixed star, being equally attracted in every direction, would keep its place. No wonder, then, that the Psalmist was so affected with the idea of the immensity of the universe, that he teems almost afraid lest he should be overlooked amidst the immen- sity of beings that must needs be under the superintendence of God; nor that any finite mortal should exclaim, when contemplating the heavens " What is man, that THOU art mindful of him !" CHAPTER XVII. FAILING, OR SHOOTING STARS. 291. THE phenomenon of shooting stars, as it is called, is com- uioii to all parts of the earth ; but is most frequently seen in tropical regions. The unerring aim, the startling velocity, and vivid brightness with which they seem to dart athwart the sky, and as suddenly expire, excite our admiration ; and we often ask. " What can they be ?" But frequent as they are, this interesting phenomenon is not well understood. Some imagine that they are occasioned by electricity, and others, that they are nothing but luminous gas. Others again have supposed, that some of them are luminous bodies which accompany the earth in its revolution around the Bun, and that their return to certain places might be calculated with as much certainty and exactness as that of any of the comets. 292. Dr. Burney, of Gosport, kept a record of all that he observed in the course of several years. The number which ne noticed in 1819 was 121, and in 1820 he saw 131. Professor 2% What argument supposed to favor the idea of a boundless universe? Allusion w Iht Psalmist? 291. Where are shooting stars most common? Are they well under ptood ? What theories stated ? 292 Or. Burney's record? Professor Gr Signior Buccari;\, ^pinion, and his rc..son for it? FALLING OR SHOOTING STARS 15 tureen is confident that a much larger number are annually seen in the United States. Signior Baccaria supposed they were occasioned by electricity, and thinks this opinion is confirmed by the following observa- tions. About an hour after sunset, he and some friends, that were with him, observed a falling star directing its course directly toward them, and apparently growing larger and larger, but jusi bdore it reached them it disappeared.. On vanishing, their faces, hands, and clothes, with the earth and all the neighboring objects, became suddenly illuminated with a diffused and lambent light. It was attended with no noise. During their surprise at tikis appearance, a servant informed them that he had seen a light shine suddenly in the garden, and especially upon the streams which he was throwing to water it. The Signior also observed a quantity of electric matter collect about his kite, whict ^ad very much the appearance of a falling star. Sometimes he saw a kind of hale iccompanying the kite, as it changed its place, leaving some glimmering of light in tl,f place it had quitted. 293. Shooting stars have been supposed by those meteorolo- gists who refer them to electricity or luminous gas, to prognos- ticate changes in the weather, such as rain, wind, &c. ; and there is, perhaps, some truth in this opinion. The duration of the orilliant track which they leave behind them, in their motion through the air, will probably be found to be longer or shorter, according as watery vapor abounds in the atmosphere. The notion that this phenomenon betokens high winds, is of great antiquity. Virjri. la the first book of his Georgics, expresses the same idea: " Sa'pe etiam Stellas vento impendente videbia I'raecipites ccelolabi; noctisque per umbram Flammarum longos a tergo albescere tractua " 44 And oft, before tempestuous winds arise, The seeming stars fall headlong from the skies, And shooting through the darkness, gild the night With sweeping glories and long trails of light." 294. The number of shooting stars observed in a single night, though variable, is commonly very small. There are, however, several instances on record of their falling in " showers " when every star in the firmament seems loosened from its sphere, and moving in lawless flight from one end of the heavens to the OtllCT As early as the year 472, in the month of November, a phe mmenon 01 this kind took place near Constantinople. As Theo 298. What are they supposed by some to prognosticate? What other ancient notion . Poetic quotation ? 294. What said of the number of shooting sfcrs? What inBtancn of " m?tcoric showers " cited f 156 ASTRONOMY. phanes relates, " the sky appeared to be on fire," with the c cations of the flying meteors. A shower of stars exactly similar took place in Canada, between the 8d and 4bserved in places so widely separated, amid the vas." and lonely deserts of South \merica, should have been seen, the same night, in the baited States, in Labrador, 'a dri ienland, and at Itterstadt, near Weimar, in Germany ! 296. We are told that thirty years before, at the city of Quito, "there was seen in one part of the sky, above the volcano of Cayambui 3, so great a number of falling stars, that the moun- tain was thought to be in flames. This singular sight lasted more than an hour. The people assembled in the plain of Exida, where a magnificent view presents itself of the highest summits of the Cordilleras. A procession was already on the point of setting out from the convent of St. Francis, when it was per ceived that the blaze on the horizon was caused by fiery meteors, which ran along the sky in all directions, at the altitude of 12 }r 13 degrees." 297. But the most sublime phenomenon of shooting stars, of which the world has furnished any record, was witnessed through- out the United States on the morning of the 13th of November, 1833. The entire extent of this astonishing exhibition has not been precisely ascertained, but it covered no inconsiderable por- tion of the earth's surface. It has been traced from the longi- tude of 61, in the Atlantic ocean, to longitude 100 in Central Mexico, and from the North American lakes to the West Indies. It was not seen, however, anywhere in Europe, nor in South America, nor in any part of the Pacific Ocean yet heard from. Everywhere, within the limits above mentioned, the lirst appearance was that of fireworks of the most imposing grandeur, covering the entire vault of heaven with myriads of fire-balls, resembling sky-rockets. Their coruscations were bright, gleam- ing and incessant, and they fell thick as the flakes in the early snows of December. (See cut on the next page.) To the splendors of this celestial exhibition, the most brilliant sky-rofkets and. fire- wcrks of art bear less relation than th-> twinkling of the most tiny star to the broad glare of the sun Thj whole heavens seemed in motion, and suggested to some the awful grandeur of the huage 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 untira-jly fi/s when she is shaken of a mighty wind." 298 One of the mo.st remarkable circumstances attending .his display was, that the meteors all seemed to emanate from : sS?6. What other similar phenomenon cited F 297, What still more sublime ipeckm fU extent? Its appearance ? 158 ASTRO NOMV. /me and the same point, a little southeast of the zenith. Follow fug the sircli of the sky, they ran along with immense velocity, describing, in some instances, an arc of 30 or 40 in a few METEORIC SHOWER Of NOVEMBER, 1888. seconds. On more attentive inspection it was seen, that the meteors exhibited three distinct varieties ; the first, consisting of phosphoric liws, apparently described by a point ; tiie second, of large /ire-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 stationary in the heavens for a long time. Those of the first variety were the most numerous, and resembled a shower of fierj tmw driven with inconceivable velocity to the north of west. The second kind appeared ir.ore \\k-zfiitting stars a spectacle which was contemplated by the more unenlightened beholders with great amazement and terror. The trains which they left weie commonl* white, but sometimes were tinged with various prismatic colors, of great beauty. 299. These fire-balls were occasionally of enormous size. Dr Smith, of North Carolina, describes one which appeared larger than the full moon rising. " I was," says he, " startled by the 2'^ U'hat remarkable circumstatici attended this phenomenon? Varletjof nietecrs f fSQ U I. at said of the firetalls seen ? Of their site? FALLING OR SHOOTING $r\KS. 159 splendid light in which the surrounding scene was exhibited, reiv "ieriug even small objects quite visible." The same ball, or a similar one, ceen at New Haven, passed off in a tirthwest direction, and exploded a Htle northward of the fitar Capella, eaving, just behind the place of ^iplosion, a train of peculiar beauty. he line of direction was at first Dearly straight; but it soon began to son tract in length, to dilate in breadth, and to assume the figure of a serpeat SCROLLING itself up, until it appeared like a luminous cloud of vapor, float- ing gracefully in the air, where it remained ir full view for several minutes. If this body v/ere at the distance of 110 miles from the observer, it must have had a diametei of one mile; if at the distance of 11 miles, its dianie- A LARGK METEOR. ter was 528 feet; and if only one mile off, it must have been 43 feet in diameter. These considerations leave no doubt thai many of the meteors were bodies of large sine. 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 pruning-hook, and apparently twenty feet long, and eighteen inches broad. It gradually UM tied toward the horizon, until it disappeared. At Niagara Falls, a large luminous body, shaped like a xqiutre table, was seen neat 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 weather, from warm to cold, accompanied the meteoric shower, or immediately followed it. In all parts of the United States, this change waa remarkable for its suddenness aud intensity. In many places, the day preceding had boen unusually warm for the season, but, before the next morning, a severe frcst ensued, unparalleled for the time of year. 302. In attempting to explain those mysterious phenomena, it is argued, in the first place, that the m/dears had t.fieir o"ic ; n 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? 301. Point from wh'ch .hey seemed to emanate ? What, change of weather fo'l : *ed ? 302. What fact asfcarx J jt. to the ditan.l's estiuiato oi diblince? 160 ASTRONOMY. The- reason on which the conclusion is tounded is this : All bodies near the cart!. Including Die atmosphere itself, have a common motion with the earU around its axij from west to east; but the radiant point, that indicated the source from which the meteors emanated, followed the course of the stars from east to west; therefore, it was independent of the earth's rotation, and consequently, at a pi-eat distance from it, ana beyond the limits of the atmosphere. The heig/Lt of the meteoric eloud, or radiant point, abovo the earth's surface, was, according to the mean average of Professor Ol'astvd'i obse rations, not less than 2238 miles. 3)3. That the meteors were constituted of very light, combus- tible materials, seems to be evident, from their exhib ting the actual phei.jinena 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 havo 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 couatry remote from e;ich other, being mutually displaced, would exchange places, the air of the warm latitude? b< 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 magnetism. 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 Yah College, who has taken much pains to collect facts, and to establish a permanent theory for the periodical rec irrence of such phenomena, came to the con* elusion, that The meteors uf November \%th, 1833, em.analed from a nebulous body, which was then pursuing its way along with the earth around the sun ; that this body continues to revolve around tJie sun; in an tUipiical orbit *"/ little inclined to the plane, of the ecliptic, a/,ia having its ophdion near the orbit of the, earth ; 2nd .finally, thai 80-3. Supposed composition of these meteors? Why? 304. Hypotheses for exp'-uo. 'ug j.henomenon? Are they satisfactory? 06. Professor Ohusttd's concluat : FALLING OR SHOOTING ST\RS 161 the body has a -period of nearly six months, and thai its perihelion is a little below the orbit of Mercury * This theory at leust accommodates itself to the remarkable fact, that almost all the phenomena of this description, which are known to have happened, have occurred in tin two opposite months of April and November. A similar exhibition of meteors to that ot Noveii. her, 1333, was observed on the same day of the week, April 20th, 1S08, at Rich- BClNl, Virginia ; Stockbridge, Massachusetts ; and at Halifax, in British America. Anothfi *as witnessed in the autumn of 1813, in the North Sea, when, in the language of t 1 - > /servers, ''all the surrounding atmosphere was enveloped in one expansive sea f fire, "cKMting the appearance of another Moscow, in tlames." * Ajter the first edition of this irorkwciit to pre*#, the author wn-s pol'ttly fur nivhecf, by Professor Olmsted, zvith tfie folio tc ! ng cotnmimication. fc 5 am happy to hear that you propose to stereotype your 'Geography of the Heavens to has done much, I believe, to diffuse a popular knowledge of astronomy, and I am pleased that your efforts are rewarded by an extended patronage. " Were 1 now to express my views on the subject (Meteoric Stimcers) in as condensed a to>-m as pnssiblo. * should statf thpnr. in snn>- mch terms as the following: The meteoric dhowers winch nave 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, thy mostly appear to radiate from a common center ; that is, were their paths in thft 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, uamely, from three to four o'clock a time about half-way from midnight to sunrise. The meteors are inferred to consist of comb not i'.-le matter, because they are seen to take firo and burn in the atmosphere. They are known to be very light, because, although they fall toward the earth with immense velocity, few, if any, ever reach the eartJi, 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 grtut size, amounting in diameter to several hundred leet, 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, combustible 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 ,s/ri/-te or extreme portions of this are brought down to the earth, while the entire extent occupies many thousands, and perhaps several millions of miles. This 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 period in time of the nebulous body is cither nearly a year, or half a year. Various n a- Bons lure induced the belief that half a year is the true period ; but this point is c.n- siderrJ somewhat doubtful. The zod ideal light, a faint light that appears at different leasons of the year, either immediately preceding the morning or following the evening i*i"i,i.t. ascending from the sun in a triangular form, is, with some degree of probability, Jmght to l>e the nebular body ilself, although the existence of such a bo-ly, revolving in '. le solar system, was inferred to be the cause of the meteoric showr-s, before auj 20i; unction of it with the zodiacal light was even thought of." VVV.I: what remarkable fact docs his theory accord ? Substance of letter from Profrawv ]32 ASTRONOMY. 306 Exactly owe year previous to the groat phenomenon of 33, namely, on the 12th of November, 1832, a similar meteoric display was seen near Mocha, on the Red Sea, by Capt. Han. moud and crew of the ship Restitution. A gentleman in South. Carolina thus describes the effect of the phenomenon of 1S33 S ipon his ignorant blacks : " I was suddenly awakened by the most distressing cries tlia iver fell on my ears. Shrieks of horror, and cries of mercy, I could hear from most ci 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 saim I o:ce still beseeching me to rise, and saying, '0, my God, the world is on fire !' I th'jn jpened the door, and it is difficult to say which excited me most the awfulness of tin icene, or the distressed cries of the negroes; upward of one hundred lay prostra'e on th? jroutd 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 ; fi lever did rain fall much thicker, than the meteors fell toward the earth ; east, w. si aorth, and south, it was the same 1" 806. What similar meteoric shower referred to? Beocription of thai of N?vnbc) 1888, tad i!d ftfects upon certain persons ? PART II. THE SOLAR SYSTEM. CHAPTER I. GENERAL PHENOMENA OF THE SOLAR SYSTEM, HISTORY, &o. 307. OCR 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 saivie 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 thorn is well-nigh limited ; almost all our reasonings in regard to them being founded on c-?n<- rxirati'veli/ few and uncertain analogies. Accordingly, our chi-f business thus far h.'Ut been to detail their number, to describe their brightness and positions, and to give lira names by which they Vi ave been designated. 308. There now remain to be considered certain other celes- tial bodies, ail of which, from their remarkable appearance and changes, and some of them from their intimate connection with the comfort, convenience, and even existence of man, must have always attracted especial observation, and been objects of the most intense contemplation and the deepest interest. Most of these bodies are situated within the limits of the Zodiac. The most important of them are, the SUN, so superior to all the heavenly bodies for its apparent magnitude, for the light and heat which it imparts, for the marked effects of its changes of position with regard to the Earth ; and the MOON, so conspicu- ous among the bodies which give light by night, and from her 807. Subject of Part II.? Of our investigations hitherto? How distinguished? theii Dumber, distance, Ac. ? What has been our chief business thus far? iS. What n" remains to be considered? ilow situated? Which the most important ol them? 164- ASTRONOMY soft and silvery brightness, so pleasing to behold ; remarkable not only for changes of position, but for the varied phases or appearances which she presents, as she waxes from her crescent form through all her different stages of increase to a full orb, and wanes back again to her former diminished figure. 309. The partial or total obscuration of these tuo bodies, which sometimes occurs, darkness taking place even at mid-day, and the face of night, before lighted up by the Moon's beams!, being suddenly shaded by their absence, have always been among the most striking astronomical phenomena, and so powerful in their influence upon the beholders, as to fill them with perplexity and fear. 310. If we observe these two bodies, we shall find that, besides their apparent diurnal motion, across the heavens, they exhibit other phenomena, which must be the effect of motion. The Sun during one part of the year will be seen to rise every day farther and farther toward the north, to continue longer and longer above the horizon, to be more and more elevated at mid- day, until he arrives at a certain limit ; and then, during the. other part, the order is entirely reversed. 311. Again ; if the Sun's motions be attentively observed, hf will be found to have another motion, opposite to his apparent diuroal motion from east to west. This may be perceived dis- tinctly, if we notice, on any clear evening, any bright star which is first visible after sunset, near the place where he sunk below the horizon. The following evening, the star will not be visible on account of the approach of the Sun, and all the stars on the east of it will be successively eclipsed by his rays, until he shall have made a complete apparent revolution in the heavens. The.se are the most obvious phenomena exhibited by these two bodies. 312. The Moon sometimes is not seen at all ; and then, \rhen she first becomes visible, appears in the west, not far from the setting Sun, with a slender crescent form ; every night sho appears at a greater distance from the setting Sun, increasing in size, until at length she is found in the east, just as the Sun is sinking below the horizon in the west. 313. There are also situated within the limits of the Zodiac certain other bodies, which, at first view and on a superficial examination, are scarcely distinguishable from the fixed stars 809. >Vhat said of their obscuration? 810. Of their motions? 811. Has tte fero an apparent eastward motion ? 312. What said of the Moon's motions and pi asej 1 E18. What other bodies and their niotior*? What called, and why ? PHENOMENA OF THE SOLAR SYSTEM. 105 But, observed more attentively, they will be seen to shine with A milder and steadier light, and, besides being carried round with the stars, in the apparent revolution of the great celestial concave, they will seem to change their places in the concave i f self. Sometimes they are stationary ; sometimes they appear i.-o be moving from west to east, and sometimes to be going back again from east to west ; being seen at sunset sometimes in the fcist, and sometimes in the west, and always apparently changing their position with regard to the earth, each other, and the Jth )i heavenly bodies, From their wandering, as it were, ir this uanuer through the heavens, they were called by the Greeks TTAavTyrat, planets, which signifies wanderers. 314. There also sometimes appear in the heavens, bodies of a very extraordinary aspect, which continue visible for a considera- ble period, and then disappear from our view j and nothing more ,s seen of them, it may be, for years, when they again present themselves, and take their place amon^ the bodies of the celes- tial sphere. They are distinguished from the planets by a dull and cloudy appearance, and by a train of light. As they 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, '.yiieu 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 entirely disappear. They have no well-defined figure ; they seem to move in every possible direction, and are found in every part of the heavens. From their train they were called by tliu Greeks Kouqrai, comets, which signifies bearded, or having long hair. The causes of these various phenomena must have early constituted a very natural subject of inquiry. Accordingly, we shall find, if we examine the history of the science, that in very early times there were many speculations upon this subject, and that differ- ent theories were adopted to account for these celestial appearances. 315. The Egyptians, Chaldeans, Indians, and 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 in the earliest iges of the world had been carried to a great degree of perfec- tion, and that while the principles and explanations of the phe- 814. Any other bodies described? How distinguished ? What called, and why ? la if probable that these phenomena were early observed ? 815. What said of the Egyptian* Chaldeans, &c. f Of the Chinese in particular? Of the Indians and Chaldeans? 166 ASTRONOMY. nomena were lost, the isolated, unconnected facts, rules of calca lation, and phenomena themselves, remained. Thus, the Chinese, who, it is generally agreed, possess the oldest autnentic obserra- tions on record, have recorded in their annals, a conjunction of five plar/ets at the sarru time, which happened 2461 years before Christ, or 100 years before the flood. By irath& matical calculation, it is ascertained that this conjunction really occurred at that time. The first observation of a solar eclipse of which the worli'1 has any knowledge, was made *>y the Chinese, 2128 years before Christ, or 220 years after the deluge. It seems, also, that the Chinese understood the method of calculating eclipses; for, it is said, that the emperor was so irritated against the great officers of state for neglecting to predict the eclipse, that he caused them to be put to death. The Chinese have, from time Imme- morial, considered Solar Eclipses and conjunctions of the planets, as prognostics of importance to the Empire, and they have been predicted as a matter of state policy. The astronomical epoch of the Chinese, according to Bailly, commenced with Pohi, their first emperor, who flourished 2952 years before the Christian era, or about 350 years before the deluge. If it be asked how the knowledge of this antediluvian astrono- my was preserved and transmitted; it is said that the columns on which it was registered have survived the deluge, and that those of Egypt are only copies which have become originals, now that the others have been forgotten. The Indians, also, profess to have many celestial observations of a very early date. The Chaldeans have been justly cele' brated in all ages for their astronomical observations. When Alexander took Babylon, his preceptor, Callisthenes, found a series of Chaldean observations, made in that city, and extending back, with little interruption, through a period of 1903 years preceding that event. This would carry us back to at least 2234 years before the birth of Christ, or to about the time of the dispersion of mankind by the confusion of tongues. 316. The Greeks, in all probability, derived many notions in regard to this science, and many facts and observations, from Egypt, the great fountain of ancient learning and wisdom, and many were the speculations and hypotheses of their philosophers. The first of the Greek philosophers who taught Astronomy was Thales, of Miletus. He flourished about 640 years before the Christian era. Then followed Anaximander, Anaximenes Anaxagoras, Pythagoras, Plato. Some of the doctrines maintained by these philosophers were, that the Earth wah round, thax it had two motions, a diurnal motion on its axis, and an annual motion around the Sun, that the Sun was a globe of fire, that the Moon received her light from the Sun, that she was habitable, contained mountains, seas, Ui.\K SYSTEM. 101 who had preceded him, spread out before him, composed a work Ji thirteen books, called the Me yaAr/ Syvra^f, or Great System 318. Rejecting the doctrine of Pythagoras, who taught that tin; Sun was the center of the universe, and that the Earth had a diurnal motioL on its axis and nn annual motion around tho S-in, as contrary to the evidence of the senses, Ptolemy endea- vored to account for the celestial phenomena, by supposing the Larth to be the center of the universe, and all the heavenly bodies to revolve around it. lie seems to have entertained an idea, in regard to the supposition, that the Earth f-evolved 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 b dies, it would certainly preceda 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, iiul 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 fro a time to time, was the prevailing theory until the middle of the 15th century. Itwa.s not, however, always received with implicit confidence ; nor were its difficulties always 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 Deity had called me to his councils at the .-reation of the world, T could have given hiro good advice." He did not, however, mean any impiety or irreverence, except what was directed against the system of Ptoletny. 320. About the middle ol the 15th century, Copernicus, 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 .vith the idea that simplicity and harmony should characterize the arrangements of the planetary system. In the complication uil disorder which he saw reigned in the hypothesis of Ptolemy, !u- perceived insuperable objections to its being considered as a '^presentation of nature." 8 3. His system of astronomy? What singular idea and reasoning? 813. What uiffltultydid he meet with, and how explain it? What further difficulty? Ho*' long lid this theory prevail? What anecdote of the King of Castile? 820. What dis- .{aguish d student of astronomy now arose ? His impressions in regard to the Ptoleraak theory f His own earlier convictions? What oilier theories did he study? 168 ASTRONOMY. In the opinions of the Egyptian sages, in those of Pythng ras, Philolaus, Aristarct.a>> arid Nicetas, he recognized his own earliest conviction that the Earth was not the centei of the universe. His attention was much occupied with the speculation of Martinut Japella, who placed the Sun between Mars and the Moon, and made Mercury and Venus revolve round him as a center, and with the system of Appollonius Pergoeus who mad ill the planets revolve around the Sun, while the Sun ani Moon were carried around the Sarth in the center of the universe. 321. The examination, however, of various hypotheses, by Copernicus, gradually expelled the difficulties with which the ubject was beset, and after the labor of more than thirty years, ue was permitted to see thue true system of the universe. The iS.un he considered as immovable, in the center of the system, while the Earth revolved around him, between the orbits of Venus and Mars, and produced by its rotation about its axis al 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 tfw Relative Distances of the. Planels* Orbits, Map L of the 'Alias.} Thus, the stations and retrogradations of the planets were the necessary consequence of their own motions, combined with that of the Earth about the Sun. Ue said that " by long observation, he discovered that, if the motions of :he 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 remov 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 Brahe, born at Knudstorp, in Norway, in 1.046. 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 linen, and established for him an observatory at an expense of about 200,000 crowns. Here Tycho continued, for twenty-one year?. 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, &c., revolve around R body comparatively insignificant. 821. How was Copernicus led to discover the true system of astronomy? What is thai system? Does it account for the stations ;.nd retrogradations of the jlanets? 82Sr What distinguished astronomer next arose- 1 What said of his detention in JVcrnarU His ocwvatinns ? HI* theory PHENOMENA (3E SOLAR SYSTEM. 100 323. .Near the close of tin 15th century, arose two men, vv'io wrought most important changes in the science ; Kepler and Galileo, the former a German, the latter an Italian. Previous to Kepler, ail investigations proceeded upon the supposition that the planets moved in circular orbits which had been a source of M ich 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 thur motions through their orbits, and the times of their revolutions, were proportioned; all truths of the greatest importance to the science. 324. 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. 325. 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 deepent 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 /icxt led t > suppose that perhaps the same power carried the 828. What two noted astronomers next arose? What did Kepler discover? 824. Olileo and his discoveries? What theory did they s*:rve to establish? 825 Wha gu>at di* v-, v ^iii made, and by whom? How IH to it? 3ucc*3Jre atcpti? 17C ASTRONOMY. primary pm^-its around the Sun. By a series of calculations, he was enabled at length to establish the fact, that the Name 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. Ta recapitulate briefly : The system (not hypothesis, for i mch of it has beea established >v mat.iematical demonstration) by which we are now enabled to explain with a beau .1- t'u' simplicity the different phenomena of the Sun, planets, moons, and comets, is, that th? Sun is the central body in the system: that the planets and comets move round him ii: elliptical orbits, whose planes are more or less inclined to each otlier, with velocities I faring to each other a certain ascertained relation, and in times related to their dis- t,in< es ; that the moons, or secondaries, .-evolve 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 In consider, one by one, the several bodies above mentioned. 326. Those bodies, thus arranged and thus revolving, consti- tute what is termed the SOLAR SYSTEM. The planets have been divided into two classes, Primary Planets and Secondary Planets. The latter arc also termed Moons, and sometimes Satellites. The Primary Planets are those that revolve around the Sun as a center. The Secondary Planets arc thoso that re- volve around their primaries. There have been discovered up to this date (1873), eight large primary planets, namely, Mercury, Venus, the Earth, Mars, Jupiter, Saturn, Uranus, and Neptune; together with one hundred and twenty-eight very small bodies, called Asteroids, or Minor Planets. These small primary, planets revolve in orbits all of which are situated between the orbits of Mars and Jupiter. Of the primary planets Mercury is the nearest to the sun, and the others follow in the order in which they are named abovn. The Asteroids are, with one exception, visible only through a telescope ; and hence are called telescopic planets. Neptune, though very much larger than any of the Asteroids, is also a telescopic planet, on account of its immense distance from us. There have been discovered eighteen secondary planets, or satellites. Of these, the earth has one, Jupiter four, SMtt.;n eight, Uranus four, and Neptune one. All these, except our own satellite, the Moon, are invisible to the naked eye. Map I. o 1 the Atlas, "exhibits a plan of the Solar System," comprising the lehttiv. .i:iiutu.l?s ?f the Sun and Planets; their comparative distances from the Sun, ar.d ('< rr M<^ .tlier; the position of their orbits, with respect to each other; the Earth ynd tt t !:'ir. together with many other particulars which are explained on the map. TLtre, !l e Ocs.-ribe the Copernicau theory? 320. What do the bodies mentioned ccnstitu'c? Uow are U-e planets divided? Describe each? What number of primaries ? Name Uwm ii- order from the Sun? Which are the Asteroids? Which telescopic? How manj lauets? How distributed ? Are ihev visible to Urt naked T 1 What ini? TUB SUN JUS DISTANCE, MAGNITUDE, ETC. 17] flm and moat prominent object which claims attention, is the representation of tb dun's circumference, with its deep radiations, bounding the upper margin of th-j napt l fc Is apparent, however, that this segment is hardly one-aixlh of the whole cireurnfei nc cf which it is a part. Were the map sufficiently large to admit the entire orb of the Sun, Men upon so diminutive a scale as there represented, we should then see the Sun an J Planets in their just proportions the diameter of the former being 112 times the diainet* ? of the Earth. It was intended, originally, to represent the Earth upon a scale of one inch in diameti.* .nd 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 htdf an inch for the Earth's diameter, which makes that of the Sun 56 inches, and the otter bodies, aa represented upon the map. The relative position of the Planets' orbits is also represented, en a scale as large as the sheet would permit. Their relative distances from the Sun as a center, and from each ether, at* there shown correctly. But had we wished to enlarge the dimensions of these rrbits, sc that they would exactly correspond with the scale to which we have drawn thu S 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 Herschel 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 460 miles ; and a circle of this diameter (containing therefore nearly 200,OuG square miles) is the least space which can be distinctly discerned on the Sun as a vixibli a?'e<(, 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 soiai spots with considerable minuteness, and have several times seen spots which wt-re not less than the one twenty-fifth part of the Sun's diameter, which would make them abou{ 12,192 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 vis) ble to the naked eye which we must believe, unless we refuse respectable testimonj- they could not have been much less than 50,000 miles in diameter." 881 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 eighteentl jentury? Dr. H^rschePs measurements ? Dr. Dick's remarks and concluaioa ? 174 ASTRONOMY. 332. The apparent directiou of these spots over the Sun's disti 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. The following diagrams may serve to illustrate : VARIOCS DIRECTIONS OF TUB SOLAR SPOTS. Alareh. June. September. December. Let E F represent the plane of the- ecliptic. In March, the spots describe a curve which is Convex to th ? 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 ii and D show the inclination of the Sun's axis. Th<3 following diagram will servf* still further to illustrate the cause v>-f the change of direction of the solar spots. SOLAR SPOTS OBSERVED FROM DIFFERENT POINTS. c DEC. iAil the student imagine himself stationed upon the earth at A, In March, looking inon .t.6 wmi ic the center, whose north or upper pole is now inclined toward Mm. The spoU ill then curve tu^- iward. Three months afterward- -viz., in June the earth will be S2 In what general direction do these spots move? What vai iations ? 338. Whal ' lie atiiutc of these varying phenomena THE SUN Hi? DISTANCE, MAGNITUDE, ETC. 175 at B ; when the sun's axis will incline to the left, arid the spots seem to pass upward ta ihe rig'at. In three mouths 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 onger, he will be at D, when the axis of the sun will incline to the rigid, 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 nat time, the spot has, in fact, gone through one revolution, together with an arc, equal to that described by the Earth in ner 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 SIDRREAL AND SYNODIC RBVOLCTIOMS OF THE SUN. 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 comes 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. '^/vj This last is a synodic revolution. It consists of one complete revolu- tion of the sun upon his axis, and about 27 over 336. The part of the Sun's disc not occupied by spots, is fiit from being uniformly bright. Its ground is finely mottled with an appearance of minute dark dots, or pores, which, attentively watched for several day.s 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 884. Are these spots supposed to adhere to the body of the Sun ? On what part of thn 9un are they found ? 835. What is their time of apparent re /olution ? The o< t mil tim?? How arrived at? 386. What snid of the part of the SUT about his polesf Of his physical organization? What does it soem to be* llow did Sir W. Hcraduit 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 glubes of ,he sys- tem, in its sipposed 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 Suii 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. 337. Laplace's speculations? What other opinions? 838. Is there a satisfactory Slifory of the physical nature of the Sun ? State the prevailing t ne ? Herschel'a suppo- iticat 889 What conjecture in regard to the inhabitants of the Suii, ami uft tbat 1 a- i j J f Who held to this ide \ t TOE PRIMARY PLANETS MERCURY AflD VENUS. 17? CHAPTER III. THE PRIMARY PLANETS MERCURT 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 twenty times less than that of the Earth. It would require more than twenty millions of such globes to compose a body equal to the Sun. H>re 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 recur to the figures of thw Map, until he is able to form in his mind distinct conceptions of 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 S,92 mfles, and that of the Earth 7,912 ; their bulks are as the cube of 2,962, to the cuba of T,912, or as 1 to 20, 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 about 35,000,000 of miles. The length of Mercury's year, therefore, is equal to about three of our months. The rotation of a placet on its axis, constitutes its day; its revolution about the Sun .onstitutes 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, *u f receives from the Sun six and a half times as much light and 340. Subject, of Chapter III. ? Size and position ^f Mercury? WiiAt map illustrates tli is subject? 341 State the time of Mercury's revolution upon his axis? How doe:! tl.s compare with the Earth? His period of revolution around the Sun ? 842. What 3uid of discoveries upon Mercury, his phases, &c. ? What proof that he is opaque f 278 ASTRONOMY. beat as the Earth. The truth of this estimate, of coursa 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 THE DIFFUSION OP UQ1IT. 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, and C receive equal quantities of light, though B is four times, and C nine times as large as A; and tic the light falling upon A is spread over four times as much surface at B, and nine times as much at C, it follows that it is only one-ninth as intense at C, and one-fourth at P., as it is at A. Hence the rule, that tJie light and heat of the planet is, inversely, asihe square* of their respective distances. The student may not exactly understand this last statement. The square of any num- ber is its product, when multiplied by itself. Now suppose we call the distances A, B, and C, 1,2, and 3 miles. Then the square of 1 is 1 ; the square of 2 is 4; and the square of 3 is 9. The light and heat, then, would be in inverse proportion at these three points, as 1, 4, and 9 ; that is, four times less at B than at A, and nine times less at C. These amounts we should state as 1, ^, and one-ninth. 344. This law of analogy, did it exist with rigorous identity at all the planets, would be no argument against their being inhabited ; because we are bound to presume that the All-wise Creator has attempered every dwelling-place in his empire to the physical constitution of the beings which he has placed in it. From a variety of facts which have been observed in relation to the production of rstloric, it does not appear probable, that the degree of heat on the surface of the differ- ent planets depends on their respective distances from the Sun. It is more probable, that It depends chiefly on the distribution of the substance of caloric on the surfaces, and throughout the atmospheres of these bodies, in different quantities, according to the dif- ferent situations which they occupy in the solar system ; and that these different quan tities of caloric are put into action by the influence of the solar rays, so as to produce that degree of sensible heat requisite to the wants, and to the greatest benefit of each 01 the planets. On this hypothesis, which is corroborated by a great variety of facts and experiments, there may be no more sensible heat experienced on the planet Mercury, Mian on the surface of Ilerschel, which is fifty times farther removed from the Sun. 345. The rotation of Mercury on its axis, was determined from the daily position of its horns, by M. Schroeter, who not only discovered spots upon its surface, but several mountains hj its southern hemisphere, one of which was lOf miles high - nearly three times as high as Chimborazo, in South America. 343. His density, and light and heat? Upon what rule is this estimate based? &44, Would not this law of analogy make against the doctrine that the planets art Inhab- ited? Is it probable that this law does prevail? Upon what may the relative heat of thd planets c'-s^ftiJ? 345. How was his diurnal revolution determined, and by whomt Wb.fU mo of lv R-arfavs? What observation respecting mountains in general? HE PRIMARY PLANETS - MERCURY AND VENUS. 179 it \9 worthy of observation, that the highest mountains which have boon discovered ii Mercury, Venus, the Moon, and perhaps we may add the Earth, are all situated in theii southern hemispheres. 346. During a few days in March and April, August and Sep- tember, Mercury may be seen for several minutes, in the morn- ing or evening twilight, when its greatest elongations happen in those months ; in all other parts of its orbit, it is too near the Sun to be seen by the naked eye. The greatest distance that if. ever departs from the Sun, on either side, varies from 16 12', to 28 20', alternately. The distance of a planet from the Sun, as seen from the Earth (measured in degrees), is called its elongation. The greatest absolute distance of a planet from the Sun is denominated its aphelion and the least its perihelion. 347. The revolution of Mercury about the Sun, like that of all the planets, is performed from west to east, in an orbit which is nearly circular. Its apparent motion, as seen from the Earth, is, alternately, from west to east, and from east to west, nearly in straight lines ; sometimes directly across the disc of the Sun, hut at all other times either a little above or a little below it. Were the orbits of Mercury and Venus in the same plane with that of the Earth, they would cross the Sun's disc at every revolution ; but as one-half of each of their orbits \A obo-ve, and the other half below the ecliptic, they generally appear to pass either above r below the Sun. B Let the right line A, joining the Earth and the Sun in the above diagram, represen the plane of the ecliptic. Now when an interior planet is in this plane, as shown at A, 11 may appear to be upon the Sun's disc ; but if it is either above or below the ecliptic. as shown at 15 and C, it will appear to pass either above or below the Sun. as shown at 1) and E. For the relative position of the planets' orbits, an ' their inclination to the plane of the ecliptic, see 1, of the Atlas. Here the dotted lines continued from the dark lines, denote the inclination of the orbits to the plane of the ecliptic, which inclination U marked in figures on them. Let the student fancy as many circular pieces of paper intersecting each other at the several angles of inclination marked on the Map, and he trill be enabled to understand more easily what is meant by the "inclination of the planets' orbits." 348. Being commonly immersed in the Sun's rays in the even ing, and thus continuing invisible till it emerges from them in the morning, Mercury appeared to the ancients like two distinct stars. A long series of observations was requisite, before they 846. Wlien aiay Mercury be seen? Why not at other times? How far does it iKpa- from the Sun on either side? What is meant by the elongation of a planet f Its apfio- Won and perifieHon ? S47. In what direction do the planets revolve around thf. Sun What is the apparent motion of Mercury? Do they ever cross the Sun's disc ? Wbj ttot at evevy revolution ? 843. How wan Mercury regarded by the anciouttjf 180 ASTRONOMY. recognized the identity of the star which was seen to recede, from the Sun in the morning with that which approached it ii the evening. But as the one was never seen until the other disappeared, both were at last found to be the same planet, wlik-li thus oscillated on each side of the Sun. 349. Mercury's oscillation from west to east, cr from east U west, is really accomplished in just half the time of its revolution which is about 44 days ; but as the Earth, in the mean time*, follows the Sun in the same direction, the apparent elongation will be prolonged to between 55 and 65 days. JI50. The passage of Mercury or Venus directly between the Garth and the Sun, and apparently over this disc, is called a Transi*. A transit can never occur except when the interior planet is in or very near the ecliptic. The Earth and the planet must be on the same side of the ecliptic ; the planet being at one of its nodes, and the Earth on the line of its nodes. FHTL060PHT OF nUVUTB. This cut represents the ecliptic and zodiac, with the orbit of an interior planet, hig nodes, Ac. The line of his nodes is, as shown, in the 16 of and the 16 of 1IJ,. Now if the earth is in 6 , on the line L N, as shown in the cut, when Mercury is at his ascending node (ft), he will seem to pass upward over the Sun's face, like a dark spot, as repre- sented in the figure. On the other hand, if Mercury is at his descending node ($), when the earth is in the 16* of TTJ,, the former will seem to pass downward across the disc of the Sun. 851. As the nodes of his orbit are on opposite sides of the ecliptic, and are passed by the Earth in May and November, it follows that all transits of Mercury must occur in one or the other of these months. They, are, therefore, called the No*h months. As is shown in the diagram, the Earth passes the &49. In what time is the oscillation of Mercury from east to west really accompiUhfetU H"hat is the apparent time, and why ? 350. What is a transit f When do they IACUT 1 What are the \wd<~# of a planet's orbit? The line of the nodes 851. What ar tlw THE PR; MARY PLANETS MERCURY AND VENUS 181 ascending Node of Mercury in November, and the descending- in May ; the former of which is in the 16th degree of Taurus, am! the latter in the 16th degree of Scorpio. All the transits of-Mercury ever noticed have occurred in one or the other of thus months, and for the reason already assigned. The first ever observed took place Noveuv ber 6, 1631 ; since which time there have been 29 others by the same planet in all 80- 8 in May, and 22 in November. 352. The last transit of Mercury occurred November 11, 1861 ; and the next will take place November 4, 1868. Besides this, there will be four more during the present century two in Maf, aud two in November. The accompanying cut ia a de- lineation of all the tranaits of Mer- uury from 1802 to the close of the 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 t>f 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 oe 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, neai Oswego, New York ; but, unfor- tunately, his sky was overhung with clouds, which liid the sun from liis view, and disappointed all his hopes. TUAXSIT8 OP MQROUBT. NORTH SOUTH 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 ail the phenomena dependent upon the relative position of the ^]arth, 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 (ind a nu nber of sidereal years, in which the pJanet complte xactly, or very nearly, a certain number of revolutions; that is, to find such a number jf planetary revolutions, as, when taken together, shall be exactly equal to one, or any .umber of revolutions of the Earth. Ir the case of Mercury this ratio will be as 87.969 3 to 305.256. Whence find that, ion S will occur ? What ratio is found between the revolution! < 182 ASTRONOMY. 1707 May 5. 1710 Nov. 6. 1723 Nov. 9. 1736 Nov. 10. 1740 Nov. 2. 1743 Nov. 4. 1758 May 5. 1756 Nov. 6. 1769 Nov. 9. 1776 Nov. 2. 17S2 Nov. 12. 17S6 May 3. 1769 Nov. 5. 1799 May 7. 1802 Nov. 8. 1S15 Nov. 11. 1S22 Nov. 4. 1S32 May 5. 1836 Nov. 7. 1S45 May 8 1S4S Nov. 9. 1S61 Nov. 11. 1S68 Nov. 4. 187S May 6. 1881 Nov. 7. 1891 May 9. 1894 Nov 10. T periodical revolutions of the Earth are equal to 20 i Mercury . 18 periodical revolutions of the Earth are equal to 54 of Mercury: 88 periodical revolutions 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 interval* of T, li, 33, I kc. years. Transits of Venus, as well as eclipses of the Sun and Moon, are calculat upon the same principle. The following is a list of all the Transits of Mercury from the time the first was obsTv. 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. 354. The suiereai 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. ADD SYNODIC REVOLUTIONS. In the adjoining cut the revolution of the Earth from A, opposite the star 13 around to the same point again, would be a sidereal revolution. Suppose the Earth and Mercury to start together from the points A C (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 j. synodic revolution will not be completed by Mercury. He starts on, however, in his 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 conjunction. Erom 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 105,330 miles an hour ; that of the Earth is 65,533 miles ; the differ- ence, 39,797 miles, is the mean relative motion of Mercury, with respect to the Earth. The sidereal revolution of Mercury is 87d. 2Sh. 15m. 44s. Its synodical revolution it r>d the Earth? 854. What is a sidereal revolution of a planet? A synodical i 806. What is the absolute motion of Mercury in his orbit? What is that of the Earth i fhe ('ifTerence, or relative motion of Mercury? What is his sidereal period? Ait T U w is the latter ascertained? THE PRIMARY PLANETS MERCCRV AND VENUS. 183 fouD' 1 , by dividing the \rh( v circumference of 360 by its relative motion in respect to the Earth. Thus, the mean daily motion of Mercury is 141 W. 556; that of the Earth is B543'.318 ; and their difference is 11184" .237, being Mercury's relative motion, or what if gAliiS on the Earth every day. Now by simple proportion, 111S4".237 is to 1 day, as 860* to ii 115d. 21h. 8 1 , 24", the period of a synodical revolution of Mercury. VENUS. 356. There are but few persons who have not observed a beautiful star in the west, a little after sunset, call the evening ft<*r Thif star is Venus 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 aow 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 13 now called the morning star. It departs farther and farther from the Sun, rising a" little earlier every day, until it is see* 856. Describe Venus. What called? Distance from the Sun ? What change of posi- tion observable ? 357- Greatest distance to which she departs from the Sun? Whaf How aud when seen? 85S. What next after these phenomena? 184 ASTRONOMY. about 4fi west of him, where it appears stationary for a few days ; then it resumes its course towards the Suu, appealing 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 Venus. U59. Venus revolves about the Sun from west to east in '22 4 Jays, at the distance of about 66,000,000 of miles, moving hi her orbit at the rate of 77,000 miles an hour. She turns arotii.-'l 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 13 equal to 7^ of our months, or 32 weeks. 360. The mean distance of the Earth from the Sun is esti- mated at 91,500,000 miles, and that of Venus being 66,000,000, the diameter of the Sun, as seen from Venus, will be to his dia- meter as seen from the Earth, as 91-|- to 66, and the surface of his disc as the square of 91 j to the square of 66, that is, aa 8372 to 4356, 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), Venus receives twice as much light and heat as the Earth. 361. The orbit of Venus 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 Venus about 4ti 9 , the orbit of Venus must be outside of the orbit of Mercury. 362. The diameter of Venus is about 7.500 miles ; but her apparent diameter and brightness are constantly varying, accord- ing to her distance from the Earth. When Venus and thu 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 158,000,000 of miles. Were the whole of her enlightened hemisphere turned towards us. when she is nearest, she would exhibit a light and brilliancy 359. 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 cursl f60. How must the Sun appear from Venus, and why? What of her li^ht and heati 861. Where & the orbit of Venus situated? What proof of this? 3C2. Venus' d>arut> terf lljr apparent diameter? Staie her least and greatest distances from the Earth TUB PRIMARY PLANETS MERCURY A?,'D VENtS. 183 twenty-five times greater than she generally does, and appear like a small brilliant moon ; but, at that time, her dark hemi- sphere is turned towards the Earth. When Venui approaches nearest to the Earth, her apparent, or observed diameter iu 61".2; when most remote, it is only 9". 6 ; now 6r.2-*-9".6=6?i. hence when nearest the Earth her apparent diameter is 6 3 i times greater than when most distant, and surface >f her disc (>f*/* or nearly 41 times greater. In this work, the apparent size of thr eavenly bodies is estimated from the apparent surface of their discs, which is always proportional to the squares of their apparent diameters. 3(3. Mercury and Venus are called Interior planets, because .heir 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 Venus lie within the Earth's orbit, it is plain, that once in every synodical revolution, each of these planets will be iu 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 CCNJUKCTION -' "T \ MARS IN" OPPOSITION Let the student imagine him- self stationed upon the earth in the cut. Then the sun and thres planets above are in conjunc- tion. The inferior and supe- rior are distinguished ; while at A, a planet is shown in quadra- 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' 8'.8, and theii difference is. 86' '9".5. Divide 860 by 86' 59".5, and it gives 5S3.920, or nearly 584 days for Venus' synodical revolution, or the period in which she is twice in conjunction with l.e Earth. 364 When Venus' right ascension is less than that of the S in, she rises before him ; when greater, she appears after his Jetting. She continues alternately morning and evening star, or a period of 292 days, each time. Hew wculd she appear if we saw her enlightened side when nearest to us? What coin- ru'ntion in the fine print? 803. How a"e Mercury and Venus distinguisled, ar<1 whv f Whnt .said ! Venus' syxiodical revolution found? 8>4." When is Venus evening star ' MorW! 186 ASTRONOMY. To those Tlio are but little acquainted with astronomy, it will seern strange, at flrsi that Venus hould 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 io considered, that while Venus moves around the Sun, at the rate of about 1* 86' of angular motion per day, the Earth follows at the rate of 59' ; so that Venus actually gains on the Earth, only 87' in a day. Now it is evident that both planets will appear to keep on the same side of the Sun, jntil Venus has gained half her orbit, or ISO" in advance of the Earth; and this, at a - ear. rate, will require 292 days, since 292 x 37'=10S04', or ISO 8 nearly. 365. Venus passes from her inferior to her superior conjunc tion in about 292 days. At her inferior conjunction, she i.' 1 J6,000,000 of miles from the Earth j at her superior conjunc tion, 158,000,000 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, us she approaches the Earth, and comes more and more into view as she recedes from it. It is to this cause alone that we 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 VENUS A3 SHE REVOLVES AROfBD THS SUM. It should be remarked, however, that Venus is never se&n when she is entirely/?//^ txcept once or twice in a century, when she passes directly over the Son's disc. A! every other conjunction, she is either behind the Sun, or so near him as to be hidden b/ the splendor of his light. The preceding diagram better illustrates the various appear- ances of Venus, as she me ves around the Sun, than any description of them could do 367. From her inferior to her superior conjunction, Venus, appears on the west side of the Sun, and is then our morniu51 periodical revolutions of the Karth are equal to 4<>.S of Venus: 211 periodical revolutions of the Karth are equal to 475 of Venus. Hence a transit of Venus tuny happen at the same node, after an interval of 8 years, but if it 40 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 those 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 dtgree of Sagit- tarius. 371. The node months of Venus are December and June. The line of her nodes lies in Gemini ( n ) and Sagittarius ( ^ ) ; and as the Eartli always passes those points in the months 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 flO,); for as the lino of Venus' nodes is only one sign ahead of that of Mercury, the Earth will reach that point 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 ia 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 llorrox, 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. llorrox, without much assistance from books and instruments, set himself to inquire into the error of the tables, and found that such a phenomenon might I , expected to happen in 1039. lie 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 .1 confidential friend residing in Matiohuster, and desired him to watch for the event, and to take observations. So anxious was llorrox 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. Hut the very hour when his calculations led him to jxpect the visible appearance of Venus on the Sun's disc, wax alxo Vie rtjpotltted how for tkii piMtc wavxhip of God on the Sublntth. 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: ft'id nearly a century and a half would elapse before another opportunity would occur. He had been waiting for the event with the most ardent anticipation for eight years, and the result promised much benefit to the science. Nuticithxtanding all this, Ilorroa twice suspended his observations t works he delighted to contemplate. When his duty was thus per - 871. Which are h r node months "t 372. When was the first, transit observed 'ntcrttting anecdo'of 190 ASTRONOMY. :ime of the next transit at the same node, whbh will accordingly happen in 1874. There will be another at the same node iu 1882, eight years afterwards. It is not more certain that this phenomenon will recur, than that the event itself will engross the attention of ail 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 Venus 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 may 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 Rerschel, have these observations appeared to astronomers, tha* 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 ona of them. The general result of all the observations made on this most memorable occasion, gave S".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, io 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 silence was gratified with full success; and he saw what no mortal eye had observed before f If anything can add interest to this incident, it is the modesty with which th.9 young astronomer apologizes to the world, for suspending his observations at all. " I observed it," says he, " from sunrise till nice o'clock, again a little before ten, *Dg lastly at noon, and from one to two o'clock ; the rest of the day being devoted ;* duties, which might not be neglected for these pastimes." When the next ? When another ? How will it DC regarded ? 873. Why shouU sucli n event excite general interest? Remark cf Sir John Herschel? What expedition and what results? 374. Upon what do the seisonsof the planets depend? \VT\t is th inclination of Venus' axif- t the plane r ^er orbit? Uow ?s her orbit aihiuwd vltt to the ecliptic? THE PRIMARY PLANETS MERCURY AM; VENUS. IMUXATCOK Of TWOS' AXD. The orbit of Venus departs from the ecliptic 8J$% while her ante is inclined lo th !ane of her orbit 75% as shown in the above figure. This distinction should be kept it finitely in view by the student. 375. The declination of the Sun on each side of Venus' 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 hei polar circles only 15 from her equator. It follows, also, thai {lie Sun must change his declination more in one day at Venus, than in five days on the Earth ; and, consequently, that he nevci' 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 a,s great on this planet as it is on the Earth. 376. At each pole of Venus, 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, thai the polar days and nights of Venus are not quite two-thirds as long as ours. Between her polar circles, which are but 15 from her equator, there 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 Venus' axis inclines towards the 20th degree o^ Aquarius ; the Earth's towards the beginning of Cau- cer ; consequently, the northern parts of Venus have summer ! n the signs where those of the Earth have winter, and nee wsA. '377. When viewed through a good telescope, Venus cxuibits oc only all t"ie moon-like phases of Mercury, but also a variety >f inequalities on her surface ; dark spots, and brilliant siiad^s, hills and valleys, and elevated mountains. But on account of <75. What 5s the amount of the Sun's declination upon Venus? What resu'ts? Wh.if supposed design in this arrangement ? 870. What said of the polar regions of V What of her seasons ? How is her north pole situated with respect to the What consequence? 377. How does Venus appear through a telescorc 1 192 ASTRONOMY. the great density of her atmosphere, these inequalities are per ceived with more difficulty than those upon the other planets. 378 The mountains of Venus, like those of Mercury and trr- 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 thac that of the Earth. Several eminent astronomers affirm, that they have repeatedly seen Venus 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 Venus on the Sun's disc, at the transits of 1761 and '1769. It probably docs not exist. THE EARTH. 379. The Earth is the place from which all our observation? of the heavenly bodies must necessarily be made. The app:::vni motions of these bodies being very considerably affected by hei figure, motions, and dimensions, these hold an important place iu 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 u, or Zebu, sometimes called Malan, one of the Philippines. One of his vessels, however, arrived at St. Lucar, near Seville, September 7, 1522. >*0. What second proof stated? Who first sailed around the world? Who nextV 381. In what direction did they s.v'l? How did these voy/iges prove the earth to hf 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 circuin- polar stars ; this is found uniformly to increase as we approach them, and to diminish as we recede from them. LATITUDE FOfND BY THB 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 46 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 wouk' sink below the horizon, and become invisible. Whence we derive the genera) rule, that the altitude of one pole, or tht depression of the other, al any ftfux 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 MOOD *n au eclipse, indicates the globular figure of the Earth, and the eouseijuent convexity of its surface. FOKM OK THK EARTH'S SHADOW .CTl^L.l ? 3S2. What further proof have we that the earth is bpherical? Whl mh .CvJ -po:i this jJienomenon ? S88. What other evidence that the earth is a jrljbn V.it remarks respecting tlie curvature of the earth's surface? What rules laid down upon this curvature? THE PRIMARY PLANETS THE EARTH. J35 Were the Earth a cube as shown at A, or in the form of a prism, as represented at B, tier shadow would be more or less cubical or prismatic, as seen in the cut ; but insteaJ i>f this, it is convex on nil ttiitet), as represented at C, plainly indicating the convexity of the Earth by which it is caused. The curvature of the Earth for one milt is S inches ; and this curvature increases with the square of the distance. From this general law it will be easy to ,heref What proof to the contrary? 885. What, then, to 'ie earth's real figure ? What difference in her polar and equatorial diameters ? Waat imronstrfit'.on that the earth ia not an exact sphere? 196 ASTRONOMY. ray have determii.ed that the mean diameter of the Earth, from the 46th 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 1x3 determined by its curvature, from a single measurement. Thui, in the adjoining figure, we have A B equal to 1 mile, and B f) equal to S 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 si'.ion 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 : (53.360 : : 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 seem strange to find the Earth classed with the heavenly bodies. For what can aonear 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 hours 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, D 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 91,500,000 of miles. It consequently moves in its orbit at the mean rate of 65,500 mil&s an hour. Its equatorial diameter being 7926 miles, it turns on its axis at the rate of 1040 miles an hour. Thus, th'j Earth on which we stand, and which has served for ages as the unshaker. foundation of the firmest structures, is every moment turning swiftly on its -HER DISTANCE, MOTIONS, PHASES. 203 CHAPTER IV. THE MOON-HE* DISTANCE, MOTIONS, PHASES, feo. 402, THERE is no object within the scope of astronomica. observation whi h affords greater variety of interesting investi- gation than the various phases and motions of the Moon. From them the astronomer ascertains the form of the Earth, the vicis- situdes of the tides, the causes of eclipses and occultatious, the d ''stance of the Sun, and, consequently, the magnitude of the solar system. These phenomena, which are perfectly obvious to the unassisted eye, served as a standard of measurement to all nations, until the advancement of science taught them the advan- tages of solar time. It is to these phenomena that the naviga- tor is indebted for that precision of knowledge which guides him with well-grounded confidence through the pathless ocean. The Hebrews, the Greeks, the Romans, and, in general, all the ancients, used to assemble at the time of new or full Moon, to discharge the duties of piety and gratitude for her unwearied attendance on the Earth, and all her manifold uses. The philosophy of the changes of the Moon is illustrated by tiie following cut : PHILOSOPHY OF TUB WOON'8 CHANG KS. This cut represents the moon revolving eastward around the Earth. In the lutsidc circle, she is represented as she would appear, if viewed from a direction at right angle* with tLs plane of her orbit. The side toward the Sun is enlightened in every case, and the appears like a half moon at every point. 402. What sail of the Moon's motions and phases? What learned from them? Ho* used anciently ? How at the present time? How did the ancienta observe the new uc: full moons ? .Q* 204 ASTRONOMY. The interior suit represents her .as she appears when viewed from the earth. At A it if New Moon ; and if seen at all so near the Sun, she would appear like a dark glebe. Al B ohe would appear like a crescent, concave toward the east. At C, more cf her e&light' ened side is visible ; at D still more; and at E the enlightened hemisphere is fully ia Tiew. We then call her a Full Mom. From E around to A again, the dark portion becomes more and more visible, as the luminous part goes out of view, till she cornea t* \xt change at A. When at D and F the moon is said to be gibbous. 403. When the Moon, after having been in conjunction with the Sun, emerges from his rays, she first appears in the evening, a little after sunset, like a fine luminous crescent, with its convex Bide towards the Sun. If we observe her the next evening, wo find her about 13 farther east of the Sun than on the preceding evening, and her crescent of light sensibly augmented. Repeat- ing these observations, we perceive that she departs farther and farther from the Sun, as her enlightened surface comes more and more into view, until she arrives at her first quarter, and comes to the meridian at sunset. She has then finished half her course from the new to the full, and half her enlightened hemisphere is earned towards the Earth. 404. After her first quarter, she appears more and more gib- bous, as she recedes farther and farther from the Sun, until she has completed just half her revolution around the Earth, and is seen rising in the east when the Sun is setting in the west. She then presents her enlightened orb full to our view, and is said to be in opposition ; because she is then on the opposite side of the Earth with respect to the Sun. la the first half of her orbit she appears to pass over our heads through the upper hemisphere ; she now desjcnds below the eastern horizon to pass through that part of her orbit which lies in the lower hemisphere. 405. After her full she wanes through the same changes of pearance as before, but in an inverted order ; and we see her in the morning like a fine thread of light, a little west of the rising San. For the next two or three days she is lost to our view, rising and setting in conjunctio-u with the Sun ; after which, she passes over, by reason of her daily motion, to the east side of the Sun, and we behold her again, a new Moon, as before. In changing sides with the Sun, she changes also the direction of her crescent. Before her conjunction it was turned to the cast ; it is now turned towards the west. These different appearances of the Moon are called her phases. They prove that she shines 103. Explain the cause of the cnanges of the Moon ? 404. How after her first quarter? 105. How after her full T WUat change in her crescent? What do the Moon's phase* wove ? THE MOON - HER MOTIONS, PHASES, ETC. 205 ;K>I by any lij/ht of her own ; if she did, being globular, we should always flee her a round full orb like the Sun. 406. The Moon is a satellite to the Earth, about which she revolves in an elliptical orbit, in 29 days, 12 hours, 44 minutes, and 3 seconds ; the time which elapses between one new moon and another. This is called her synodic revolution. Her revo- lution from any fixed star to the same star again, is called her periodic or sidereal revolution. It is accomplished in 27 days, 7 Lours, 43 minutes, and 11 seconds ; but in this time, the Earth has advanced nearly as many degrees in her orbit ; consequently, the Moon, at the end of one complete revolution, must go as many degrees farther, before she will come again into ^he same position with respect to the Sun and the Earth. 8IDKBKAX AND SYNODIC REVOLUTIONS OF THK MOON. REVOLUTION SUN AND MOON IN CONJUNCTION- NEW MOON/ On the right, the earth is shown in her orbit, revolving around the sun, and the mooi in her orbit, revolving around the earth. At A, the sun and moon are in conjunction^ or it is New Moon. As the earth passes from D to E, the moon passes around from A to B, or the exact point in her orbit where she was 27% days before. But she is still west of the sun, and must pass on from B to 0, or 1 day and 20 hours longer, before she can again come in conjunction with him. This 1 day and 20 hours constitutes the difference Between a sidereal and a synodic revolution. The student will perceive that the difference between a sidereal and synodic revolution of the moon, like that between solar and sidereal time, is due to the same cause, namely, the revolution of the earth around the sun. 407. Lying along the Moon's path, there are nine conspicu- ous stars that are used by nautical men for determining their longitude at sea, thence called nautical stars. These stars are, Arietes, Aldebaran, Pollux, Regulus, Spica Virginit. Antares, Ateaire, Fomalhaut, and Markab. The true places of these stars, for every day in the year, are given in the Nautical Umanac, a valuable work published annually by the English " Board of Admiralty," tC ju)de mariners in navigating the seas. They are usually published two or thtee years in Advance. LT th>3 benefit of long voyages Let A in the cut represent Greenwich Observatoi f,near London. B is the Moon, anj her apparent pi ace among the distant stars, about 40* west of the star D. The ship B, having Greenwich time, as well as her own local time, sails from London westward ; 406. Form of the lunar orbit ? Time of synodic revolution? Of sidereal revolution t Ti-at difierence? 407. What are the nautical stars f Can ym explain howlojgitudit iMl by them? 206 ASTRONOMY . but on observing the Moon when, by Greemdct time, she ought to be at C, she is found to bs at F, o only about 20 west of the star D. It ia, therefore obvious that the ship is west of Greenwich, as tfca Moon appears east of her Greenwich place. From this difference between her place as laid down in the tables, and ter observed place, as referred to cer- tain prominent stars, the mariner determines how far he is east or west of the meridian of Greenwich. The Moon's geocentric place (or place as viewed from the center of the Earth) may be given instead of her Greenwich place, and the same conclusions arrived at. In either case, this is called the lunar method of determining the longitude. It is also asoei tallied by simple comparison of local and standard time, that a man, says Sir John Herschel, by merely measuring the Moon's apparent distance from a star with a little portable instrument held ui hid hand, and applied to his eye, even with so unstable a foot- ing as the deck of a ship, shall say positively within five miles whe re he is, on a boundless ocean, cannot but appear to persons ignorant of physical astronomy an approach to the miraculous. And yet, says he the alternatives of life and death, wealth and ruin are daily and Iwurly staked, with perfect confidence on these marvellous computations. 408. The Moon is the nearest of all the heavenly bodies, being about thirty times the diameter of the Earth, or 239,000 miles, distant from us. Her mean daily motion in her orbit is nearly fourteen times as great as the Earth's ; since she not only accom- panies the Earth around the Sun every year, but, in the mean time, performs nearly thirteen revolutions about the Earth. Although the apparent motion of the Moon in her orbit is greater than that of any other heavenly body, since she passes over, at a mean rate, no less than 18 10 86" in a day; yet this is to be understcod as angular motion, motion in a small orbit and therefore embracing a great number of degrees, and but comparatively few miles. 409. The point in the Moon's orbit nearest the Earth is called Perigee, from the Greek peri, about, and ge, the earth. The point most distant is called Apogee, from apo, from, and ge, the earth. These two points are also called the apsides of her orbi f ; and a line joining them, the line of the apsides. See the Moon in apogee and perigee in the cut The singular of apsides is apsis. 410. The line of the apsides of the Moon's orbit is not fixed in the ecliptic, but revolves slowly around the ecliptic, 408. The Moon's distance? Daily motion in orbit? How many degrees? 409 Perigee anl Apogee? Derivation? What other name for these two points? What li the lint'. 'j( the apsides? 410. la this line stationary? What motion? Ita period of THE MOON HER MOTIONS, PHASES, ETC 207 from west to east, in the period MOTI * OP TO of about nine years. In the adjoining cut, an attempt is made to represent this motion. At A, the line of the 4 apsides points directly to the right and left ; *"\/. but at B, C, and D, it is seen changing its if direction, till at E the change is very percep- // tible when compared with A. But the same J^ ratio of change continues ; and at the end of ^VlBV" R year, when the Earth reaches A again, the *\^(s jine of the apsides is found to have revolved eastward to the dotted line I K, or about 40. \ In nine years the aphelion point near A will have made a complete revolution, and return- eSX*? ed to its original position. *.,''' 411. The line of the Moon's nodes is also in revolution ; but it retrogrades or falls back westward t making the circuit of the ecliptic once in about nineteen years. 412. Though her orbit is an ellipse, B ^r.. l9 ^..-.. with respect to the Earth, it is, in reality, an irregular curve, always concave toward the Sun, and crossing jfa * .'.-/-.. the Earth's orbit every 13 nearly. /A* A*' . ^ &H&- ; II the Earth stood still in her orbit, the Moon '..;.-, fL-/^ '"' would describe just such a path in the ecliptic as /' ^QsJ^ ": \ she describes with respect to the Earth. ^ @ ^ ' If the Earth moved but slowly on her wny, the '../.. ./' s Moon would actually retrograde on the ecliptic at ';''.' ~/V"" tho time c/ her change, and would cross her own ; @) * l) . path at e?iry revolution, as shown in the adjoin- V Ing ngurf. But as the Earth advances som* 1 46,000,lW. '.f miles, or near 100 times the diameter of the Aio-ri's orbit, during a single lunation, it is eviden* that the Moon's orbit never can return into itself, or retrograde, as here repi t- sentcd. That the lunar orbit is always concave toward the Sun, may be demonstrated by the above diagram. THB HOOK'S ORBIT ALWAYS CONCAVE TOWARD THB SUN. B-tfi Let the upper curve line A B represent an arc of the Earth's orbit, equal tc that passed through by the Earth during half a lunation. Now the radius and arc being known, it is found that the chord A B must pass more than 400,000 miles within tlu Earth. But as the Moon departs only 240,000 fmrr. the Earth, as shown in the figure, ft follows that she must describe the curve denoted by the middle line, which is conca-M toward the Sun. TbU subject may be still further illustrated by the following cut : 411. HJW with the line of the Moon's nodes? 412. What is the actual form of tna Hoon's orbit? How if the Earth stood still? How if she moved but slowly? 3o j ie Moon's orbit, demonstrated to be always concave t wards the Sun? ASTRONOMY. TH3 HOOS'9 PATE DURING A COMPLETK LONATIOH. C ilcre the plain line represents the Earth's orbit, and the dotted one that of the Moot, 11 1 the Moon crosses the Earth's track 240,000 miles behind her. She gains on the Ea;"i, till in seven days she passes her at B as a Full Moon. Continuing to gain on the Earth., she crosses her orbit at C, 240,000 miles ahead of her, being then at her Third Qiutrter. From this point the Earth gains upon the Moon, till seven days afterward she overtakes 'KT at D as a New Moon. From D to E the Earth continues to gain, till at E the Moua jrosses 240,000 beJtind the Earth, as she had done four weeks before at A. Thus the Moon w'nds her way along, first within and then without the Earth ; always gaining upon us when outside of our orbit, and falling behind us when within it. The small circles in the cut represent the Moon's orbit with respect to the Earth, whic.i is a.* regular to us as if the Earth had no revolution around the Sun. 413. The moon never retrogrades on the ecliptic, or returns \nto her own path again ; but is always advancing with the Earth, at the rate of not loss than 63,200 miles per hour. KOON'S PATH. The Moon's orbitual velocity, with respect to the Earth, is about 9300 miles per hour. When outside the Earth, as at B, in the last figure, she gains 28/0 miles per hour, which added to the Earth's velocitj would give 67,800 miles as the hourly velocity of the Moon. When within the Earth's orbit, as at D, she loses 2300 miles per hour, which, substracted from (55,500 miles (the Earth's hourly velocity), would leave 63.200 miles as the slowest motion of the Moon in space, even when she is falling behind the Earth. Could we look down perpendicularly upon the eclip- tic, and see the paths of the Earth and Moon, we should see the latter pursuing her serpentine course, first within and then outside our globe, somewhat as repre- sented by the dotted line in the annexed figure. Hei path, however, would be concave toward the Sun, as shown on the preceding page, and not convex, as we tferv' obliged to represent it here in so small a diagram. 414. In her journeyings eastward, the Moon often seems tc run over and obscure the distant planets and stars. This phenomenon is called an occultation. The adjoining cut represents the new Moon as ju? about to obscure a distant star, by passing between us and it. In 1850, she occulted Jupiter for three revolutions in succession viz., Jan. 30th, Feb. 27th, and March 26th. Through a telescope, the Moon if seen to be constantly obscuring stars that are inyisi ble to the naked eye. They disappear behind the Moon's eastein limb, and in a short time reappear from behind her western ; thus distinctly exhibiting her eastward motion. 418. Does she ever* retrograde on the ecliptic? What :'s her slowest motion? Hoi JemonBtrated ? 414. What is an occultation f Remarks respecting this phenomenal THE MOON -HER MOTIONS, PIUSES, TO. 201) 415. The Moon revolves once on her axis exactly in the time lhat shi; performs her revolution around the Earth. This is evt 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 wculd be presented to a spectator on the Earth, in the course of her synodical revolution. It fol- lows, then, that there is but on day :nd night in tier year, containing, ooth together, 29 'days, 12 hours, Y (4 minutes, and 3 seconds. /^ **\ Suppose a unr.uro^t erected upon the Moon's / \ surface, so as u. pc.nt toward the Earth at New ^^ "jSifBjSX /i-s. Moon, as represented at A. From the Earth it }-C (NfSi) A HBi would appear in the Moon's center. Now if the ^-^ $&,<%' y' Moon so reTolve upon her axis, in the direction of .he arrows, as to keep the pillar pointing directly toward the Earth, as shown at A, B, C, and I), and 'Wv \^>X the intermediate points, she must make just one fl ) D If} revolution on her axis during her periodic revolu- ^-v"^^ 1 .^-^ tion. At A, the pillar points from the /Sun, and at "" \-""" C toward him : showing that, in goin^ half-way round the Earth, she lias 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, MOON'S us* ATIO*. as it were, on her eastern and west- ern limbs. This rolling motion east and west is called her lilration in longitude. The accompanying cut will illustrate the subject of the Moon's derations in longitude. From A around to C, the angular motion is skncer than the average, and the diurnal motion gains upon it, ho that the pillar points west of the llarth, and we see more of the eastern limb of the moon. From C to A, again, the Moon advances/aster than a mean rate, and gains upon the diurnal MX ^S revolution; so that the pillar points east of the ^^'-v m) Karth, and we see more of the Moon's western ^-. _/ limb. Thus she seems *r librate or roll, Grst o -.e way and then *^.c 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 he/ srbit 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 folio-re from this fact? 418. What are the Moon's librations? In Lonff-itudef 417. Is Ltiindet 210 ASTRCNOMY. 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 lib rations in latitude As trie inclination of the Earth's axis brings first one pole and then the other toward the iSwi, 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 12$, the iibration in latitude Ja very slight. 418. As the Moor 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 moor.: in our winter, must happen when the Moon is on the north side of tue equinoctial, 418. Can all the Lunarians see the Earth? lie?/ large must she appear from thi Unon ? 419. What said of her light and phases ? How, then, are the two hemispheres .? Jhe Moi-n enlightened? 420, How must the Earth appear to the Lunarians, and what may they infer from the motion of the spots seen <" it, they would that night see the Moon hide her face in anger, and put on a dreadfully iark and threatening aspect. This artifice had the desired effect; for the eclipse had no V'on:r begun, than the frightened barbarians came running with all kinds of provisions, tnd throwing themselves at the feet of Columbus, implored his forgiveness. Almagest^ tol. 7.,55<;. v. 2 434. An eclipse of the Sun takes place, when the iark body of the Moon, passing directly between the Earth and the Sun, intercepts his light. This can happen only at the instant of new nioon, 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. oetween 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 ize> 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 Sue i, much larger than any of the planets, the shadows which they rast 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 ulji net from the Sun. 4T,4. When do aolar eclipses occur? Why only then? Lunar? Why only At full moon? 435. Do all the planets cast shadows? Suppose the Sun and planet were oj Wit! samt size, what would be the form of their shadows? 436. What if the planet wa largest? How as they are smaller than the Sun? How is the length of the shadov mxiified by the Jixktnce of the planet from the Sun ? . 216 ASTRONOMY. In this cut, the opaque body is the larger, and the shadow projected from it dvoo \ or grows more broad as the distance from the planet increases. If the opaque body is smaller than the luminous one, the shadov converge* point. COSVERGIKQ SHADOW. Here the luminous body is the larger, and the shadow converges to a noint, and ti it the form of a cone. The opaque body being smaller than the luminous one, the length of its shadow will e modified by its distance, as in the following: Here, also, the luminous body is the larger, and both precisely oi i,he f-.me size as 1 the cut preceding; but being placed nearer each other, the shadow is i.hown to be coi siderably shorter. 437. All the planets, both primaries and secondaries, cas shadows in a direction opposite the Sun (see cut on rext 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 planet off into space ; and the nearer the Sun, the more divergent the shadow would be. But as the planets are all much rmatUr 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. 487. Why have the largest and most dh *an t planets the longest shadows ? Do Any of 3u primary planets eclipse each other? SOLAR AND LUNAR ECLIPSES 217 SHADOWS OF THE PLANETS. Tiese principles are partly illus- tated 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 lhadow long enough to reach the next \teri or 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- riai y 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 tc ellipse ar.y other body. The shadow of a satellite or Moon, may also, on V-rtain occasions, fall on the primary, md eclipse it. \ \ I \ 1 (Mi) ) \ 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 14,000 miles beyond. When tbe Sun is at his least distance from the Earth, and the Moon at her greatest, her shadow will not reach the Earth's sur- race 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- :ic, she would eclipse the San 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 a* 4S8 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? Wb;i*. when the Sun and Moon are at their mean distances? 439. At wha' time of the ^fooir ii 5 i.rlar eclipses always occur? Lunar? Why? 440. Why not two solar and 218 ASTRONOMY the time of her change, or above or below the Earth's shadow At the time of her full. NEW AND FULL MOONS WITHOUT KCLIPSBO. Shadow .ubove &e Earth. Abo-.o the Earth's shiviow. Shadow below the Earth. Let the line joining the Earth and the Sun represent the plane of the ecliptic. Now aa tio orbit of the Moon departs from this plane about 5 9', she may appecir either a,bov6 or below the Sun at New Moon, as represented in the figure, and her shadow may fall above the north pole or below the south. At such times, .then, there can be no solar eclipse. On the right, the Moon is shown at her full, both above and below the Earth's shadow, In which case there can be no lunar eclipse. 441. As the Moon passes from one of her nodes to the other in 173 days, there is just this period between two successive eclipses of the Sun, or of the Moon. In whatever time of the year, then, we have eclipses at either node, we may be sure that in 173 days afterwards, we shall have eclipses at the other node. As the Moon's nodes fall back, or retrograde in the ecliptic, at the rate of 19)3 J every year, they will complete a backward revolution entirely around the ecliptic to the same point again, in 18 years, 225 days ; in which time there would always be a regular periol of eclipses, if any complete number of lunations were finished without a remainder. But this never happens; for if both the Sun and Moon should start from a line of conjunction with either of the nodes in any point of the ecliptic, the Sun would perform IS annuai revolutions and 222 of another, while the Moon would perform 230 lunations, and 85 of another, before the node would come around to the same point of the ecliptic again ; s that the Sun would then be 138* from the node, and the Moon 85' from the Sun. But after 223 lunations, or 13 years, 11 days, 7 hours, 42 minutes, and 31 seconds, ths Sun, Moon, ami Earth, will return so nearly in the same position with respect to eacL other, that there will be a regular return of the same ecMpses for many agen. This grand period was discovered by the Chaldeans, and by them called Saros. If, therefore, to the mean time of any eclipse, either of the Sun or Moon, we add the Chaldean period of J8 years ind 11 days, we shall have the return of the same eclipse. This mode of pre- dicting eclipses will hold good for a thousand years. In this period there are usually TO eclipses ; 41 of the Sun and 29 of the Moon 442. The diameter of the Earth's shadow, at the distance of the Moon, is nearly three times as large as the diameter of the Moon ; and the length of the Earth's shadow is nearly four times a?, great as the distance of the Moon ; exceeding it in the same ratio that the diameter of the Earth does the diameter of the MODI;, which is as 3.063 to 1. 4 13. The number of eclipses in any one year, cannot be less ibiu two, nor more than seven. In the former case, they will \-xc, lunar eclipses every lunar month? 441. How often may eclipses occur at oppo- lite nodes? What cycle of eclipses described? Number of ec'ipaes in this eyclftf 142. What is the diameter of the Earth's shadow at the distan -e of the Moon? 448. nuuiber of eclipses may o'-rur in any one year? U bat two, what will they bn? SOLAR AND LUNAR ECLIPSES. both be of the Sun ; and in the latter, there will be five of th Sun, and two of the Moon those of the Moon will be toual. There are sometimes six ; but the usual number is four : two oi the Sun, and two of the Moon. The cause of this variety is thus accounted for. Although the Sun usually passea $y both nodes only once iu a year, he may pass the same node again a little befon the end of the year. In consequence of the retrograde motion of the Moon's nodes, toe will come to either of them 173 days after passing the other. He may, there fcre, return to the same node in about 346 Jays, having thus passed one node twice, and the other once, making each time, at each, an eclipse of both the Sun and the Moon, or site it- all. And since 12 lunations, or 854 days from ihzjirtt eclipse, in the beginning of Hie 3 lar, leave room for another New Moon before the close of the year, and since this New Moon may fall within the ecliptic limit, it is possible for the Sun to be eclipsed again. Tims there may be seven eclipses in the same year. 444. Eclipses of the Sun always come on from the west, and pass over eastward ; while eclipses of the Moon come on from the east, and pass over westward. This is a necessary result of the eastward motion of the Moon in her orbit. SOLAR ECLIPSE. L0KAI ECUPSK. In the right hand cut, the Moon is seen revolving eastward, throwing her shadow upon the Earth, and hiding the western limb of the Sun. In some instances, however, when the eclipse is ve-y slight, it may first appear on the northern or nouthern nnib of the Sun that is, the upper or lower side ; but even then its direction must be from west to east. It will also be obvious from this figure, that the aha- dow of the Moon upon the Earth must also tra- verse her surface from *re?t to east ; conse- quently the eclipse will be visible earlier in the west than in the east. On the left, the Moon is seen striking into the Earth's shadow from the west, and having her eastern limb f..-st obscured. By holding the book up south of him, the student will see at once why the revolution of the Moon eastward must caust a solar eclipse to proceed from west to east, and & lunar eclipse from east to west. To locate objects and motions correctly, the student should generally imagine himself look- ing to the south, as we are situated north of the equinoctial. The student should bear in mind that nearly all the cuts in the bo->k are drawn to represent a view from northern latitude upon the Earth. Hence, by holding the book up ftoutft of Lira, the cuts will generally afford an accurate illustration both of the positions and motions of the bodies represented. 44. * The time which elapses between two successive changes the Moon is called a Lunation, which, at a mean rate, is about W given? What is the usual number? Can you explain the cawie of this variety! 441. WLai is the direction of ,* solar eclipse? A lunar? Why this difference? 445. What fc a lunation T What would be the effect if the solar and lunar months wer H4ua.lt What tesult from the existing inequality? 10 220 ASTRONOMY. 29-J days. If 12 Innar months were exactly equal to the 12 solai months, the Moon's nodes would always occupy the same points in the ecliptic, and all eclipses would happen in the same montha of the year, as is the case with the transits of Mercury and Venus : but, in 12 lunations, or lunar months, there are only 354 days ; and in this time the Moon has passed through both her nodes, but has not quite accomplished her revolution around the Sun ; the consequence is, that the Moon's nodes fall back in the ecliptic at the rate of about 19^ annually ; so that the eclipses happen sooner every year by about 19 days. 446. Eclipses can never take place, except when the Moon is near the ecliptic ; or, in other words, at or near one of her nodes At all other times, she passes above or below the Sun, and also above or below the Earth's shadow. It is not neces- sary that she should be ex.actly at her node, in order that an eclipse occur. If she is within 17 of her node, at the time of her change, she will eclipse the Sun ; and if within 12 of her node at her full, she will strike into the Earth's shadow, and be more or less eclipsed- These distances are called, respectively, I lie solar and lunar ecliptic limits. Tills subject may be understood by consulttag the following figure. THK MOON CHANGING AT DIFFERENT DISTANCSS FROM HBR NODBS. Let the line E K represent the ecliptic, and the line O the plane of the Moon'? orbit. The light globes are the Sun, and the dark ones the Moon, which may be imagined as much nearer the student ; hence their apparent diameter is the same. Let the point A represent the no le of the Moon's orbit. Now if the change occui when the Moon is at H, she will pass below the Sun. If when at C, she will just touch his lower limb. At C, she will eclipse him a little, and so on to A ; at which point, if th< change occurs, the eclipse would be central, and probably total. If the Moon was at G, H, 1, or J, in her orbit, when the change occurred, she woulrf 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 Soldr Ecliptic. Limits. The mean ecliptic limit for the Sun is 165$ on each side of the node ; the mean eclii 1 - *;ic limit for the Moon is 10% on each side of the node. In the former case, then, there are 3? degrees about each node, making, in all, 66 out of 860, in which eclipses of ths Sun-mny happen ; in the latter case there are 21 about each node, making, in all, 42 Mil of 360 in which eclipses of the Moon usually occur. The proportion of the S"!ar to '.he 'uE-ir eolinsea, therefore, is as 66 to 42, or as 11 to 7. Yet, there are more visible 'O-'V/oes of ';.,; Moon, at any given place, than of the Sun; because a lunar eclipse id viable to a whole hemisphere, a solar eclipse only to a- small portion of it. 447. All parts of a planet's shadow are not alike dense. Thp 446. Where must the Moon be, with respect to the ecliptic anil her nodes, in order Is. 1 AD erlipse? What meant by ecUptif limit* 7 Name the distance of each, respectively, itora the node. Dluatrate. 44T. (Vhal is the umlrn of the Earth or Moon? Thf SOLAR AND LUNAR ECLIPSES. 221 darkest portion is called the umbra, and the partial shadow th yenumbra. CHBRA AND PBXUKBRA Of TUB EAKTH AND MOOI. / 'enumbra is from the Latik pene, almost, and wnibra,a. shadow. In this cut, the Earth's umbra and penumbra will be readily found by the lettering ; while A is the umbra, ami 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 vithin the umbra ; while to all on which the penumbra falls, a portion of the Sun's disc 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 arc subject to variations. The length of the 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 130 miles ; but the penumbra may cover a space on the Earth's surface 4850 miles' in diameter. When the Moon but just touches the iimb 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 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 ? Whjrt 449. Average length of the Moon's umbra ? Does it vary? Why? Greatest diametei at the Earth's surface? Of penumbra? What is an appulsef 450. A partuii eclipse? A total T A central t Are all central 'jcHpses total ? Why not ? What call? thcs? Why? 223 ASTRONOMY. whole disc of the Sun. In that case, the edipse would be annular (from annulus, a ring), because the Moon only hides th winter of the Sun, and leaves a bright ring unobscured. PROGRESS OF f. CENTRAL ECLIPSE. Annular. 151. It has already in.-eti shown that the tudcs 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, ft hiie others are partial and annular. TOTAL AND ANNULAR ECLIPSES OF THK SCN At A, the Earth is at her aphelion, and the Sun being at his most distant point, will 'lave his least apparent magnitude. At the same time, the Moon is in perigee, and appears 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 bo^C! central eclipses total, and others partial and annular? 482, Bow long may an ann/ubir eclipse continue ? A total eclipse of the Sun f Of the Moon? 669. Which kind of eclipses ia most fre-iuent? Why? The greatest number in a year 1 SOLAR AND LUNAR ECLIPSES 223 , viz., five solar and two lunar ; but the most usual number is four. There can never be less than two in a year ; in wb.ch 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 366 days and 15 hours. This cycle is called the Period of tht 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 genera] gloom overspreads the landscape. Such were the effects of the great eclipse of 1806. In a lunar eclipse, the Moon begins tc 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, istronomers usually state which "limb" of the bociy is to be }clipsed the southern or northern the time of tin? first con- tact, of the nearest approach of centers, direction, And numbei of digits eclipsed. FIVE DIGITS ECLIPSED. TWELVB DIGITS. 456. The last annular eclipse visible in the United Stated, 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 egarded eclipses with amazement and fear, as uupematurftl events, indicating the displeasure of the gods. Co jnibus is said How many of each? Least number, and which? Usual number? What said of th* order of eclipses ? Time of cycle ? 464. Describe the effects of r total eclipse of thi km. The process of a lunar eclipse? 456. How are eclipses men. ared and recorded! vit'>. When the next annular eclipse visible in this country ? The nrzt total? How havi 234 ASTRONOMY. to have made a very happj use of this superstition, as already stated on a previous page. (Art. 433.) 457. Eclipses can be calculated with the greatest precision, not only for a few years to come, but for centuries and ages either past or to come. This fact demonstrates the truth of the Copernican theory, and illustrates the order and stability that everywhere reign throughout the planetary regions. The following 1s a iist of all the solar eclipses visible in Europe and America fto 1858 to the close of the present century. To those visible in New England, the number f digits is annexed. Year Month. Day and hour. Digits. Year. Month. Day and hour. Digits. 1868, Mar. 15 6 14 A. M. 1% 1878, July 29 4 56 P. M. 7^3 1869, July 29 5 82 P. M. 2^ 1879, July 19 2 A. M. I860, July 18 7 23 A. M. Q* 1880, Dec. 31 7 80 A. M. 5^ 1861, Dec. 31 7 30 A. M. *K 1882, May 17 1 A. M. 1SC3, May 17 1 P. M. 1SS5, Mar. 16 35 A. M. C:* 1S65, Oct. 19 9 10 A. M. S% 1886, Aug. 29 6 30 A. M. OVi 1SG6, Oct. 8 11 12 A. M. 1887, Aug. 18 10 P. M. 18(57, Mar. G 8 A. M. 1890, June 17 3 A. M. VSGS, Feb. 23 10 A. M. 1891, June 600 Mer. ISG'J, Aug. 7 5 21 A. M. 10 \ 1892, Oct. 20 19 P. M. 8i4 1ST.., Dec. 22 6 A. M. 1895, Mar. 26 4 A. M. 1873, May 26 3 A. M. 1896, Aug. 900 Mer. 1S74, Got 10 4 A. M. 1897, July 29 9 S A. M. fM 1375, Sept. 29 5 56 A. M. n% 1899, June 800 Mer. 1870, Mar. 25 4 11 P. M. 8% 1900, May 28 8 9 A. M. 11 The eclipses ot 18C9, 1S75, and 1900 yrlll I* Tery large. In those of 1873, 187? -a .880, the Sim wili rise eclipsed. That of 1875 will b* annular. The scholar can continue this table, or extend It bad:- ran 1 ?, by adding or substracting tho Chaldean period of 18 years, 11 days, 1 hours, M minutes, and 81 stconds. CHAPTER VI. PRIM IKY PLANETS CONTINUED MARS AND THE ASTEROIDS. 458. MARS is the first of the exterior planets, its orbit lying immediately without, or beyond, that of the Earth, while those of Mercury and Venus are within. He appears, to the naked eye, of a fine ruddy complexion ; resembling, in color, and appa- Ihe ignorant and superstitious regarded eclipses f 457. What said of the calculation o1 eclipses? VVhat does this demonstrate and illustrate? 458. Positi( n of Mars' orfeiti How does he appear to the naked eye? When most brilliant? When least? THE PRIMARY PLANETS MARS AND THE ASTEROIDS. 225 rent magnitude, the star Antares, or Aldebaran, near which it frequently passes. It exhibits its greatest brilliancy about the time that it rises when the Sun sets, and sets when the Sun rises ; because it is then nearest the Earth. It is least brilliant when it rises and sets with the Sun ; for then it is five times farther removed from us than in the former case. 459. Its distance from the Earth at its nearest approach is *]>ont 33.000,000 of miles. Its greatest distance from us is fii. out 24o,000,000 of miles. In the former case, it appears more chan 50 times as large as in the latter. When it rises before the Sun, it is our morning star ; when it sets after the Sun, it is our evening star. The distance of thy interior planets from tho earth, varies within the limits of lh< diameters of Uieir respective orbits; for when a planet is in that part of its orbit whirl. is nearest the Earth, it is evidently nearer by the whole diameter of its orbit, than it is when at a point opposite, on the other side of its orbit. The exterior planets vary ir iistance within the limits of the diameter of the Earth's orbit. 460. Mars is sometimes seen in opposition to the Sun, and sometimes in superior conjunction with him ; sometimes gibbous, but never horned In conjunction, it is never seen to pass over the Sun's disc, like Mercury and Venus. These prove uot only that its orbit is exterior to the Earth's orbit, but that it is an opaque body, shining only by the reflection of the Sun. 461. The motion of Mars through the constellations of the zodiac is but little more than half as great as that of the Earth; it being generally about 57 days in passing over one sign, which is at the rate of a little more than half a degree each day. Thus, if we know what constellation Mars enters to-day, we may con- clude that two months hence it will be in the next constellation ; four months hence, in the next ; six months, in the next, and so on. Its mean idereal revolution is performed in 6S6.9796468 solar days; or in 686 days, 2* hours, 80 minutes, 41.4 seconds. Its si/nodical revolution is performed in 779.986 solku days ; or in 779 days. 22 hours, 27 minutes, and 50 seconds. 462. Mars performs his revolution around the Sun in one year and 10^- months, at the distance of 140,000,000 of miles ; moving in its orbit at the mean rate of 53,000 miles an hour. Its diurnal rotation on its axis is performed ik 24 hours, 39 469. Its distance frcm the Earth? What efifect upon its apparent magnitude ? When rairraing and evening star ? How do the distances of the planets from the Earth vary 't Vheir apparent diameters ? 460. Is Mars ever in opposition to the Sun? In conjunc- tion T Its phases? Does it ever transit the Sun? What do these facts prove? 461. What is his rate of motion through the constellations ? What calculation based upon it? 4! His periodic time ? Distance from the Sun ? Mean rate of motion per tour? T'catf u rotation on his uxi. ? How does his day compare with ours ? 226 ASTEONOMY. aimutes, and 21^ seconds ; which makes its day about 44 mmatei longer than ours. 463. Its form is that of an oblate spheroid, whose polar dia- meter is to its equatorial as 55 is to 56, nearly. Its diameter is 4,300 miles. Its bulk, therefore, is 7 times less than that of the K-ulli ; and being nearly 50,000,000 of miles farther from tho Bun, it receives from him less than half as much light and heat. 464. The inclination of its axis to the plane of its orbit, is about 28 1. Consequently, its seasons must be very similar to chose of the Earth. Indeed, the analogy between Mars and the Earth is greater than the analogy between the Earth and any other planet of the solar system. Their diurnal motion, and of course the length of their days and nights, are nearly the same ; the obliquity of their ecliptics, on which the seasons depend, are not very different ; and, of all the superior planets, the distance of Mars from the Sun is by far the nearest to that of the Earth ; nor is the length of its year greatly different from ours, when compared with the years of Jupiter, Saturn and Uranus. 465. To a spectator on this planet, the Earth will appear alternately, as a morning and evening star ; and will exhibit all the phases of the Moon, just as Mercury and Venus do to us ; and sometimes like them, will appear to pass over the Sun's disc like a dark round spot. Our Moon will never appear more than a quarter of a degree from the Earth, although her distance from it is 239,000 miles. If Mars be attended by a satellite, it is too small to be seen by the most powerful telescopes. When it is considered that Vesta, the smallest of the asteroids, which is once and a half times the distance of Mars from us, and only 269 miles in diameter, is perceivable In the cpen space, and that without the presence of a more conspicuous body to point it out, we may reasonably conclude that Mars is without a Moon. 466. The progress of Mars in the heavens, and indeed of all the superior planets, will, like Mercury and Venus, sometimes appear direct, sometimes retrograde, and sometimes he will seem stationary. The portion of the ecliptic through which a planei seems to retrograde is called the Arc of Retrogmdation. Thb more remote the planet the less the arc, and the longer the time of its retrogression. These retrograde movements and stations, as they appear to a spectator from the Earth, are common to all the planets, and demonstrate the truth of the Cc/pernican system. 468. Form of Mars ? Diameter? Bulk? Light and heat? 464. Inclination cf his Wris to the plane of his orbit? His seasons? llesemblance to our globe? 465. How rould the Earth appear to a spectator upon Mars ? Our Moon ? Has Mars a satellite? 56. What . 1S45. On the 30th of the same month he appeared as represented on the left. ln twiddle view is from a d-awing by Dr. Dick. 467. The telescopic phenomena of Mars afford peculiar interest to astronomers. They behold its disc diversified with numerous irregular and variable spots, and ornamented with zones and belts of varying brilliancy, that form, and disappear, by turns. Zones of intense brightness are to be seen in its polar regions, subject, however, to gradual changes. That of the southern pole is much the most brilliant. Dr. Herschel supposes that they arc produced by the reflection of the Sun's light from tNi frozen regions, and that the melting of these masses of polar iet Is the cause of the variation in their magnitude and appearance Arc of Retroffradatton f What do these motions prove? 467. How does Mar* appe.ii through a telescope ? Dr. Herschel's opinion if its polar region* ? H^w contrmeU it- 10* J828 ASTRONOMY He wa the raoro confirmed in these opinions by observing that after the exposure ot the luminous zone about the north pole to a summer of eight months, it was considerably decreased, while that on the south pole, which had been in total darknese during eight months, had considerably increased. Ue observed, farther, that when this spot waa most luminous, the disc of Mars did not appear exactly round, and that the bright part of its southern limb seemed to be swollen or arched out beyond the proper curve. 468. The extraordinary height aud density of the atmosphere of Mars, are supposed to be the cause of the remarkable redness of its light. It has been found, by experiment, that when a beam of white light passes through any colorless transparent ncedium, its color inclines to red, in proportion to the density of ihe medium, and the space through which it has traveled. Thus the Sun, Moon, and stars, appear of a reddish color when near the horizon ; and every luminous object, seen through a mist, is of a ruddy hue. This phenomena may be thus explained : The momentum of the red, or least refrangi- ble rays, being greater than that of the violet, or most refrangible rays, the former wil make their way through the resisting medium, while the latter are either reflected or absorbed. The color of the beam, therefore, when it reaches the eye, must partake of the color of the least refrangible rays, and this color must increase with the distance. The dim light, therefore, by which Mars is illuminated, having to pass twice through its atmosphere before it reaches the Earth, must be deprived of a great proportion of ita violet rays, and consequently then be red. Dr. Brewster supposes that the difference ot color among the other planets, and even the fixed stars is owing to the different heights and densities of their atmospheres. THE ASTEROIDS, OR TELESCOPIC PLANETS. 469. Ascending higher in the solar system, we find, between the orbits of Mars and Jupiter, a numerous cluster of small plan- ets, which present a variety of anomalies that distinguish them from all the older planets of the system. The first of these, namely, Ceres, was discovered by Piazzi, at Palermo, January 1, 1801 ; and three others, namely, Pallas, Juno, and Vesta, have been known since 1807. More than one hundred of these plan- ets have been discovered since that time, the greater part of them since 1853. [See Table, p. 231.] 470. The scientific Bode entertained the opinion, that the planetary distances, above Mercury, formed a geometrical series, 3ach exterior orbit being double the distance of its next interior one, from the Sun ; a fact which obtains with remarkable exact- ness between Jupiter, Saturn, and Uranus. But this law seemed to be interrupted between Mars and Jupiter. Hence he inferred, that there was a planet wanting in that interval ; which is now Ifeia opt ion ? 46S. Supposed cause of the ruddy color of Mars ? Philosophical expla- nation ? Dr. Brewster's opinion ? 469. Position and numi or of the asteroids ? When iisoovcrd? 470. Bode's iheory? What seeming interruption? What conclvuiot! THB PRIMARY PLANETS MARS AND THE ASTEROIDS. 229 happily supplied by the discovery of the numerous star-form plauets, occupying the very space where the unexplained vacancy presented a strong objection to his theory. According to Bode, the distances of the planets may be expressed nearly ai follows : tht /Earth's distance from the Sun being 10. Mercury 4 = 4 Venun 4+8x1 = 7 The Ear tli 4 + 3x2 = 10 jlars 4 + 3x2* = 16 Asteroids 4 + 3x23 = 28 Jupiter 4 + 8x# = 52 Saturn 4+8x2 = 100 Herschel 4+8x26 = 1 Comparing these values with the actual mean distances of the planets from the Sun, ;*<, cannot but remark the near agreement, and can scarcely hesitate to pronounce that the respective distances of the planets from the Sun, were assigned according to a law, although we are entirely ignorant of the exact law, a,nd of the reason fcr that law. Brinkley's Elements, p. 89. 471. The Asteroids are much smaller in size than the older planets they all revolve at tiearly the. same distances from the Sun, and perform their revolutions in nearly ttie same periods rheir orbits are much more eccentric, and have a much greater indi/ \ation to the ecliptic and what is altogether singular, except in the case of comets some of their orbits cross each other ; so that ";here is even a possibility that two of these bodies may, some time, in the course of their revolutions, come into collision. The orbit of Vesta is so eccentric, that she is sometimes farther from the Sun than either Ceres, Pallas, or Juno, although her mean distance is many millions of miles less than theirs. The orbit of Vesta crosses the orbits of several other asteroids, in two opposite points. The student should here refer to the Figures, Map I. of the Atlas, and verify such of these particulars as are there represented. It would be well for the teacher t / - require him to observe particularly the positions of their orbits, and to state th<;V different degrees of inclination to the plane of the ecliptic. 472. From these and other circumstances, many eminent astronomers are of opinion, that these telescopic planets arc the fragments of a large celestial body which once revolved between Mars and Jupiter, and which burst asunder by some trempndous convulsion, or some external violence. The dis- covery of Ceres, by Piazzi, on the first day of the present cen- tury, drew the attention of all the astronomers of the age to that region of the sky, and every inch of it was minutely explor- ed The consequence was, that in the year following, Dr. Olbers, of Bremen, announced to the world the discovery of Pallas, situated not many degrees froi> Ceres, and very much resembling it in size. Now substantially jwv.fied? 471. Size of the asteroids? Distance from; tho Sun? Periodic time? Forms of their orbits? Position with respect to the e Jiptk ' other singularity in their orbits? What remarkable facts respecting the'rtoit o. 419. Whal conclusion has been drawn froir these facts? Progress 01 d 230 ASTRONOMY, 473. From this discovery, Dr. Olbers first conceived lh^ ideu that these bodies might be the fragments of a former world ; and if so, that other portions of it might be found either in the same neighborhood, or else, having diverged from the same point, " they ought to have two common points of reunion, or two nodes in opposite regions of the heavens through which all th0. Massilia Jl. Lutetia 22. Calliope 23. Thalia 24 Themis . . Hind . . , Hind ... . Chacornac... Goldschmidt. Hind ..... Hind De Gasparis. Chacornac.. . Luther Hind 25. Phocaea 26. Proserpine. . 27. Euterpe 28. Bellona 29. AmpWtrite.. 30. Urania 31. Euphrosyue. 32. Pomona 33. Polyhymnia. 34 Circe Luther Marth Hind Ferguson Goio8chui!t. Chacernac.. . Cho comae.. Lnth-'r. 35. Leucothea. . 36. Atalanta 37, Fides 8 Leda Goiclechmidt. Luther Chacornac.. . Chacornac. . Goldbchmidt. Goldschmidt. Pogson Pogson Goldschmidt. Goldschmidi. Pogson Luther Goldschmidt. Goldschmidt. Fergu son 89 Lsetitia 40 Harmonia. . . 41 D-sphne 42 Isi . . 48 Ariadne 44 Ny8^l 45 Eugenia, , . . 46 Hestia 47. Aglaia 4S, Doris....... *9. Pales 50. Virginia 232 ASTBOKOMY. No, Same. Dist. from the Sun iu miles. Period- ic time in days. Date of discovery. By whom discovered. Where ditcoTcred. 51. Hemausa... 52. Europa 53. Calypso ... 54. Alexandra . 55. Pandora. .. 50 Mekte 57 Mnemosyne 56 Cc-ncordia. 59 Olympia... 50 Echo 81. Danae 62. Erato 33. Ausonia... . 64. Angelina... 65. Cybele 66. Maia 216.296,571 263,431,110 239,521,473 247.986.795 252,262,491 237.347,157 288,602.121 246,889,315 248,059,106 218,796,250 272,898,017 286,145,013 218,971,905 245.117,875 312,737,913 242,404,596 221,419,105 254,212,089 271,702,518 238,931,095 207,187,414 251.934,1:38 243,806,171 253,964,819 244,101,375 309,736,915 244,294,717 239,798.051 223,379,507 209,950.819 261,151,257 252,372,105 222,061,135 216,457,309 242,618,417 282,591,045 319,337,561 253,278,071 233,131,645 285,155.396 237,333,994 291,844,560 251,981,082 280,175,900 280,598,670 279,227,220 244,02d,675 245,398,120 251,375,426 273/349.992 235,249,390 243,478.090 247,043,860 290,747,415 217,603,400 292.667,430 325,758,300 291,935,989 246,638,250 1,329 1,994 1,549 1,632 1,674 1,528 2,048 1.621 1.632 1,352 1.883 2,022 1,354 1,603 2,311 1.577 1,377 1,6<)3 1,871 1,5-13 1,246 1,671 1,590 1,691 1,593 2.277 1,595 1,551 1,395 1^271 1,763 1,675 1,383 1,331 1,573 1,985 2,384 1.684 1,486 2,011 1,528 2,081 1.872 2,062 1,960 1,949 1,591 1,506 1,660 1,891 1,507 1,588 1,621 2,069 1.340 2,091 2,454 2,084 1,616 Jan. 22, 1858 Feb. 4, " April 4, " Sept. 11, " Sept. 11, " Sept. 9, 1859 Sept. 22. " March 24, 1860 Sept. 12, " Sept. 15, " Sept. 19, " Oct. 10, " Feb. 10, 1861 March 2, " March 4, " April 9, " April 17, " April 20, " April 29, " May 5, May 29, " Aug. 13, " April 7, 1862 Aug. 29, " Sept. 22, " Oct. 21, " Nov. 12, " March 15, 1863 Sept. 14, " May 2, 1864 Sept. 30, " Nov. 27, " April 26, 1865 Aug. 25, " Sept. 19, " Jan. 4, 1866 May 17, " June 15, " Aug. 6, " Oct. 1, Nov. 24, " July 26, 1367 Aug. 24, " Sept. 6, " Nov. 10, " Feb. 17, 1803 Feb. 17,' u April 18, " Mav 28, tl Julr 11, " Ang 15, Aug 24, "' Sept. 7, " Sept. 13, " Sept. 16, u Oct. 10, " 1869 Laurent Goldschmidt. Luther Goldscbmidt. Searle Goldschmi-lt. Luther Luther Chacornac.. . Ferguson Goldechmidt. Foster Nismes. Paris. Bilk. Paris. Albany, S. Y, Paris. Bilk. Bilk. Paris. Washington. D.O Paris. Berlin. Naples. Marseilles. Marseilles. Cambridge, Maas Madras. Bilk. Milan. Paris. Clinton, N. Y. Bilk. Cambridge, Mass Marseilles. Clinton, N. Y. De Qasparis Tempel Tempel Tuttle Pogson Luther Schiaparelli. . Goldschmidt. Peters Luther 68. Leto .... 69. Hesperia... 70. Panopea. ... 71. Feronia 72. Niobe 73 Clytie ... Tuttle Tempel. . . . Peters 74. Galatea,... 75. Eurydice.. 76. Preia 77. Frigga 78. Diana 79. Eurynoine.. 80. Sappho.. .. 81. Terpsichore 82. Alcmene... &3. Beatrix . . . 84. Clio 85. lo D' Arrest Peters Copenhagen. Clinton, N. Y. Bilk. Ann Arbor, Mich Madras. Marseilles. Bilk. Naples. Bilk. Clinton, N. Y. Berlin. Madras. Clinton, N. Y. Marseilles. Bilk. Marseilles. Clinton. N. Y. Ann Arbor, Mi'-h Ann Arbor, Mic) 1 Bilk. Marseilles. Marseilles. Clinton, N. Y. Marseilles. Ann Arbor, Mich Ann Arbor, Mich Clinton N. Y . Aim Arbor, Mich Ann Arbor, Mich Ann Arbor, Mich Ann Arbor, Mich Madras. Bilk. Clinton, N. Y. Luther Watson Pogson Tempel Luther De Gasparis. Luther. Peters Tietjcn Pogson Peters 86. Semele 87 Sylvia 88. Thisbe 89 Julia 90. Antiope 91. Jffigina 92. Undina .... 93. Minerva 94. Aurora 95. Arethusa... 96. Mgle 97. Clotho 93. Ian the 99. Dike 100. Hecate 101. Helena 102. Miriam 103. Hera 104. Clymene.... 105. Artemis i06. Dione 107. Camilla... 108, Hecuba.... 109. F3 CHAPTER VII. PRIMARY PLANETS JUHTER AN.3 SATURN. 47 J. JUPHEK is tlie largest of all the planets belonging to the 8.>iar system. It may be readily distinguished from the fived Mars, by its peculiar splendor and magnitude ; appearing to the Jiked eye almost as resplendent as Venus, although it is niora ilia.i 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 Hie Sun rises ; 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 .1 day ; ft'hich amounts to only 30" 20' 82" in a year. For 12 years to come, he will, at a mean rate, pass through the constellations of the zodiac, as follows : 1S67, Capricornua. 1S6S, Aquarius. 1869, Pisces. 1870, Aries. 1571, Taurus. 1572, Gemini. 1873, Cancer. 1874, Leo. 1875, Virgo. 1S7G, Libra. 1877, Scorpio. 1S73, Sagittarius. 479. Jupiter is the next planet in the solar system above the asteroids, and performs his nnnual revolution around the Sun in nearly 12 of our years, at the mean distance of 475,000,000 of miles ; moving in his orbit at the rate of 29,000 miles an hour. The exact period of Jupiter's sidereal revolution is 11 years, 10 months, 17 d;>ys. 1-1 hours, 21 minutes, 25 , l seconds. His exact mean distance from the Sun 18476.603,0)10 miles; consequently, the exact rate of his motion in his orbit is '28,744 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 ; so that his year contains 10,471 days and nights ; each about D hours long. His form is that of an oblate spheroid, whose polar diameter 478. Comparative size of Jupiter? How distinguished from the fixed stars? When aacrning star, &c. ? Is he easily traced ? 479. His position in the system? His e Sun ? Distance from the Sun ? Hate of motion? 480. Time of diurna. revciu <.n? Position of axis? Length of his days? Number in his year ? His form Caxun "Ufa obJateness? Difference of equatorial and p^lar diameters? The Earth? 234 ASTRONOMY 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 5000 Biiles. The difference between the polar and equatorial diameters of the Earth, is only i miles. Jupiter, even on the most careless view through a good telescope, appears to fce oval ; the longer diameter being parallel to the direction of his belts, which are alwo parallel to the ecliptic. 481. By this rapid whirl on its axis, his equatorial inhabitants are carried around at the rate of 27,600 miles an hour; which i* 2700 miles farther than the equatorial inhabitants of the Earth are carried, by its diurnal motion, in twenty-four hours. The true mean diameter of Jupiter is 85,390 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, set Map I.) 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 comes 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 Jupitei revolves in an orbit which is exterior to that of the Earth. 482. As the variety in the seasons of a planet, and in th$ length of its days and nights, depends upon the inclination of it* axis to the plane of its orbit, and as the axis of Jupiter hat little or no inclination, there can be no difference in his seasons, on the same parallels of latitude, nor any variation in the lengtl 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 ; and at his poles everlasting winter ; but yet equal day and equal night at each. This arrangement seems to have been kindlj 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. 4H. Motion at Jupiter's equator* His mean diameter? His volume? Lirfht amlheati flot'% he ever transit the Sun? What proof that his orbit is exterior to tlmtof thjEarthf 48'J. What "f the seasons of Jupiter ? What apparent manifestation of Divine Wisdom , THE PRIMARY PLA.NETS JUPITER AND SATURN. 235 TKLRSOOPIC VIEW Of JUPITKk. 483. Jupiter, when dewed through a telescope, appears to be surrounded by a number of luminous zones, usually termed belts, 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 and number. Sometir.es eight have been seen at once ; sometimes only oue > but more usually three. Dr. Herschel once perceived his A'hole 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 little, or no variation, and sometimes a new belt has been seen to form m 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 pheno-me'tia, 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 tho 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 tn the form and magnitude of the spots, and the parallelism of the belts. 483. How does Jupiter appear through a telescope? Where are his belts usually seen? Their number? Are they permanent ? 484. What else seen upon Jupiter'i surface? Are they permanent? Is the cause of these phenomena well understood ^ What different opinions? ASTRONOMY. Che spot first observed by Cass-'ai, in 1666, which has botli disappeared and reappeared IB 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 if 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, und that the clouds which float in it, being '.hrown into parallel strata by the rapidity cf .'is diurnal motipn, form regular inatersUces, through which are seen its "opaque body, o; aty of the permanent spots which may come within the range of the opening. TELESCOPIC VIEWS OF THB MOONS O3 JUPITER. MOONS OF JUPITER. 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 occupy 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. Thev 4th. COMPARATIVE DISTANCES OF JUPITKIt'S MOON* 3d. 2d. 1st. 487 Their periods of revolution are from 1 day 18 hours to 1 7 days, according to their distances. This rapid motion ii necessary, in order to counterbalance the powerful centripetal force of the planet, and to keep the satellites from falling to Ms surface. 486. How many moons has Jupiter? How seen? Why not all seen at once? 4dil2T's moons? Explain the process? THE PRIMARY PLANETS JUPITER AND SATURN. 230 This progress may be demonstrated as follows : 1(5m. ?fis. = 98Gs If the radius of the Earth's orliit be 91.500,000 miles, the diameter must bo twice ^har, or 1 S3,000,0(K) Divide 1S3.000,000 miles hy 0G seconds, and we luive lS5.r>8 $% miles ns tiie progress of lii?ht in earh second. At tins rate. lirv mi'mt ! 4 1 J1. Jupiter, when seen from his nearest satellite, appears a '/' '/.< nisi /iwua largo tliaii our Moon does to us, exhibiting cu a vfilt of inconceivable magnificence, the varying forms of a crcs .sent, a half moon, a gibbous phase, and a full moon, every 42 hours. SATURN. 495. SATURN is situated between the orbits of Jupiter and Uranus, arid 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 hie 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 2)3 years in passing over a single sign or constellation. Saturn's mean daily motion among the stars is only about 2 , the tkirtielh part of a degree. 496. The mean" distance of Saturn from the Sun is nearly double that of Jupiter, being about 872,000,000 of miles. Ills diameter is about 70,000 miles ; his volume, therefore, is seven hundred times greater than the Earth's. Moving in his orbit at the rate of 21,000 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 10 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 *he belts on his surface ; three of which were dark and two ^rijflit. The dark belts have a yellowish tinge, and generally .r>ver a broader zone of the planet than those of Jupiter. To tl.e inhabitants of Saturn, the Sun appears 90 times less than he appears ar th Carth; and they receive from him only one ninetieth part as much light and heat. But 4. Siluation of Saturn f Jl< w listinguished? How trac"? His rate of motion in the heavens? 496. Distance *rom th Sun ? Diameter? Volume? Rate of motion in orbit ? Periodic time? Diur a*! revolution? Days in his year? 497. Appearance of his surface? Belts? Tin ui us seen from Satnrn' Light ami he:-.t of that p'.ane*. f Estimated atrt-ngth of Hit 240 ASTRONOMY. .t is conn uted that even the ninetieth part of the Sun's light exsceds the Uhiminattog power of 8000 full moons, which would be abundantly sufficient for all the purpose* of life. 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 froir. ?very other in the system, is a magnificent zone or ring, encir- ling it with perpetual light. 'Hn adjoining out is an excel- TELESCOPIC VIKW OF SATURN. *j; , representation of Saturn as seen through a telescope. The oblatenessyof the planet is easily perceptible, and his Khddou. can be seen upon the rings h:..jk of the planet. The shadow of the rings may also t>e seen running across his disc. The writer has often seen the opening between the body of the planet and the interior ring aa 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- definite number of concentric circles, doubtful by Sir John ilerschel. 499. The light of the ring is more brilliant than the planet itself. It turns around its center of motion in the same tiim; 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 third division was distinctly seen by I'rof. Encke, on the 25th of April, 1337, and also by Mr. Lassel, on the 7th of September, 1S43, at his observatory near Liverpool, England, Six different rings ^ere 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 ail probability, these wonderful rings arejftMi!.' It is well known that under tho most pc/werful instruments they seem to be almost indefinitely subdivided. 600. As our view of the rings of Saturn is generally ai, ./blique 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^ 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 lolar radiance? 498. Telescopic appearance of Saturn? For what distinguished! 1 499 Comparative light of his rings ? Time of -otation around the planet ? How do'.-s it nsu't'.ly appea. i What furthe* discoveries? 500. What the general apparent ligurt >f the rings? Why elliptical ? What periodic rariat on of expansion ? Of i Wtoen nearly invisible? THE PRIMARY PLANETS JUPITER AND SATURN. 241 next fifteen it appears to drop below 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 ringn vary also in their inclination, sometimes dipping, tc the right;, and at others to the left. TELESCOPIC PHASES OP THE RINGS OP 8ATCRN. The above is a good representation of the various indin-ations and degrees of expan si >n o f the rings of Saturn, during his periodic journey of 30 years PERPENDICULAR VIEW OF THE RIXGS 'F SATURN. 50 J. 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 romaln parallel to themselves. The revolution of the planet about the Earth every 30 years, must therefore bring first one side of the ings to view, and then the other causing all the variations of expansion, position, and inclination which the rings present. 501. HOT are the rings situated with respect to the Earth? ITow w< nld they *\pper.r 1.' e.ther pole of Saturn -were toward us? 502. How arc tbc various phases of Satutrj rinifs accounted for? 242 ASTRONOMY. EATTJRH AT DC-FEETM 1 POIKT8 IS HIS ORBIT. Here observe, first, that the axis of Saturn, like those of all the other planets, renr-ntt; permanent, or parallel with itself; and as the rings are in the plane of his equator, ami at right angles with his axis, they also must remain para.lel 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 lie passes from K to A again, upon the upper or noiVi side; and as it requires about 30 years for the planet to traverse these fvo semicircles, it is plain that the alternate day and night on the rings .vill be 15 years each. A and K are the equinoctial, and C and Q the solstitial points in the orbit of Saturn. At A and K the rings are edgewise toward the Sun, 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 O, and from G to A. Again : from A to E the front of the rings will appear above the planet's center, am! 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, J856, Ws rlnjza continued to expand. From that time to June, 1863, they contracted, until ho reached his other equinox at E, and the rings became invisible. From Juno 19G8, to September, 1870, 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 thai time (January, 1849), they appeared as a bright line of light, as represented at A and 5, in the first cut on the preceding page. 503. The dimensions of the rings of Saturn maj be stated in round numbers as follows : Miles Distance from the body of the planet to the first ring 18,*oO Width of interior ring . 16.5^C Spuco between the interior and exterior .rings . . fc,u06 \\idthofexteiiorring I0.00 Thickness of the rings V*8 State the distances and dimensions of his rings, beginning at the body ol the p'.nor4 Ui '-iiBBiriB outward? What additional statistics from lleischel? THE PRIMARY PLANETS - JUPITER AND SATURN. 243 In a recent work, entitled " The New Theory of Creation and Deluge," it is predicted iKat, at some future time, the fluid rings of Saturn may descend and deluge the planet, Re ouis was deluged in the days of Noah. Sir David Brewster says : " Mr. Otto Struve and Mr. Bond have lately studied with the great Munich telescope at the Observatory of Pulkoway, the third ring of Saturn, which Mr. Dassels and Mr. Bond discovered to be fluid. These astronomers are of opinion that this fiuid ring is not of very recent .formation, and that it is not subject to rapid change , and they have come to the extra- ordl.iary conclusion that the inner border of the ring has, since the time of Huygens, bc-C'i gradually Approaching the body of Saturn, and that we may expect, sooner or ihtt r, perhaps in some dozen of years, to see the rings united with the body of the planet," 504. The rins of Saturn serve as reflectors to reflect th 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 met full moon, and spanning the irhole heavens like a stupendous rainbow. In the annexed cut, the beholder is supposed to be situated some 30 north of the equator of Saturn, and looking directly soutii. The shttdow 5t' the planet is seen travelling up the arch as che night advances, while a New Moon is shown 'n the west, and a Futt Moon in the east at the 34ime time. 505. The two rings united are nearly 13 times as wide as tho diameter of the Moon ; and the nearest is only -J^-th as fo\ from the planet as the Moon is from us. The two rings united are i7,500 miles wide; whicln-2160 the moon'd diameter =l*y?j 3o 240,000 miles, the Moon's distance -*- 19,000 the distance of Saturn's intcrir, At the distance of only 19,000 miles, our Moon would appear some forty tiroes P.J la:g is she does at her present distance. How magnificent and. inconceivably ^rs^id. then, must these vast rings appear, with a thousand times the Moon's mago'cu^d, and onty one-twelfth part of her distance! 506. The periodic time of Saturn being nearly thirty years, his motion eastward among the stars must be ver^ slo\v, amount- ing to only 1 2 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 ho performs his vast circuit around the heavens. MOONS OF SATURN. tM)7. Besides the magnificent rings already described, th telescope reveals fight satellites or moons, revolving around Saturu. But these are seen only with good instruments, a'ad under favor- able circumstances. 504 What purpose do the ringi of Saturn serve? How appear in his evening iky. ft05. Width of two rings, s>s compared with Moon ? Distanc?? Dc-ironstrate both. How would our Moon sippear at the iistance of -^turn's rings? r>i>(?. Kn-tward motion of 4:itnrn? How traced? 5li7. MOii of Shturn ? How s.-i-n ? Be t time for obst.-rvinz? 844 ASTRONOMY. S1.TKIJJTES 0? &1TUWI. The best time for observ- r ag them is when the planet (B at his equinoxes, and his tings are nearly invisible. lii January, 1849, the author saw five !( these satellites, as represented in the adjoining cut. The rings appeared only as a lit e 1 light extending each way from the planet, and the satellites were in the direction o t^i; line, 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, L*om the planet's center are from 123,000 to 2,366,000 miles ; and their periods from 22 hours to 79 days, according 10 their distances. The distances and periods of the satellites of Saturn are as follows : Dist;ii. ce In m'les. Peiio lie times. Distance in miles. Periodic times. 1st, 121,000 days 22? hours I 5th 343,000 4 days 12 hour i 2d 155,000 1 " 9 " I 6th 796.000 15 - 22 " ?d. . ..191.000 1 " 21 " 7th 1,1 06,00 ' 22 " .. " tth 246,000 2 " 17 " | 8th 2,313,000 79 " 7 ' l COMPARATIVK DISTANCES OP THB MOONS OF SATURN. iJ. 1 * * e 509. The most distant of these satellites is the largest, sup to be about the size of Mars ; and the remainder grow smaller as they are nearer the primary. They are seldom eclipsed, on recount 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 al! revolve on their respective axis in the same manner. SYSTEM OF SATURN NO ECLIPSES. Let the line A B represent the plane >f the planet's orbit, C D his axis, and ' ' I V the plane of his rings. The satellites U-ing in the plane of the rings will evolve around the shadow of the pri- aary, instead of passing through it, and in|c ec"psed. At th 1 time of his equinoxes, however, vhen tho rings are turned toward the luu i see A and E, cut, page 242) they oust "be in the center rf the shadow on 508. The revtJutions? Shape and ytositior s f cJ eir orbits? Distant-':." fn *Wj). O>.T..Mjftt.'v'. size f THE PRIMARY P'ANETS JUPITER AND SATURN. 45 Ifio opposite side ; and the moons, revMvlujr in the plane of the rings, must pasj Urough the shadow at every revolution. The eighth, however, may sometimes escape, on account of his departure from the plam oi the rlugs, iu shown in the cut. 510. The theory of the satellites of Saturn is less perfect than than 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 moone, oic 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 iu the came hemisphere, in one bright assemblage 1 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, arc scenes worthy of the majesty of the Divine Being to imfoid, and of rational creatures to contemplate. Such displays of Wisdom and Omnipotence, lead us to conclude ths*t the numerous splendid objects connected with this planet, were not created wrtly U shed their luster on naked rocks and barren sands ; but that an immense population of iute'ligent beings i? placed in those regions, to enjoy the bounty, and adore the goo4nfcss, of their great Creator. CHAPTER VIII. PRIMARY PLANETS. URANUS AND NEPTUNfc. 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, oi discernible spots. His apparent diameter is about 4", from which he never varies much, owing to the snmllness of our orbit In comparison with his own. 510 Is the system of Saturn well understood? Why not? Of what are we sore! What scenes must it present? To what conclusion must these phenomena Uad 7( 511 Poniticn and appearance r.f Uranus? Through a telescooe? ASTRONOMY. ?ir John Herschel says he -is without discernible spots, nnd yet in his ;abls lu lays down the time of the plan< t's rotation (which could only be ascertained by the rotalit.K of spots upon the planet's disc;, at 9^ hours. This time is probably given on the luthority of Schroeter, and is marked as doubtful by Dr. Herschel. 512. The motion of Uranus in longitude is still slower tlinii that of Saturn. It moves over but one degree of its orbit ii. 85 days ; hence he will be seven years in passing over one sign or constellation. His periodic time being 84 years 27 duys, his eastward motion can amount to only about 4 17' in a whole year. To detect this motion requires instruments and close observations. At this date (1866), Uranus has made tlio entire circuit of the heavens since bis 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 tliis body was observed as far back as 1690. It was seen three times by Flamstead, once by Kradley, 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 1,754,000,000 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 15,000 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 33,000 miles ; which would make his volume more than 70 times larger than the Earth's. To his inhabitants the Sun appears only the -gj^ 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 shown, however, that the S J 5 part of tiie 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. 518 His motion in lor^itude ? Periodic time? Angular motion per year ? How ftur bar he been traced since his disco very 1 Whon complete his revolution ? Was he ever een previous to 1781 V By whom ? Why are they not the discoverers, then ? 518. Wan hia existence suspected previous to 1781 'i What ground for the suspicion ? How proved to be a planet ? 514. Mean distance ? Sidctcal revolution? Hourly motion in orbit 1 dotation en axis ? 515. Diameter? Volume? Light and he-it ? Use of satellites ? THE PRIMARY PLACETS URANUS AND KEPTUNE. 247 516. Uranus is known to be attended by four moons or satel- lites, which revolve about him in different periods, and at various distances. Two of them were discovered by Sir William Uc-r- schel, and the others, in 1847, by Lassell and O. Struve. The four others, supposed to exist by Herschel, have not been seen by other observers. Most of the satellites revolve from west to east around their primaries; but the satellites of Uranus are an exception to Ihk 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 cast to west. The distance from the planet, and the periodic times of the satellites of Uranus, respectively, are as follows ; Dist. in miles. Periodic times. Dist. in miles. Periodic times. D. H. D. H. - 123,000 2 12 I 3. . ...281,000... ...9 17 171,000 4 3 | 4 376,000 13 11 NEPTUNE. 517. This is the most distant of the primary planets, and in ome respects one of the most interesting. It is about 37,000 miles in diameter, is situated at the mean distance of 2,746,000,000 miles from the Sun, and revolves around him in 1 64 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 ten thousand years ! 518. The circumstances of the discovery of this planet are at. ouce 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 It 81, his orbit was computed, and a table constructed for determining his future positions iu the heavens, but instead of following the prescribed path, or occupying his estimated positions, he was found to be yielding tc 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 Mocns? By whom discovered? Is it certain that Uranus has sij iUellites? Why doubtful ? 517. Distance and diameter of Neptune? Period? How Song to pass from the Sun to it at railroad speed? 518. What remarkable ckcunn 9feU!cei respecting Us discovery* Perturbation f 848 ASTRONOMY. 519. At first this discrepancy between the observed and the bsiimated places of Uranus, was charged upon the talks, and A 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 g.nd 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. Le- 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 nis 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 be 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 I 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 eems 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 remarkably computation and letter? Result >f Dr. Galle's search? 522. Who else investigates tbe subject at the same time? His conclusions ? What fact does this establish? WhJ not Ad,,m.s the discoverer? THE PRIMARY Sl^lS SAjpyg^NjfO) NEPTUMfc. 243 lish the fact, that the new planet was discovered by calc illation, 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, ire perfectly accounted for by the influence of the new planet. 524. Neptune is attended by but one satellite, so far as is known. It was discovered by Mr. Lassell, of Starfield, near Liverpool, October 12, 1846. It revolves around its primary in days and 21 hours, at a distance of 220,000 miles from the planet's centre. Its orbit is inclined to the plane of the ecliptic 29, and its motion in its orbit is supposed to be 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 cleai 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, i)T their appearance and motion. The appearance of the planets 5L8. lias Neptune ever been seen prior to 1S46? What supposed to be? D< 38 it account far the perturbation of Uranus? i>24. Uas Neptune a satellite? When, and by whom discovered? What said of rhigat 525. Subject of this chapter? Hovr .oir.eta regar led by the uninstructed? By the astronomer? 526. How distinctive J 250 ASTJIOMOMV. is globular, and their motion around the Sun is nearly in thi 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 loi.g 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. OV A OOMKT. 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 to be nothing more than vapor, becoming more luminous and transparent when *cm other bodies? Form? Orbits? What practical difficulty mentioned? 521 What is the nucleus of a comet? The envelope ? The tail? Have all comets thes^, three parts? Do -ve understand of what they a~e composed? What evidence of theii Mtreuie tenuity? COMETS - THEIR NATURE, MOTIONS, ORBITS, ETC. 2o>] approaching the Sun. As the comets pass between us and the fixed stars, their envelope! and tails are so thin, that stars of very small magnitude may be seen through them. Borne 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 wain.- taineti that the nucleus is sometimes solid and opaque. II 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. In 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 cornet 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 m 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 628, What difference of opinion respecting t>e nucleus of comets? What probabk solution? 529 How do they appear when viewed through a telescope at a dUtaurt from the Sun? As it approaches him? Where seen to best advantage? lirection of the trains of comets? Other positions? Comet of 1744? Of Itoil 581. Influence of sittraUion upon comets? Illustrations? Count of 1< .1) r ASTRONOM/. 4 to Jupiter, which seoras by some strange fatality to be constaoflj in their way, and to serve as a perpetual stumbling-block to them. " The remarkable comet of 1770, which was found by Lexell to revolve in a moderate 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 has not been heard of since. Herschel, p. 310. By this extraordinary rencontre, the motions of Jupiter's satellites suffered not the least perceptible derangement ; a sufficient proof of the 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, have as yet detected nothing of their nature. Tycho Brahe and Appiau 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 cornet, 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 supposed them to lie streams of electricity. u That the luminous part of a comet," says Sir John Herschel, " is something in the nature of a smoke, fog, or cloud, suspended in a transparent atmosphere, is evident from a fact whicli 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 ol 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 cea?q to wonder that they produced universal alarm. According to the testimony of ihe early writers, a comet which could be seen 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 Caesar, 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 HOC, and then resembling the Sun in brightness, being of a great iixe, and having an immense tail. In the year 1402, a comet was seen, so brilliant as to be discerned it noon-day. 534. It 1456, a large comet made its appearance. It spread 582. What said of their i hysical natures ? Opinion of Tycho Brahe ? Of Kepler and Euler? Of Newton an J Dr. Hamilton? Of Sir John Herschel? 533. How have comets usually been regarded by Ihe ignorant? What remarkable comet mentioned? 684. What comet in 1456? KITct of its appearance? Has it appeared since? Itw period? COMETS THEIR JNATLKE, MOTIONS, ORBITS, E'IC. 233 a frider terror tlian was ever known before. The belief was verj general, among all classes, that the comet would destroy the Earth, and that the Day of Judgment was at hand ! The same comet appeared again in the years 1531, ] 607, 1682, 1758 and 1835. It passed its perihelion in November, 1835, and will re-appear every 75f years thereafter. At the time of the appearance of this comet, the Turks extended their victorious arms across the 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 re- gardless of the present, and anxious only for the future. The Romish Church held nt 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. The comet, after some months, began to show signs of retreat, and soon disappeared from those eyes in which it found no favor. Joy and tranquillity soon returned. 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 firewater'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 0.00608 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 surface of the Sun. Again, if we divide the Earth's mean distance from the Sun, by the comet's perihelion distance, we sh?.ll find that the latter is only l-166th part of the Earth's distance. Now thi square of 166 is 27,556; and this expresses the number of times that the Sun appears larger to the comet, in the above situation, than it does to the Earth. Squire niakea it 84,596 times larger. According to Newton, the velocity is 880,000 miles per hur More recent disouver:>e indicate a velocity of 1,240,108 miles per hour. Incidents respecting the Turks and Church of Rome ? 585. Comet of 1680 ? Length b :tn tnil? Aphelion and perihelion distances? Rapidity of its motion when nearest the Si Whnt error corrected ? Appearance of the Sun from that point! Ueat of the :onio* l.!ii:uU:s what? Fanciful theory of Dr. Whiston. and remarks upon it ? 254. ASTKONOMY. part of its orbit which is nearest the San, it flies with the amus- 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 ol yapor, 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 intensify of both heat and cold. This ; the comet which, according to the reveries of Dr. Winston and others, deluged the wr jd in the time of Noah. Whiston was the friend and successor of Newton ; but, anxicus 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 a^ful prison-house in which, as ii 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 seventies of his justice. Such theories* may be tugeidotu, aut 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 alludec 1 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 oven 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's comet of 1832. 537. The nucleus of the comeN of 1811, according to observa- tions made near Boston, was 2617 miles in diamete , 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 uomet, including its envelope, 50,617 miles. It had a verj PSC. Why not strange that these comets were regarded as ev J omens ? Are such super- stitions peculiar to any age or country? What illustrations? 537. Size cf the cotief of 1811 ? Its motion at its perihelion ? COMETS THEIR NATURE, MOTIONS, ORBITS, ETC. 255 luminous tail, whose greatest length was one hundred millions of miles. Map TX., Fig. 16. This comet moved, hi 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 1710, which passed through 50 of a great circle in the heavens in 24 hours. Another cornet, which appeared in L759, passed o^er 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 vight 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 o'ne which can produce a collision between the two bodies." "Admitting, then," say they, "for a moment, that the comets which may strike the F-arth with their nucleuses, would annihilate the whole human race; the danger of death to each individual, resulting from the appearance of an unknown conict, would b exactly equal to the risk he would run, if in an urn there was only one single white ball among a total number of 281,000,000 balls, and that his condemnation to death would be the inevitable consequence of the white ball being produced at the first drawing." A little reflection, however, will show that all such fears are groundless. The samo unerring hand that guides the ponderous planet in its way, directs also the majestic comet ; and where infinite wisdom and almighty power direct, it is almost profane to talk of collision or accident. 540. We have before stated that comets, unlike the planets, observe no one direction in their orbits, but approach to, ano recede from their great center of attraction, in every possible 688. Velocity of the comet of 1472? Of 1770? Of 1759? Dr. Halley's conjecture? Or. Brewster's ? Could a comet produce any such effects? 639. Is such a colliaioo probable? Why not? 540. What said of the orbits of comets and their 7 According to observations made upon it in 1S05, by the celebrated Dr. Olbers, in diameter, including its envelope, is 42,280 miles. It is a curious fact, that the path \>f Biela's Comet passes very near to that of the Earth; so near, that at th'e moirent ilw center of the comet is at the point nearest to the Earth's path, the matter of the cornet extends beyond that path, and includes a portion within it. Thus, if the Earth were a: that point of its orbit which is nearest to the path of the comet, at the same moment that the comet should be at that point of its orbit which is nearest to the path of thj Darin, the Earth would be enveloped in the nebulous atmosphere of the comet. With respect to the effect which might be produced upon our atmosphere by sach a 'ircumstance, it is impossible to offer anything but the most v;igue conjecture. Sir John fijrsc-hei was atle to distinguish stars as minute as the 16th or 17th magnitude through 'Jie body of thl co-met! Hence it seems reasonable to infer, that the nebulous matter of r'.iich it is composed, must be inQnitcly more attenuated than our atmosphere; bo that fi'T every particle of comttary matter which we should inhale, we should inspire millions if pai titles of atmospheric air. 543 This is one of the comets that was to come into collision with ',he Earth, and to blot it out from the Solar System. In returning to its perihelion, November 26th, 1832, it was comput- ed that it would cross the Earth's orbit at a distance of only 18,500 miles. It is evident that if the Earth had been in that part of her orbit at the some time with the comet, our atmos- phere would have mingled with the atmosphere of the comet, and the two bodies, perhaps, have come in contact. But th comet passed the Earth's orbit on the 29th of October, in the 8th degree of Sagittarius, and the Earth did not arrive at tluit point un f il the 30th of November, which was 32 days after- wards. If we multiply the number of hours in 32 days, by 68,000 (the velocity of the Earth pel hour), we shall find that the Earth was more than 52,000,000 miles behind the comet when it crossed her orbit. Its nearest approach to the Earth at &ny time, was about 51,0(!(i,(mo of miles ; its nearest approach to the Sun, was about 83,000,000 of miles. Its mean dis- tance from the Sun, or half the longest axis of its orbit, is 537,000,000 of miles. Its eccentricity is 253,000,000 of miles ; consequently, it is 507,000,000 of miles nearer the Sun in its perihelion than it is in its aphelion. The period of its sidereal revolution is 2460 days, or about 6% days. 544. Although the comets of Encke and Biela are objects of very great interest, yet their short periods, the limited space within which their motion is circumscribed, and consequently the very slight disturbance which they sustain from the attraction of the planets, render them of less interest to physical astrono- my thar those of longer periods. They do not, like them, rush from the invisible and inaccessible depths of space, and, after sweeping our system, depart to distances with the conception of which the imagination itself is confounded. They possess none of that grandeur which is connected with whatever appears to break through the fixed order of the universe. ft hat curious fact stated ? What result if the Earth were to be enveloped in the con-.-t 648. What mischief formerly anticipated from Biela's comet? IU return in 1!-: Ih.w ne;.r a collision in distance and in time f Its nearest approach to the Earth ? To t!;f ?i.n? Its mean distance from him? Its eccentricity and period? 541. Whj are iln < tic ts of short periods less interesting than others? For what comet is it reserved u ;, '--.' giounds for the proudest triumphs of mathematical science? 258 ASTRONOMY. It is reserved for the ;omet of Halley alone to afford the proudest triumphs to tho*.; powers of calculation by which we are enabled to follo-y it in the depths of s->ac>.', 2,000,000,000 \>f miles bryond the extreme verge of the solar system; and, notwithstand- ing the disturbances which render each succeeding period >f its return different from the last, to foretell that return with precision. To be able to predict the very day and circumstances of the return of such a bodiless and eccentric wanderer, after the lapse of so many years, evinces a perfection of the astronomical calculus that may justly Aallenge our admiration. 545. " The re-appearance of Biela's comet," says Herschel, ' whose return in 1832 was made the subject of elaborate cal- 'juidtiom: by mathematicians of the first eminence, did not disap- point the expectations of astronomers. It is hardly possible to imagine anything more striking than the appearance, after the lapse of nearly seven years, of such an all but imperceptible cloud or wisp of vapor, true, however, to its predicted sime and place, and obeying laws like those which regulate the planets.''* Herschel, whose Observatory was it Stott-gh, England, observed the daily progress of this comet from the 24th of September, until its disappearance, compared its actual posi lion from day to day, with its calculated position, and found them to agree within four or five minutes of time in right ascension, and within a. few seconds of declination. Its position, then, as represented on a planisphere which the author prepared for hi? pupils, and afterwards published, was true to within a less space than one-third of its projected diameter. Like some others that have been observed, this comet has no lumi- nous train by which it can be easily recognized by the naked eye, except when it is very uear the Sun. This is the reason why it was not more generally observed at its late -eturn. Although this comet is usually denominated "Biela's comet," yet it seems tha M. Gambart, director of the Observatory at Marseilles, is equally entitled to the honor of identifying it with the comet of 1772, and of 1805. He discovered it only 10 days aftei Biela, and immediately set about calculating its elements from his own observations, which are thought to equal, if they do not surpass, in point of accuracy, those of every othei astronomer. 546. Up tc the beginning of the 17th century, no correct notions had been entertained in respect to the paths of comets. Kepler's first conjecture was that they moved in straight lines ; but as that did not agree with observation, he. next concluded that they were parabolic curves, having the Sun near the vertex, and running indefinitely into the regions of space at both extre- mities. There was nothing in the observations of the earlier astronomers to fix their identity, or to lead him to suspect that any one of them had ever been seen before ; much less that they formed a part of the solar system, revolving about the Sun it) elliptical orbits that returned into themselves. 54 1. This grand discovery was reserved for one of the most industrious and sagacious astronomers that ever lived this was Dr. Halley, the cotemporary and friend of Newton. When tho comet of 1682 made its appearance, he set himself about observ- ing it with great care, and found there was a wonderful resem- S4ft. Remarks on the re-appearance of Biela's comet? What remarkal)!- calculating referred to? Form ef this comet? Is it ready Biela's comet? 546. Former know- Oder f the orbits of comets? 647. What .*u discovery, and by whom ? Pro-crti C-OMETa THEIR NATURE, MOTIONS, ORBITS, ETC 25$ bhmce between it and three other comets that he found recorded, the comets of 1456, of 1531, and 1607. The times of their appearance had been nearly at equal and regular intervals ; their perihelion distances were nearly the same ; and he finally proved them to be one and the same comet, performing its circuit around the Sun in a period varying a little from 76 years. It is, there- fore, called Halley's comet. Map IX., Fig. 78.) The orbit of Halley's comet extends outward about 1 20,000,00f of miles beyond the orbit of Neptune, as represented in the fol lowing cut : OMIT OF HALLKT'S COMST. This is the same- somet that filled the eastern world with so much consternation in 1456 as stated on page 253, and became an object of such abhorrence to the Church of Rome The periodic times of the three comets just described, are a, Eneke's, 1212 days. Biela's, 2461 days. Halley's, 28,000 days. Halley's comet, true to its predicted time and place, is now (Oct. 1S35) visible in the evening sky. Bui we behold none of those phenomena which threw our ancestors of the middle ages into -agonies of superstitious terror. We see not the cometn horreixlit. maffnitudinis, as it appeared in 1305, nor that tail of enormous length which, in 1456, extended over two-thirds of the interval between the horizon and the zenith, nor even a star as brilliant as was the same comet in 1682, with its tail of 30. Its mean distance from the Sun is 1,713,700,000 miles; the eccentricity of its orbit is 1,658,000,000 miles; consequently it is 3,316,000,000 miles farther from the Sun in its aphelion than it is in its perihelion. In the latter case its distance from the sun is only 65,700,000 miles; but in the former it is 3,871,700,000 miles. Therefore, though its aphe- lion distance be great, its mean distance is less than that of Uranus ; and great as is the aphelion distance, it is but a very small fraction less than one-Jive thousandth part of that distance from the Sun, beyond which the very nearest of the fixed stars must be situated; and, as the determination of their distance is negative and not positive, the nearest of them may be at twice or ten times that distance. of the discovery? Aphelion distance of Halley's comet? What former visit to our 97* Lem referred to? Periods of the three comets just described? Appearance of Halley'i fomet in 1885? Its mean distance from the Sun? How compare with that of Uranus Bo* does his greatest distance compare with that of the Fixed Stars? 260 ASTRONOMY. 548. The orbit of Eucke's cornet is wholly within the orbit > ft of Jupiter, while that of Biela's extends but a short distance beyond it. The aphelion dis- tauce of Halley's comet is 3,400,000,000 of miles, or 550,000,000 of miles beyond the orbit of Neptune. And even this is, in reality, a comet of short period compared with many that belong to our sys- tem. 549. The comet of 181 9 was re- markable for its straight wedge- shaped appearance not altogether unlike a shuttle-cock. It exhibited none of that curvature in its form which is an almost universal characteristic of cometary bodies. Map IX., Fig. 79. 550. The comet of 1843 was one of the most magnificent of modern times (See Map IX., Fig. 80). It was more than 00 in length. In the Southern Hemisphere it was so brilliant as to throw a very strong light upon the Earth. As its distance from the Sun varied, its color varied, from pale orange to " rose red," and then to white. " It passed its perihelion on the 27th of February, at which time it almost grazed the surface of the Sun, approaching nearer to that luminary than any comet hitherto observed. Its motions at this time were astonishingly swift, and its brilliancy such as to induce the belief that it was at a white heat through its whole extent. Its period is supposed to be 21J years ; consequently this must be its eighth return since 1668 ; and it will visit our sphere again in 1865." At the time of the appearance of this comet, Rev. Mr. Miller and othern were earnestly warning the people of the United States, that the world was to be burned up on the 2S<1 of April following; and the appearance cf the comet was regarded by many as an indica- tion that the end of all things was at hand. 551. The number of comets which have been observed rinco the Christian era, amounts to 650. Scarcely a year has passed without the observation of one or two. And sir.oe multitudes of them must escape observation, by reason of their traversing that part of the heavens which is above the horizon in the day BiS. Where are the orbits of Encke's and Biela's comets situated? What said of Hal- fcy's sorneU 549. Comet of 1S19? 550. That of 1843? Its length? Brilliancy? What variation in its color ? Its perihelion pass-ipe ? Heat? Its period? Next appear- ance? Incident of its last appearance ? 551. Number of comets 9 Why so few ne;uf COMETS THEIR NATURE, MOTIONS. ORBITS, ETC. 261 time, their wholo number is probably many thousands. Come* 8 so circumstanced, can only become visible by the rare coinci- dence of a total eclipse of the Sun a coincidence which hap- pened, as related by Seneca, 60 years before Christ, when o large comet was actually observed very near the Sun. But M. Arago reasons in the following manner, with respect to the number of comets : DK number of ascertained comets, which, at their least distances, pass within the orbH l/f Mercury, is thirty. Assuming that the comets are uniformly distributed throughout tho jolar system, there will be 117,649 times as many comets included within the orbit cf L'lanus, as there are within the orbit of Mercury. But as there are 80 within the oibit if Mercury, 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 Venus ; 21 between the orbits of Venus 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 ISof , 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 oar 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, ty their mutual action on each other. Neither could it be where it Phenomenon 60 years before Christ? M. Arago's reasoning and conclusion? 568, Perihelion distances of various comets ? Directions in longitude ? Number whose paths have been ascertained? 553. What inquiries awakened by the visits of comptarj boJies? 5U4. Remarks respecting the date of the sola" system? What supposed ^-oas that the whole system wus created at once? 362 ASTRO?" MY. is, nor move as it docs, nor appear as we see it, unless tliey 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 forma tioL waa simultaneous. CHAPTER X. OF THE FORCES BY WHICH THE PLANETS ARE RETAINED IN THEIR ORBITS. 555. HAVING described the real and apparent motions of tha 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, namely, the LAW OF UNIVERSAL GRAVITATION. By graritation 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 til to itself. It is said, that Sir Isaac Newton, when he was drawing to a close the demonstration ol f.he great truth, that gravity is the cause which keeps the heavenly bodies in their crbrt:, WHS 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 planets, while they in turn attract the Sun. The 555. Bubjfect of this chapter? What is meant by gravitation? Upon what does th amount of this attraction dtpend? Influence of the Earth? Anecdote of Newton 1 Vxi. la attraction reciprocal? What illustration r'ed ? Ways in which ;ttra liov LAW OF GRAVITATION. 263 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 conn tor- balancing that of the ball, but also producing a motion of the ball towards itself. T iis disposition, or tendency towards the Earth, is manifested in whatever falls, whether M b>; a pebble from the hand, an apple from a tree, or an avalanche from a mountain 111 terr.-sti-il bodies not excepting the waters of the ocean, gravitate towards the centei >i'thc 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 ihe semi-diameter of the Earth, the gravitating force would be only one-fourth of what it is at the surface. But Mow the sur- face, it decreases in the direct ratio of the distance from the center ; so that at a distance of. halt 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 lea. veighs a pound, or 16 ounces; but if by any means it could be raised 4000 miles abov<* 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 )nly one-fourth of a pound, or four ounces; an-3 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 3 n OC miles, three-fourths of a pound ; and at 4000 miles, or at tiie surface, one pound. It is a universal law of attraction, that its power decreases as ike square of the distance increases. The converse of this is also true, viz.: The power increases as the square of the distance, deceases. 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' tiameters of the Earth, from the Earth's center. That is, when ^Atnrests itself? 557. Where is the power of terrestrial gravitation greatest? How timinishel ? In what ratio as we ascrnd above the Earth ? As we descend toward tf jenter T Are weight and gravity the same ? 558. What would be the weight of a bodj it the Earth's center? At 100 miles from the center ? At '.''KM) miles? At 4000 f Whaj inhpnrul aw? What rule based upon this !HW? \Vh;it. illustrations srirei;? What, ruli 264 ASTROXOMY. the gravity is increasing, multiply the weight by the square oi 1 the distance : but when the gravity is decreasing, divide lilt weight by the square of the distance. Suppose a body weighs 40 pounds at 2000 miles above the Earth's surface, what woul'J It, weigh at the surface, estimating the Earth's semi-diameter at 4000 miles. From ti>t ji.nter to the given height, is lj semi-diameters; the square of 1}, or 1.5 is 2.25, which, multiplied into the weight (40), gives 90 pounds, the answer. Suppose a body which weighs 256 pounds upon the surface of the Earth, be raised to ,1 e distance of the Moon (240,000 miles), what would be its we ght? Thus, 4000)240,000,60 st m'.-rtiameters, the square of which is 3600. As the gravity in this case is decreasing, divide the weight by the square of the distance, and it will give 8600)256(l-16th cf a pound, or 1 ounce. To find to what height a given weight must be raised to lose a certain portion cf ii.s weight. RDLB. Divide the weight fit the surface ~by the required weight, and extract th square root of the quotient. Ex. A boy weighs 100 pounds, how high must he be carried tc weigh but 4 pounds ? Tims, 100 divided by 4, gives 25, the square root of which is fi Henii-diameters, or 20,000 miles above the center. 559. Bodies of equal magnitude do not always contain equal quantities of matter , a ball of cork, of equal bulk with one of Load, contains less matter, because it is more porous. The Sun, though fourteen bundled thousand times larger than the Earth, lining much less dense, contains a quantity of matter only 355,000 as great, and hence can exert an attractive force onjy 355,000 times greater than that which the Earth is capable of exorting. The quantity of matter in the Sun is "SO times greater tlum that of all the pinners jm7tf common center. ATTRACTIVE AND PROJECTILE FORCES. 563. All simple motion is naturally rectilinear ; that is, all bodies put in motion would continue to go forward in straight lines, as long as they met with no resistance or diverting force. On the other hand, the Sun, from his immense size, would, by the potver of attraction, draw all the planets to him, if his attractive force were not counterbalanced by the primitive im- pulse of the planetary bodies to move in straight lines. 564. The attractive power of a body drawing another body tut :ne body in the universe? 561. Suppose the Earth was the only body revolving tround the Sun ? Is the center of gravity always at the same distance from the Sun J Why not? How would it be if all the planets were on one side of him? 562. What ia Ihe amount of matter in the Earth as compared with the Moon? How with f.he second- ry planets? With other systems in the universe? 563. What is the character of all ' tuple motion? What illustrations given ? 564 What is the attract! ?e power called? 266 AS'l RONOMY. towards the center, is denominated Centripetal force ; and the ten dency of a revolving body to fly from the center in a Vangeiit line, is called the Projectile or Centrifugal force. The joint action of these two central forces gives the planets a circular motion, and retains them in their orbits as they revolve, the pri- maries about the Sun, and the secondaries about their primaries. ;>65. The degree of the Sun's attractive power at each par- ticular planet, whatever be its distance, is uniformly equal to the centrifugal force of the planet. The nearer any planec is to the Sun, the more strongly is it attracted by him ; the farther any planet is from the Sun, the less is it attracted by him ; therefore, those planets which are the nearer to the Sun, must move the faster in their orbits, in order thereby to acquire cen- trifugal forces equal to the power of the Sun's attraction ; and those which are the farther from the Sun, must move the slower, in order that they may not have too great a degree of centri- fugal force, for the weaker attraction of the Sun at those distances. LAWS OF PLANETARY MOTION. 566 Three very important laws, governing the movements of the planets, were discovered by Kepler, a German astronomer, in 1609 In honor of their discoverer, they are called Kepler's Laws. Kepler was a disciple of Tycho Brake, a noted astrono mer of Denmark, and was equally celebrated with his renowned tutor. His residence and observatory were at Wirtemburgh, in Ger- many. The first of these laws is, that the orbits of all the planets are elliptical, having the Sun in the common focus. The point in a planet's orbit nearest the Sun is called the perihelion point, and the point most remote the aphelion point. Perihelion is from peri, about or near, and helios, the Sun ; and aphelion, from apo, from, and fiettos, the Sun. PEKIUKUOJJ. i'rom this first law of Kepler, it results that the pianeis move with different velocities In different parts of thoir orbits. From the aphelicu 10 the perihelion -vvnts, the centripetal force combines with the centrifugal to accelerate the planet's molicn; while from perihelion to aphelion points, the centripetal acts against the centrifugal broe, and retards it. tfhe tendency to depart from the center? What does the joict action of these two force* produce? 566. What relation between the Sun's attraction ard the centrifugal fore* of the planets? What effect has the clittttince of a planet from tht Sun, upon his attrac- tive force? How is this increased tendency counterbalanced? 5(16. What important laws when and by whom discovered? S'.ate the first? What are the aphelion .13? points? Derivation V What results from this first law? LAWS OF PLANETARY MOTION. 207 From A to II in the diagram, the centrifugal force, represented by the line C, acts with the tendency tc revolve, and the planet's motion is accelerated; but from B to A the same force, shown by the line D, acts against the tendency to advance, and the planet is rciui'ded. Hence it comes to aphelion with its least velocity, and to perihelion with its greatest. In ;he statement of velocities on page 45, th* mean 5r a wage velocity is given. 567. The second law is, that the radius rector of a planet describes equal areas in equal times. The radius is an imaginary Hue joining the center of the Sun and the center of the planet, in any part of its orbit. Vector is from re/io, to carry ; hence the radius vector is a radius carried round. By the statement that it describes equal areas in iqua* limes, is meant that it sweeps over the same surface in an hour, when a planet is near the Sun, and moves swiftly, as, whcu furthest from the Sun, it moves most slowly. The nearer a planet is to the Sun, the more rapid ita . RADIUS VECTOR. motion. It follows, therefore, that if the orbit of a /lanet is an ellipse, with the Sun in one of the foci, ita rate of motion will be unequal in different parts of its orbit swiftest at perihelion, and slowest at aphelion. From perihelion to aphelion the centripetal more di- rectly counteracts the centrifugal force, and the planet is retarded. On the other hand, from the aphelion to the perihelion point, the centripetal and centrifugal forces are united, or act in a similar direction. They consequently hasten the planet onward, and its rate of motion is constantly accelerated. Now suppose, when the planet is at a certain point near its perihelion, we draw a line from its center to the center ol the Sun. This line is the radius vector. At the end cf one day, for instance, after the planet has advanced considera- bly in its orbit, we draw another line in the same man- ner to the Sun's center, and estimate the area between the two lines. At another time, when the planet is near its aphelion, we note the space over which the radius vector travels in one day, and esti- mate its area. On comparison, it will be found, that notwithstanding the unequal velocity of the planet, and consequently of the radius vector, at the two ends of the ellipse, the area over which the radius vector has traveled is the same in both cases. I'he same principle obtains in every part of the planetary orbits, whatever may be thsir ellipticity or the mean distance of the planet from the Sun ; hence the rule that thts rvdiw vector describes equal areas in equal times. In the preceding cut, the twelve triangles, numbered 1, 2, S, &c., over each of which th69. What results from these principles, a$ respects the weight of bodies on the Earth's rarfacti ? How increased or diminished? What illustrations given? 570. Upon > r.at. Dir.ti, does the weigh-t of bodies upon the placets depend? What illustrations f Vfi. la the Sun a fixed body? What motior in space? Who firt ;uh;in .ji-d tins i.l*>a I PROPER MOTION OF TIIL SUN IN SPACE. This opinion was first advanced, we think, by Sir William Herschel; but the hocor o. Actually determining this interesting fact, belongs to Struve, who ascertained uot only he direction of the Sun and Soiar System, but also their velocity. The point of tend- ency is towards the constellation Hercules, Right Ascension 259*, Declination 86. The velocity of the Sun, &c., in space, is estimated at about 20,000 miles per hour, or uearlj 9 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 some centra) 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 great ceiit-cr Vliat great discovery in 1847, and by whom? By what process? What conclusion firs! reached? What liar afterward designated? Further description of the progress of tin discovery? What conclusion respecting the passage of light from the centr.il Sun to \u 1 270 ASTRONOMY , . , ABO OF THE SOS'S 574. The enormous orbit which our own Sun. with the Bar tli, and the other planets, Is thus inferred to be describ- ing about that distant cen- ter not, indued, under its 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 mil lions 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 -$ w th part of his 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 .Icgrees 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 ^32 degrees. CHAPTER XII. PRECESSION OF TI1E EQUINOXESOBLIQUITY 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 P3ECESSION T OF THE EQUINOXES. The equinoxes, as we have learned, are the two opposite 5f4 Supposed period of the Sun's revoluti( n ? What portion of his orbit gone ovei rtii(Ni the creation of our race? Situation rf Us orbit with respect to the ecliptic? Lot* iTitud* of ascending node? 575. Subject of this chapter? What are the equinoxes < PRECESSION OF THE EQUINOXES. 271 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 equl- i.octial, 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, tc call it, as it is, the Recession of the Equinoxes ; for the equinoc- tial points do actually recede upon the ecliptic, at the ra*-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, thc^e is the vernal equinox ; and wherever he crosses it in the autumn, there is the autumnal equinox ; and these points are constantly moving to the west. To render this subject familiar, PBBCKSSION OF THB EQUINOXES. we will suppose two carriage roads, extending quite around the Earth ; I 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 forme/ 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 oxacu; in the former track, he need not fear being run over, for the carriage will cross thi road 100 rods west of him, that is 100 rods west of the meridian on which he stood. It ]> 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 sccon4 What n.eant by their precession ? 576. With reference to what is it a precession? 1* It really a precession of the equinoxes ? Where are the equinoxes spring and fall ? Can Tru illustrate by the iwo carriage roads, &c. ? By the other diagram? Does the 8aB m ASTROJNOMY. circuit, cross the equinoctial ] ath 200 rods west of the meridian whence it first set or* on the third circuit, 300 rods west; on the fourth circuit, 400 rods, and GO on, continual!/ After 71% circuits, the point of intersection would be one degree west of its place at tU* 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 aga'u the point from whence it first departed. The application of this illustration will be ma>i fest when we consider, further, that this interesting phenomenon RECESSION OF THE EQUINOXES. may be explained in another way by the adjoining diagram. Let the point A represent the rernal equinox, readied, for in- stance, at 12 o'clock on the 20th of March. The next year the gun will be in the equinoctial 22 minutes 33 seconds earlier, at which time the Earth will be 60 i4" on the ecliptic, back of the point at which the Sun was in the equinoctial the year before. The next year the same will oc- cur again ; and thus the equi- noctial point will receda west- ward little by little, as shown by th rfinall lines from A to B, and from C to D. It is in reference to the stars going forward, or seeming to precede the equi- noxes, that the phenomenon is called the Precession of the Equi- noxes. But in reference to the motion of the equinoxes them- helves, "A is rather a recession. 571 The Sun revolves from one equinox to the same equinox ugain, in 365(1 5h. 48' 47" .81. This constitutes the natural, or tropical year, because, in this period, one revolution of the sea- sons is exactly completed. But it is, meanwhile, to be borne in mind, that the equinox itself, during this period, has not kept its position among the stars, but has deserted its place, and fallen lack a little way to meet the Sun ; whereby the Sun has arrived at the equinox before he has arrived at the same position among the stars from which he departed the year before ; and, consequently, must perform as much more than barely a tropical revolution, to reach that point again. To pass over this interval, which completes the Surfs sidereal revolution, takes (20' 22".94) about 22 minutes and 23 seconds longer. By adding 22 minutes and 23 seconds to the time of a tropical revolution, we obtain 365d. 6h. 9m. lOfs. for the length of a sidereal revolution ; or the time in which the Sun revolves from one fixed star to the same star again. Though we speak of the revolution of the Sun, we mean simply his apparent revoJutior eastward around the hea rens, caused wholly by the actual revolution of the Earth in hei actually revolve? Why, then, speak of his revolution? 577. What is the length af a tTTJical ye*r? Hw different from a sttereal year? Difference oftinti? Lengtb vf * sidereal year ? PRECESSION OF THE EQUINOXES. 273 r*lt, no a distant object would appear to sweep around the horizon if ire were walking or sailing around it. This may be illustrated by the cut, page 28b, where the paasag* of the Earth from A to B would cause the Sun to appear to move from to D j aud so on around the whole circle of the Zodiac. 578. As the Sun describes the 'whole ecliptic, or 360, in a tropical year, he moves over 59' 8" of a degree every day, at a meau rate, which is equal to 50^" of a degree in 20 minutes and 23 seconds of time ; consequently he will arrive at the equinox or solstice when he is 50^'' of a degree short of the. star or fixed point in the heavens, from which he set out the year before. 80 that, with respect to the fixed stars, the Sun and equinoctial points fall back, as it were, 1 m 7 If years. This will make the stars appear to hare gone forward 1, with respect to the signs in the ecliptic, in that time ; for it must be observed, that the, same signs always keep in the same points of the. tdiptic, without regard to tfie place of the constellations. Hence it becomes necessary to have new plates engraved for celestial globes and maps, at least once in 50 years, in order to exhibit truly the altered position of the stars. At the present rate of motion, the recession of the equinoxes, as it should be called, or the precession of the stars, amounts to 30, or one whole sign, in 2 140 years. PKKCKSIOM Or THIS STABS. To explain this by a figur : Suppose the Sun to have been in conjunction with a fixea Btar at S, in the first degree of Taurus (the second sign of the ecliptic), 840 years befora the birth of our Saviour, or about the seventeenth year of Alexander the Great ; then having made 2140 revolutions through the ecliptic, he would be found again at the end ol so many sidereal years at S ; but at the end of so many Julian years, he would be found t J, and at the end of so many tropical years, which would bring it down to the begin- ning of the present century, he would be found at T, in the first degree of Aries, which 578. Daily progress of the Sun ? What is the amount of the annual recession of the iquinoxes? What effect will this have upi T the apparent positions of the stars? Hence what bf comes necessary? How long does it require for the equinoxes to recede a w'loln tfjff * Do you understand the diagram, and the reference to the sidereal, Julian, and Tt'jfrJcal years? Explain the difference io these three kinds of yearn. # ASTRONOMV baa receded from S to T in that time by the precession of Ihe equinoctial points Aries ami Libra. The arc S T would be equal to the amount of the precession ( for precession w must still call it) of the equinox in 2140 years, at the rate of 50".23572 of a degree, or * minutes and 28 seconds of time annually, as above stated. 579. From the constant retrogradation of the equinoctial points, and with them of all the signs of the ecliptic, ii follows that Ihe longitude of the stars must continually increase. The same cause affects also their right ascension and declination. Hence, those stars which, in the infancy of astronomy, were in the sign Aries, we now find in Taurus ; and those which were in Taurus, we now find in Gemini, and so on. Hence likewise it is, that the star which rose or set at any particular time of the year, in the time of Hesiod, Eudoxus, Virgil, Pliny, and others, by DO means answers at this time to their descriptions. Hesiorf n his Opera et Dies, lib. ii. verse 185, says : " When from the solstice sixty wintry days Their turns have finished, mark, with glitt'ring rays, From Ocean's sacred flood, Arcturus rise, Then first to gild the dusky evening skies." But A rcturus now rises acronically in latitude 37 45' N. the latitude of Hesiod, and nearly that of Richmond, in Virginia, about 100 days after the winter solstice. Suppos- ing Hesiod to be correct, there is a difference of 40 days arising from the precession of the equinoxes since the days of Hesiod. Now, as there is no record extant of the exact pericd of the world when this poet flourished, let us see to what result astronomy wil! lead us. As the Sun moves through about 89 of the ecliptic in 40 days, the winter solstice, in the time of Hesiod, was in the 9th degree of Aquarius. Now, estimating the precession of the equinoxes at 50 i' in a year, we shall have 5u^" : 1 year : : 39 : 2814years since the time of Hesiod : if wj subtract from this our present era, 1S55, it will give 958 years before Chrst. Lempriere, in his Classical Dictionary, says Hesiod lived 907 years before Christ. See a similar calculation for the time of Thales, page 89. 580. The retrograde movement of the equinoxes, and the annual extent of it, were determined by comparing the longitude of the same stars, at different intervals of time. The most care* ful and unwearied attention was requisite in order to determine the cause and extent of this motion a motion so very slow as scarcely to be perceived in an age, and occupying not less than 25,000 years in a single revolution. It has not yet completed one quarter of its first circuit in the heavens -since the creation of Mars. 581. This observation has not only determined the absolute motion of the equinoctial points, but measured its limit ; it has also shown that this motion, like the causes which produce it, is not uniform in itself ; but that it is constantly accelerated by a 79. What effect has the recession of the equinoxes upon the longitude of the stars, .nbliquely to the base. 585. The precession of the equinoxes, thus explained, consists in a real motion of the pole of the heavens among the stars, in a small circle around the pole of the ecliptic as a center, keeping constantly at its present distance of nearly 23^- from it, in a direction from east to west, and with a progress so very slow, as to require 25,000 years to complete the circle. During this revolution, it is evident that the pole will point successively to every part of the small circle in the heavens which it thus describes. Now this cannot happen without producing corre- sponding changes in the apparent diurnal motion of the sphere, and in the aspect which the heavens must present at remote periods of time. Let the line A A in the figure re- present the plane of the ecliptic; B B, tne poles of the ecliptic ; C, the poles of the Earth ; and D D, the equin 'dial. 3 E is the obliquity of the ecliptic. The star C, at the top, represents the pole star, and the curve line passing to the right from it, may represent the circular orbit of the north pole of the heavens 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 pole star, has not always been, nor will always continue to be, our polar star. At the time of the JOB- 584. What said of the cause of this recession? 585. vrhat, then, does it consist! What sa^lof the pole of the ecliptic, and the aspects of t.- neavens during this rovolu- Uoii? 585. How is the effect of tins motion manifest? How witl the Pole atarf MUTATION OF TDK EARTH'S AXIS. B I'KECESSiOM OF THE EQUINOXES. 27? Bt! action 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 unde -stood, merely, as the vanishing point ol the Earth's axis; or that point in the concave sphere which ia ahoayt appetite the terrsstial pole, and which consequently must move as that moves. 581. 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 27' towards the tropic of Cancer, the circumpolar stars will be suc- cessively at the least distance from it, when their longitude i? 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- conu, 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'.51455; consequently the equinoctial points have receded since the creation, 2s. 14 8' 21". The longitude of the star Beta Arietis, was in 1820, 81 27' 28" : Meton, a famoiw mathematician of Athens, who flourished 480 years before Christ, says, this star, in Ma time, was in the vernal equinox. If he is correct, then 31 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 *xis 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 ? 587. Where is the precession of the atari most apparent? Where least? When are the circumpolar stars nearest the tropic ol Cancer, and why ? 588. Where was the pole star in 1855? When wilJ it be nearesrt the true pole? How near then? What said of Alpha Draconic f Of . r /y a ? Mean overage recession for 5800 years? Amount? Longitude of Beta A r-iettj 600. Instead of a single tide-wave upon the waters 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, which accounts for both a flood and an ebb tide every twelve hours. 597 Are the tides uniform? What variation of time? As to amount? What art j'.jse extraordinary high and low tides called? 59S. The cause of tides? How bun for this influence? 599. What most obvious effect of tho Moon's attraction? Substance if note? Remark of Dr. Herschel? 600. How many tide-waves are there on the floDe a.id how situatjd? 282 ASTRONOMY. In this cut, we have a representation of the tide-waves as they actually exist, e*Uipt 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 B, Vff see another high tide at C on the opposite side of the globe. At the same time it if Low tide at D 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 attrao f.on on different sides of the Earth. If the student well understands the subject of gravitation, he will easily perceive icw a difference of attraction, as above described, would tend to produce an elongation if the huge drop of water called the Earth. The diameter of the Earth amounts to about gJ-th of the Moon's distance; so that, by the rule (568), the difference in her attraction 6n the side of the Earth toward her, and the opposite side, would be about y^th. The attraction being stronger at B (in the last cut) than at the Earth's center, and stronger at her center than at C, would tend to separate these three portions of the globe, giving the waters an elongated form, and producing two opposite tide-waves, as shown in the cut. 602. A secondary cause of the tide-wave on the side of the Earth opposite the Moon, is the revolution of the Earth around the common center of gravity between the Earth and Moon, thereby generating an increased centrifugal force on that side of the Earth. The center of gravity between the Earth and Moon is the point where they would exactly balance each other, if connected by a rod, and poised upon a fulcrum. CENTER OF GRAVITY BETWEEN TUB KARTH AND MOON. Moon This point which, according to Ferguson, is about 6000 miles from the Earth's center Is represented at A in the above, and also in the next cut. SECONDARY CACSK OF HIGH TIUK OPPOSITE THK MOON. Tl e point A represents the center of gravity between the Earth and Moon ; ami as it Ij I); IB point which traces the regular curve of the Earth's orbit, it is represented in the arc of that orbit, while the Earth's center is 6000 miles one side of it. Now, the law of gravitation requires that while both the Moon and Earth revolve around the Sun, they ihould also revolve around the common center of gravity between them, or around the This would give the Earth a third revolution, in addition to that around th< 601. State the principal cause of the wave opposite the Moon '( Demonstrate by dih /ram. 602. What other cause operates with the one just stated to produce the Ud- Fare opposite the Moon? What is the center of gravity between the Earth and tb< ?*oo\? Where is it situated ? Illustrate the operation of this secondary cause. PHILOSOPHY OK THE TIDES 2&) Bun and >n her axis. The small circles show her path around the center 01 gravity, and the arrows her direction. This motion of the Earth would slightly increase the centrifugal tendency al B, and thus helj) to rais<; the tide-wave opposite the Moon. But as this 'motion is slow, corre- upending with the revolution of the Moon around the Earth, the centrifugal force c.ouUl Eot be greatly augmented by such a cause. 603. As the Moou, which is the principal cause of the tides, is revolving eastward, and comes to the meridian later and late* every night, so the tides are about 50 minutes later each success fve day. This makes the interval between twc successive high tides 12 hours and 25 minutes. Besides .,. , ., , . ..1^1 ,T ^ TIDE-WAVES BEHIND THE MOON. this daily lagging with the Moon, the ^^ highest point of the tide-wave is found ..- *J -^ to be about 46 behind, or east of the .-'''^r ^* Moon, so that high tide does not /' occur till about three hours after the Moon has crossed the meridian. The inters do not at once yield to the im- pulse of the Moon's attraction, but continue to rise after she has passed over. In the cut, the Moon is on the meridian, but the highest point of tht wave is at A,'oj 15 east of the meridian; and the correspond ing wave on the opposite side at B is equalN Behind. 604. The time and character of the tides are also affected Ly winds, and by the situation of different places. Strong winds may either retard or hasten the tides, or may increase or diminish their height ; and if a place is situated on a large bay, witli bnt a narrow opening into the sea, the tide will be longer in rising. as the bay has to fill up through a narrow gate. Hence it is uot usually high tide at New York till eight or uinc hours after the Moon has passed the meridian. 605. As both the Sun and Moon are concerned in the produc- tion of tides, and yet are constantly changing their positions with respect to the earth and to each other, it follows that they sometimes act against each other, and measurably neutralize each other's influence ; while at other times they combine their forces, and mutually assist each other. In the latter case, an unusually high tide occurs, called the Spring Tide This happens both a* new and full Moon. 608. What daily lagging of the tides? Interval between two successive Ji.'^h tidei ? What other lagging? Cause of this last? 604. What modification of the time and character of the tides? 605. Do the Sun and Moon always act together in attracting Ihe waters ? Why not ? How affect each other's influence ? Effect on the tides ? What we Spring Tide# 'f When do they occur ? Illustrate by diagram the cause of spring tirfes, when 'he Sun and Moon are in conjunction. 84 ASTRONOMY. OAC3K or anno Tinas. Here the Sun and Moon, being in conjunction, un te their forces to produce au extra- uidinary tide. The same effect follows when they are in opposition ; ao that wo have tvo spring tides every month namely, at new and full Moon. If the tide-waves at A and B are one-third higher at the Moon's quadrature than uscal, those of C and D will be one-third lower than usual. 606. When the Moon is in quadrature, and her influer.ee ia partly neutralized by the Sun, which now acts against her. the result is a very low tide, called Neap Tide. SPRING AND NEAP Tir>K8. Tfhe whole philosophy of spring and neap tides may be illustrated by the an- nexed diagram. On the right sidft of the cut, the Sun and Moon are in conjunction, and unite to produce a spring tide. At the first quarter, their attraction acts at right angles, and the Sun, instead of contributing to the lunar tide-waves, letracts from it to the amount of his own attractive force. The tendency to form a tide of his own, as represented in : the figure, reduces the Moon's wave to O the amount of one-third. At the full Moon, she is in opposition to the Sun, and their joint attraction acting again in the same line, tends to elongate the fluid portion of the Earth, and a second spring Ude is produced. Finally, at the third quarter, the Sun and M*oon act against each other again, and the second neap tide is the result. Thus we have two spring and two neap tides during every lunation the former at the Moon's cyzygies, and the latter at her quadratures. 607. Although the Sun attracts the Earth much more power fully, as a whole, than the Moon does, still the Moon contributes more than the Sun to the production of tides. Theii relative influence is as one to three. The nearness of the Moon make? 606. Wimt are Neap Tides? Their cause? Illustrate entire philosophy by diagram 807. Comparative influence of Sun and Moon in the production of tides? Why Vooa'i InSuence the greatest ? Substance of n' te ? Deuior st. atioi ? PHILOSOPHY OF THE TIDES. 285 t;.e difference, of her attraction on different sides of the Earth much greater than the difference of the Sun's attraction on dif- ferent sides It mudt not be forgotten that the tides are the result not so much of the attraction o\ the Sun and Moon, r/.s n whole, as of the difference in their attraction on different sides of the Earth, caused by a difference in the distances of the several parts. The attrac- *.iot b=ing inversely as the square of the distance (558), the influence of the Sun and jloon, respectively, must be in the ratio of the Earth's diameter to their distances. Now .he difference i- the distance of two sides of the Earth from the Moon is -jj^th of the 5f v . 3 distance ; as 240,000-*-8,000=30 ; while the difference, as compared with the dis- ten.e of the Sun, is only yytTs th ' as 95,000,000+8,000=11,875. 608. The tides arc subject to another periodic variation, caused by the declination of the Sun and Moon north and south of the equator. As the tendency of the tide-wave is to rise directly under the Sun and Moon, vhen they are in the south, as in winter, or in the north, as in summer, every alternate tide is higher than the iiiterin<*- one. TIDES AFFECTED BY DECLINA- TION. X At the time of the equinoxes, the Sun being over the quatpr, and the Moon within 5% of it, the crest of the ;reat tide-wave wilt be on the equator; but as the Sun md Moon decline south to A, one tide-wave forms in the south, as fit B, and the opposite one in the north, as at . If the declination was north, as shown at D, the order of the tides would be reversed. The following diagram, if carefully studied, will more fully illustrate the subject of the klternate high and low tides, in high latitudes, in winter and summer : ALTERNATK HIGH AND LOW TIDES. B Let the line A A represent the plane of the ecliptic, and B B the equinoctial. On the 21st of June, the day tide-wave is north, and the evening wave south, so that the tide following about three hours after the Sun and Moon, will be higher than (he intermediate one at 3 o'clock in the morning. Oil the 23d of December, the Sun and Moon being over the southern tropic, tho highest wave in the southern hemisphere will be about 2 o'clock P. M , and the lowesl about 3 o'clock A.M.; while at the north, this order will be reversed. It is on thil Account that in high latitudes every alternate tide 's higher than the intermediate ones ; the evening tides in summer exceeding the morning tides, and the morning tides in win- ter exceeding those of evening. i>09. All spring and neap tides are not alike as to their eleva tion and depression. As the distances of the Sun and Moon are 508. What other periodic variations mentioned? Explain cause, and illustrate. Soy. Are nil spring and neap u )*>s alike? By what are they modified? Illustrate LI 286 ASTRONOMY. varied, so are the tides varied, especially by the variations of the Moon. T1HIATIONS IN TBB SPRING TIDES. At A, the Earth is in aphelion, and the Moon in apogee. As both the Sun and Mooa are at their greatest distances, the Earth is least affected by their attraction, ai.d th spring tides are proportionately low. Ai, B, the Earth is in perihelion, and the Moon in perigee; so that both the Sun and Moon exert their greatest influence upon our globe, and the springtides are highest, as ehown in the figure. In both cases, the Sun and Moon are in conjunction, but the Taria- tion iu the diskmces of the Sun and Moon causes variations in the spring tides. 610. In the open ocean, especially the Pacific, the tide rises and falls but a few feet ; but when pressed into narrow bays or channels, it rises much higher than under ordinary cir cumstances. The average elevation of the tide at several points on our coast is as follows : Cumberland, head of the Bay of Fundy 71 feet Boston \\\ " Now Haven S " New York 5 " Charleston, 8. C 6 " 611. As the great tide-waves proceed from east to west, they are arrested by the continents, so that the waters are per- manently higher on their east than on their west sides. The Gulf of Mexico is 20 feet higher than the Pacific Ocean, on the other side of the Isthmus ; and the Red Sea is 30 feet highei than the Mediterranean. Inland seas and lakes have no per- ceptible tides, because they are too small, compared with the whole surface of the globe, to be sensibly affected by the attrao Lion of the Sun and Moon. ATMOSPHERICAL TIDES. SI 2. Air being lighter than water, and the surface of the atmosphere being nearer to the Moon than the surface of tho sea, ii. cannot be doubted but that the Moon raises much higner 6!0. Height of tides in open seas? How in r arrow bays and channels? Height at dif- ferent points on our coast ? 611. Direction of tide-waves? What result? Instance! Cited? Have inland eas and lakes any tides? Why not ? Remarks respecting pM' loaopby of tides? (il'-J Atmospheric tides ? T.ifc SEASONS. 287 tides in the atmosphere than in the sea. According to Sii John Herschel these tides are, by very delicate observation^ rendered not only sensible, but mensurable. Upjn the supposition that there is wator on the s'irfacc of the Moon of the s.ime *pecific gravity as our own, we might easily determine the height to which the Earth louhl raise a lunar tide, by the known principle, that the attraction of one of thesa 'o^ie? .vi the other's surface is directly as its quantity of matter, and inversely is ita iian:v,er. 15y making the calculation, we shall find the attractive power of the iarth pon the Moon to be '21,777 times greater than that of the Moon upon the Earth. 613. We have thus stated the principal facts connected with ihis complicated phenomenon, and the causes to which they are generally attributed. And yet it is not certain that the philoso- phy of tides is to this day fully understood. La Place, the great trench mathematician and astronomer, pronounced it one of the most difficult problems in the whole range of celestial mechanics. Jt is probable that the atmosphere of our globe has its tides, as well as the waters ; but we have no means, as yet, for definitely ascertaining the fact CHAPTER XIV. THE SEASONS DIFFERENT LENGTHS OF THE DAYS AND NIGHTS. 614. THE vicissitudes of the seasons, and the unequal lengths of the days and nights, are occasioned by the annual revolution of the Earth around the Sun, with its axis inclined to the plane of its orbit. The temperature of any part of the Earth's sur- face depends mainly, if not entirely, upon its exposure to the Sun's rays. INCLINATION OF THE EARTH'S AXIS TO THE PLANE OF THB ECLIPTIC. THE ECLIPTIC X<^ r>15. Whenever the Sun is above the horizon of any place, that place is receiving heat ; when the Sun is below the horizon it is parting with it, by a process which is called radiation. The -juuntities of heat thus, received and imparted in the course of Jie year, must balance each other at every place, or the equi- fij8. Is it certain that this subject is even yet well understood? Remark of Laplace? 614. I'tMise of the seasons, and the unequal length cf the days and nights? Teraperatw f>f the Earth ? CIS. When does any plaee gnin heat, and when lose ? Upon what 288 ASTTCONCM librium of temperature would not be supported. Whenever tne Sun remains more than twelve hours above the horizon of any place, and less beneath, the general temperature of that place will be above the mean state ; when the reverse takes place, tho vsmperature, for the same reason, will be below the mean state Now, the continuance of the Sun above the horizon of any place, depends entirely upon his declination, or altitude at noon. 616. About the 20th of March, when the Sun is in the ver- nal equinox, and consequently has no declination, he rises at six i& the morning and sets at six in the evening ; the day and night are then equal, and as the Sun continues as long above our horizon as below it, his influence must be nearly the same at the same latitudes, in both hemispheres. From the 20th of March to the 21st of June, the days grow longer, and the nights shorter, in the northern hemisphere ; the temperature increases, and we pass from spring to midsummer ; while the reverse of this takes place in the southern hemisphere. From the 21st of June to the 23d of September, the days nnd nights again approach to equality, and the excess of tem- perature in the northern hemisphere abo\ethe mean state, grows less, as also its defect in the southern ; so that, when the Sun arrives at the autumnal equinox, the mean temperature is again restored. 617. From the 23d of September until the 21st of December, our nights grow longer and the days shorter, and the cold increases as before it diminished, while we pass from autumn to mid-winter, in the northern hemisphere, and the inhabit- ants of the southern hemi- sphere from spring to mid- summer. From the 21st of Dec. to the 20th of March, the cold relaxes as the days grow Icnger, and we pass from OAPSE OF TBB 8KASOM3. B EPUI'NOX \ SERTI.23 the length of the days depend? 616. How about the 2(!lh of Mat *,h? From March SOth to June 21st? From June 2 t to September '23d ? 617. Froi:. September 28d to lwmber *lst F From December 21st to March 2oth? H< w with the seasons in the THE SEASON3. 289 the dreariness of winter to the mildness of spring, when the seasons tire completed, and the mean temperature is again restored. The same vicissitudes transpire, at the same time, in the southern hemisphere, but in a contrary order. Thus are produced the four seasons of the year. In the preceding cut, the Earth is shown in her orbit, with her axis inclined 23^ ; the JN >rth Pole being towards the eye of the student. At A find B the Sun shines from pole to pole, and the days and nights are equal in both hemispheres. On the right, the North Pole is in the light, and we have summer in the northern hemisphere. On the laft, tbt reverse is the case. And the gradual shortening or lengthening of the days, and th change of temperature, are produced by the passage of the Earth from one point to another, with her axis thus inclined. 618. But I have stated not the only, nor, perhaps, the most efficient cause in producing the heat of summer and the cold of winter. If, to the inhabitants of the equator, the Sun were to remain 16 hours below their horizon, and only 8 hours above it, for every day of the year, it is certain they would never expe- rience the rigors of our winter ; since it can bo demonstrated, that as much heat falls upon the same area from a vertical Sun iii 8 hours, as would fall from him, at an angle of 60, in 1C hours. JS T ow, as the Sun's rays fall most obliquely when the. days art thortest, and most directly when the days are longest, these two causes namely, the duration and intensity of the solar heat, together, produce the temperature of the different seasons. The reason why we have not the hottest temperature when the days are longest, and the coldest temperature when the days are shortest, but in each case about a month afterwards, appears to be, that a body once heated, does not grow cold instantaneously, but gradually, and so of the contrary. Hence, as long as more heat comes from the Sun by day than is lost by night, the heat will increase, and vice versa. BEGINNING AND LENGTH OF THE SEASONS. h. ni. s. Bun enters \3 (Winter begins) 1849, December 21, 7 25 4C M. T. Wash. " " T (Spring " ) 1860, March 20, 8 56 S3 ' (Summer ) June 21 8 9 11 " ^ (Autumn " ) " Sept. 22, 19 58 21 " " 3 (Winter " ) " December 21, 13 21 57 " outhem hemispl ere ? 618. Is the simple fact that a place ie enlightened by the Bon, ufficieat cause for its being warm? What circumstance determines the intensity o. tn .Hnn'B raya ? Why, then, is it not warmest during the longest days, and on the cca fW ? How at the other polo* To what are these various apoarenl Tir-tion of thu Sun really due ? H.O. 13 ASTRONOMY. las advanced considers- PHILOSOPHI OF THE BBA8OHB.* My furtlier into the light, while the south pole has proportionally declined from It: the summer days are now waxing 'enger in the northern fiemisphere, and the eights shorter. The 21st of June, when she Sun enters the sign ikwcer, is the first day f summer in the astro- nomical year, and the longest day in the north- ern hemisphere. The aorth pole now has its greatest inclination to the Sun, the light of which, as is shown by the boundary of light and darkness, in the figure, extends to the utmost verge of the Arctic Cir- zie; the whole of which is included in the enlight- ened hemisphere of the Karth, and enjoys, at (his season, constant day during the complete revo- lution of the Earth on its axis. The whole of the Northern Frigid Zone is now in the circle of perpetual illumi- nation. On the 23d of July, the Sun enters the sign Leo, and as the line of the Earth's axis always continues parallel to itself, the boundary of light and darkness begins to approach near if to the poles, and the length of the day in the northern hemisphere, which had arrived at its maximum, begins gradually to decrease. On the 23d of August, the Sun enters the sign Virgo, increasing the appearances mentioned in Leo. On the 23d of September, the Sun enters Libra, the first of the autumnal signs, when the Earth's axis having the same inclination as it had in the opposite sign, Aries, is turned neither //wi the Sun, nor towards it, but obliquely to it, so that the Sun again now shines equally upon the whole of the Earth's surface from pole to pole. The days and nights are once more of equal length, throughout the world. On the 23d of October, the Sun enters the sign Scorpio ; the days visibly decrease in length in the northern hemisphere, and increase in the southern. On. the 22d of November the Sun enters the sign Sagittarius, the last of the autumnal signs, at which time the boundary of light and darkness is at a considerable distance from the north pole, while the south pole has proportionally advanced into the light ; the length jf the day continues to increase in the southern hemisphere, and to decrease in the northern. On the 21st of December, which is the period of the winter solstice, the Sun enters tin. sign Capricorn. At this time, the north pole of the Earth's axis is turned from the Sun, into perpetual darkness; while the south pole, in its turn, is brought into the light of the Sun, whereby the whole Antarctic region comes into the circle of perpetual illumi- nation. It is now that the southern hemisphere enjoys all those advantages with which ii-.e northern hemisphere was favored on the 21st of June; while the northern hemi- sphere, it its turn, undergoes the dreariness of winter, witji short days and long lights. * This diagram and the accompanying explanations should be carefully studied 'ill ''icy -arc thoroughly understood by the learner. The cause of the reasons and of the 3& oual lengths of the days and nights, is a matter of which no professedly educated persof ought to be ignorant, or to entertain confused and indefinite notions. By all toeans iO! this point be studied till the student can tell the cause of everj particular phe- nomenon of the seasons and the length of the t ays, without any particular interrj {ration. THE HARVEST MOON AND HORIZONTAL MOON. 29 624. By carefully observing the figure, it may be seen that the orbit of the Earth is slightly elliptical, that the Suii is to the left of the center, and that consequently, the Earth is nearer the San on the .21st of December, than on the opposite side of the ecliptic, on the 21st of June. This may seem strange to tin /earner, that we should have our winter when nearest the Sun, and our summer when most distant ; but it must be remembe' eii that the temperature of any particular part of the Earth is not so much affected by the distance of the Sun, as by the direct- ness or obliquity of his rays. Hence, though we are farther from the Sun on the 21st of June than on the 21st of December, yet, as the north pole of the Earth is turned more directly into the light at that time, so that the Sun's rays strike her surface less obliquely than in December, we have a higher temperature at that period, though at a greater distance from the Sun. 625. The difference, however, between the aphelion and peri- helion distances of the Earth is so slight, in comparison with the whole distance, as scarcely to cause a perceptible difference in the amount of light received at her respective positions. The eccen- tricity of the Earth's orbit, or the distance of the Sun from its center, is only about 1,618,000 miles, so that the variation is only 3,236,000 miles, or about ora-thirtieth of the mean distance. The true orbit of the Earth could not be distinguished from a circle. The only effect of the eccentricity of the Earth's orbit upon her temperature is, that she has probably a greater degree of heat, during summer in the southern hemisphere, when the Earth is at her perihelion, than we ever have at the north iu the same lati tude. But this difference must be very slight, if indeed it is at all perceptible. CHAPTER XY. THE HAKVEST MOON AND HORIZONTAL MOON 626. TEE daily progress of the Moon in her orbit, from west lu east, causes her to rise, at a mean rate, 48 minutes and 44 seconds later every day than on the preceding. But in places of considerable latitude, a remarkable deviation from this rule 624. What said of the form of the Earth's orbit? When are we nearest the Sun I Why is it not then the warmest in the United States? 625. What is the amount of th Karth's variation in distance from the Sun? What effect upon the light and heat of th< 626. Subject of this chapter? Mean rate of the Moon's daily delay ia risii R ASTRONOMY. takes place, especially about the time of narvest, when the fuli Moon rises to us for several nights together, only from 18 to 25 minutes later in one day, than on that immediately preceding. JFroiL the benefit which her light affords, in lengthening out thf day, when the husbandmen are gathering in the fruits of tht 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 mud Ku-lier 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. 621. About t,,e equator, the Moon rises throughout the year with nearly the equal intervals of 48f minutes ; and there the 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 continue* full from her first to her third quar ler; but that she never set* to the North Polar regions, when, at this season of the year, he is within 90* of that point in her orbit, where she is at her full. In other words, ae the Sun illun ines 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- lified 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 >ver by the index ; the intervals of time between the marks coming to the horizon, will sh r the diurnal difference of time between the Moon's rising. 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 netting. 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 aer setting, and the contrary. The reason why you mark every 12 is, that the Moon gains 12 11' on the apparent cours* -f the Sun every day, and these marks serve to denote the place of t'.ie Moon from day to day. It is true, this process supposes that the Moon revolves in (Jie plant of tht eettptic, 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- Bidei sd as coinciding ; that is, we may take the ecliptic for the representative cf tha 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 ancientlj was this phenomenon observed? To what attributed? 627. Is the Harvest MOOP known at the equator? How at the Polar circles ? At the poles? Does she there exhi- bit hei usual phases * Can you illustrate the phenomenon of the Harvest Moon by t globe 1 628. To wl at is the different lengths of the lunar nights attributable? THK HARVEST MOON .tND 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 ab at Pisces &mi 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 fur 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 tho smallest angles, set with the greatest ; and those which rise witb the greatest, set with the least. And whenever this angle is least, a greater portion of the ecliptic rises in equal times thai: 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 se ts 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 tho meridian, and Libra rising in the east. In this position, the ecliptic has a high elevation, making an angle with the horizon of 72 }$ . But let the globe be turned half round on its axis, till Capricorn comes to the meridian, and Aries rises in the east, then the ecliptic will have a low elevation above the horizon, making an angle with it of only 25j. This angle is 47" less than the former angle, and & equal to the distance between the tropics. 630. In iwrtkern latitudes, the smallest angle made by the ecliptic and horizon is when Aries rises ; at which time Libra sets ; the greatest is, when Libra I'ses and Aries sets. The eclip- tic rises fastest about Aries, and slowest about Libra. Though Pisces and Aries make an angle of only 25 with the horizon when they rise, to those who live in the latitude of New York, yet the same signs, wfien they set, make an angle of 12^-. The daily difference of the Moon's rising, when in these signs, is, in New England, about 22 minutes ; but when she is in the oppo- site signs, Virgo and Libra, the daily difference of her rising is almost four times as great, being about one hour and a quarter 631. As the Moon can never be full but when she is opposite to the Sun, and the Sun is never in Virgo or Libra except in our autumnal months, September and October, it is evident that the Moon is never full in the opposite signs, Pisces and Aries, except in those two months. We can, therefore, have only two full Moons in a year, which rise, for a week together, very near the time of sunset. The former of these is called the Harvest Moon, and the latter, the Hunter's Moon. 629. What said of the angles under which the signs rise and set ? What result follow? fts to time of the Moon's rising and setting? How illustrate by sjlobe ? 630. When U the angle smallest in northern latitudes? When greatest? What difference of aii|-e red, crim- son red, blood red, greenish red, orange red, and lake red. The arches 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. llalley 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, amagnetical 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 not in the direction of the true north, but in that of the mag netie needle at the place of observation ; and that when the arch rises- towards the zenith, it constantly crosses the heaven? at right angles, not to the true magnetic meridian. 64. What said of the colors, &c., of these polar lights? 655. Is there a satisfactory explanation of these phenomena ? What conjecture? Dr. Halley's objection ? Ilia vwt inpular opinion ? 660. What evidences that the Aurora Jlorealis is of irtffto? 504 ASTRONOMY. (2.) When the beams of the aurora shoot up so {is to pasf *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 ol an active and brilliant aurora, the magnetic needle often becomes restless, varies sometimes several degrees, and does not resume 'is former position until after several hours. From these facts, it has been generally inferred that the aurora is in some Tray e jC- aected with the magnetism of the Eurtli ; and that the simultaneous appearance tt' 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. G57. 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 Ae, 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 an* celestial object seen from the Earth's surface, and the altitud'e 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 ^Jarth 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 tha" 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 f When parallax greatest? Least? Ca. Jed what, and why? What objects the greatest parallax \ PARALLAX tr THE PLANSTS. AURORA BOREAL1S AND I'ARAl.LAX. o03 of a aeavenly body is greatest when' in the horizon, and 11 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, views the object at B, it appears to he at C, when, a. lie sume time, if viewed from the center of the Eiirt'i, would uppear to be at D. The parallax is the angle 4 C D or A B E, which is the difference between the altitude of the object B, when seen from the Earth's rf tee, and 'vhsn seen from her center. It is also ,ht- angle UK ler which the semi-diameter of the Earth, i E, is seen from the objeoc B. As the object advances from the horizon to tha aenith, 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 neurext 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 t;.e 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 dopn-ss 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 tttbtract* the refraction, to and from the Sun's observed altitude, in order to obtain t. v e 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 oe known also, because we know the exact periods of their sidereal revolutions, and, according to the third law of Kepler, ihe squares of the times of their revolutions arc proportional to the cubes of their mean distances. Hence, the first great desideratum in astronomy, where measure and magnitude aro concerned, is the determination of the true parallax. By means of observations of the transit of Venus, in 1769, the Sun's horizontal pai al Cfi) Kffeet of parallax? How obtain true altitude? How differ 'from refract 1 1 iw then obtain true altitude? 661. Use of parallax? How employed * Note? 306 ASTRONOMY. lax was settle'! at 8".5776. according to whu h the mean distance of the Sun from the Earth was thought to be about 95,000,000 of -niles. Careful observations and calcula- tions of recent date agree in proving that the true parallax is somewhat larger than this; and, hence, that the Sun's distance is not so great as above stated. Hansen, by lunar observations, has fixed the parallax at 8 r/ .916 ; Winnccke and Stone, by detenniaii'g tb parallax of Mars in opposition, have found it to be 8".964 and 8". 93 respectively, Fon~ eault, by experiments on the velocity of light, has fixed it at 8''.96 ; and Leverrier, from observations on Mars, Venus, and the Moon, at 8 /x .950. The approximation to agreement in all these determinations shows that they cr.nnot be far from the truth ; and for the present it will be safe to assume the average of them (8' / .944) as correct. This will mak(j he Sun's mean distance 91,500,000 miles, nearly; and, of course, the distances and dia- meters of the other heavenly bodies have all been somewhat reduced to agree wilh this fundamental fact. After the observations to be made in 1876, of the transit of Veuas, to occur in that year, this determination of the solar parallax will be again reviewed, And, if necessary, corrected. TABLE OF THE SUN 1 8 PARALLAX AT PI1TEBENT ALTITUDES. Surfs Alt. Parallax. Surfs Alt. Parallax. Sun's Alt. Par allay.. 0" 10' 20" 30 8". 944 8''.808 8".405 7".746 40 45' SO- BS 6".852 6".325 6 '.749 5".130 60 TO 8 80 90" 4".47-2 3".059 1".B68 0".000 662. 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 183,000,000 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: l,et A represent a fixed star in the plane of the Earth's orbit, B. At C, the Earth in 183,000,000 of miles nearer the star than it will be at D six months afterward ; and yet thiS serai-annual variation of 183,000,000 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, or; 182. What meant by Earth's annual p< \rallax? Effect of variation ol Farth'o dia on ttie fixed stars? Diagram. 663. What stars have perce^tiLie parallax t AURORA BOREALIS AND PARALVnX 307 account of its almost imperceptible quantity. PAKALLAX OF TE , gtl]8a So distant are they, that the variation of 183 r OOO,000 miles in the Earth's plae c \ / causes an apparent change- of less than 1" in \ / the nearest and most favorably situated eV fixed star. / \ Let A represent the Earth on the 1st of January, and B a /' \ Btar observed at that tirc3. Of course, its apparent place in / the more distant heavens will be at 0. 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 amouc'^ to about 48, whereas the real / parallax of the stars is less than ^.^th of one degree, or / mVwjth part of this amount. Lines approaching each other / ~~*~~-~>X thus slowly would appear parallel ; and the Earth's orbit, if jV ^S filial with a globe of fire, and viewed from the fixed stars, A V* J. would appear bat a point of light 1" in diameter I Fora J "*~ splendid diagram illustrative of the annual parallax of the stars, see Map I., of the Atlas ABERRATION OF LIGHT. 664. Iii 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 froic 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 183,000,000 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 tht Ea^th in its orbit, causes tfte 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 ana Bradley? With what results ? 665. What further observations for the same purpoai t What discovery made while investigating the subject of parallax ? What is the abemv- tion of light? 666 What remarks upon the principle or law of observation ? Hcwfe ASTRONOMY. not only very plain, but self-evident. For if light be progrea 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 plwjo to which the telescope is directed will be different from the *,rue place of the object. The quantity of this aberration is determined by a simjk proposition. The Earth describes f9' 8" of her orbit in a day = 3548", and a ray of light comes from the Sun to us in 3' 1 7" = 497": now 24 hours or 8G400" : 497 : : .3548 : 20" 4; whirl, 'is the change in the star's place, arising from the cause above mentioned. CHAPTER XVIII. PRACTICAL ASTRONOMY REFLECTION AND REI-'RAu- 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 demonstration 1 .' 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 th : a purpose mainly that w 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 ihe quantity of aberration determined? 667. Subject of Chapter XVIII.? What ia practical aJstronomy f How far discussed In *,his treatise? 668. Define light. For what indebted to it? 669. Different *enae in which the term is used ? What It REFLECTION ANT) REFRACTION OF LIGHT. 309 tn opposition to darkness. Hut it should be borne in mind, that darkness is merely the absence of that degree of light whu;h 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 loss light, even in the darkest night, and in the deepest dungeon. "Those unfortunate individuals," says Dr. Dick, "who have been confined in the dark- pel dungeons, have declared, that though, on their first entrance, no object could be per- i, perhaps for a d;iyor two, yet, in the course of time, as the pupils of their eye* CYpivaued, they could readily perceive rats, mice, and other animals that infested theit teJIo, ami likewise the walls of their apartments; which shows that, even in such situa- t'cus, 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 vas the opinion of Descartes, Euler, Iluygens, 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, tind 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 he seen from every point in the solar system, and far hence into space 'n every direction, even till he appears but a faint and glimmering star, it is evident tha 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 mny 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, &c., can see day or night; while the owl, that sees well in the night, sees poorly in the day-time. 673. Light may be turned out of its course either by reflection dark'i^ss? Can it be dark anc light at the same time? Is there any place without light? Quotation from Dr. DicV G70. What theories of the nature of light, and 05 yhom supported respectively? Remark of author? 671. How light proceeds fron> uminous bodies? Radiations liom Sun and stars? 672. How improve vision, am 1 Animals ? 673. llow is light turned out of its course? 310 ASTRONOMY. or refraction. It isrejleded when it falls upon the Lighly polished surface of metals arid other in transparent substances ; and refracted when it passes through transparent substances of diffe- rent densities, as already illustrated in Chapter XVI. REFRACTION BY GLASS LENSES. G74. A lensis a piece of glass, or other transparent substance of such a form as to collect or disperse the rays of light thai 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-ccmvesK, 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-convene lens, or one that ia bounded by two convex surfaces. D is a double-concave lens, or a circular piece of glass hollowed out on both sides. E is a concavo-convex, lens, whose curves differ, but do not meet, if produced. P is a meniscus, or a concavo-convex lens, the curves of whose surfaces meet. LENSES OF DIFFERENT FORMS. 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 corvtxity In the first of these cuts, the lens is quite thick, and the focus of the rays is quite near; but AV FOCAL DISTANCT.. light is refracted both when it enters, and when it lea fes a double ccn?3x lens, and in both instances Ju ~v-_*r is gone, so that ths rays i: : *ot so soon refracted to a ;"ci3. 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 local distance is only equal to the radius of such sphere. In the cut, the parallel rays A are refracted to a focus at 1>, by the plano-concave lens C ; and the distance C B is the diame-ter of the circle l>, .'ormed by the convex surface of the lens C produced. RAYS DISPERSED BY REFRACTION. 678. A doulk-can- cave 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 B; 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 the concave surface of the lens produced. 6t9. Common spectacles, opera-glasses, burning-glasses, and refracting telescopes are made by converging light to a focus, by the use of double-convex lenses. BURNING-GLASS. The ordinary burning-glass, which may be bought for a few shillings, is a double-convex disk of glass two or three inches in diameter, 'nclosed 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 ;>ipes 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. T l ie adjoining cut represents a large burn- ing-gliss converging the rays of the Sun to a ibcu:?. and setting combustible substances on ftre. Such glasses have been made powerful e.v;vh to melt the most refractory substances, 3 piatinum, agate, &c. " A lens three feet in r-imeter," says Professor Gray, "has been vMi-^'n to melt cornelian in 75 seconds, and a fifve of white agate in 80 seconds." plano-convex lens ? Diagram. 678. Effect of duuJjlf-convfiK lrn-? Amount of diver w;cy of rays ? 879. What articles i^ade with double-convex lensea? Uses? I'owr- >f c urnitig glasses ? ASTRONOMY RKFKECTION BT A PLAHU JIIKKOB. REFLECTION BY A CONCAVK MIRROR. REFLECTION OF LIGHT. 680. We have DOW shown how light may be turned out of ita course, and analyzed, dispersed, or converged to a point by refradion. Let us now consider how it may be converged to a focus by reflection. When light falls upon a highly-polished surface, especially ol jietals, it is reflected or thrown off in a new direction, and the angles of contact and departure are always ftqual. 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 reflection or departure which angles are seen to be equal. 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 th? principles upon which telescopes are constructed; and, fcr further particulars, shall refer the student to books on Natural Philosophy. 880. What now shown in this chapter? What next? What is reflection, and when rices it take place? What law governs it? Diagram. 681. How does a con&ivt mirro.* reflect parallel rays ! Distance of focus ? Diagram. How would you ccnstrcx/t ft concave mirror with a 10 feet focus? 6.M2. Is all the light falling upon a polH\u4 wrfee 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 term telescope is derived from two Greek words, viz., tele, at a distance, and skopeo, to see. So far as is now known, the ancients bad no knowledge of the telescope. Its invention, which occurred in 1609, is usually attributed to Galileo, a philosopher of Florence, in Italy. The discovery of the principle upon which the refracting telescope is constructed wai purely accidental. The children of one Jansen, a spectacle-maker of Middleburgh, in Holland, being at play in their father's shop, happened to place 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, soor 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 bo full of ine- qualities, like mountains and valleys ; the spots on the Sun ; the* phases of Yenus ; 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 th telescope towards its present state, that in 1816, Bonnycastle speaks of the 80-fold mag- uifying power of the telescope of Galileo as " nearly the greatest perfection that thli Kind 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 preserved in the British Museum. A pigmy, indeed, in its way, but the honored progenitor of a race of .ants ! 686. The discovery of the telescope tended greatly to sustain 653. Subject of Chapter XIX. ? Telescope? Derivation? Ancient or modern? In- ventor? Incidents of discovery? 684. Galileo's telescope? Discoveries with it? Progress in telescope making? GS5. Is Galileo entitled to the honor of inventing the Wl-ere is his? G8G. Relation of discovery to Copermcan theory? Kffcetu 514 ASTRONOMY. the Copernican theory, which had just been promulgated, and ol 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 28,1688: ' -, Galileo, in the seventieth year of my age, on bended knes before your eminences, having before my eyes and touching with my hands the H )ly 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 advaoc- iag, the grave received him from the malice of his persecutors. DIFFERENT KINDS OF TELESCOPES. 687. Telescopes are of two kinds Reflectors and Refractors. 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 undei 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 .Hameter. Our vision is thus made as perfect bj art as if nature had given us ability to enlarge the eye till the pupil was a foot m diameter. 688. Refracting telescopes may consist of a double-convex lend 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. KVRAGTIMQ TKLBSOOPB WITH A SINQLK tEHS. Hare 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 it thus virtually enlarged t tje 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. apon Galileo? His renunciation? Death? 687. Kinds of telescopes? DcecHJns Bow assist vioion ? Illustration. 683. Simplest form of refracting telescope V TELESCOPES REFRACTORS AND REFLECTORS. 315 689. The Galilean telescope consists of two glasses a dov,lu& wnvex 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 us to be capable of entering the eye. ,- THLESCOPS. 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 Janaen, 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. LEK3E3 PLACED IN A TUBE. A is 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 in 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- 68ft. Galilean telescope ? Why called Galilean f 690. How common astronomies ttl<*cop8 m.idi? Why in tube? 691. How object-glass protected? Wh-t s*iJ rt B.U. 14 31G ASTRONOMY REFRACTING TKLKSOOPK HOOVTKO O2i JL dTUID, ent 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 focus, 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 amounted 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 E, 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 snddle in which tli telescope rests with the top of the bolt, allows it to be directed to any point between tht 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 bei.ip once found, by setting the instrument for its right ascension and declination, or by tlic aid of the Finder a smail 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 Equcttorhil, or i.s said to be equatofiatty mounted, because it sweeps east and west in the heavens parallel to the Kjnatoi . 093. 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 89i. noxr refractors mounted, and why? When equatorial, and -vh> ? *Miji:t-gla&be made ? What a knc ? A BarlM 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. Lenses have also been formed by putting two concavo-convex glasses together aud Qlling the space between them with some transparent fluid. These are called JJurloit 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 Achromatic 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 Franco ; but a number of very fine instru- ments have been made in this country, most of them by Mr. Henry Fitz, Jun., 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, No\ ember 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 nuike his capabilities known to the American public. He made his first telescope in 1835. In the Winter ol I!>i4 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 1S45 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 Mi. Van Dtizee, of Buffalo, N. Y. He made two of 13 inches one for the Dudley Observa tory, at Albany, and the other for an association of gentlemen, at Allcghany City, Pa. Of 12 inches aperture, he produced one for the Observatory at Ann Arbor, Michigan, and another for the Vassar Female College. Ho made for M. L. Rutherford, of New York, at various times, telescopes of 4, 5}, b\ 9, and 11J inches aperture; the last, an instrument cf 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 Uharg6 d 1 Af- faires ut Montevideo has a 9-inch. Mr. Campbell, of New York, has an 8-inch. Of a large number of C inches aporture, one very fine instrument was ordered by the United Btates Government, for Ueut. 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. Robert 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 ttat building. [Removed on the rebuilding of the school edifice in 1365. Ft?.] 2. For a list of telescopes in this country, with the names of their respective makers, focal lengths, size of object glasses, Ac., see table on subsequent page. 695. What said of the manufacture of telescopes? What other Americana have mad iheni (What said of Mr. Fitz ? Telescopes ?) ASTRO NO1CY. RUTHERFORD'S EQUATOEIAL REFRACTOU. G9'J. The above cut represents an equatorial telescope nii'im factored by Mr. Henry Fitz, of New York the one usod bj the author in making most of his observations. Its object- glass is six inches in diameter, and its focal length eight f< et. It is perfectly achromatic, and performs all the tests laid clown in Dick's Piactical Astronomer, as evidence of a good instru- ment, with perfect ease. Under favorable circumstances, it &ho\\s the sixth star in the trapezium of Orion, and to show Pohris double is a very easy test indeed. A f'indtr is seen attached to the lower end of the large Instrument. It takes in a targ^i field of vie\v in the heavens than the latter, and enables the observer to look ui ofc/ l !ts with facility, and bring them into the field of the larger instrument MFRACTIXG TELESCOPES. 319 THE PHILADELPHIA KEFBACTOB.* 697. Tins 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 $2,2^00. * We are indebted to the courtesy of Messrs. Harper Brothers, of New York, fv. copies <>f several of these cuts from their Monthly Magazine for June, 185. C97 The Philadelphia refractor? Size? By whom made? Cost? 32C ASTRONOMY HAHH.T09 OOUJtaB BV&AOTO&. C98. 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 usaal 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 M 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. 93. Biro of the Hamilton College telescope? WLat peculiarity as to leogtl ? By whom made? Cost? REFRACTING TELJSSCOPK8. 321 GREAT BKFBAOTINO TBI.E8COPB AT CINCINNATI, OHIO. G99. 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 lute Prof. O. M. Mitchel, by whose instru- mentality .t was purchased and mounted. The objcct-crlass is nhont 12 inches in diameter, with a focal distance of 17 feet 1; VHS purchased in Munich, Germany, in 1S44, at an expense of nearly ten ject to be ti >en is 10% the index must be moved 10* from 0, as the degrees an the circle and the altitude of the object will correspond. 70J What is a transit Instrument? Size? How mounted? Describe parts a* aho U the vr.t How act the instrument for tke altitude f a star? Waal 326 ASTRONOMY. TBANSIT INSTRUMENT, WASHINGTON, D. O. 704. This instrument is located in the National Observatory at Washington, D. C. It is mounted upon piers of granite, whicb rest firmly upon a foundation of stone, extending ten feet below the surface of the ground. The object glass was furnished b; Merz ilasej-vatories names? Telescopes by whom mostly made t What olhei table? 334 ASTBONOMY. CHAPTER XX. PROBLEMS AND TABLES. PROBLEM I. TO CONVERT DEGREES, ETC., INTO TIME. RULE I Divide the degrees by 15, for hours ; and multiply th icinamder, if any, by 4, for minutes. 2. L>ivide the odd minutes and seconds in the same manner by 15 for minutes, seconds,