*** *** * * **, . . . w ** ~ : w - * +: “ * # * ~ ºft. *r" • f . . * , , , . *::: ~ : " "... * **-*. ** * # * w ***. * * º ** , -: Yº: i- * -- T A. * { Af 3 r * ** -- 7 A. i. * + - & THE ; wº y r. EOGRAPH 'Y OF THE GEOGRAPHY OF THE HEAVENS, * f *: 3' ,” < * st ACCOMPANIED BY A * *. f F # * º % -3. * . * xt * § K * , *: *** ". . t OMAS DICK, LL.D., ; *... * * * * Aº Christian Philosºher:” # * * listian philºss * *... º, i. j * , , *. * * -- tº * > **-* *: * ¥ º * * : * * * * , , * * *, * g : 4. ... " '.” * * * $ - wrºt ** -rº gº NEW-Yo R K #. r 2 : , ºf * E. ......” “ w * *~ k X. PUBLISHEºix R. J. HUNTINCTON AND Co. . . . #, 3. &º 3. - * .” 3. - * A. W. º . . . . ." .174 fearl street: " º * ... ºr *- : *. * * t * r *> ºf; * } . . 1837; * • , ; $ .* ‘. . r * #. -wr-- * , . . . . & $. --> * Kº: J. - . . . . . . . . . . . s * & ‘..., * , .." , * s", *. 3. l ſ J. AVA ſº, 2.Éy Wºº J.B.'. of the ºn ! ( ) % É. º # ...!, sº Jº, ſº ..º.º. º. # º º º | ~% E E H E. E E ſº E E E E E H E. H E ſº- * * * * |- ||||||III * * * * * * * * * *** sº as a sºw ººs we wº, as ºn THE GIFT OF Dr. Warner G. Rice is sº º sº º | E. | f º THE GEOGRAPHY OF THE HEAVENS, AND CLASS B00K OF ASTRONOMY; ACCONIPANIED BY A CELESTIAL ATLAS. * *-*. FIFTH DDITION. WITH AN INTRODUCTION, BY THOMAS DICK, I.L. D. Author of the Christian Philosopher, &c. ºn tº • & ——-----— p * * º N E W - Y O R K : PUBLISHED BY F. J. HUNTINGTON AND CO. 174 PEARL-STREET. 1838. F. J. HUNTINGTON & Co. have recently published, in one small volume 16mo., suitable for children just entering upon the study of Astronomy, and introductory to the “Geography of the Heavens,” A S T R O N O MY FOR BEGINNERS, with a Map and 27 Engravings. By Francis Fellowes, A. M. “This is one of the most successful attempts to simplify sublime sci- ence to the comprehension of children. The author has employed an arrangement and style entirely new, with a clear and luminous pen, and in the happiest manner. . I cordially commend to palents, to teachers, and to children, this result of his labours.”—Mrs. Sigourney. ENTERED, according to Act of Congress, in the year 1833, by F. J. HUNTINGTON, in the Clerk’s Office of the District Court of Connecticut. -- * ~ * --sº-sº "PUBLISHER's NOTICE. In presenting a new edition of this work to the public, it is pro- per to point out several very important improvements which have been made. Dr. Dick of Scotland, so well known both in Europe and in this country, as the author of the Christian Philosopher, and other scientific and popular works, has prepared, expressly for the work, an Introduction on the Advantages of the Study of Astrono- my. So far as authority and name can go to give currency to the work, and to establish the confidence of teachers in it as a proper text book, this simple fact, the publisher flatters himself, ſurnishes every testimonial which can be desired: beside which, the con- tributions of Professor Olmsted, of Yale College, cannot but be read with extreme interest. The work has been thoroughly revised, and the errors of for- mer editions corrected: subsequent to which, it has undergone a thorough examination from one of our most eminent mathema- ticians and astronomers. It will be observed that several new Chapters, on the important subjects of Planetary Motion, The Phe- momena of Day and Night, The Seasons, The Tides, The Obliquity of the Ecliptic, The Precession of the Equinoaces, &c., have been added. It is only necessary to observe the Atlas, to discover that the Plates have been engraved entirely anew, upon steel, and in a very superior and beautiful style. The figures of the Constella- tions are far more natural and spirited than those of the former Atlas. Especially, the characters which represent the stars are distinct, so that the pupil can discern, at once, to what class they belong. One new plate has been introduced, illustrating to the seye, the Relative Magnitudes, Distances, and Positions of the dif- ferent bodies which compose the Solar System. This plate the teacher will find to be of very important service, and to aid him much in his verbal explanations. The arrangement of the Plates in the present Atlas, is such, that the teacher and pupil can easily place them, in mind, so as to have a distinct view of the entire surface of the visible Heavens. Such are the principal improvements which have been made in the work. They speak for themselves. The publisher knows not what could express his satisſaction with the past, or his hopes for the future success of the work, better than such improvements. P #R E F A C E. -assº I HAVE long felt the want of a Class Book, which should be to the starry heavens, what Geography is to the earth; a work that should exhibit, by means of appropriate delineations, the scenery of the heavens: the various constellations arranged in their order, point out and classify the principal stars, according to their magnitudes and places, and be accompanied, at the same time, with such fami- liar exercises and illustrations, adapted to recitation, as should bring it within the pale of popular instruction, and the scope of juvenile understandings. - - - - Such a work I have attempted to supply. I have endeavoured to make the descriptions of the stars so familiar, and the instructions for finding them so plain, that the most inexperienced should not fail to understand them. In accomplishing this, I have relied but little upon globes and maps, or books. I very early discovered that it was an easy matter to sit down by a celestial globe, and, by means of an approved catalogue, and the help,0f a little graduated slip of brass, make out, in detail, a minute description of the stars, and discourse quite familiarly of their position, magnitude and ar- rangement, and that when all this was done, I had indeed given the pupil a few additional facilities for finding those stars upon the artificial globe, but which left him, aſter all, about as ignorant of their apparent situation in the heavens, as before. I came, at length, to the conclusion, that any description of the stars, to be practically useful, must be made from a careful observation of the stars them- selves, and made at the time of observation. To be convinced of this, let any person sit down to a celestial globe or map, and from this alone, make out a set of instructions, in regard to some favourite constellation, and then desire his pupil to trace out in the firmament, by means of it, the various stars which he has thus described. The pupil will find it little better than a fancy sketch. The bearings and distances, and especially, the com- parative brightness, and relative positions, will rarely be exhibited with such accuracy that the young observer will be inspired with much confidence in his guide. I have demonstrated to myself, at least, that the most judicious in- structions to put on paper for the guide of the young in this study, are those which I have used most successfully, while in a clear eve- ning, without any chart but the firmament above, I have pointed out, with my finger, to a group of listeners, the various stars which compose this and that constellation. - In this way, the teacher will describe the stars, as they actually appear to the pupil—taking advantage of those obvious and more striking features that serve to identify and to distinguish them froja all others. Now iſ these verbal instructions be committed to wri- PREFACE. 4ing and placed in the hands of any other pupil, they will answer nearly the same end. This is the method which I have pursued in this work. The descriptive part of it, at least, was not composed by the light of the Sun, principally, nor of a lamp, but by the light of the stars themselves. Having fixed upon the most conspicuous star, or group of stars, in each constellation, as it passed the meri. dian, and with a pencil º noted all the identifying circum- stances of position, bearing, brightness, number and distance—their geometrical allocation, if any, and such other descriptive features as seemed most worthy of notice, I then returned to my room to tran- scribe and classify these memoranda in their proper order; repeat- ing the same observations at different hours º same evening, and on other evenings at various periods, for a succession of years ; al- ways adding such emendations as Subsequent observations matured. To satisfy myself of the applicability of these descriptions, I have given detached portions of them to different pupils, and sent them out to find the stars; and I have generally had the gratification of jhearing them report, that “every thing was just as I had described it.” If a pupil ſound any difficulty in recognizing a star, I re-ex- amined the description to see if it could be made better, and when i found it susceptible of improvement, it was made on the spot. It is not pretended, however, that there is not yet much room for im- rovement; for whoever undertakes to delineate or describe every visible star in the heavens, assumes a task, in the accomplishment Of which, he may well claim some indulgence. The maps which accompany the work, in the outlines and ar- rangement of the constellations, are essentially the same with those of Dr. Wollaston. They are projected upon the same principles as maps of Geography, exhibiting a faithful portraiture of the hea: vens for every month, and consequently for every day in the year, and do not require to be rectified, for that purpose, like globes. They are calculated, in a good measure, to supersede the neces- sity of celestial globes in schools, inasmuch as they present a more natural view of the heavenly bodies, and as nearly all the problems which are peculiar to the celestial globe, and a great number be- sides, may be solved upon them in a very simple and satisfactory manner. They may be put into the hands of each individual in a class at the same time, but a globe cannot be. The student may ‘conveniently hold them before his eye to guide his survey of the heavens, but a globe he cannot. There is not a conspicuous star in the firmament which a child of ten years may not readily find by their aid. Besides, the maps are always right and ready for use, while the globe is to be rectified, and turned to a particular meri- dian; and then if it be not held in that position for the time being, it is liable to be moved by the merest accident or breath of wind. There is another consideration which renders an artificial globe of very little avail as an auxiliary for acquiring a knowledge of the stars while at School. . It is this:—the pupil spends one, perhaps two weeks, in solving the problems, and admiring the figures on it, in which time it has been turned round and round a hundred times; it is then returned safely to its case, and some months afterwards, or it may be the next evening, he directs his eye upwards to recog: PREFACE. nize his acquaintance among the stars. He may find himself able to recollect the names of the principal stars, and the uncouth forms by which the constellations are pictured out; but which of all the positions he has placed the globe in, is now so present to his mind that he is enabled to identify it with any portion of the visible hea- vens 7 He looks in vain to see, “Lions and Centaurs, Gorgons, Hydras rise, And gods and heroes blaze along the skies.” He finds, in short, that the bare study of the globe is one thing, and that of the heavens quite another; and he arrives at the con- clusion, that if he would be profited, both must be studied and com- pared together. This, since a class is usually furnished with but One globe, is impracticable. In this point of view also, the maps, are preſerable. I have endeavoured to teach the Geography of the heavens in, nearly the same manner as we teach the Geography of the earth. What that does in regard to the history, situation, cztent, popula: tion and principal cities of the several kingdoms of the earth, I. have done in regard to the constellations; and I am persuaded, that a knowledge of the one may be as easily obtained, as of the. other. The systems are similar. It is only necessary to change the terms in one, to render them applicable to the other. For this rea- son, I have yielded to the preference of the publisher in calling this work “Geography of the Heavens,” instead of URANogRAPHY, or Some other name more etymologically apposite. tº That a serious contemplation of those stupendous works of the Most High, which astronomy unfolds, is calculated above all other departments of human knowledge, to enlarge and invigorate the powers of religious contemplation, and subserve the interests of ra- tional piety, we have the testimony of the most illustrious charac- ters that have adorned our race. Iſ the work which I now submit, shall have this tendency, I shall not have written in vain. Hitherto, the science of the stars has been but very superficially studied in our schools, for want of pro- per helps. They have continued to gaze upon the visible heavens without comprehending what they saw. ey have cast a vacant eye upon the splendid pages of this vast volume, as children amuse themselves with a book which they are unable to read. They have caught here and there, as it were a capital letter, or a picture, but they have failed to distinguish those smaller characters on which the sense of the whole depends. Hence, says an eminent English Astronomer, “A comprehensive work on Descriptive Astronomy, detailing, in a popular manner, all the facts which have been ascer- tained respecting the scenery of the heavens, accompanied with a variety of striking delineations, accommodated to the capacity of youth, is a desideratum.” How far this desirable end is accom- lished by the following work, I humbly leave to the public to ecide. - Hartford, Feb. 1833. I N D E X. Page Andromeda, . . . . . . . . . . . . . . . . . . . . . Aries, the Ram, . . . . . . . . . . . . . . . . . . Auriga, the Charioteer, . . . . . . . . . . Argo Navis, the Ship Argo, . . . . . . . Asterion et Chara, vel Cancs Ye- malici, the Greyhounds, . . . . . . . . Aquila et Antinous, the Eagle and Antitious, . . . . . . . Aquarius, the Water Asteroids, . . . . . . . . Aurora Borealis, Lights, . . . . . . . . . #Bootes, the Bear Drivi r... £assiopeia, . . . . . . . . . . . . . . . . 3Cepheus,.......... . . . . 3Cetus, the Whale, . . . . . £olumba the Dove, . . . . . . . . . . . . . . ACamelopardalus, the Cataelopard, Canis Minor, the little Dog, . . . . . . {Xanis Major, the Great bog,...... Cancer, the Crab, . . . . . . . . . . . . * * * * * g º ſº º Bearer, . . . . . line Northern * c & ſº tº $ 3 & Coma Berenices, Berenice’s IIair, Corvus, the Crow,. . . . . . Centaurus, the Centaur, . . . . . . . . . Corona Borealis, ille Northern Crown, . . . . . . . . . . . . . . . . . . . . . . . . Cygritis, the Swan, . . . . . . . . . . . . . . . Capricornus, the Goaf, . . . . . . . . . . . Constellations—origin of . . . . . . . . . Comets. . . . . . . . . . . . . . . . . . . . . . . . . . Draco, the Dragon. . . . . . . . . . Delphinus, the Dolphin, ... . Dick’s Introduction. . . . . . . . . . . . . . Geography, . . . . . . . . . . . Navigation, . . . . . . . . . . . . . . . . . . Agriculture, . . . . . . . . . . . . . . . . . hronology, ..... a * : º tº º Propagation of Religion, .. Dissipates superstitious No. tions, . . . . * * * * * * s tº e e s a g. v. Days and Nights, different lengths * a s g º a e º º is a s tº º º º ſº ſº tº e * * * * * * * * * * * * * * : * * * * * * * * * * * * a s a y Eridanus, River Po, . . . . . . . . . . . . . . Equulus, vel Equi Sectio, the Lit- tle Horse, or the Horse’s IIead, Farth, . . . . . . . . . . . . . . . . . . . . . . . . . . . Equinoxes, Precession of . . . . . . . . Ecliptic,+Obliquity of . . . . . . . . . . . Eclipses, Solar and Lunar, ... . . . . Forces, Attractive and Projectile,. Gemini, the Twins................ Gravitation, Universal Law of . . . . Hydra, the Water Serpent and thc • e e s • e s a e e s • 3 s = e e s - e = e o e s a s up, Hercules. . . . . . . . . . . . . . . . . . . . . . . . 3.5 Page II erschel. . . . . . . . . . . . . . . . 1 ſeavenly Bodies, Parallax Jupiter, . . . . . . . . . . . . . . . . Lepus, the Hare, . . . . . . . . . . . . . . . . Ly 113, . J.eo, the lion. . . . . . l.co Mitnor, tile Littie Lion,...... . . Lupus, the Wolf, . . . . . . . . . . . . . . . . libra the Balance, . . . . . . . . . . . . . . . 1.yra, the Harp, . . . . . Monoceros, the Uinicorn, . . . . . . . . . Miars. . . . . . of . . . . sº e º gº tº s º º q is ſº tº ſº tº 8 a s tº a tº a º e s tº e º ºs Mercury, . . . . . & º e s is a tº gº s ºr s a g º e º 'º º Moon. . . . . . . . . . . . e ºf a lº & e s tº sº tº º Mooti— Harvest and Horizontal,... Meteorit: Showers. Professor Oin- sºci's lieularks upon, .......... Oriotl, . . . . . . . . . . . . . . . . . Pisces, the Fishes........ . . . . . . tº tº Perseus et Caput Medusae, Perseu and Medusa's Head. . . . . . . . . . . . Pegastis, the Flyi; ig Jorse ....... Piscis Australis, wel Notius, the Southern Fish, . . . . . . . . . . . Preliutiuary Chapter, . . . . . . . . . . . l’ia; lets, forces by which they are retained in ſhei: Orbits,... . . . . . Trobleins and ‘i’ables, . . . . . I&E ſtaction, . . . . . . . . Sextans, the Sextant, . . . . . . . . . . . . te Serpens, tire Serpetuſ, . . . . . . . . . . . . Scorpio, the Scorpion. . . . . . . . . . . . . Sagittarius, the Archer, . . . . . . . . . . Serpentarius, vel Ophiuchus, the Serpent Ištarer, . . . . . . . . . . . . . . . Stars— varialiſe. . . . . . . . . . . . . . . Double, . . . . . . . . . . . . . . . . . Clusters of . . . . . . . . . . . . . Nebulae, . . . . . . . . . . . . . . . . Number, Distance, and Eco- uotny of . tº gº tº 8 tº º sº e º ºs & tº g º & & ºt Falling, or Shooting. . . . . . . . . . . Solar System—General Phenome- na of . . . . . . . . . . . . . . . . . Sun. . . . . . . . . . . . . . . . . . . . . . Saturn. . . . . . . . . Seasons, . . . . . . . . tº e º $ ſº & a º º tº º Taurus, the Bull, . . . Titles, . . . . . . . . . . . . . . . . . . . . . . . . . . . Twilight. . . . . . . . . . . . . . . . . . . . . . . . . Ursa Major, the Great Bear, ... . . . Ursa Minor, the Little Bear, . . . . . . Virgo, the Virgin. . . . . . . . . . . . . . . . . Via Lactea, the Milky Way, . . . . . . Venus. . . . . . . . . . . . . . . . . . ...?. . . . . tº § 3 ; ºn tº ſº tº g * * * * * * * * * * * * * * * * * * * * * * * * * * g º $ tº 24 | 293 INTRODUCTION. ADVANTAGES OF THE STUDY OF ASTRONOMY BY THOMAS DICIK, L.L. D. AsTRONOMY is a science which has, in all ages, engaged the at- tention of the poet, the philosopher, and the divine, and been the subject of their study and admiration. Kings have descended from their thrones to render it homage, and have sometimes enriched it with their labours; and humble shepherds, while watching their flocks by night, have beheld with rapture the blue vault of heaven, with its thousand shining orbs moving in silent grandeur, till the morning star announced the approach of day.—The study of this science must have been co-eval with the existence of man. For there is no rational being who, for the first time, has lifted his eyes to the nocturnal sky, and beheld the moon walking in brightness among the pianetary orbs and the host of stars, but must have been struck with awe and admiration at the splendid scene, and its sub- lime movements, and excited to anxious inquiries into the nature, the motions, and the destinations of those far-distant orbs. Com- pared with the splendour, the amplitude, the august motions, and the ideas of infinity which the celestial vault presents, the most re- splendent terrestrial scenes sink into inanity, and appear unworthy of being set in competition with the glories of the sky. Independently of the sublimity of its objects, and the pleasure arising from their contemplation, Astronomy is a study of vast utility, in consequence of its connexion with terrestrial arts and sciences, many of which are indebted to the observations and the Tº. of this science for that degree of perfection to which they have attained. Astronomy has been of immense utility to the science of GEO G R A PHY; for it is chiefly in consequence of celestial observations that the true figure of the earth has been demonstrated and its density as: certained. It was from such observations, made on the mountain Schehalliem in Scotland, that the aſ traction of mountains was de- termined. The observations were made by taking the meridian distances of different fixed stars near the zenith, first on the South, and afterwards on the north side of the hill, when the plumb line of INTRODUCTION, lx d the Sector was found, in both cases, to be deflected from the per- pendicular towards the mountain; and, from calculations founded on the quantity of this deflection, the mean density of the earth was ascertained. It was likewise by means of celestial observations that the length of a degree of the meridian was measured, and the circumference of the globe, with all its other dimensions accurately ascertained; for, to ascertain the number of degrees between any two parallels on the Earth's surface, observations must be taken, with proper instruments, of the sun or of the stars, at different sta- tions; and the accurate measurement of the terrestrial distance be- tween any two stations or parallels, partly depends on astronomical observations combined with the principles and operations of Trigo- nometry. So that without the aids of this science, the figure and density, the circumference and diameter of our terrestrial habita- tion, and the relative position of places on its surface, could never have been ascertained. Astronomy is likewise of great utility to the art of NAVIGATION: without a certain knowledge of which the mariner could never have traced his course through pathless oceans to remote regions— the globe would never have been circumnavigated, nor an inter- course opened between the inhabitants of distant lands. It is of essential importance to the navigator, not only to know the situation of the port to which he is bound, but also to ascertain with pre- cision, on what particular portion of the terraqueous globe he is at any time placed—what course he is pursuing—how far he has tra- velled from the port at which he embarked—what dangerous rocks or shoals lie near the line of his course—and in what direction he must steer, in order to arrive, by the speediest and the safest course, to his destined haven. It is only, or chiefly, by astronomical obser- vations that such particulars can be determined. By accurately observing the distance between the moon and certain stars, at a particular time, he can calculate his distance East or West from a given meridian; and, by taking the meridian altitude of the sun or of a star, he can learn his distance from the Equator or from the poles of the world. In such observations, a knowledge of the con- stellations, of the polestar, and of the general positions of all the stars of the first and second magnitude, is of particular importance; and, therefore, a navigator who is unacquainted with the science of the heavens, ought never to be appointed to conduct a ship through the Indian, the Atlantic, or the Pacific Oceans, or through any por- tions of the sea which is not within sight of land. By the observa- tions founded on astronomical Science, which have been made in different regions, by mariners and travellers of various descriptions, the latitudes and longitudes of the principal places on the globe, and their various bearings and relations have been determined, so that we can now take a view of the world we inhabit in all its mul- tifarious aspects, and direct our course to any quarter of it, either for business, for pleasure, or for the promotion of philanthropic ob- jects. Thus, Astronomy has likewise become of immense utility to Trade and Commerce, in opening up new emporiums for our X in TRODUCTION. ınanufactures, in augmenting and multiplying the sources of wealth, in promoting an intercourse between the most distant nations, and enabling us to procure, for Onr accommodation or luxury, the pro. ductions of every climate. If science has now explored almost every region; if Politics and Philosophy have opened a communi- Cation between the remotest inhabitants cf the globe; if alliances have been formed between the most distant tribes of mankind; if Traffic has explored the multifarious productions of the earth and seas, and transported them ſrom one country to another, and, if heathen lands and barbarous tribes have been “visited with the Day-Spring from on high, and the knowledge of salvation,”—it is Owing to the aids derived from the science of the stars, without which the continents, the islands, and the different aspects of our globe would never have been explored by those who were separa- led from them by intervening oceans. This science has been no less useful to A GR ICULTURE, and to the cultivators of the earth. The successful cultivation of the Soil depends on a knowledge of the course of the Sun, the exact length of the seasons, and the periods of the year most proper for the opera- tions of tillage and sowing. The ancients were directed in these operations, in the first instance, by observing the courses of the moon, and that twelve revolutions of this luminary corresponded nearly with one apparent revolution of the sun. But finding the coincidence not exact, and that the time of the seasons was chang- ing—in order to know the precise bounds of the sum's annual course, and the number of days corresponding to his apparent yearly revo- lution, they were obliged to examine with care ‘what stars were successively obscured in the evening by the sun, or overpowered by the splendour of his light, and what stars were beginning to emerge from his rays, and to re-appear before the dawn of the morning. By certain ingenious methods, and numerous and at- entive observations, they traced out the principal stars that lay in the line of the sun's apparent course, gave thern certain names by which they might be afterwards distinguished, and then divided the circle of the heavens in which the sun appears to move, first into quadrants, and afterwards into 12 equal parts, now called the signs of the Zodiac, which they distinguished by names correspond- ing to certain objects and operations connected with the different seasons of the year. Such were the means requisite to be used for "ascertaining the length of the year, and the commencement of the different seasons, and for directing the labours of the husbandman; —and, were the knowledge of these things to be obliterated by any extensive moral or physical convulsion, mankind would again be under the necessity of having recourse to astronomical observations for determining the limits of the solar year, and the course of the seasons. Although we find no difficulty, in the present day, and require no anxious observations, in determining the seasons, yet, before astronomical observations were made with Some degree of accuracy, the ancient Greeks had to watch the rising of Arcturus the Pleiades and Orion, to mark their seasons, and to determine the INTRODUCTION, XI proper time for their agricultural labours. The rising of the star Sirius along with the sun, announced to the Egyptians the period when they might expect the overflowing of the Niie, and, conse- quently, the time when they were to sow their grain, cut, their ca- mals and reservoirs, and prepare the way for their expected harvest. The Science of C H R O N O L O G Y, likewise depends on celestial observations. The knowledge of an exact measure of time is of considerable importance in arranging and conducting the affairs of life, without which, society in its movements would soon run into confusion. For example, if we could not ascertain, within an hour or two, when an assembly or any concourse of human beings was to meet for an important purpose, all such purposes would soon be frustrated, and human improvement prevented. Our ideas of time or succession in du- ration, are derived from motion ; and in order to its being divi- ded into equal parts, the motions on which we fix as standards of time must be constant and uniform, or at least, that any slight de- viation from uniformity shall be capable of being ascertained. But we have no uniform motion on earth by which the lapse of duration can be accurately measured. Neither the flight of birds, the motion of the clouds, the gentle breeze, the impetuous whirl- wind, the smooth-flowing river, the roaring cataract, the falling rain, nor even the flux and reflux of the ocean, regular as thcy generally are, could afford any certain standard for the measure of time. It is, thereſore, to the motion of the celestial orbs alone that we can look for a standard of duration that is certain and inva- riable, and not liable to the changes that take place in all terrestrial movements. Those magnificent globes which roll around us In the canopy of the sky—whether their motions be considered as real or only apparent, move with an order and regularity which is not ſound in any physical agents connected with our globe; and when from this quarter we have derived any one invariable mea- sure of time, we can subdivide it into the minutest portions, to subserve all the purposes of civil life, and the improvements of science. Without the aids of astronomy, therefore, we should have had no accurate ideas of the lapse of time, and should have been obliged, like the rude savage of the desert, to compute our time by the falls of snow, the succession of rainy seasons, the melting of the ice, or the progress and decay of vegetation. º Celestial observations, in consequence of having ascertained a regular measure of time, have enabled us to fix chronological dates, and to determine the principal epochs of History. Many of those epochs were coincident with remarkable eclipses of the sun or moon, which the ancients regarded as prognostics of the loss of battles, the death of monarchs, and the fall of empires; and which are recorded in connexion with such events, where no dates are mentioned. The astronomer, therefore, knowing the invariable movements of the heavenly orbs, and calculating backwards through the past periods of time, can ascertain what remarkable eclipses must have been visible at any particular time and place, and con- Sequently, can determine the precise date of contemporary events. xii INTRODUCTION. Calvisius, for example, ſounds his Chronology on 144 eclipses o. the Sun, and 127 of the moon, which he had calculated for the pur- pose of determining epochas and settling dates. The grand com- junction of the planets Jupiter and Saturn, which occurs once in 800 years, in the same point of the zodiac, and which has happened only eight times since the Mosaic Creation, furnishes Chronology With incontestable proofs of the date of events, when such phenomena happen to be recorded. On such data, Sir Isaac Newton deter- mined the period when Thales the philosopher flourished, particu- larly from the famous eclipse which he predicted, and which hap- pened just as the two armies under Aſgattes, king of Lydia, and Cyaxares the Mede were engaged; and which has been calculated to have happened in the 4th year of the 43d Olympiad, or in the year before Christ 603. On similar grounds Dr. Halley, a cele- brated astronomer of the last century, determined the very day and hour of the landing of Julius Cesar in Britain, merely from the circumstances stated in the “Commentaries” of that illustrious general. Astronomy has likewise lent its aid to the PRO PAGATION OF RELIGION, and the conversion of the heathen world. For, without the light derived from this celestial science, oceans would never have been traversed, nor the continents and islands explored where benighted nations reside, and, conscquently, no messengers of Peace could have been despatched to teach them “the knowledge of salvation, and to guide their steps in the way of peace.” But, with the direction afforded by the heavenly orbs and the magnetic needle, thousands of Christian missionaries, along with millions of bibles, may now be transported to the most distant continents and islands of the ocean, to establish among them the “Law and Testimony” of the Most High—to illume the darkness and counteract the moral abomina- tions and idolatries of the Pagan world. If the predictions of an- cient prophets are to be fulfilled; if the glory of Jehovah is to cover the earth; if “the isles aſar off,” that have not yet heard of the fame of the Redeemer, nor seen his glory, are to be visited with the “Day-spring from on high,” and enrolled among the citizens of Zion; if the world is to be regenerated, and Righteousness and Praise to spring forth before all nations—those grand events will be accomplished partly through the influence and direction of those celestial luminaries which are placed in the firmament to be for signs, and for seasons, and for days and years. The light reflected from the material heavens will lend its aid in illuminating the minds of the benighted tribes of mankind, till they be prepared for being transported into those celestial mansions where knowledge shall be perfected, and Sovereign power triumphant. It will be likewise from aid derived from the heavenly orbs that the desolate wastes of the globe in every region will be cultivated and replenished with inhabitants. For the Almighty “created not the earth in vain, but formed it to be inhabited ;” and his purpose in this respect must ul- timately be accomplished; and the process of peopling and cultiva- tion is now going forward in New Holland, Van Diemen's Land, INTRJ O'CC' ſ ON. xiii Africa, the Western States of America, and other regions where sterility and desolation have prevailed since the universal Deluge. But how could colonies of men be transported from civilized na- tions to those distant regions unless by the guidance of celestial lu- minaries, and by the aid of those arts which are founded on the ob- servations of astronomy 3 So that this science exerts an extensive and beneficial influence over the most important affairs of mankind. In short, astronomy, by unfolding to us the causes of certain ce- lestial phenomena, has tended to D IS SIP A T E S U P E R S T IT I O U S N OT I O N S and vain alarms. In former ages the approach of a blazing comet, or a total eclipse of the sun or moon, were regarded with universal consternation as prognostics of impending calamities, and as har- bingers of Divine vengeance. And even in the present day, such notions prevail among most of those nations and tribes that are un- acquainted with astronomical science. During the darkness occa- sioned by a solar eclipse, the lower orders of Turkey have been seen assembling in clusters in the streets, gazing wildly at the sun, running about in wild distraction, and firing volleys of muskets at the sun to frighten away the monster by which they º it was about to be devoured. The Moorish song of death, or the howl they make for the dead, has been heard, on such occasions, resounding from the mountains and the vales, while the women brought into the streets all the brass pans, and vessels, and iron utensils they could collect, and striking them with all their force, and uttering dreadful screams, occasioned a horrid noise that was heard for miles around. But astronomy has put to flight such ter- rific phantoms and groundless alarms, by unfolding to us the true causes of all such phenomena, and showing us that they happen in exact conformity with those invariable laws by which the Almighty conducts the machine of the universe—that eclipses are merely the effects of the shadow of one opaque globe falling upon another, and that comets are bodies which move in regular, but long elliptical orbits—which appear and disappear in stated periods of time, and are destined to subserve some grand and beneficent designs in the sys- tem to which they belong. So that we may now contemplate all such celestial phenomena, not only with composure and tranquillity, but with exultation and delight. In short, astronomy has under- mined the absurd and fallacious notions by which the professors of Judicial Astrology have attempted to impose on the credulity of mankind, under pretence of disclosing the designs of Fate, and the events of futurity. It shows us, that the stars are placed at im- measurable distances from our terrestrial sphere—that they can have no influence upon the earth, but what arises from the law of universal gravitation—that the great end for which they were crea- ted was to diffuse light, and to perform other important services in regions infinitely distinct from the sphere we occupy—that the pla- nets are bodies of different sizes, and somewhat similar to the globe on which we live—that all their aspects and conjunctions are the result of physical laws which are regular and immutable—and that mo data can be ascertained on which it can be proved that they xiv. INTRODUCTION. exert a moral influence on the temperaments and destinies of men except in So far as they tend to raise our affections to their Al- mighty Author, and excite us to confide in his care, and to contem- plate the effects of his wisdom and omnipotence. The heavens are set before us, not as the “Book of Fate,” in which we may pry into the secrets of our future destiny, which would only servé to destroy activity, and increase the pressure of our present afflictions —but as the “Book of God,” in which we may read his wondrous works, contemplate the glory of his eternal empire, and be excited to extend our views to those expansive scenes of endless ſelicity which await the faithful in the realms above. Independently of the considerations above stated, the study of as- tronomy is attended with many advantages in a moral, intellectual, and religious point of view. - 1. This department of Science unfolds to us the most striking dis- ſº of the perfections of the Deity,+particularly the grandeur of is Omnipolence. His Wisdom is conspicuously displayed in the general arrangement of the heavenly orbs, particularly in reference to the globes which compose the solar system—in placing near the centre of this system that immense luminary the Sun, from whence light and heat might be distributed, in due proportion, to all the worlds that roll around it—in nicely proportionating the motions and distances of all the planets primary and secondary—in uniting them in one harmonious system, by one grand universal law which prevents them from flying off in wild confusion through the infini- ty of space—in the constancy and regularity of their motions, no one interfering with another, or deviating from the course pre- scribed—in the exactness with which they run their destined rounds, finishing their circuits with so much accuracy as not to de- viate from their periods of revolution, the hundredth part of a mi- nute in a thousand years—in the spherical figures given to all those mighty orbs, and the diurnal motions impressed upon them, by which a due proportion of light and heat is diffused over every part of their surface. The Benevolence of the Deity shines no less con- spicuous in those upper Tegions, in ordering all the movements and arrangements of the celestial globes so as to act in subserviency to the comfort and happiness of Sentient and intelligent beings. For, the wisdom of God is never employed in devising means without an end; and the grand end of all his arrangements, in so far as our views extend, is the communication of happiness; and it would be inconsistent with the wisdom and other perfections of God not to admit, that the same end is kept in view in every part of his domin- ions, however far removed from the sphere of our contemplation. The heavens, therefore, must be considered as presenting a bound- less scene of Divine benevolence. For they unſold to view a count- less number of magnificent globes, calculated to be the habitations of various orders of beings, and which are, doubtless, destined to be the abodes of intellectual life. For the character of the Deity would be impeached, and his wisdom virtually denied, were we to sup- pose him to arrange and establish a magnificent series of means without an end corresponding, in utility and dignity, to the gran- deur of the contrivance. When, therefore, we consider the innu. INTRODUCTION. Xy merable worlds which must exist throughout the immensity of space, the countless myriads of intelligences that people them; the various ranks and orders of intellect that may exist among them, the innumerable diversified arrangements which are made for pro- moting their enjoyment, and the peculiar displays of Divine benig- nity enjoyed in every world—we are presented with a scene of Di- vine goodness and beneficence which overpowers our conceptions, and throws completely into the shade all that we perceive or enjoy within the confines of this sublunary world. And, although the minute displays of Divine benevolence in distant worlds are not yet particularly unfolded to our view, yet this circumstance does not prove that no such displays exist;-and as we are destined to an immortal life, in another region of creation, we shall, doubtless, be favoured with a more expansive view of the effects of Divine benignity in that eternal scene which lies before us. But this science exhibits a more striking display than any other of the Omnipotent emergies of the Eternal Mind. It presents before us objects of overpowering magnitude and splendour-planetary globes a thousand times larger than the earth—magnificent rings which would nearly reach from the earth to the moon, and would enclose within their vast circumference 500 worlds as large as ours—suns a million times larger than this earthly ball, diffusing their light over distant worlds—and these suns scattered in every direction through the immensity of space, at immeasurable distances from each other, and in multitudes of groups which no man can number, presenting to the eye and the imagination a perspective of starry systems, boundless as immensity.—It presents to our view motions so astonishing as to overpower and almost terrify the ima- gination—bodies a thousand times larger than the earth flying with a velocity of 29,000 miles an hour, performing circuits more than three thousand millions of miles in circumference, and carrying along with them a retinue of revolving worlds in their swift career; nay, motions, at the rate of 880,000 miles an hour, have been per- ceived among the celestial orbs, which as far Surpass the motions we behold around us in this lower world, as the heavens in height surpass the earth. Such motions are perceived not only in the so- lar system, but in the most distant regions of the universe, among double stars—they are regular and uninterrupted—they have been going ſorward for thousands, perhaps for millions of years—there is perhaps no body in the universe but is running its round with similar velocity; and it is not unlikely that the whole machine of universal nature is in perpetual motion amidst the spaces of immen- sity, and will continue thus to move throughout all the periods of endless duration. Such objects and such motions evidently display the omnipotence of the Creator beyond every other scene which creation presents; and, when seriously contemplated, cannot but inspire us with the most lofty and impressive conceptions of the “eternal power” and majesty of Him who sits on the throne of the universe, and by whom all its mighty movements are conducted. They demonstrate, that his agency is universal and uncontrollable —that he is able to accomplish all his designs, however incompre- hensible to mortals—-that no created being can frustrate his pur- xvi INTRODUCTION. poses, and that he is worthy of our highest affection, and our inces. sant adoration. 2. Astronomy displays before us the eatent and grandeur of God's wnºversal empire. . The globe we inhabit, with all its appendages, forms a portion of the Divine empire, and, when minutely investi. gated, exhibits a striking display of its Creator's power, benignity, and intelligence. But it forms only one small province of his uni- Versal dominions—an almost undistinguishable speck in the great map of the universe; and iſ we confine our views solely to the lim- its of this terrestrial ball, and the events which have taken place on its surface, we must form a very mean and circumscribed idea of the extent of the Creator’s kingdom and the range of his moral go- vernment. . But the discoveries of astronomy have extended our yiews to other provinces of the empire of Omnipotence, far more spacious and magnificent. They demonstrate, that this earth, with all its vast oceans and mighty continents, and numerous population, ranks among the smaller provinces of this empire—that the globes composing the system to which it belongs, (without including the Sun,) contain an extent of territory more than two thousand times larger than our world—that the sun himself is more than 500 times larger than the whole, and that, although they were all at this mo- ment buried in oblivion, they would scarcely be missed by an eye that could survey the whole range of creation.—They demonstrate, that ten thousands of Suns, and ten thousand times ten thousands ol revolving worlds are dispersed throughout every region of bound- less space, displaying the creating and supporting energies of Om- nipotence; and consequently, are all under the care and superin- tendence of Him “who doth according to his will in the armies of heaven, and among the inhabitants of the earth.” Such an empire, and such only, appears corresponding to the perfections of Him who has existed from etermity past, whose power is irresistible, whose goodness is unbounded, and whose presence fills the Immen- sity of space; and it leads us to entertain the most exalted senti- ments of admiration at the imſinvite intelligence implied in the super- intendence of such vast dominions, and at the boundless beneficence displayed among the countless myriads of sensitive and intellectual beings which must people his wide domains. 3. The objects Nº. this science discloses, afford subjects of sub- lime contemplation, and tend to elevale the soul above vicious passions and grovelling pursuits. In the hours of retirement and solitude what can be more delightful, than to wing our way in magination amidst the splendid objects which the firmament displays—to take our flight along with the planets in their wide career—to behold them running their ample rounds with velocities forty times swifter than a cannon ball—to survey the assemblages of their moons, re- volving around them in their respective orders, and carried at the same time, along with their primaries, through the º of space —to contemplate the magnificent arches which adorn the firmament ºf Saturn, whirling round that planet at the rate of a thousand miles in a minute, and displaying their radiance and majestic movements to an admiring population—to add scene to scene, and magnitude to magnitude, till the mind acquire an ample conception of such INTROI) UCTION. XWii august objects—to dive into the depths of infinite space till we be surrounded with myriads of suns and systems of worlds, extending beyond the range of mortal comprehension, and all running their appointed rounds, and accomplishing the designs of beneficence in obedience to the mandate of their Almighty Author | Such objects afford matter for rational conversation, and for the most elevated contemplation. In this ample field the most luxuriant imagination may range at large, representing scenes and objects in endless va- riety and extent; and, after its boldest excursions, it can scarcely go beyond the reality of the magnificent objects which exist within the range of creating power and intelligence. The frequent contemplation of such objects tends to enlarge the capacity of the mind, to ennoble the human faculties, and raise the soul above grovelling affections and vicious pursuits. For the dis- positions of mankind and their active pursuits generally correspond to the train of thought in which they most frequently indulge. If these thoughts run among puerile and vicious objects, such will be the general character of their affections and conduct. If their train of thinking take a more elevated range, the train of their actions, and the passions they display, will, in some measure, be correspondent. Can we suppose, that a man whose mind is daily conversant with the noble and expansive objects to which I have adverted, would have his soul absorbed in the pursuits of ambition, tyranny, oppres- sion, war, and devastation 4 Would he rush like a madman through burning cities, and man- gled carcasses of the slain, in order to trample under ſoot the rights of mankind, and enjoy a proud pre-eminence over his fellows—and find pleasure in such accursed pursuits Would he fawn on statesmen and princes, and violate every moral principle, in order to obtain a pension, or a post of opulence or honour ! Would he drag his fellow-men to the stake, because they worshipped God according to the dictates of their consciences, and behold with pleasure their bodies roasting in the flames : Would he drive men, women, and children from their homes, loaded with chains and fetters, to pine in misery and to perish in a distant land, merely because they asserted the rights to which they were entitled as citizens and as rational beings 4 Or, would he degrade himself below the level of the brutes by a daily indulgence in rioting and drunkenness, till his faculties were benumbed, and his body ſound wallowing in the mire 4 It is scarcely possible to suppose that such passions and conduct would be displayed by the man who is habitually engaged in celes- tial contemplations, and whose mind is familiar with the august ob- jects which the firmament displays. “If men were taught to act in view of all the bright worlds which are looking down upon them, they could mot be guilty of those abominable cruelties” which some scenes so mournfully display. We should then expect, that the iron rod of oppression would be broken in pieces—that war would cease its horrors and devastations—that liberty would be 2* xvii) INTRODUCTION. proclaimed to the captives—that “righteousness would run down our streets as a river,” and a spirit congenial to that of the inhabit- ants of heaven would be displayed by the rulers of nations, and by all the families of the earth. For all the scenes which the firma- ment exhibits have a tendency to inspire tranquillity—to produce a love of harmony and order, to stain the pride of human grandeur- to display the riches of Divine beneficence—to excite admiration and reverence—and to raise the soul to God as the Supreme Director 3f universal nature, and the source and centre of all true enjoy- ment;-and such sentiments and affections are directly opposed to the degrading pursuits and passions which have contaminated the society of our world, and entailed misery on our species. - I might have added, on this head, that the study of this subject has a peculiar tendency to sharpen and invigorate the mental ſac- ulties. It requires a considerable share of attention and of intel- lectual acumen to enter into all the partigulars connected with the principles and facts of astronomical science. The elliptical form of the planetary orbits, and the anomalies thence arising, the muta- tion of the earth's axis, the causes of the seasons, the diſficulty of reconciling the apparent motions of the planets with their real mo- tions in circular or elliptical orbits, the effects produced by centri- fugal and centripetal forces, the precession of the equinoxes, the ab- erration of light, the method of determining the distances and mag- nitudes of the celestial bodies, mean and apparent time, the irregul- larity of the moon's motion, the diſficulty of forming adequate ideas of the immense spaces in which the heavenly bodies move, and their enormous size, and various other particulars, are apt, at first view, to startle and embarrass the mind, as if they were beyond the reach of its comprehension. But, when this science is imparted to the young under the guidance of enlightened instructors—when they are shown not merely pictures, globes and Orreries, but direct- ed to observe with their own eyes, and with the assistance of teles- copes, all the interesting phenomena of the heavens, and the mo- tions which º whether real or apparent—when they are shown the spots of the Sun, the moons and belts of Jupiter, the phases of Venus, the rings of Saturn, and the mountains and vales which diversify the surface of the moon—such objects tend to awaken the attention, to expand the faculties, to produce a taste for rational in- vestigation, and to excite them to more eager and diligent inquiries into the subject. The objects appear so grand and novel, and strike the senses with so much force and pleasure, that the mind is irre- sistibly led to exert all its energies in those investigations and ob- servations by which it may be enabled to grasp all the principles and facts of the science. And every difficulty which is surmounted adds a new stimulus to the exertions of the intellect, urges it for- ward with delight in the path of improvement, and thus invigorates the mental powers, and prepares them for engaging with spirit and alacrity in every other investigation. 4. The study of astronomy has a tendency to moderate the pride of "mam, and to promote humility. Pride is one of the distinguishing characteristics of puny man, and has been one of the chief causes of all the contentions, wars, devastations, oppressions, systems of INTRODUCTION. XIX slavery, despotisms, and ambitious projects which have desolated and demofalized our sinful world. Yet there is no disposition more incongruous to the character and circumstances of man. Perhaps there are no rational beings throughout the universe among whom pride would appear more unseemly or incompatible than in man; considering the abject situation in which he is placed. He is ex- posed to innumerable degradations and calamities, to the rage or storms and tempests, the devastations of earthquakes and volcanoes, the fury of whirlwinds, and the tempestuous billows of the ocean, the ravages of the sword, pestilence, famine, and numerous dis eases, and, at length, he must sink into the grave, and his body be- come the companion of worms. The most dignified and haughty of the sons of men are liable to such degradations, and are frequent- ly dependent on the meanest ſellow creatures whom they despise, for the greater part of their accommodations and comforts. Yet, in such circumstances, man, that puny worm of the dust, whose knowledge is so limited, whose follies are so numerous and glaring —has the effrontery to strut in all the haughtiness of pride, and to glory in his shame. When scriptural arguments and motives pro- duce little effect, I know no considerations which have a more pow- erful tendency to counteract this deplorable propensity of human beings than those which are borrowed from the objects connected with astronomy. They show us what an insignificant Seing—what a mere atom, indeed, man appears amidst the immensity of crea- tion. What is the whole of this globe, compared with the solar sys- tem, which contains a mass of matter ten hundred thousand times greater ? What is it in comparison of the hundred millions of suns and worlds which the telescope has descried throughout the starry regions, or of that infinity of worlds which doubtless lie beyond the range of human vision in the unexplored regions of immensity ? What, then, is a kingdom, or a province, or a baronial territory, of which we are as proud as if we were the lords of the universe, and for which we engage in so much devastation and carnage What are they when set in competition with the glories of the sky | Could we take our station on the lofty pinnacles of heaven, and look down On this scarcely distinguishable speck of earth, we should be ready to exclaim with Seneca, “Is it to this little spot that the great de- signs and vast desires of men are confined 7 Is it for this there is So much disturbance of nations, so much carnage, and so many ru- i...ous wars? O folly of deceived men, to imagine great kingdoms in the compass of an atom, to raise armies to divide a point of earth with the sword l’ It is unworthy of the dignity of an immortal mind to have its affections absorbed in the vanishing splendours of earthly grandeur, and to feel proud of the paltry possessions and distinctions of this sublunary scene. To foster a spirit of pride and yainglory in the presence of Him who “sitteth on the circle of the heavens,” and in the view of the overwhelming grandeur and im- mensity of his works, is a species of presumption and arrogance of which every rational mind ought to feel ashamed. And, therefore, we have reason to believe, that those multitudes of fools, “dressed in a little brief authority,” who walk in all the loftiness of pride, have not yet considered the rank they hold in the scale of universal XX | N'TRO DUCTION'. * being;-and that a serious contemplation of the immensity of crea- tion would have a tendency to convince us of our ignorance and nothingness, and to humble us in the dust, in the presence of the Former and Preserver of all worlds. We have reason to believe that the most exalted beings in the universe—those who are fur- nished with the most capacious powers, and who have arrived at the greatest perfection in knowledge—are distinguished by a pro- portional share of humility; for, in proportion as they advance in their surveys of the universal kingdom of Jehovah, the more will they feel their comparative ignorance, and be convinced of their limited faculties, and of the infinity of objects and operations which lie beyond their ken. At the same time they will feel, that all the faculties they possess were derived from Him who is the original fountain of existence, and are continually dependent for their exer- cise on his sustaining energy. Hence we find, that the angelic tribes are eminently distinguished for the exercise of this heavenly virtue. They “cover their faces with their wings” in the presence of their Sovereign, and fly, with cheerfulness, at his command, to our degraded world, “to minister to the heirs of salvation.” It is only in those worlds where ignorance and depravity prevail (if there be any such besides our own) that such a principle as pride is known or cherished in the breast of a dependent creature—and therefore every one in whom it predominates, however high his station or worldly accomplishments, or however abject his condition may be, must be considered as either ignorant or depraved, or more prop- erly, as having both those evils existing in his constitution, the one being the natural and necessary result of the other. 5. The studies connected with astronomy tend to prepare the soul for the employments of the future world. In that world, the glory of the Divine perſections, as manifested throughout the illimitable tracts of creation, is one of the objects which unceasingly employ the contemplation of the blessed. For they are represented in their ado- rations as celebrating the attributes of the Deity displayed in his operations: “Great and marvellous are thy works, Lord God Al- mighty thou art worthy to receive glory and honour and power, for thou hast created all things, and for thy pleasure they are and were created.” Before we can enter that world and mingle with its inhabitants, we must acquire a relish for their employments, and some acquaintance with the objects which form the subject of their sublime investigations; otherwise, we could feel no enjoyment in the society of heavenly intelligences, and the exercises in which they engage. The investigations connected with astronomy, and the frequent contemplation of its objects, have a tendency to pre- pare us for such celestial employments, as they awaken attention to such subjects, as they invigorate the faculties, and enlarge the ca- pacity of the intellect, as they suggest sublime inquiries, and desires for further information which may afterwards be gratified; as they form the groundwork of the Fº we may afterwards make in that state in our surveys of the Divine operations, and as they ha- bituate the mind to take large and comprehensive views of the em- pire and moral government of the Almighty. Those who have made progress in such studies, under the influence of holy disposi- INTRODUCTION XXI tions, may be considered as fitted to enter heaven with peculiar ad- vantages, as they will then be introduced to employments and inves- tigations to which they were formerly accustomed, and for which they were prepared—in consequence of which they may be prepared for filling stations of superior eminence in that world, and ſor di- recting the views and investigations of their brethren who enjoyed few opportunities of instruction and improvement in the present state. For we are informed, in the sacred records, that “they who are wise,” or as the words should be rendered, “they who excel in wisdom shall shine as the brightness of the firmament, and they that turn many to righteousness, as the stars for ever and ever.” 6. The researches of astronomy demonstrate, that it is in the power of the Creator to open to his intelligent offspring endless sour- ces of felicity. In looking forward to the scene of our future desti- nation, we behold a series of ages rising in succession without any prospect of a termination; and, at first view, it might admit of a doubt, whether the universe presents a scene so diversified and boundless, that intelligent beings, during an endless duration, could expect that new scenes of glory and felicity might be continually opening to their view, or, whether the same series of perceptions and enjoyments might not be reiterated so as to produce satiety and indifference. Without attempting positively to decide on the par- ticular scenes or sources of happiness that may be opened in the cternal world, it may be àº, that the Deity has it in his power to gratify his rational creatures, during every period of duration, with new objects and new sources of enjoyment; and, that it is the science of astronomy alone which has presented us with a demon- stration, and a full illustration of this important truth. For, it has displayed before us a universe boundless in its extent, diversified as to its objects, and infinite as to their number and variety. Even within the limits of human vision the number of worlds which exist cannot be reckoned less than three thousand millions ; and those which are nearest to us, and subject to our particular examination, present varieties of different kinds, both as to magnitude, motion, º colour and diversity of surface—evidently indicating, that every world has its peculiar scenes of beauty and grandeur. But, as no one will be so presumptuous as to assert, that the bound- aries of the universe terminate at the limits of human vision, there may be an assemblage of creation beyond all that is visible to us, which as far exceeds the visible system as the vast ocean exceeds In magnitude a single drop of water; and this view is nothing more than compatible with the idea of a Being whose creating energies are infinite, and whose presence fills immensity. Here, then, we have presented to our contemplation a boundless scene, correspond- ing in variety, and extent of space, to the ages of an endless dura- tion; so that we can conceive an immortal mind expatiating amidst objects of benignity, sublimity and grandeur, ever varied and ever new, throughout an eternal round of existence, without ever arri- ving at a point, where it might be said, “Hitherto shalt thou come, but no farther.” And we have reason to conclude that such will be the privilege and enjoyment of all holy beings. For we are in- formed on the authority of inspiration, that “in God’s presence XX]] - INTRODUCTION. there is fulness of joy, and at his right hand are pleasures for ever more.” 7. The science of astronomy is a study which will be prosecuted without intermission in the eternal world. This may be inferred from what has been already stated. For, it is chiefly among the numerous worlds dispersed throughout the universe that God is seen, his perfections manifested, and the plans of his moral govern- ment displayed before the eyes of unnumbered intelligences. The heavens constitute by far the grandest and most extensive portich of the empire of Omnipotence ; and if it shall be one part of the happiness of immortal spirits to behold and investigate the beauty, grandeur and beneficence displayed throughout this empire, we may rest assured, that they will be perpetually employed in such exercises; since the objects of their investigation are boundless as immensity;--or, in other words, astronomy, among other branches of celestial Science, will be their unceasing study and pursuit. As it has for its object, to investigate the motions, relations, phenomena, scenery, and the ultimate destimation of the great bodies of the uni- verse, the subject can never be exhausted. Whatever may be said in regard to the absolute perfection of other sciences, astronomy can never be said, at any future period of duration, to have arrived at perfection, in so far as it is a subject of study to finite minds; and, at this moment, even in the view of the Infinite Mind that created the universe, its objects may not yet be completed. For we have reason to believe that the work of creation is still going forward, and, com- sequently, that new worlds and systems may be continually emerg- ing from nothing under the energies of Creating Power. However capacious, therefore, the intellects of good men, in a future world, may be, they will never be able fully to explore the extent and va- riety, “the riches and glory” of Him “who dwells in light umap- proachable;”—yea, the most exalted of created intelligences, where. ever existing, although their mental powers and activities were incomparably superior to those of man, will be inadequate to a full investigation and comprehension of the grandeur and sublimities of that kingdom which extends throughout the regions of immensity. And this eircumstance will constitute one ingredient of their hap- piness, and a security for its permanency. For, at every period of infinite duration, they will be enabled to look forward to a suc- cession of scencs, objects and enjoyments different from all they had previously contemplated or experienced, without any prospect of a termination. We may therefore conclude, that; unless the material universe be demolished, and the agtivities of immortal minds suspended, the objects of astronomy will continue throughout eternity to be the subject of study, and of unceasing contemplation. Such are some of the advantages attending the study of the sci- ence of astronomy. It lies at the ſoundation of our geographical knowledge—it serves as a handmaid and director to the traveller and navigator—it is subservient to the purposes of universal com- merce—it determines the seasons, and directs the operations of the husbandman—it supplies us with an equable standard of time, and settles the events of history—it lends its aid to the propagation of re- ligion, and undermines the foundation of superstition and astrology. INTRODUCTION. xxiii Above all, it illustrates the glory of the perfections of the Deity-- displays the extent and grandeur of his universal empire—affords subjects of sublime contemplation, enlarges the conceptions, and in- vigorates the mental powers—counteracts the influence of pride, and promotes the exercise of humility—prepares the soul, for the employments of the ſuture world—and demonstrates, that the Cre- ator has it in his power to open up endlessly diversified sources of happiness to every order of his intelligent offspring, throughout all the revolutions of eternity. The moral advantages arising from the study of this science, however, cannot be appreciated or enjoyed, unless such studies and investigations be prosecuted in connexion with the facts and principles of Revelation. But, when associated with the study of the Scriptures, and the character of God therein delineated, and the practice of Christian precepts, they are calcula- ted “to make the man of God perfect,” to enlarge his conceptions of Divine perfection, and to expand his views of “the inheritance of the saints in light.” Such being the advantages to be derived from the study of this science, it ought to form a subject of attention in every seminary intended for the mental and moral improvement of mankind. In order to the improvement of the young in this science, and that its objects may * a deep impression on their minds, they should be directed to make frequent observations, as º offers, on the movements of the nocturnal heavens, and to ascertain all the facts which are obvious to the eye of an attentive spectator. And, while they mark the different constellations, the apparent diurnal motion of the celestial vault, the planets in their several courses, and the moon walking in her brightness among the host of stars— they should be indulged with views of the rings of Saturn, the belts and satellites of Jupiter, the phases of Mercury and Venus, the numerous groups ...” stars in the Milky Way, the double and treble stars, the most remarkable Nebula, the mountains and plains, the caverns and circular ridges of hills which diversiſy the surface of the moon, as they appear through good achromatic or reflecting telescopes. Without actual observation, and the exhibition of such interesting objects, the science of astronomy makes, comparatively, little impression on the mind. Our school books on astronomy should be popular in their lang”, ge and illustrations, but, at the same time, they should be comprehensive in their details, and every exhibition should be clear and well aeſinued. They should contain, not merely descriptions of facts, to be received on the authority of the author or the instructer, but illustrations of the reasons or argu- ments on which the conclusions of astronomy are founded, and of the modes by which they have been ascertained. And, while pla- netariums, celestial globes, and planispheres of the heavens are ex- hibited, care should be taken to direct the observations of the pupils as frequently as possible, to the objects themselves, and to guard them against the limited and distorted notions which all kinds of artificial representations have a tendency to convey. There is still room for improvement in all the initiatory books on this subject I have examined; but such books are now rapidly improving, both as to their general plan, and the interesting nature xxiv INTRODUCTION. of their details. I have seen nothing superior in this respect, or better adapted to the purpose of rational instruction, than Mr. Bur- rett's excellent work, entitled “The Geography of the Heavens,” second edition, comprising 342 closely printed pages. It contains, in the first place, a full and interesting description of all the con- stellations, and principal stars in the heavens, interspersed with a great variety of mythological, historical and philosophical informa- tion, calculated to amuse and instruct the general reader, and to arrest the attention of the young. The descriptions of the bodies connected with the solar system, are both popular and scientific, containing a lucid exhibition of the facts which have been ascer- tained respecting them, and a rational explanation of the phenomena connected with their various aspects and motions. The Celestial Atlas which accompanies the work is varied, comprehensive, and judiciously constructed, and forms the most complete set of planis- heres, for the purpose of teaching, which has hitherto been pub- ished. It consists of four maps about fourteen inches square, de- lineated on the same principles as geographical projections, exhi- biting the stars that pass near the meridian at a certain hour, along with the circumjacent constellations for every month, and for every day of the year. Besides these there are two circumpolar maps of the northern and southern hemispheres of the heavens, and a pla- misphere on the principle of Mercator’s projection, which exhibits at one view the sphere of the heavens, and the relative positions of the different constellations and principal stars. With the assistance of these maps, which in a great measure supersede the use of a cclestial globe, an intelligent teacher may, at certain intervals in the course of a year, render his pupils familiar with most of the visible stars in the heavens; and they will make a deeper impres- Sion on their minds when taught in this way, than by the use of a globe. This work, on the whole, indicates great industry and re- search on the part of the author, and a familiar acquaintance with the various departments of the science of the heavens. He has de- rived his materials from the most valuable and modern works of science, and has introduced not a few illustrations and calculations of his own, which tend to enhance the general utility of the work. The moral and religious reflections which the objects of this science naturally suggest, have not been overlooked, and, I trust, will have a tendency to raise the minds of the young to that Almighty Being whose power, wisdom, and superintending providence are so stri. kingly displayed throughout the regions of the firmament. P R. E LIMIN A R Y CHA PTE R. IN entering upon this study, the phenomena of the heavens, as they appear in a clear evening, are the first objects that demand our attention. Our first step is to learn the names and positions of the heavenly bodies, so that we can identify, and distinguish them from each other. g In this manner, they were observed and studied ages before books were written, and it was only after many, careful and repeated observations, that systems and theories of Astronomy were formed. To the visible heavens, then, the attention of the pupil should be first directed, for it is only when he shall have become in some measure, familiar with them, that he will be able to locate his Astronomical knowledge, or fully comprehend the terms of the science. For the sake of convenient reference, the heavens were early divided into constellations, and particular names assign- ed to the constellations and to the stars which they contain. A constellation may be defined to be a cluster or group of stars embraced in the outline of some figure. These figures are in many cases, creations of the imagination, but in others, the stars are in reality so arranged as to form figures which have some resemblance to the objects whose names have been as- signed to them. These divisions of the celestial sphere, bear a striking analogy to the civil divisions of the globe. The constellations answer to states and kingdoms, the most brilliant clusters to towns and cities, and the number of stars in each, to their respective population. The pupil can trace the boundaries of any constel- lation, and name all its stars, one by one, as readily as he can trace the bounda- ries of a state, or name the towns and cities from a map of New England. In this sense, there may be truly said to be a Geography of the Heavens. The stars are considered as forming, with reference to their magnitudes, six classes; the brightest being called stars or the first magnitude, the next brightest, stars of the second magnitude, and so on to the sixth class, which consists of the smallest stars visible to the naked eye. In order to be able Why, in entering upon the study of Astronomy, should the attention of the pupil be first directed to the visible heavens? Why were the heavens early divided into con- stellations, and mames assigned to the constellations and the stars? What is a con- tellation? Do these figures really exist in the skies? In what sense may there truly e said to be a Geography of the Heavens 2 How many classes are the stars considered as forming with reference to their magnitude. *. 26 PRELIMINARY CHAPTER. to designate, with precision their situations, imaginary circles have been considered as drawn in the heavens, most of which correspond to and are in the same plane with similar circles, supposed, for similar purposes, to be drawn on the surface of the Earth. In order to facilitate the study of it, artificial representations of the heavens, similar to those of the surface of the Earth, have been made. Thus, a Celestial Atlas, composed of se- veral maps, accompanies this work. Before, however, pro- ceeding to explain its use, it is necessary to make the pupil acquainted with the imaginary circles iºd to above. CIRCLEs of THE SPHERE.—The Aavis of the Earth is an imaginary line, passing through its centre, north and south, about which its diurnal revolution is performed. The Poles of the Earth are the extremities of its axis. The Aavis of the Heavens is the axis of the Earth pro- duced both ways to the concave surface of the heavens. The Poles of the Heavens are the extremities of their axis. The Equator of the Earth is an imaginary great circle passing round the Earth, east and west, everywhere equally distant from the poles, and dividing it into northern and southern hemispheres. The Equator of the Heavens, or Equinoctial, is the great circle formed on the concave surface of the heavens, by pro- ‘ducing the plane of the Earth’s equator. A plane is that which has surface but not thickness. The plane of a circle is that imaginary superficies which is bounded by the circle. The Rational Horizon is an imaginary great circle, whose plane, passing through the centre of the Earth, divides the heavens into two-hemispheres, of which the upper one is called the visible hemisphere, and the lower one, the invisi- ble hemisphere. It is the plane of this circle which deter- mines the rising and setting of the heavenly bodies. The Sensible or Apparent Horizon, is the circle which terminates our view, where the Earth and sky appear to meet. To a person standing on a plaim, this circle is but a few miles in diameter. If the eye be elevated five feet, the radius of the sensible horizon will be less than two miles and three quarters; if the eye be elevated six feet, it will be just three miles. The observer being always in the centre of the sensible horizon, it will move as he moves, and enlarge or contract, as his station is elevated or depress- ed. What expedient has been devised for designating, with precision, the situations of the heavenly bodies? What is the axis of the Farth? What are the poles of the Earth? What is the axis of the heavens? What are the poles of the heavens 3 ...What is the equator of the Earth? What is the equator of the beavens or the equinoctial? What is a plane? What is the plane of a circle 2 What is the rational horizon? What is the sensible or apparent horizon? What is the diameter of this circle to a person stand- ăng on a plain 2 What will its radius be if the eye be elevated five feet? If it be ele- tated Sta: feet 2 On what does the place Qf its centre &nd its circumference depènd 2 PRELIMINARY CHAPTER. 27 The Poles of the Horizon are two points, of which the one is directly over head, and is called the Zenith ; the other is directly under foot, and is called the Nadir. Vertical Circles are circles drawn through the Zenith and Nadir of any place, cutting the horizon at right angles. The Prime Vertical is that which passes through the east and west points of the horizon. The Ecliptic is the great circle which the Sun appears to describe annually among the stars. It crosses the Equinoc- tial, a little obliquely, in two opposite points which are called the Equinoaces. 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#9. This angle is called the obliquity of the Ecliptic. The axis of the Eclip- tic makes the same angle with the axis of the heavens; so that the poles of each are 23#9 apart. This angle is prºpetually decreasing. At the commencement of the Christian era, it was about 23°45'. At the beginning of 1836, it was only 23° 27' 3S ’’, show- ing an annual diminution of about half a second, or 45".70 in a hundred years. A time will arrive, however, when this angle, having reached its Illininium, Will again increase in the same ratio that it liãd before diulinished, 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'. The ecliptic, like every other circle, contains 360°, and it is divided into 12 equal arcs of 300 each, called signs, which the ancients distinguished by particular mames. This division commences at the vernal equinox, and is continued east- wardly round to the same point again, in the following order: Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scor- pvo, Sagittarius, Capricornus, Aquarius, Pisces. The Sun, commencing at the first degree of Arles, about the 21st of March, passes, at a mean rate, through one sign every month. The Zodiac is a zone or girdle, about 16 degrees in breadth, extending quite round the heavens, and including all the heavenly bodies within 89 on each side of the ecliptic. It in- cludes, also, the orbits of all the planets, except some of the asteroids, since they are never seen beyond 89 either north or south of the ecliptic. Parallels of Latitude are small circles imagined to be What are the poles of the horizon? What are vertical circles What is the prime vertical? What is the ecliptic What are the equinoxes? The vermal equinox? The autumnal equinox! How is the ecliptic situated with respect to the equinoctial? What is the obliquity of the ecliptic A. Describe the ºn anner in which this angle varies. I)e- scribe the division of the ecliptic into signs. How much, at a mean rate, does the Sun tºº,” the ecliptic every month What is the zodiac What are parallels ºf all tuluid & - - . 28 PRELIMINARY CHAPTER. 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 consid- ered as circles formed by producing the parallels of latitude to the heavens. The Tropic of Cancer is a small circle, which lies 23#2 north of the equinoctial, and parallel to it. The Tropic of Capricorn is a small circle, which lies 23}o south of the equinoctial, and parallel to it. On the celestial sphere, these two circles mark the limits of the Sun’s farthest declination north and south. On the terrestial sphere, they divide the torrid, from the two temperate zones. That point in the ecliptic which touches the tropic of Cancer, is called the Sum- mer Solstice; and that point in the ecliptic which touches the tropic of Capricorn, is called the Winter Solstice. The distance of these two points from the equinoctial, is always equal to the obliquity of the ecliptic, which, in round numbers, is 23c.9; but as we have seen the obliquity of the ecliptic is continually changing; thcreſore the position of the tropics must make a correspondent changc. The Colures are two great circles which pass through the poles of the heavens, dividing the ecliptic into four equal parts, and mark the seasons of the year. One of them passes through the equinoxes at Aries and Libra, and is thence called the Equinoctial 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 23d of Septem- ber. He is in the solstitial points the 22d of June and the 22d of December. The Polar Circles are two small circles, each about 6630 from the equator, being always at the same distance from the poles that the tropics are from the equator. The northern is called the Arctic circle, and the southern the Antarctic circle. Meridians are imaginary great circles drawn through the poles of the world, cutting the equator and the equinoctial at right angles. - Every place on the Earth, and cvery corresponding point in the heavens, is considered as having a meridian passing through it; although astronomers apply What are parallels of declination? What is the tropic of cancer? What is the tropic of capricorn? What is the summer solstice? What is the winter solstice? ... H//iai is their distance from? the equator, compared with the obliquity of the ecliptic 2 Is this distance always the same 2 What are the colures 3 What is the equinoctial colure? What is the solstitial colure? . Om what days of the year is the sum in the equinoctial points? On what days, is he in the solstitial points? What are the polar circles? By what names, are they distinguished ? What are meridians? How many meridiaris arg there 2 Iſow many, d0 astropºnner's ſºphy to the heavens 2 PRELIMINARY CHAPTER, 29 bul 24 to the heavens, thus dividing the whole concave surface into 24 sections, each 150 in width. These meridians mark the space which the heavenly bodies appear to describe, every hour, for the 24 hours of the day. They are thence sometimes denominated Hour Circles. In measuring distances and deteriuining positions on the Earth, the equator, and soune fixed meridian, as that of Greenwich, contain the primary starting points; in the heavens, these points are in the ecliptic, the equinoctial, and that great meridian which passes through the Yoint of Aries, called the equinoc- tial º Latitáde on the Earth, is distance north or south of the equator, and is measured on a meridian. Latitude in the Heavens, is distance north or south of the ecliptic, and at right angles with it. Tongitude on the Earth, is distance either east or west from some fixed meridian, measured on the equator. Longitude in the Heavens, is distance east from the first point of Aries, measured on the ecliptic. Declimation is the distance of a heavenly body either north or south of the equinoctial, measured on a meridian. Q 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 declination and right ascension, than by their latitude and longitude, since the former correspond to terrestrial latitude and longitude. Latitude and declimation may extend 90° and no more. Terrestrial longitude may extend 180° citlyer east or west ; but celestial longitude and right ascen- § being reckoned in only one direction, extend entirely round the circle, or In consequence of the Earth’s motion eastward in its orbit, the stars seem to have a motion westward, besides their apparent diurnal motion caused by the Earth’s revolution on its axis; so that they rise and set sooner every succeeding day by about four minutes, than they did on the preceding. This is called their daily acceleration. It amounts to just two howrs a month. ExAMPLE.—Those stars and constellations which do not rise until 10 o’clock this evening, will, at the same hour, one month hence, be 30° above the horizon; and, for the same reason, those stars which we see directly over head this evening, will at the same hour, three months hence, be seen setting in the Nº. having in this time, performed one fourth of their apparent annual revo- Ull 10Il. The following table of sidereal revolutions, shows the difference between solar and sidereal time. The first column contains the numbers of complete revolu- tions of the stars, or of the Earth’s rotation on its axis; the second exhibits the Into how many sections, do these meridians divide the concave surface of the heavens 2 Of what width are these sections 2 Why are these meridians sometimes called hour cir- cles? In measuring distances on the Earth, what circles contain the primary starting points? Where are these points in measuring distances in the heavens 2 What is la: titude on the Earth? What is latitude in the heavens? What is longitude on the Earth? What is longitude in the heavens What is declination? What is right ascension? f{hy is it more convenient to describe the site:ation of the heavenly bodies by their de- climation and right ascension, than by their latitude and longitude 2 How many de- grees may latitude and declination eaſt&nd 2. How migny terrestrial longitude 2 Hoºv ſº Célestigl long it?ttle 2 What is meant by the daily acceleration of the stats To lºw many minutes does it amount? Iłintstrate this subject with an evample. • * * J 30 PRELIMINARY CHAPTER. times in which these revolutions are made; and the third, shows how much the Stars gain on the Sun every day—that is, how much sooner they rise and come to the meridian every succeeding day, than they did on the preceding Revolutions Times in which Revolutions Daily acceleration. Of the Of the Stars. are made. days. ho. min. SCC. h. min. SøC. 1 0 23 56 4 0 3 55 2 1 23 52 8 0 7 51 8 2 23 48 12 0 11 47 4 3 23 44 16 0 15 43 5 4 23 40 20 0 19 39 6 5 23 36 24 0 23 35 7 6 23 32 28 0 27 31 8 7 23 28 32 0 31 27 9 8 23 24 0 35 23 10 9 23 20 41 0 39 19 1 I 10 23 16 45 0 43 14 12 11 23 12 49 0 47 10 13 12 23 8 53 0 51 6 14 13 23 4 57 0 55 15 14 23 1 I 0. 58 58 16 15 22 57 5 I 2 54 17 16 22 53 9 l 6 50 18 17 22 49 13 I 10 46 19 18 22 45 17 I 14 42 20 19 22 41 22 l 18 88 2] 20 22 37 26 1 22 33 22 21 22 33 30 l 26 29 23 22 22 29 34 I 30 25 24 23 22 25 38 I 34 21 25 24 22 21 42 1 38 17 26 25 22 17 46 l 42 13 27 26 22 13 50 l 46 9 28 27 22 9 54 1 50 5 29 28 22 5 58 } 54 l 30 29 22 2 3 I 57 57 40 39 21 22 44 2 37 16 50 49 20 43 25 3 16 35 100 99 17 26 50 6 33 10 200 199 10 53 40 13 6 9 300 299 4 20 30 19 39 29 360 359 0 24 36 23 35 23 365 364 0 4 56 23 55 3 366 365 0 1. 0 23 59 O On this account, we have not always the same constella- tions visible to us throughout the year. While some, that were not visible before, are successively rising to view in the east, and ascending to the meridian, others sink beneath the western horizon, and are seen no more, until, having passed through the lower hemisphere, they again reappear in the east. It is easy..to convert right ascension into time, or time into right ascension; for iſ a heavenly body is one hour in passing over 15°, it will be one fifteenth of an hour, or 4 minutes, in passing over 19. If the first point of Aries be on the meridian at 12 o'clock, the next hour line, which is 15° E. of it, will come to the meridian at 1 o’clock; the second hour line at 2 o’clock; the third at 3, &c. Of any two bodies whose right ascensions are given, that one will pass the meridian first which has the least right ascension. The first map of the atlas represents, upon a large scale, a general view of the solar system. * This will be more fully described in the Second Part of the work. Do we always see the same constellations? Eaſplain themanner of converting right ascension into time, and time ºn to right ascension. PRELIMI ºn ARY CHAPTE R. 31 The next six maps represent different sections of the concave surface of the heavens. The first of these exhibits the principal constellations visible to us in October, November and Decem- ber; the second, those visible in January, February and March; the third, those visible in April, May and June; and the fourth, those visible in July, August and September; with the exception, however, of the constellations which lie be- ond the 50th degree of north and south declination, of which, indeed, those around the North Pole are always, and those around the South Pole, never, visible to us. These constellations are represented on the sixth and seventh maps, called circumpolar maps, which are an exact continu- ation of the others, and if joined to them at their correspond- Ing degrees of right ascension and declination, they might be considered as constituting one map. The scale on which all the above-mentioned maps are drawn is that of a 16 inch globe. The limes drawn on the maps have been already de- fined; 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 159, are called Meridians of Right Ascension, or Hour Circles. The scale at the top and bottom of the first four maps, and in the circumference of the circumpolar maps, in- dicates the daily progress of the stars in right ascension, and shows on what day of the month any star will be on the me- ridian at 9 o'clock in the evening. The constellation called the Great Bear is an exception to this rule; in this constellation the principal stars are marked in the order of their right ascension. That point of projection for the maps which would exhibit each successive º of the heavens directly over head at 9 o'clock in the evening, was chosen, ecause in Summer at an earlier hour the twilight would bedim our observation of the stars, and at other seasons of the year it is easier to look up to stars that . an hour of their meridian altitude than to those which are directly over Ça.C. It will be readily seen that the stars are so represented on the maps as to show their relative magnitudes. The method invented by Bayer, of designating them by the letters of the Greek and Roman alphabets, is adopted. Thus in each con- Stellation the stars are marked alpha, beta, &c., and should the letters of the Greek alphabet be exhausted, those of the Roman are employed. Some of the stars have also proper names. The first four maps of the heavens are so constructed that the For whatemonths does the first map repuesent the heavens 2 . For what months does the second map represent the heavens 'The third? The fourth? What constellations are represented on the sixth and soventh maps? In what-manner must these six maps be arranged to form onc completc map of the heavens? On what scale are these maps drawn? What is the use of the scale at the top and bottom of the first four maps, and in the circumference of the circumpolar maps? Why was that point of projection for the 2naps, which would represent each successive portion of the heavens directly over head at 9 o'clock 3/2 the evening, chosex 2 | What is the method by which the stars are designated on the maps? How must the pupil, in using either of the first four maps, Imagine himself to stand and to hold it q sº. 32 PRELlMINARY CHAPTER. pupil in using them must suppose himself to face the south, and to hold them directly over head 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 mapsſhe must suppose himself to face the pole, and to hold them in such a manner that the day of the given month shall be up- permost\ The Celestial Planisphereſ represents the whole heavens lying between 70 degrees of horth and south decli- nation, not as the surface of a concave sphere, but of a con- cave cylinder, and spread out so as to form a plain surface. A great variety of interesting problems, including almost all those that are peculiar to the celestial globe, may be solved upon it with facility and readiness. We may now imagine the pupil ready to begin the study of the visible Heavens. The first thing of importance is to fix upon the proper starting point. This, on many accounts, "Would seem to be the North Polar Star. . Its i. is ap- arently the same every hour of the night throughout the year, while the other stars are continually moving). Many of the stars also in that region of the skies never set, so that when the sky is clear, they may be seen at any hour of the night, They revolve about the Pole in small circles, and never disappear below the horizon. On this account they are said to be within the circle of perpetual apparition, On the other hand, the identity of the North Polar Star, strange as it may appear, is not so easily determined, by those who are just entering upon this study, as that of some others. For this reason, the point directly over head, called the zenith, is preferable, since upon this point every one can fix with cer- tainty 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 imperceptibly to refer the bearing, motion, and dis. tances of the heavenly bodies. - - That meridional point in each map, whose declimation corresponds with the latitude of the place of observation, represents the zenith of #. heavens at that place; and those constellations of stars which occupy this position on the maps, will be seen directly over head 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 situated in this meridian near the 33d degree of north declination, while in New England it should be those which are situated in it near the 42d degree. How, in using the circumpolar maps? Describe the construction and use of the Ce lestial Planisphere. When the pupil is ready to begin the study of the visible heav ens, what is the first step to be taken? What advantages has the North Polar Star, as a proper starting point? What disadvantages What point is preferable to the Polar Star? Why is it preferable? How may the point corresponding to this befownd wyon the maps? At what time in the evening, will the stars which are near this point on the maps, be seen directly over head 2 Is it indispensably necessary to begin with the §tars near this central nieridian - PRELIMINARY CHAPTER, 33 We might, nowever, 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 over head 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 all the heavenly bodies are measured; but especially because the student will thus be enabled to observe and compare the progressive motion of the constellations ac- cording to the order in which they are always arranged in catalogues, and also to mark the constellations of the Zodiac passing over head as they rise one after another in their or- der, and to trace among them the orbits of the Earth and of the other planets. As Greek letters so frequently occur in catalogues and maps of the stars and on the celestial globes, the Greek alphabet is here introduced for the use of those who are unacquainted with it. The capitals are seldom used for designating the stars, but are here given for the sake of regularity. - THE GREEK ALPHABET. Alpha Beta Gamma Delta. Epsilon Zeta Eta Theta Iota Kappa Lambda Mu Nu Xi Omicron Pi Rho Sigma Tau Upsilon Phi Chi PSi Omega O long : short long i hZ short ; In 1603, John Bayer, of Augsburg, in Germany, published a complete Atlas of all the constellations, with the useful invention of denoting the stars in every What is the only rule of selection? What is the starting point chosen for this work? What advantages has this meri-dian as a starting pointi 's 34 PRELIMINARY CHAPTER. constellation by the letters of the Greek and Roman Alphabets; assigning the Greek letter,a to the principal stars in each constellation, 3 to the second in magnitude, 27 to the third, and so on; and when the Greek alphabet was ex- hausted, the notation was carried on with the Roman letters, a, b, c, &c. That the memory might not be perplexed with a multitude of ...; this convenient method of designating the stars has been adopted by all succeeding astronomers, who have farther enlarged it by the Arabic notation, 1, 2, 3, &c. whenever the stars in the constellations outnumbered both alphabets. INCREASE OF SIDEREAL TIME IN MEAN SOLAR HOURS, &c. Increase. Incr. Incr. Incr. Incr. Hours. m. sec. Min. sec. | Min. Sec. Sec. sec. Sec. sec. l 0 9.857 I 0.164 31 5.093 1 0.003 31 0.085 2 19.713 2 329 32 257 2 006 32 3 29.569 3 493 33 421 3 33 090 4 39.426 4 657 34 585 4 011 093 5 49.282 5 821 35 750 5 014 35 096 6 59. 139 6 986 36 914 6 016 36 099 7 1 8.995 7 | 1.150 37 6.078 7 0.19 37 101 8 18,852 8 314 38 242 8 022 38 104 9 28.70S 9 479 39 407 9 0.25 39 107 10 38.565 10 643 40 57.1 10 0 40 110 11 48.421 11 807 41 735 11 030 41 112 12 58.278 12 971 42 900 12 033 42 115 13 2 8.134 13 || 2. 136 43 7.064 13 036 43 118 14 17,991 14 300 44 228 14 038 44 121 15 27,847 15 464 45 392 15 041 45 123 16 37.704 16 628 46 557 16 044 46 126 I7 47.560 17 793 47 721 17 047 47 129 18 57.4.17 18 957 48 885 18 049 48 131 19 3 7.273 19 || 3. 121 49 8.050 19 052 49 134 20 17.130 20 286 50 214 20 055 50 137 21 26.986 2I 450 51 37 21 058 51 140 36.842 22 614 52 542 22 060 52 142 23 46.699 23 778 53 707 23 063 53 145 24 56.555 24 943 54 871 24 066 54 148 −|| 25 4. 107 55 9.035 25 069 55 151 Daily acceleration| 26 271 56 199 || 26 07.1 : 56 153 of a star In passing| 27 435 57 364 27 074 57 156 the meridian, 28 600 58 528 || 28 077 58 159 Im. Sec. 29 7 59 692 29 079 59 }62 3 55.9095 30 928 60 857 30 60 164 THE GEOGRAPHY OF THE HEAVENS. C H A P T E R. I. DIRECTIONS FOR TRACING THE CONSTELLATIONS WHICH ARE ON THE MERIDIAN IN NOWEMBER. ANDROMED A. IF we look directly over head at 10 o’clock, on the 10th & November, we shall see the constellation celebrated in fable, by the name of ANDROMEDA. It is represented on the map by the figure of a woman having her arms extended, and chained by her wrists to a rock. It is bounded N. by Cassiopeia, E. by Perseus and the head of Medusa, and S. by the Triangles and the Northern Fish. It is situated between 200 and 500 of N. declination. Its mean right ascension is nearly 15°; or one hour E. of the equinoctial colure. 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 presence of the moon, but the bright star Almaack, of the 2d magnitude, in the left foot, may be seen 139 due E., and Merach, of the same magnitude, in the girdle, 79 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, 39 and 40 apart, and are called Merach, Mu and Nu. About 29 from Nu at the northwestern extremity of the girdle, is a 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 $o in length, and #9 in breadth. If we look directly over head at 10 o'clock on the 10th of November, what constella- tion shall we see? How is it represented on the map? How is it bounded? What are its º ascension and declimation? How many visible stars has it? . Describe the girdlé of Andromeda. Describe the appearance of a remarkable nebula which lies at ità forthwestern Cxtremity, 36 PICTURE OF THE IIEAVENS. If a straig tº line, connecting Almaack with Merach, be produced southwesterly, 8° farther, it will reach to Delta, a star of the 3d magnitude in the left breast. This star j be otherwise known by its forming a line, N. and S. wit 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, Merach and Delta, but curving a little to the N. 79 farther, is a lone star of the 2d magnitude, in the head, called Alpheratz. This is the N. E. corner of the great “Square of Pegasus,” to be hereafter de- scribed. ... It will be well to have the position of Alpheratz well fixed in the mind, because it is but one minute west of the great equinoctial colure, or first meridian of the heavens, and ſorums nearly a right line with Algenib in the wing of Pegasus, 14° S. of it, and with Beta 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 commex- ion with the North Polar Star point out to astronomers the position of that great circle in the heavens from which the right ascension of all the heavenly bodies is measured. * HISTORY.--The story of Andromeda, from which this constellation derives its name, is as follows: She was daughter of Cepheus, king of Æthiopia, by Cassio- peia. She was promised in marriage to Phineus, her uncle, when Neptune drowned the kingdom, and sent a séa monster to ravage the country, to appease the resentment winich his favourite Nymphs bore against Cassiopcia, because she had boasted herself fairer than Juno and the Nereides. The oracle of Ju- piter Ammon was consulted, and nothing could paciſy 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, mear Joppa, (now Jaffa, in Syria,) and at the moment the monster was going to devour her, Perseus, who was then returning through the air ſºon the conquest of the Gorgons, saw her and was captivated by her beauty. “Chained to a rock she stood; young Perseus stay’d His rapid ſlight, to woo the beauteous maid.” He promised to deliver her and destroy the monster if Cepheus womló 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 Gorgom’s head. • * * The morals, maxims, and historical events of the ancients, were usually coln- municated in fable or allegory. The fable of Andromeda and the sea monster, might mean that she was courted by some monster of a sea-captain, who at- tempted to carry her away, but was prevented by another more gallant and suc- cessful rival. ..ºf PISCES. THE FISHEs.—This constellation is now the first in order, of the 12 constellations of the Zodiac, and is usually repre- sented by two fishes tied a considerable distance apart, at the extremities of a long undulating cord, or riband. It occupies Describe the magnitude and position of Delta. How may this star be otherwise known? Describe the position and magnitude of Alpheratz. What position does this Star Occupy in the great sº. of Pegasus? Why is it important to have the position this star well fixed in the mind? What is the present order of the Fishes among the constellations of the Zodiac How is it reproscated ? Describe its Outline and space in the heavens. PISCES. 37 a large triangular space in the heavens, and its outline at first is somewhat difficult to be traced. - In consequence of the annual precession of the stars, the constellation Pisces has now come to occupy the sign Aries; each constellation having advanced one whicle sign in the order of the Zodiac. The sun enters the sign Pisces, while the earth enters that of Virgo, about the 19th of February, but he does not reach the constellation Pisces before the 6th of March. The Fishes, therefore, are now called the “Leaders of the Celestial Hosts.”—See Aries. That loose assemblage of small stars directly south of Merach, in the constellation of Andromeda, constitutes the Northern Fish, whose mean length is about 169, and breadth, 79. Its mean right ascension is 159, and its declimation 25° N. Consequently, it is on the meridian the 24th of Novem- ber; and, from its breadth, is more than a week in passing over it. The Northern Fish and its riband, beginning at Merach, may, by a train of small stars, be traced, in a S. S. easterly direction, for a distance of 33°, until we come to the star El Rischa, of the 3d magnitude, which is situated in the node, or flexure of the riband. . This is the principal star in the constellation, and is situated 29 N. of the equinoctial, and 53 minutes east of the meridian: - Seven degrees S. E. of El Rischa, passing by three or four very small stars WG CODIle to Mira, in the Whale, a star of about the 3d magnitude, and known as the “Wonderful Star of 1596.” El Rischa may be otherwise identified by means of a re-markable cluster of five stars in the ſorm of a pentagon, about 15° E. of it.—See Cetus. From El Rischa the riband or cord makes a sudden flexure, doubling back across the ecliptic, where we meet with three stars of the 4th and 5th magnitude situated in a row 30 and 40 apart, marked on the map Zeta, Epsilon, Delta. From Delta the riband runs north and westerly along the Zodiac, and terminates at Beta, a star of the 4th magnitude, 11o S. of Markab in Pegasus. This part of the riband including the Western Fish at the end of it, has a mean declination of 5° N., and may be seen throughout the month of November, passing the meridian slowly to the W., near where the sun passes it on the 1st of April. Twelve degrees W. of this Fish, there are 4 small stars situated in the form of the letter Y. The two Fishes, and the cord between them, make two sides of a largé triangle, 30° and 40° in length, the open part of which is towards the N. W. When the Northern Fish is on the What are the size and position of the Northern Fish? When, and how long is it on the meridian? How may it be traced? What is the principal star in this constellation, and where is it situated? How far, and in what direction from Alpha, is Mira, in the Whale? By what paculiar appellation is this starknown? What is the direction of the riband from Alpha} hat stars do we meet with, where the riband doubles back across the eclip- tic? What is the direction of this part of the riband from Delta, and where does it ter- minate? What are its mean declimation, and the time of its passing the meridian & What striking cluster is seem about 12° W. of the Westerm Fish? What geometrical figure may be conceived to be formed by thc two Fishes and the cord between them? Where is the Western Fish when the Northcrn is on the meridian : 4. 38 PICTURE OF THE IHEAVENS. |Nov. . meridian, the Westerm is nearly 2 hours past it. This con- stellation is bounded N. by Andromeda, W. by Andromeda and Pegasus, S., by the Cascade, and E. by the Whale, the Ram and the Triangles. * º When, to enable the pupil to find any star, its direction from another is given, the latter is always understood to be on the meridian. After a little experience with the Imaps, even though unaccompanied by di. rections, the ingenious youth will be able, of himself, to devise a great many ex- pedients and facilities for tracing the constellations, or selecting out particular Stal'S. HISTORY..—The ancient Greeks, who have some ſable to account for the ori- gin of almost every constellation, say, that as Venus and her son Cupid were one day on the banks of the Euphrates, they were greatly alarmed at the appearance of a terrible giant, named Typhon. Throwing themselves into the river, they were changed into fishes, and by this means escaped danger. To commemorate this event, Minerva placed two fishes among the stars. According to Ovid, Homer, and Virgil, this Typhon was a famous giant. He had a hundred heads, like those of a serpent or dragon. Flames of devouring fire darted from his mouth and eyes. He was no sooner born, than he made war against heaven, and so frightened the gods, that they fled and assumed diſ. ferent shapes. Jupiter became a ram; Mercury, an ibis; Apollo, a crow ; Juno, a cow; Bacchus, a goat ; Diana, a cat; Venus, a fish, &c. The father of the gods, at least, put Typhon to flight, and crushed him under Mount HEtna. The obvious sentiment implied in the ſable of this hideous monster, is evi- dently this: that there is in the world a description of men whose unouth is so “full-of cursing and bitterness,” derision and violence, that modest virtue is sometimes forced to disguise itself, or flee from their presence. In the Hebrew Zodiac, Pisces is allotted to the escutcheon of Simeon. No sign appears to have been considered of more malignant influence than Pisces. The astrological calendar describes the emblems of this constellation as indicative of violence and death. Both the Syrians and Egyptians abstained from eating fish, out of dread and abhorrence; and when the latter would re- ºn: any thing as odious, or express hatred by hieroglyphics, they painted a US/º. In using a circumpolar map, face the pole, and hold it up in your bands in such a manner that the part which contains the name of the given month shall be uppermost, and you will have a portraiture of the heavens as seem at that time. The constellations about the Antarctic Pole are not visible in the United States; those about the Arctic or northern pole, are always visible. CASSIOPEIA. CAssiopBIA is represented on the celestial map, in regal state seated on a throne or chair, holding in her left hand the branch of a palm tree. Her head and body are seen in the Milky Way. Her foot rests upon the Arctic Circle, upon which her chair is placed. She is surrounded by the chief personages of her royal family. The king, her husband, is on her right hand—Perseus, her son-in-law, on her left—and Andromeda, her daughter, just above her... " This constellation is situated 26° N. of Andromeda, and midway between it and the North Polar Star. It may be what are the boundaries of this constellation? How is the censtellation Cassiopela represented on the map? By whom is she surrounded? How is this constellation situated in respect to Andromeda and the polar star! MAP VI.] CA:33IOPEIA. 39 seen, from our latitude, at all hours of the might, and may be traced out at almost any season of the year. Its mean decli- nation is 600 N. and its right ascension 129. 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 apparent motion of the stars becomes slower and slower, as they approximate the poles. Cassiopeia is a beautiful constellation, containing 55 stars that are visible to the naked eye; of which five are of the 3d magnitude, and so situated as to form, with one or two smaller ones, the figure of an inverted chair. - - — “Wide her stars Dispersed, nor shine with mutual aid improved; Nor dazzle, brilliant with contiguous flame: Their number fifty-five.” ſºaph, 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. [See note to Androme- da.] Gaph is therefore on the meridian the 10th of Novem- ber, and one hour past it on the 24th. It is the westernmost star of the bright cluster. Shedir”, in the breast, is the up- permost star of the five bright ones, and is 50 S. E. of Caph: the other three bright ones, forming the chair, are easily dis- tinguished, 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 connexion with observations on the Polar Star, for determi- ning the latitude of places, and for discovering the magnetic variation of the needle. It is generally supposed that the North Polar Star, so called, is the real immove. able pole of the heavens; but this is a mistake. It is so near the true pole that it has obtained the appellation of the North Polar Star; but it is, in reality, more than a degree and a half distant from it, and revolves about the true pole every 24 hours, in a circle whose radius is 1° 35'. It will consequently, in 24 hours, be twice on the meridian, once above, and once below the pole; and twice at its greatest elongation E. and W. [See North Polar Star.] - The Polar Star not being exactly in the N. pole of the heavens, but one degree and 35 minutes 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 * Sheilir, from El Seder, the Seder tree; a name given to this constellation by Ulugh Beigh. ...When may it be seen from this latitude? When is it on our meridian? How is the ºtion of the stars affectell as they approach the poles? How many principal stars in this constellation, and what is their *...; Descrihe the situation of Caph. When is Caph on the meridian -What ſs the relative position of shedjº why is the position of Caph important? s * 4() PICTURE OF THE HEAVENS. NOW. of this star. It is equidistant from the pole, and exéctly op- posite another remarkable star in the square of the Great Bear, on the other side of the pole. [See Megrez.] It also serves to mark a spot in the starry heavens, rendered memo- rable as being the place of a lost star. Two hundred and fifty years ago, a bright star shone 50 N. N. E. of Caph, where now is a dark void On the 8th of November, 1572, Tycho Brahe and Corne- lius Gemma saw a star in the constellation of Cassiopeia, which became, all at once, so brilliant, that it surpassed the splendour of the brightest planets, and might be seen even at noonday ! ... Gradually, this great brilliancy diminished, until the 15th of March, 1573, when, without moving from its place, it became utterly extinct. - Its colour, 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 any thing more tremendous than a conflagration that could be visible at such a distance. It was seen for sixteen months. Some astronomers imagined that it would reappear again after 150 years; but it has never been discovered since. This phenomenon alarmed all the astronomers of the age, who beheld it; and many of them wrote dissertations con- cerning it. - Rev. Professor Vince, one of the most learned and pious astronomers of the age, has this remark:—“The disappear- ance of some stars may be the destruction of that system at the time appointed by the DEITY for the probation of its in- habitants; and the appearance of new stars may be the for mation of new systems for new races of beings then called into existence to adore the works of their Creator.” Thus, we may conceive the Deity to have been employed from all eternity, and thus he may continue to be employed for endless ages; forming new sys. tems of beings to adore him; and transplanting beings already formed into hap- pier regions, who will continue to rise higher and higher in their enjoyments, and go on to contemplate system aſter system through the boundless universe. 1.A 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, produced by extraordinary causes, take place on their surface. This conjecture, continues he, is confirmed by their change of colour, 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 What memorable spot dogs Caph serve to mark out? Describe the phenomenon of the lost star. What does Mrs. Somery ille say of it? How long was it seen? Has any thing been discovercd of it since? How did this phenomenon affect the astronomers of the age? What does Vince say of the disappearance of some stars, and the new ap- pearance of others? Repeat the observations of Dr. Good upon the subject of new stars appearing and disappearing. MAP VI.] CEPHEUS. 41 wre not only perpetually creating, but also perpetually disappearing... It is, ºn extraordinary fact, that within the period of the last century, not less than thir- een stars, in different constellations, 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 be- ings, together with the different planets by which it is probable they were sur- rounded, have utterly vanished, and the spots which they occupied in the hea- vons, have become blanks : What has befallen other systems, will assuredly befall our own. Of the time and the manner we know nothing, but the fact is incontrovertible; it is foretold by revelation; it is inscribed in the heavens; it is felt through the earth. Such is the awſul and daily text; what then ought to be the comment? * * - The great and good Beza, falling in with the superstition of his age, attempted to prove that this was a comet, or the same luminous appearance which conduct- ed the magi, or wise men of the East, into Palestine, at the birth of our Saviour and that it now appeared to announce his second coming ! About 60 N. W. of Caph, the telescope reveals to us a grand nebula of small stars, apparently compressed into one mass, or single blaze of light, with a great number of loose stars surrounding it. History.—Cassiopeia was wife of Cepheus, king of HEthiopia, and mother of Am- dromeda. She was a queen of matchless beauty, and seemed to be sensible of it; ſor she even boasted herself fairer than Juno, the sister of Jupiter, or the Nerei- des—a mame given to the sea nymphs. This so provoked the ladies of the Sea that they complained to Neptune of the insult, who sent a frightful monster to ravage her coast, as a punishment for her insolence. But the anger of Neptune and the jealousy of the nymphs were not thus appeased. They demanded, and it was finally ordained that Cassiopeia should chain her daughter Andromeda, whom she tenderly loved, to a desert rock on the beach, and leave her exposed to the ſury of this monster. She was thus left, and the monster approached; but just as he was going to devour her, Perseus killed him. “The saviour youth the royal pair confess, And with heav'd hands, their daughter’s bridegroom bless.” Ewsden’s Ovid, CEPHEUS. CEPHEUs is represented on the map as a king, in his royal robe, with a sceptre in his left hand, and a crown of stars upon his head. He stands in a commanding posture, with his left foot over the pole, and his sceptre extended towards Cassio- peia, as if for favour and defence of the queen. º - -----—“Cepheus illumes The neighbouring heavens; still faithful to his queen, With thirty-five ſaint luminaries mark'd.” This constellation is about 25° N. W. of Cassiopeia, near the 2d coil of Draco, and is on the meridian at 8 o’clock the 3d, of November; but it will linger near it for many days. Like Cassiopeia, it may be seen at all hours of the night, when the sky is clear, for to us it never sets. By reference to the lines on the map, which all meet in the pole, it wife's. - dent that a star, near the pole, moves over a much less space in one hour, than There is a remarkable nebula in this constellation; describe its stuation and ap- pearance. How is Cepheus represented 7 What is hi SUll)" - - Stellation situated? p I t is his posture? Whº Ys s this con * 4% --> > 42 PICTURE OF THE HEAVENS. |Nov. one at the equinoctial; and generally, the nearer the pole, the narrower the space, and the slowder the motion, - The stars that are so near the pole may be better described by their polar distance, than by their declination. By polar distance, is meant—the distance from the pole; and is what the declination wants of 90°. 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 Alderamim, which with two others of the same brightness, 89 and 129 apart, form a slightly-curved line towards the N. E. The last, whose letter name is Gam- ma, is in the right knee, 199 N. of Caph, 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 from another, as given in this treatise, are strictly applicable only when the former one is on, or near the meridian. The bearings given, in many cases, are not the least approximations to what appears to be their relative position; and in some, if relied upon, will lead to errours. 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 199 due west of Caph ; and six months hence, will appear to be the same distance east of it. The reason is obvious; the circle which Cepheus appears to describe about the pole, 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, west of Cassiopeia. And for the same reason, when Cepheus is on the west side of the pole, it is between that and Cassiopeia, or east of it. Let it also be remembered, that in speaking of the poie, which we shall have frequent occasion to do, in the course of this work, the North Polar Star, or an imaginary point very near it, is always meant; and not as some will vaguely ap- prehend, a point in the 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.) There are also two smaller stars about 99 E. of Alderamin and Alphirk, with which they form a square; Alderamin being the upper, and Alphirk the lower one on the W. 89 apart. In the centre of this square there is a bright dot, or semi-visible star. The head of Cepheus is in the Milky-Way, and may be known by three stars of the 4th magnitude in the crown, which form a small acute triangle, about 90 to the right of Alderamin. The mean polar distance of the constellation is 259, while that of Alderamin is 289 10ſ. The right ascension of the former is 3389; consequently, it is 229 E. of the equi- noctial colure. . The student will understand that right ascension is reckoned on the equinoc- tial, from the first point of Aries, E., quite round to the same point again, which How many, and what are the principal stars in it? Describe the last star, In, the curve. Describe the middle one. What four stars form a square in this constellation? Where is the head of Cepheus, and how may it be known? What is the mean polar º of this constellation? How far, and which way is it from the equinoctiał CO!uro 2 **. MAP II.] ARIES, 43 is 360°. Now 338°, measured from the same point, will reach the same point again, within 22°; which is the difference between 360° and 338°. This rule will apply to any other case. HISTORY.—This constellation immortalizes the name of the king of Æthiopia. The name of his 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 ex- #. or to persons some way connected with it. Thus, he observes that as usaxus, one of the Argonauts, was the first Greek who made a celestial sphere, he would naturally delineate on it those figures which had some reference to the expedition. Accordingly, we have on our globes to this day, the Golden Ram, the ensign of the ship in which Phryxus fled to Colchis, the scene of the Argo- nautic achievements. We have also the Bull with brazen hooſs, tamed by Ja- son; the Twins, Castor and Pollux, two sailors, with their mother Leda, in the form of a Swan, and Argo, the ship itself; the watchful Dragon Hydra, with the Cup of Medea, and a raven upon its carcass, as an emblem of death; also Chi- rom, the Master of Jason, with his Altar, 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, reſer 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 the constellation of that name, as well as in Cassiopeia, Cepheus, An- dromeda and Cetus; that of Calisto and her son Arcas, in Ursa Major ; that of Icareus and his daughter Erigone, in Bootes and Virgo, Ursa Minor relates to one of the nurses of Jupiter; Auriga, to Erichthonius; Ophiuchus, to Phorbas; Sagittarius, to Crolus, the son of one of the Muses; Capricorn, to Pan, and Aquarius to Ganymede. We have also Ariadne's crown, Bellerophon's horse, Neptune's dolphin, Ganymede’s eagle, Jupiter's goat with her kids, the asses of Bacchus, the fishes of Venus and Cupid, with their parent, the southern fish. These, according to Deltoton, comprise the Grecian constellations mentioned by the poet Aratus; 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 disa- greement which appears in the mythological account of them, proves that their invention must have been of greater antiquity than that event, and that these constellations were received for some time among the Greeks, before their poets referred to them in describing the particulars of that memorable exhibition. C H. A P T E R II. DIRECTIONS FOR TRACING THE CONSTELLATIONS WHICH ARE ON THE MERIDIAN IN DECEMBER. ARIES. THE RAM.–Twenty-two centuries ago, as Hipparchus in- forms us, this constellation occupied the first sign in the ecliptic, commencing at the vernal equinox. But as the con- stellations gain about 50/1 on the equinox, at every revolution of the heavens, they have advanced in the ecliptic nearly 310 beyond it, or more than a whole sign: so that the Fishes now What was the position of Arles in the ecliptic, 22 centuries ago? 44 PICTURE OF THE HEAVENS. | DEC. occupy the same place in the Zodiac, that Aries did, in the time of Hipparchus; while the constellation Aries is now in the sign Taurus, Taurus in Gemini, and Gemini in Cancer, and so on. ARIES is therefore now the second constellation in the Zodiac. It is situated next east of Pisces, and is midway between the Triangles and the Fly on the N. and the head of Cetus on the S. It contains 66 stars, of which, one is of the 2d, one of the 3d, and two of the 4th magnitudes. “First, from the east, the Ram conducts the year; Whom Ptolemy with twice mine stars adorns, Of which two only claim the second rank; The rest, when Cynthia fills the sign, are lost.” It is readily distinguished by means of two bright stars in the head, about 40 apart, the brightest being the most north- easterly of the two. The first, which is of the 2d magnitude, situated in the right horn, is called Alpha Arietis, or simply Arietis; the other, which is of the 3d magnitude, lying near the left horn, is called Sheratan, and may be known by an- other star of the 4th magnitude, in the ear, 13° S. of it, called Mesarthim, which is the first star in this constellation. Arietis and Sheratan, are one instance out of many, where stars of more than ordinary brightness are seen together in pairs, as in the Twins, the Little Dog, &c., the brightest star being commonly on the east. The position of Arietis affords important facilities to nau- tical 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 meri- dian or harbour on the earth. . - Lying along the moon’s path, there are nine conspicuous stars that are used by nautical men for determining their lon- gitude at sea, thence called nautical stars. These stars are Arietis, Aldebaran, Polluar, Regulus, Spica Virginis, Antares, Altair, Fomalhaut, and Markab. The true places of these stars, for every day, in the year, are given in the Nau- tical Almanac, a valuable work published annually by the English “Board of Ad- miralty,” to guide mariners in navigating the seas. They are usually published two or three years in advance, for the benefit of long voyages. That a man, says Sir John Herschel, by merely measuring the moon’s appa- rent distance from a star, with a little portable instrument held in his hand, and What is its present position? How is it new situated with respect to the surround- ing constellations? What are the number and magnitude of its stars? How is this constellation readily distinguished? Describe the two bright stars in the head. For what purposes is the position of some of the stars in Arietis important? How many stars are used for determining longitude at sea, and where are they situated? By what general name are they called? Enumerate them MAP II.] ARIES. 45 applied to his eye, even with so unstable a footing as the deck of a ship, shall say positively within five miles, where he is, on a boundless ocean, cannot but appear to persons ignorant of physical astronomy, an approach to the miraculous. And }. says he, the alternatives of liſe and death, wealth and ruin, are daily and hourly staked, with perfect confidence, on these marvellous computations. Capt. Basil Hall, of the royal navy, relates that he had sailed from San Blas on the west coast of Mexico, and after a voyage of 8000 miles occupying eighty-nine days, arrived off Rio Janeiro, having in this interval passed through the Pacific ocean, rounded Cape Horn, and crossed the South Atlantic without making any land or seeing a single sail on the voyage. Arrived within a few days’ sail of Rio, he took a set of lunar observations, to ascertain his true position, and the bearing of the harbour, and shaped his course accordingly. “I hove to,” says he, “ at 4 in the morning, till the day should break, and then bore up ; for although it was hazy, we could see before us a couple of miles or so. About 8 o'clock it became so foggy that I did not like to stand in farther, and was just bringing the ship to the wind again before sending the people to breakfast, when it suddenly cleared off, and I had the satisfaction of seeing the great Sugar-loaf rock, which stands on one side of the harbour’s Inouth, so nearly right ahead that we had not to alter our course above a point in order to hit the entrance of Rio. This was the first land we had seen for three months, after crossing so }. seas, and being set backwards and forwards by immunerable currents and oul Winds.” Arietis comes to the meridian about 12 minutes after She- ratan, on the 5th December, near where the sun does in mid- summer. Arietis, also, is nearly on the same meridian with Almaach, in the foot of Andromeda, 190 N. of it, and culmi- nates only four minutes after it. The other stars in this con- stellation 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 Cassio- peia are a little past the meridian, n º over head, and Per- seus with the head of Medusa, is as far to the east of it. Taurus and Auriga are two or three hours lower down; Orion appears in the S. E. and the Whale on the meridian, just below Aries, while Pegasus and the Swan are seen half way over in the west. The manner in which the ancients divided the Zodiac into 12 equal parts, was both simple and ingenious. Having no instrument that would measure time exactly, “They took a vessel, with a small hole in the bottom, and having filled it with water, suffered the same to distil, drop by drop, into another vessel set beneath to receive it, beginning at the moment when some star rose, and con- tinuing till it rose the next following night, when it would have performed one complete revolution in the heavens. The water falling down into the receiver, they divided into 12 equal parts; and having twelve other small vessels in readi. ness, each of them capable of containing one part, they again poured all the wa- ter 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 #. and thus continued the process through the year, until the 12 vessels were Gd,” Thus the Zodiac was divided into 12 cqual portions, corresponding to the 12 When does Arietis pass the meridian? What other brilliant star is on the meridian nearly at the same time? When Aries is on the meridian, what other constellations are immédiately in view3. Describe the manner in which the ancients divided the 20&iac. At what point of the Zodiac did this division commence? 46 PICTURE OF THE HEAVENS. [DEC, months of the year, commencing at the vermal equinox. Each of these portions served as the visibie representative or sign of the month it appeared in. All those stars in the Zodiac which were observed to rise while the first vessel was filling, were constellated and included in the first sign, and called Aries, an animal held in great esteem by the shepherds of Chaldea. All those stars in the Zodiac which rose while the second vessel was filling, were constellated and included in the second sign, which ſor a similar reason, was denominated Tau- rus ; and all those stars which were observed to rise while the third vessel was filling, were constellated in the third sign, and called Gemini, in allusion to the twin season of the flocks. - - Thus each sign of 30° in the Zodiac, received a distinctive appellation, accord- ing to the fancy or superstition of the inventors; which names have ever since been retained, although the constellations themselves have since left their nom- inal signs more than 30° behind. The sign Aries, therefore, included all the stars embraced in the first 30° of the Zodiac, and no more. The sign Taurus, in like manner, included all those stars embraced in the next 30° of the Zodiac, or those between 30° and 60°, and so of the rest. Of those who imagine that the twelve constellations of the Zodiac reſer to the twelve tribes of Israel, some ascribe Aries to the tribe of Simeon, and others, to Gad. - HISTORY.—According to ſable, this is the ram which bore the golden fleece, and carried Phryxus and his sister Helle through the air, when they fled to Col. chis 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 ſell from his back into that part of the sea which was after- wards called Hellespont, in commemoration of the dreadful event. Phryxus arrived safe at Colchis, but was soon murdered by his own father-in-law, Hètes, who envied him his golden treasure. This gave rise to the celebrated Argo- . expedition under the command of Jason, for the recovery of the golden 116 CC e. 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 life, was aſterwards changed into a cloud, as a reward for her parental solicitude; and the Greeks ever after called the clouds by her name. But the most probable account of the origin of this constellation is given º al, ºding paragraph, where it is referred to the flocks of the Chaldean Shepnerſis. During the campaigns of the French army in Egypt, General Dessaix discov- ered among the ruins at Dendera, mear the banks of the Nile, the great temple, supposed by some to have been dedicated to Isis, the ſelmale deity of the Egyp- tians, who believed that the rising of the Nile was occasioned by the tears which #: ºnally shed for the loss of her brother Osiris, who was murdered by Typhon. Others suppose this edifice was erected for astronomical purposes, from the circumstance that two Zodiacs were discovered, drawn upon the ceiling, on op- posite sides. On both these Zodiacs the equinoctial points are in Leo, and not in Aries; from which it has been concluded, by those who pertinaciously en- deavour to array the arguments of science against the chronology of the Bible and the validity of the Mosaic account, that these Zodiacs were constructed when the sun entered the sign Leo, which must have been 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 what- ever is true in fact and correct in inference on this subject will be found, in the end, not only consistent with the Mosaic record, but with the common meaning of the expressions it uses. The discovery of Champollion has put this question ſor ever at rest; and M. Latronne, a most learned antiquary, has very satisfactorily demonstrated that these Egyptian Zodiacs are merely the horoscopes of distinguished personages, or the précise situation of the heavenly bodies in the Zodiac at their nativity. The idea that such was their purpose and origin, first suggested itself to this gentleman on finding, in the box of a mummy, a similar Zodiac, with such What did each of these portions of the Zodiac serve? What stars were placed in the Jirst sign. 2 What name was given to the constellation thus formed? What Stars were placed in the second sign 2 What was the second constellation called 2 What stars were placed in the third sign, and what was it called 2 Are the same names still retained 2 What does this precession, or going forward of the stars amount to in a year? MAP II.j CETUS. 47 inscriptions and characters as determined it to be the horoscope of the deceased person. - - Of all the discoveries of the antiquary among the relics of ancient Greece, the ruins of Palmyra, the gigantic pyramids of Egypt, the temples of their gods, or the sepulchres of their kings, scarcely one so aroused and riveted the curiosity of the learned, as did the discovery of Champollion the younger, which deciphers the hieroglyphics of ancient Egypt. * The potency of this invaluable discovery has already been signally manifested in settling a formidable controversy between the champions of infidelity and those who maintain the Bible account of the creation. It has been shown that the constellation Pisces, since the days of Hipparchus, has come, by reason of the annual precession, to occupy 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 appa- rent 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 revo- lution of the heavens since the creation; so that were the world to light upon any authentic inscription or record of past ages, which should give the true position or longitude of any particular star at that time, it would be easy to fix an unques- tionable date to such a record. Accordingly, when the famous “Egyptian Zo- diacs,” which were sculptured on the walls of the temple at Dendera, were brought away en m&sse, and exhibited in the Louvre at Paris, they enkindled a more exciting interest in the thousands who saw them, than ever did the en- trance of Napoleon. “Educated men of every order, and those who had the vanity to think themselves such,” says the cominentator of Champollion, “rush- ed to behold the Zodiacs. These Zodiacs were immediately published and corn- mented upon, with more or less good faith and decoruin. Science struck out into systems very bold; and the spirit of infidelity, seizing upon the discovery, flattered itself with the hope of drawing from thence new support. It was unjus- tifiably taken for granted, that the ruins of Egypt furnished astronomy with mon- uments, containing observations that exhibited the state of the heavens in the most remote periods. Starting with this assumption, a pretence was made of demonstrating, by means of calculations received as infallible, that the celestial appearances assigned to these monuments extended back from forty-five to six- ty-five centuries; that the Zodiacal system to which they must belong, dated back fifteen thousand years, and must reach far beyond the limits assigned by - Moses to the existence of the world.” Among those who stood forth more or less bold as the adversaries of revelation, the most prominent was M. Dupuis, the famous author of L' origine de tous les Cultes. The infidelity of Dupuis was spread about by means of pamphlets, and the ad- vocates of the Mosaic account were scandalized “until a new Alexander arose to cut the Gordian knot, which men had vainly sought to untie. This was Cham- pollion the younger, armed with his discovery,” The hieroglyphics now speak a language that all can understand, and no one gainsay. “The Egyptian Zodiacs, then,” says Latronme, “relate in no respect to astronomy, but to the idle phan. tasies of judicial astrology, as connected with the destinies of the emperors who made or completed them.” CETUS, THE WHALE.—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 500 in length, E. and W., with a mean breadth of 209 from N. to S. It is situated below Aries and the Triangles, with a mean declination of 12° S. It is represented as making its way to the E., with its body below, and its head elevated above the equinoctial: and is six weeks in passing the meridian. Its What is the comparative size of the Whale? What is its extent? Where is it situ- atcd? How long is the Whale in passing the meridian? 48 PICTURE OF THE HEAVENS. [DEC. tail comes to the meridian on the 10th of November, and its head leaves it on the 22d of December. This constellation contains 97 stars; two of the 2d mag- nitude, seven of the 3d, and thirteen of the 4th. The head of Cetus may be readily distinguished, about 20° S. E. of Aries, by means of five remarkable stars, 49 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 349 N. of the equinoctial, and 150 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 with 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, 30 W. of it, called Gamma, placed in the south middle angle of the pentagon. - Nu is a star of the 4th magnitude, 4° N. W. of Gamma, and these two constitute the S. W. side of the pentagon in the head of the Whale, and the N. E. side of a similar oblong figure in the neck. Three degrees S. S. W. of Gamma, is another star of the 3d magnitude in the lower jaw, marked Delta, constituting the E. side of the oblong pentagon; and 60 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 mag- nitude so as to become invisible once in 334 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 determined. The whole number of stars ascertained to be variable, amounts to only 15; while those which are suspected to be variable, amount to 37, Mira is 70 S. S. E. of El Rischa, in the bend or knot of the riband which connects the Two Fishes. Ten degrees S. of Mira, are 4 small stars, in the breast and paws, about 39 apart, which form a square, the brightest being on the E. Ten de- When does it approach, and when does it leave the meridian? What is the whole number of stars in Cetus? What is the magnitude of the principal ones? How may the head of Cetus be distinguished What are the name and position of the brightest? How far is it from the equinoctial, and the principal star in the Fishes? What is its direction from Algol and the Fly . With what stars does it form an equi- lateral triangle? How may it otherwise be known? Describe the position of Nu. Describe the situation of Delta and Mira. When and by whom was this star discover- ed to be variable? What are the extent and period of this variation? How long does Herschel make it? What does Hevelius say of it? Has the true perio of Mira been satisfactorily determined? How far, and which way is Mira from Alpha, in the knot of the riband? What tour small stars do you observe 10° S. of Mira 3 MAP II.] PERSEUs, ET CAPUT MEDUSE. 49 grees 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, an equilateral triangle with Mira and the eastern- most one in the square. A great number of geometrical figures may be formed from the stars in this, and in most of the other constellations, merely by reference to the maps; but it is better that the student should exercise his own ingenuity in this way with reference to the stars themselves, ſor 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 their own observations upon the relative position, magnitude and figures of the principal stars 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 be 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. or shorter side of an irregular square, with El Rischa in the mode of the riband, and another star 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; ſrom which, to the middle star is 10°, thence to the W. one 12%; and S9 or 9° S. of this line, in a triangular direction, is a bright star of the second magnitude in the coil of the tail, called Diphola. In a southerly direction, 25° below Diphoia, is Alpha in the head of the Phe- nix, and about the same distance S. W. is Fomalhaut, in the mouth of the Southern Fish, forming together a large triangle, with Diphola in the vertex or top of it. - That fine cluster of small stars S. of the little square in the Whale, constitutes a part of a new constellation called the Chymical Furmace. The two stars N. E. and the three to the southward of the little square, are in the river Eridanus. HISTORY..—This constellation is of very early antiquity; though most writers consider it the ſamous sea monster sent by Neptune to devour Andromeda be- cause her mother Cassiopeia had boasted herself fairer than Juno or the Sea Nymphs; but slain by Perseus and placed among the stars in honour of his achievement. - “The winged hero now descends, now soars, And at his pleasure the vast monster gores. Deep in his back, swiſt 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 Arios, which is right over the head of Cetus, opened the year, it was denominated the Preserver of Deliverer, by the idolaters of the East. On this account, according to Pausa. nias, the Sun Was Worshipped, at Eleusis, under the name of the Preserver or Saviour A “With gills pulmonic breathes the enormous whale, And spouts aquatic columns to the gale; Sports on the shining wave at noonſide hours, And shifting rainbows crest the rising showers.”—Darwin, PERSEUS, ET CAPUT MEDUSAE. PERSEUs is represented with a sword in his right hand, the head of Medusa in his left, and wings at his feet. It is situ- How is Baten Kaitos situated? What is sqīd of the various figures that different ºstellºgg's eghibit?. Give an eºgºmple. Qfxphât constellation does that fine º: Qf stars of the little Square in the Whale, constitute a part? How is the consteitation Perseus represented? 6 50 PICTURE OF THE HEAVENS. [DRC, ated directly N. of the Pleiades and the Fly, between Andro- meda on the W. and Auriga on the E. Its mean declination is 49° 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 stars. g --------- “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 Sirty-seven ; and two of these he boasts, Nobly reſulgent in the second rank— One in his vest, one in Medusa's head.” THE HEAD OF MEDUSA is not a separate constellation, but forms a part of Perseus. * It is represented as the trunkless head of a frightful Gor- gon, 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 Me- dusa ; three of the 4th magnitude, and one, varying alter- nately from the 2d to the 4th magnitude. This remarkable star is called Algol. It is situated 120 E. of Almaach, 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 (Eng.) to be 2 days, 20 hours, 48 minutes, and 56 seconds. Dr. Herschel attributes the variable appearance of Algol to spots upon its surface, and thinks it has a motion on its axis similar to that of the sun. He also observes, of variable stars generally:—“The rotary motion of stars upon their axes is a capital feature in their resemblance to the sun. It appears to me now, that we cannot refuse to admit such a motion, and that indeed it may be as evidently proved as the diurnal mo- Where is it situated? What is its declination, and when is it on the meridian? What is the whole number of its stars? What is the magnitude of its principal ones?... Of what constellation does Caput Medusae form a par’? How is it represented? What is the whole number of its stars? What is the magnitude of thc principal Ones? What are the name and position of the variable star in this constellation? When is it on the meridian, and how long may it be seen 3 In what time does it vary from the 2d to the 4th magnitude, and back again? How long ls, it steadily brilliant? When and by whom was its periodical variation determined? What is its exact period? To what does Dr, Herschel attribute its variable appearance? MAP III.] PERSEUs, ET CAPUT MEDUSAE. 51 tion of the earth. Dark spots, or large portions of the surface, less luminous than the rest, turned alternately in certain di rections either towards, or from us, will account for all the phenomena of periodical 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 Lalande, who died at Paris in 1807, was wont to reimain whole nights, in his old age, upon the Pont Newf, to exhibit to the curious the variations in the brilliancy of the star Algol. - Nine degrees E. by N. from Algol, is the bright star Alge- mib, of the 2d magnitude, in the side of Perseus, which with Almaack, makes a perfect right angle at Algol, with the open part towards Cassiopeia. By means of this strikingly perfect figure, the three stars last mentioned may always be recog- nised 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 to- wards Ursa Major. - Algenib comes to the meridian on the 21st December, 15 minutes after Algol, at which time the latter is almost di- rectly over head. When these two stars are on the meridian, that beautiful cluster, the Pleiades, is about half an hour E. of 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.” The Milky-Way around Perseus is very vivid, being un- doubtedly a rich stratum of fixed stars, presenting the most wonderful and sublime phenomenon of the Creator's power and greatness. Kohler, the astronomer, observed a beautiful nebula near the face of Perseus, besides eight other nebulous clusters in different parts of the constellation. - The head and Sword of Perseus are exhibited on the circumpolar map. That very bright star 23° 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 hu- manity, and intrusted them to the care of the priests of Minerva’s Temple. His rising genius and manly courage soon made him a favourite of the gods. At a . How may Algemib be distinguished? When is it on the meridian? How long after Algol? When these two stars are on the meridian, what beautiful cluster is half an hour east of it? What is the general appearance of the eastern hemisphere at that time? What is the appearance of the Milky Way around Perseus? What nebulae have been Observed in this constellatºun * 52 PICTURE OF THE HEAVENS. [JAN, great feast of Polydectes, all the mobles were expected to present the king with a superb and beautiful horse; but Perseus, who owed his benefactor Inuch, 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 mor- tality. The names of the other two were Stheno and Euriale. They were ra- presented with serpents wreathing round their heads instead of hair, having yellow wings and brazen hands; their bodies which grew indissolubly together, were covered with impenetrable scales, and their very looks had the power of turning into stones all those on whöm they fixed their eyes. To equip Perseus for this perilous enterprise, Pluto, the god of the infernal regions, lent him his helmet, which had the power of rendering the wearer in- visible. Minerva the goddess of wisdom, furnished him with her buckler, which ... was as resplendent as a polished mirror; and he received from Mercury, wings for his feet, and a dagger Imade of diamonds. Thus equipped, he mounted into the air, conducted by Minerva, and came upon the monsters who, with the watchful snakes about their heads, were all asleep. He approached them, and with a courage which amazed and delighted Minerva, cut off with one blow Me- dusa's head. The noise awoke the two immortal sisters, but Pluto’s helmet rem- dered Perseus invisible, and the vengeful pursuit of the Gorgons proved fruitless. “In the mirror of his polished shield Iłeflected, saw Medusa slumbers take, And not one serpent by good chance awake; Then backward an unerring blow he sped, And from her body lopped at once her head.” Perseus then made his way through the air, with Medusa's head yet reeking in his hand, and from the blood which dropped from it as he flew, sprang all those innumerablo serpents that have ever since infested the sandy deserts of Lybia. The victor Perseus, with the Gorgon head, O'er Lybian sands his airy journey sped, The gory drops distilled, as swift he flew, And from each drop envenomed serpents grew.” The destruction of Medusa rendered the name of Perseus immortal, and he was changed into a constellation at his death, and placed among the Stars, with the head of Medusa by his side. CHAPTER III. DIRECTIONS FOR TRACING THE CONSTELLATIONS WHICH ARE ON THE MERIDIAN IN JANUARY. The constellations which pass our meridian in the months of January, Febru- ary and March, present to us the most brilliant and interesting portion of the heavens; embracing an annual number of stars of the highest order and bright- ness, all so conspicuously situated, that the most inexperienced can easily trace them out. TAURUS. THE BULL is represented in an attitude of rage, as if about to plunge at Orion, who seems to invite the onset by provo cations of assault and defiance. Only the head and shoulders of the animal are to be seen; but these are so distinctly TWhat 3S the comparative brilliancy of the constellations which pass the meridian in January, February and March & How is Taurus represented? What parts of the animal are to be Seen? - MAP. III.] TAU18 US$. 53 marked that they cannot be mistaken. Taurus is now the second sign and third constellation of the Zodiac; but ante- rior 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 sum about the last of May, when the opposite constellation. the Scorpion is seen to rise in the S. E. It is situated between Perseus and Auriga on the north, Gemini on the east, Orion and Eridanus on the south, and Aries on the west, having a mean declimation of 16° N. It contains 141 visible stars, including two remarkable clusters called the PLEIADEs and HyADEs. The first is now on the shoulder, and the latter in the face of the Bull. The Pleiades, according to fable, were the seven daughters sof Atlas and the nymph Pleione,” who were turned into stars, with their sisters the Hyades, on account of their amiable virtues and mutual affection. Thus we every where find that the ancients, with all their barbarism and idolatry, entertained the belief that unfºblemished virtue and a mueritorious life would meet their reward in the sky. Thus Virgil represents Magnus Apollo as bending from the sky to address the youth Iulus:— - - “Macte nova virtute puer; sic ifur ad astra; 2 T}iis genite, et geniture Deos.” “Go on, spotless boy, in the paths of virtue; it is the way to the stars; offspring of the gods thyselſ—so shalt thou become the father of gods.” Our disgust at their superstitions may be in some measure mitigated, by seri- ously reflecting, that had some of these personages lived in our day, they had been ornaments in the Christian church, and Inodels of social virtue. The names of the Pleiades are Alcione, Merone, Maia, Electra, Tayeta, Sterope and Celeno. Merope was the only one who married a mortal, and on that account her star is dim among her sisters. - Although but six of these are visible to the naked eye, yet Dr. Hook informs us that, with a twelve feet telescope, he saw 78 stars; and Rheita affirms that he counted 200 stars in this small cluster. The most ancient authors, such as Homer, Attalus, and Geminus, counted only siz Pleiades; but Simonides, Varro, Pliny, Aratus, Hipparchus, and Ptolemy, reckon them seven in number; and it was asserted, that the seventh had been seen before the burning of Troy ; but this difference might arise from the dif. ſerence in distinguishing them with the naked eye. * Dr. Hutton is of opinion that Atlas being the first astronomer who disco- vered these stars, called them by the names of the daughters of his wife Pleiome. What is the numerical order of Taurus among the signs and constellations of the Zodiac 3 What was its position in the Zodiac before the time of Abraham! How long did it continue to lead the celestial host? What constellation succeeded next? Where is Taurus now situated? How many stars does it contain? What remarkable clusters are in this constellation? Where are these placed? Mention the names of the Pleiades. Which of these seven stars is not seen, and why? Are these six all that can be seen through the telescope? 5* • 54 PICTURE OF THE HEAVENS, [JAN The Pleiades are so called from the Greek word, TAgew, pleein, to sail; because, at this season of the year, they were considered “the star of the ocean” to the benighted mariner.” Alcyone, of the 3d magnitude, being the brightest star in this cluster, is sometimes called the light of the Ple- iades. The other five are principally of the 4th and 5th magnitudes. The Pleiades, or as they are more familiarly termed, the seven stars, come to the meridian 10 minutes before 9 o'clock, on the evening of the 1st of January, and may serve, in place of the sun, to indicate the time, and as a guide to the sur- rounding stars. According to Hesiod, who wrote about 900 years before the birth of our Saº viour, the heliacal rising of the Pleiades took place on the 11th of May, about the time of harvest. “When, Atlas-born, the Pleiad stars arise Defore the sun above the dawning skies, 'Tis time to reap; and when they sink below The morn-illumin’d west, 'tis time to sow.” Thus, in all ages, have the stars been observed by the husbandman, ſor “signs and ſor seasons.” Pliny says that Thales, the Miletan astronomer, determined the cosmical setting- of the Pleiades to be 25 days after the autumnal equinox. This would make a diſference between the setting at that time and the present, of 35 days, and as a day answers to about 59% of the ecliptic, these days will make 34° 25'. This di- vided by the annual precision (50}^^), will give 2465 years since the time of Thales. Thus does astronomy become the parent of chronology. Iſ it be borne in mind that the stars uniformly rise, come to the meridian, and set about ſour minutes earlier every succeeding might, it will be very easy to determine at what time the seven stars pass the meridian on any might subse- quent or antecedent to the 1st of January. For example: at what time will the * Virgil, who flourished 1200 years before the invention of the magnetic needle, says that the stars were relied upon, in the first ages of nautical enterprise, to guide the rude bark Over the Seas. “Tung almos primum fluvii sensere cavatas; Navita tum stellis numeros, et nomina fecit, Pleiadas, Hyadas, claramgue Lycaonis Arcton.” “Then first on seas the shallow alder swam ; Then Sailors quarter'd heaven, and found a name For overy fix’d and every wand'ring star— The Pleiads, Hyads, and the Northcrn Car.” The Same º: also describes Palinurus, the renowned pilot of the Trojan fleet, as “watching the face of the nocturnal heavens.” “Stüera cumcta notat tacito labentia cqelo, Arcturum, pluviasque Hyadas, gemimosque Triomes, ** Armatumque auro circumSp1cit Oriona.” “Observe the stars, and notes their sliding COurSe, The Pleiads, Hyads, and their wat'ry force ; And both the Bears is careful to behold And bright Orion, arm'd witn ournish’d gold.” Indeed, this sagacious pilot was once so intent in gazing upon the stars while at the helm, that he fell overboard, and was lost to his companions. “Headlong he fell, and, struggling in the main, Cried out for helping hands, but cried in vain.” - From what circumstance do the Pleiades derive their name? What is the brightest of the Pleiades called? What is the size of the rest? When are the Pleiades. On the meridiam? How much carlier do the stars rise, come to the meridiart, and 86t, every succeeding night? MAP III.] TAURUS. 55 seven stars culminate on the 5th January 3 Multiply the 5 days by 4 and take the result from the time they culminate on the 1st, and it will give 30 minutes aſter 8 o’clock in the evening, The Pleiades are also sometimes called Vergilia, or the “Virgins of spring;” because the sun enters this cluster in the “season of blossoms,” about the 18th of May. He who made them alludes to this circumstance when he demands of Job: “Canst thou bind the sweet influences of the Ple- iades,” &c.—[Job 38: 31.] The Syrian name of the Pleiades is Succoth, or Succoth-Benoth, derived from . a Chaldaic word, which signifies “to speculate, to observe,” and the “Men of Succoth,” (2 Kings 17: 30.) have been thence considered observers of the StarS. The Hyades are situated 11° S. E. of the Pleiades, in the face of the Bull, and may be readily distinguished by means of five stars” so placed as to form the letter V. The most irilliant star is on the left, in the top of the letter, and called Aldebaram ; from which the moon’s distance is computed. “A star of the first magnitude illumies His radiant head; and of the second rank. Another beams not far remote.” Aldebaran is of Arabic origin, and takes its name from two words which signify, “He went before, or led the way”— alluding to that period in the history of astronomy when this star led up the starry host from the vernal equinox. It comes to the meridian at 9 o'clock on the 10th of January, or 48% minutes after Alcyone, on the 1st. When Aries is about 270 high, Aldebaran is just rising in the east. So MANILIUs:— “Thus when the Ram hath doubled ten degrees, And join’d seven more, then rise the Hyades.” A line 1539 E. N. E. of Aldebaran will point out a bright star of the 2d magnitude in the extremity of the northern horn, marked Beta or El Nath ; (this star is also in the foot of Auriga, and is common to both constellations.) From Beta in the northern horm, to Zeta, in the tip of the southern horn, it is 89, in a southerly direction. This star forms a right angle with Aldebaram and Beta. Beta and Zeta, then, in the button of the horns, are in a line nearly north and south, 89 apart, with the brightest on the north. That very bright star 173° N. of Beta, is Capella, in the constellation Auriga. * The ancient Greeks counted seven in this cluster:— “The Bull's head shines with seven reſulgent flames, Which, Grecia, Hyads, from their showering, names.” At what time will the seven stars culminate on the 5th January 2 By what other names are they sometimes called, and why? What allusion is made to this cluster in the ancient Scriptures? Describe the situation and appearance of the Hyades, What is the brightest of them called 3 What is the origin of the word Aldebaran, and to what does it allude? When does Aldebaran culminate? Describe the position of Seta? What are the name and direction of the star in the southern horn? What is the Yelative position of these stars? What very bright star is seen 179 30′ N, of Beta? 56 PICTURE OF THE HEAVENS. [JAN. HISTORY..—According to the Grecian mythology, this is the animal which bore Europa over the seas to that country, which derived from her its name. She was the daughter of Agenor, and princess of Phoenicia. She was so beautiful that º became enamoured of her; and assuming the shape of a snow-white bull, he mingled with the herds of Agenor, while Europa, with her female at- tendants, were gathering flowers in the meadows. Europa caressed the beau. tiful animal, and at last had the courage to sit upon his back. The god now took advantage of her situation, and with precipitate steps retired towards the shore, and crossed the sea with Europa upon his back, and arrived safe in Crete. Some suppose she lived about 1552 years before the Christian era. It is probaole, however, that this constellation had a place in the Zodiac before the Greeks be- gan to cultivate a knowledge of the stars; and that it was rather an invention of the Egyptians or Chaldeans. Both the Egyptians and Persians worshipped a deity under this figure, by the name of Apis ; and Belzoni is said to have found an embalmed bull in one of the notable sepulchres near Thebes. In the Hebrew Zodiac, Taurus is ascribed to Joseph. O}RION. Whoever looks up to this constellation and learns its name, will never forget it. It is too beautifully splendid to need a description. When it is on the meridian, there is then above the horizon the most magnificent view of the celestial bodies that the starry firmament affords; and it is visible to all the habitable world, because the equinoctial passes through the middle of the constellation. It is represented on celestial maps by the figure of a man in the attitude of assaulting the Bull, with a sword in his belt, a huge club in his right hand, and the skin of a lion in his left, to serve for a shield. Manilius, a Latin poet, who composed five books on as- tronomy a short time before the birth of our Saviour thus describes its appearance:— “First,next the Twins, see great Orion rise, His arms extended stretch o'er half the skies His siride as large, and with a steady pace He marches om, and measures a vast space; On each broad shoulder a bright star display’d, And three obliquely grace his hanging blade. In his vast head, immers’d in boundless spheres, Three stars, less bright, but yet as great, he bears, But farther off removed, their splendour's lost; Thus grac'd and arm’d he leads the starry host.” The centre of the constellation is midway between the poles of the heavens and directly over the equator. It is also about 80 W. of the solstitial coluze, and comes to the me- ridian about the 23d of January. The whole number of visible stars in this constellation is 78; of which, two are of the first magnitude, four of the 2d, three of the 3d, and fif- teen of the 4th. - Those four brilliant stars in the form of a long square or What is the general appearance of the constellation Orion? When this constellation is on the meridian, what is the appearance of the starry firmament? To whom is it visible, and why? How is Orion º; on celestial maps? Describe its position. How is it situated with respect to the solstitial colure, and when is it on the meridian? What remarkable Stars form the outline of the Constellation? MAP III.] ORION, 57 parallelogram, intersected in the middle by the “Three Stars,” or “Ell and Yard,” about 25° S. of the Bull's horns, form the outlines of Orion. The two upper stars in the par- allelogram are about 15° N. of the two lower ones; and, peing placed on each shoulder, may be called the epaulets of Orion. The brightest of the two lower ones is in the left foot, on the W., and the other, which is the least brilliant of the four, in the right knee. To be more particular : Bella- trix is a star of the 2d magnitude on the W. shoulder; Be- telguese is a star of the 1st magnitude, 73° E. of Bellatrix, on the E. shoulder.}{It is brighter than Bellatrix, and lies a little farther towards the north ; and comes to the meridian 30 minutes after it, on the 21st of January. These two form the upper end of the parallelogram. Rigel is a splendid star of the 1st magnitude, in the left foot, on the W. and 15° S. of Bellatrix. Saiph, is a star of the 3d magnitude, in the right knee, 83° E. of Rigel. These two form the lower end of the parallelogram. —“First in rank The martial star upon his shoulder flames: A rival star illuminates his foot; And on his girdle beams a luminary Which, in vicinity of other stars, . Might claim the proudest honours.” *There is a little triangle of three small stars in the head of Orion, which forms a larger triangle with the two in his shoulders. In the middle of the parallelogram are three stars of the 2d magnitude, in the belt of Orion, that form a straight line about 30 in length from N. W. to S. E. They are usu- ally distinguished by the name of the Three Stars, because there are no other stars in the heavens that exactly resemble them in position and brightness. They are sometimes de- nominated the Three Kings, because they point out the Hyades and Pleiades on one side, and Sirius, or the Dog-star on the other. In Job they are called the Bands of Orion ; while the ancient husbandmen called them Jacob’s rod, and sometimes the Rake. The University of Leipsic, in 1807, gave them the name of Napoleon. But the more common appellation for them, including those in the sword, is the Ell and Yard. They derive the latter name from the circum- stance that the line which unites the “three stars” in the belt measures just 39 in length, and is divided by the central star Describe the two upper ones in the group. Describe the two lower ones. Give a Thore particular description of the stars in the shoulder. How do you distinguish Be- telguese from Bellatrix? When does betelguese come to the meridian? Describe the Stars Which form the lower end of the parallelogram. What stars do you observe in the head of Orion? Describe the situation and appearance of the “Three Stars?” Why are they called the three stars? What else are they denominated, and way 2 What mames were given to them by the ameients? What by the University of Leipsic? What is the more familiar term for them. and whence is it derived? 58 PICTURE OF THE HEAVENS. LJAN, into two equal parts, like a yard-stick; thus serving as a graduated standard for measuring the distances of stars from each other. When therefore any star is described as being so many degrees from another, in order to determine the dis- tance, it is recommended to apply this rule, It is necessary that the scholar should task his ingenuity only a few evenings ºn applying such a standard to the stars, before he will learn to #. of their relative distances with an accuracy that will seldom vary a degree from the truth. The northernmost star in the belt, called Mintika, is less than 30 S. of the equinoctial, and when on the meridian, is almost exactly over the equator. It is on the meridian, the 24th of January.* : The “three stars” are situated about 80 W. of the solstitial colure, and uniformly pass the meridian one hour and fifty minutes after the seven stars. There is a row of stars of the 4th and 5th magnitudes, S. of the belt, running down obliquely towards Saiph, which forms the sword. This row is also called the Ell because it is once and a quarter the length of the Yard or belt. A very little way below Thabit, in the sword, there is a ne- bulous appearance, the most remarkable one in the heavens. With a good telescope an apparent opening is discovered, through which, as through a window, we seem to get a glimpse of other heavens, and brighter regions beyond. As the telescope extends our knowledge of the stars and greatly increases their visible number, we behold hundreds and thousands, which, but for this almost divine improvement of our vision, had forever reulained, unseen by us, in an unfathomable void. tº $ tº A star in Orion's sword, which appears single to the unassisted vision, is mul- tiplied into six by the telescope; and another, into twelve. , Galileo found 80 in the belt, 21 in a nebulous star in the head, and about 500 in another part of Orion, within the compass of one or two degrees. Dr. Hook saw 78 stars in the Pleiades, and Rheita with a better telescope, saw about 200 in the same cluster, and more than 2000 in Orion. About 9° W. of Bellatrix are eight stars, chiefly of the 4th magnitude, in a curved line running N. and S. with the con- cavity towards Orion; these point out the skin of the lion in his left hand. Of Orion, on the whole, we may remark with Eudosia — “IHe who admires not, to the stars is blind.” History.—According to some authorities, Orion was the son of Neptune and queen Euryale, a famous Amazonian huntress, and possessing the disposition of * Though the position of this star, with respect to the equator, is the same at all imes, whether it be on the mieridian or in the horizon; yet it appears to occupy this, position, only when it is on the pieridian. * How may the distances of the stars from each other be measured by reference to the yard? How are the three stars situated with respect to the solstitial colure, and how with respect to the seven stars? Describe the stars which form the Sword of Qrion. What else is this row called? Describe the nebulous appearange which is visible in this cluster. What other discoveries has the telescopé made in this constellation ? What stars about 9° W. of Bellatrix? MAP III.] ORION. 59 his mother, he became the greatest hunter in the world, and even boasted that there was not an animal on earth which he could not conquer. To punish this yanity, it is said that a scorpion sprung up out of the earth and bit his foot, that he died; and that at the request of Diana he was placed among the stars directly opposite to the Scorpion that caused his death. " Others say that Orion had no mother, but was the giſt of the gods, Jupiter, Neptune, and Mercury, to a peasant of Boeotia, as a reward of piety, and that he was invested with the power of walk- ing over the sea without wetting his feet. In strength and stature he surpassed all other mortals. He was skilled in the working of iron, from which he ſabri- cated a subterranean palace for Vulcan; he also walled in the coasts of Sicily against the inundations of the sea, and built thereon a temple to its gods. . Orion was betrothed to the daughter of QEnopion, but he, unwilling to give up his daughter, contrived to intoxicate the illustrious hºro and put out his eyes on the seashore where he had laid himself down to sleep. Orion, finding liimself blind when he awoke, was conducted by the sound to a neighbouring forge, where he placed one of the workmen on his back, and, by his directions, went to a place where the rising sun was seen with the greatest advantage. Here he turned his face towards the luminary, and, as it is reported, immediately recov- ered his sight, and hastened to punish the perfidious cruelty of CEnopion. 'The daughters of Orion distinguished themselves as much as their father; and, when the oracle had declared that Baeotia should not be delivered from a idreadful pestilence, before two of Jupiter's children were immolated on the altars, they joyfully accepted the offer, and voluntarily sacrificed themselves ſor the good of their country. The deities of the infernal regions were struck at the patriotism of the two females, and immediately two stars were seen to ascend up from the earth, still smoking with their blood, and they were placed in the heavens in the form of a crown. Ovid says their bodies were burned by the Thebans, and that two persons arose from their ashes, whom the gods soon after changed into constellations. As the constellation Orion, which rises at noon about the 9th day of March, and sets at noon about the 21st of June, is generally supposed to be accompani- ed, at its rising, with great rains and storians, it became extremely terrible to mariners, in the early adventures of navigation. Virgil, Ovid, and iſorace, with Some of the Greek poets, make mention of this. Thus Eneas accounts for the storm which cast him on the Aſrican coast on his way to Italy:— “To that blest shore we steer'd our destincó way, When sudden, dire Orion rous’d the sca: All charg’d with tempests rose the baleful star, And on our navy pour’d his wat'ry war.” To induce him to delay his departure, Dido's sister advises her to *Tell him, that, charg’d with deluges of rain, Orion rages on the wintry main.” - , The name of this constellation is mentioned in the books of Job and Amos, and in Homer. . The inspired prophet, penetrated like the psalmist of Israel, with the omniscience and power displayed in the celestial glories, utters this sublime injunction: “Seek Him that maketh the seven stars and Orion, and turmeth the shadow of death into morning.” Job also, with profound veneration, adores His awful majesty who “commandeth the sum and sealeth up the stars; who alone ; out, the heavens, and maketh Arcturus, Orion, and Pleiades, and the §hambers of the south :" And in another place, the Almighty demands of him. “Knowest thou the ordinances of heaven? Canst thou bind the sweet influen- ges of the Pleiades, or loose the bands of Orion; canst thou bring forth Mazza. roth in his season, or canst thou guide Arcturus with his sons?” Calmet supposes that Mazzaroth is here put for the whole order of celestial bodies in the Zodiac, which, by their appointed revolutions, produce the various Seasons of the year, and the regular succession of day and night. Arcturus is the name of the principal star in Bootes, and is here put for the constellation itself. The expression, his sons, doubtless refers to Asterion and Chara, the §. $ºnº with which he seems to be pursuing the great bear around the - - €, , The ſollowing limes are copied from a work entitled “Astronomical Recrea. tions.” by J. Green, of Pennsylvania, to whom the authoris indebted for many valuable hints concerning the mythology of the ancient constellations. 60 PIC'TURE OF THE HEAVENS, |JAN, “When chilling winter spreads his azure skies, Behold Orion’s giant form arise ; His golden girdle glitters on the sight, And the broad falchion beams in splendour bright; A lion’s brindled hide his bosom shields, And his right hand a ponderous weapon wields. The River’s shining streams beneath him pour, And angry Taurus rages close beſore; Behind him Procyon barks, and Sirius growls, While ſull in front, the monster Cetus howls. See bright Capella, and Medusa there, With horrid serpents hissing through her hair, See Cancer too, and near the Hydra dire, With roaring Leo, filled with ſurious fire. The timid Hare, the Dove with olive green, And Aries, fly in terrour from the scene ; The warrior Perseus gazes from above, And the Twin offspring of the thunderér Jove. Lo! in the distance, Cassiope fair In state reposes on her golden chair; Her beauteous daughter, bound, before ner stands, And vainly strives to free her fettered hands; For aid she calls on royal Cephews near, But shrieks from her reach not her father's ear. See last of all, around the glowing pole, With shiming scales, the spiry Dragon roll A grizzly J3ear on either side appears, Creeping with lazy motion 'mid the stars ” .. These lines are easily committed to memory, and would assist the pupil in re- 3alling the names of the constellations in this very interesting portion of the ilea,VellS. LEPUS, THE HARE,--This constellation is situated directly south of Orion, and comes to the meridian at the same time; namely on the 24th of January. It has a mean declimation 18° S. and contains 19 small stars, of which, the four princi- pal ones are of the 3d magnitude. It may be readily distin- guished by means of four stars of the 3d magnitude, in the form of an irregular square, or trapezium. Zeta, of the 4th magnitude, is the first star, and is situa- ted in the back, 50 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. Alpha and Beta otherwise called Armeb, form the N. W. end of the trapezium, and are about 39 apart. Gamma and Delta form the S. E. end, and are about 2%0 apart. The upper right hand one, which is Arneb, is the brightest of the four, and is near the centre of the con- ...Where is the constellation of the Hare situated? When does it come to the merly dian? What is the whole mumîber of its stars? What is the magnitude of its principal ones? How may it be distinguished? In what part of the animal are these stars pla– ced? Describe the principal star in Lepus. What are the distance and direction of the square from Zeta? Describe the stars at each end of this square. Which is the t) rightest of the four? MAP III.] COLUMBA–ERIDANUS. 61 stellation. 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 Dogs which, from the motion of the 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 hunting, and which, for this reason, was made into a constellation and placed near him among the stars. - COLUMBA. NoAH's DOVE.—This constellation is situated about 16° S. of the 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 mag- nitudes; of these, Phaet and Beta are the brightest, and are about 239 apart. Phaet, the principal star, lies on the right and is the highest of the two ; Beta may be known by means of a smaller star just east of it, marked Gamma. A line drawn from the easternmost star in the belt of Orion, 329 di- rectly south, will point out Phaet; it is also 1130 S. of the lower left hand star in the square of the Hare, and makes with Sirius and Naos, in the ship, a large equilateral triangle. HISTORY.—This constellation is so called in commemoration of the dove which Noah “sent forth to see if the waters were abated from off the face of the ground,” after the ark had rested on mount Ararat. “And the dove came in to him in the evening, and lo, in her mouth was an olive leaf plucked off.” —“The surer messenger, A dove sent forth once, and again to spy Green tree or ground, whereon his foot may light: The second time returning, in his bill An olive leaf he brings, pacific sign ſ” ERIDANU.S. THE RIVER Po.—This constellation meanders over a large and very irregular 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 1309; which, for the sake of a more easy reference, 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 Streaſºn. The Northern stream commences near Rigel, in the foot Are these all the stars that are visible in this constellation? Describe the situation of Noah's Dove. How many stars does it contain, and what are the principal? Which of these are the brightest, and how situated? How may Beta be known? What is the QSition of Phaet with regard to Orion? Describe the general form of the constellation ridanus. What is its entire length, and how is it divided? By what names are these SCCtions distinguished? What are the course and distance of the Northern stream? 62 PICTURE OF THE HEAVENS. [JAN. of Orion, and flows out westerly, in a serpentine course, nearly 40°, to the Whale, where it suddenly makes a com- plete circuit and returns back nearly the same distance to- wards its source, but bending gradually down towards the south, when it again makes a similar circuit to the S. W. and finally disappears below the horizon. West of Rigel there are five or six stars of the 3d and 4th magnitudes, arching Ş. in a semicircular form, and marking the first bend of the northern stream. About 8° below these, or 19° W. of Rigel, is a bright star of the 2d magnitude, in the second bend of the northern stream, marked Gamma. This star cul- minates 13 minutes after the Pleiades, and one hour and a quarter before Rigel. Passing Gamma, and a smaller star west of it, there are ſour stars nearly in a row, which bring us to the breast of Cetus, 8° N. of Gamma, is a small star gº Ried, which is thought by some to be considerably nearer the earth than Şll lll:S Theemim, in the southern stream, is a star of the 3d magnitude, about 17° S. W. of the square in Lepus, and may be known by means of a smaller star, 19 above it. Achermar is a brilliant star of the 1st magnitude, in the extremity of i. ºthern stream; but having 58° of S. declimation, can never be seen in this atitude. The whole number of stars in this constellation is 84; of which, one is of the 1st magnitude, one of the 2d, and eleven are of the 3d. Many of these cannot be pointed out by ver- bal description; they must be traced from the map. History.—Eridanus is the name of a celebrated river in Cisalpine Gaul, also called Padus. Its modern name is Po. Virgil calls it the king of rivers. The Latin poets have rendered it memorable from its connexion with the ſable of Phaeton, who, being a son of Phoebus and Clymene, became a ſavourite of Venus, who intrusted him with the care of one of her temples. This favour 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 he required, and no sooner was the oath uttered, than— “The youth, transported, asks without delay, To guide the sun’s bright chariot for a day. The god repented of the oath he took, For anguish thrice his radiant head he shook;- My son, says he, some other proofrequire, Rash was my promise, rash was thy desire— Not Jove himselſ, the ruler of the sky, That hurls the three-ſorked thunder from above, Dares try his strength; yet who as strong as Jove 7 Besides, consider what impetuous ſorce Turns stars and planets in a diff'rent course. I steer against their motions; mor am I Borne back by all the current of the sky: But how could you resist the orbs that roll In adverse whirls, and stem the rapid poll?” Phoebus represented the dangers to which he would be exposed in vain. He undertook the aerial journey, and the explicit directions of his father were for. gotten. No sooner had Phaeton received the reins than he betrayed his igno- rance of the manner of guiding the chariot. The flying coursers became sem- sible of the confusion of their driver, and immediately departed from the usual track. Phaeton repented too late of his rashmess, and already heaven and earth Describe its first bend? Describe the position of Gamma, and tell when it comes to the meridian? What stars are between Gamma and the While’." What mºtº. about 89 above Gamma, and what is its distance from the earth compared with that % Sirius 2 Describe the situation of Thee?ntm. Describe the position and magnitude of Archernar? What is the whole mumber of stars in this constellation? What is the magnitude of the principal ones? MAP III.] AtjRigA. 63 were threatened with a universal conflagration as the consequence, when Jupi- ter, perceiving the disorder of the horses, struck the driver with a thunderbolt, and hurled him headlong from heaven into the river Eridanus. His body, con. sumed with fire, was found } the nymphs of the place, who honoured him with a decent burial, and inscribed this epitaph upon his tomb :— “Hic situs est Phaeton, currus auriga paterni : Queme si non tenuit, magnis tamen earcidit ausis.” º sisters mourned his unhappy end, and were changed by Jupiter into poplars. “All the long night their mournſul watch they keep, And all the day stand round the tomb and weep.”—OvID. It is said the tears which they shed, turned to amber, with which the Phoenl. cians and Carthaginians carried on in secrecy a most lucrative trade. The great heat produced on the occasion of the sun’s departing out of his usual course, is said to have dried up the blood of the Ethiopians, and turned their skins black; and to have produced sterility and barrenness over the greater part of Lybia. “At once from life and from the chariot driven, Th? ambitiºus boy fell thunderstruck from heaven.” “The breathless Phaeton, with flaming hair, Shot from the chariot like a falling star, That in a summer's evening from the top Of heav'n drops down, or seems at least to drop, Till on the Po his blasted corpse was hurl’d, Far from his country, in the western world.” The fable of Phaeton evidently alludes to some extraordinary heats which were experienced in a very remote period, and of which only this confused tra- dition has descended to later times. AURIGA. -- THE CHARIOTEER, called also the Wagoner, is represented on the celestial map by the figure of a man in a declining posture, resting one foot upon the horn of Taurus, with a goat and her kids in his left hand, and a bridle in his right. It is situated N. of Taurus and Orion, between Perseus on the W. and the Lynx on the E. Its mean declimation is 450 N.; so that when on the meridian, it is almost directly over head in New England. It is on the same meridian with Orion, and culminates at the same hour of the night. Both of these constellations are on the meridian at 9 o'clock on the 24th of January, and 1 hour and 40 minutes east of it on the 1st of January. - The whole number of visible stars in Auriga, is 66, inclu- ding one of the 1st and one of the 2d magnitude, which mark the shoulders. Capella is the principal star in this constel- lation, and is one of the most brilliant in the heavens. It takes its name from Capella, the goat, which hangs upon the 1eft shoulder. It is situated in the west shoulder of Auriga, T - How is the constellation Auriga represented? Where is it situated? What is its mean declination, and what its position on the meridian? How is, it situated in respect to Orion? When are these constellations on the meridian? What is the whole number of visible stars in Aurigal How many of the 1st and 2d magnitude? What is the name of the principal star, and whence derived? Where is this situated? * 64 PICTTTRE OF THE HEAVENS. | JAN. 240 E. of Algol, and 280 N. E. of the Pleiades. It may be known by a little sharp-pointed triangle formed by three stars, 39 or 49 this side of it, on the left. It is also i8° 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, 73° E. of Capella, and culminates the next minute after Betelguese, 373° S. of it. Theta, in the right arm, is a star of the 4th magnitude, 89 directly south of Menkalima. It may be remarked as a curious coincidence, that the two stars in the shoul- ders 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, irlark the extremities of a long, marrow 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, halfway between them at El Nath, in the north- ern 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° S., 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, 4° W. of the solstitial colure. “See next the Goatherd with his kids; he shines With seventy stars, deducting only four, Of which Capella never sets to us,” And scarce a star with equal radiance peams Upon the earth : two other stars are seen Due to the second order.”—Eudosia. IIISTORY..—The Greeks give various accounts of this constellation; some sup- pose it to be Erichthonius, the fourth king of Athens, and son of Vulcan and Mi- nerva, who awardcq him a place among the constellations on account of his many useful inventions. He was of a monstrous shape. He is said to have invented chariots, and to have excelled all others in the management of horses. In allu- sion to this, Virgil has the following limes:— “Primus Erichthonius currus et quatuor ausus Jungere equos, rapidisque rotis insistere victor.” Georgic, Lib. iii. p. 113 “Bold Erichthonius was the first who join’d Four horses ſor the rapid race design'd, And o'er the dusty wheels presiding sate ’’—Dryden. Other writers say that Bootes invented the chariot, and that Auriga was the son of Mercury, and charioteer to OEnomaus, king of Pisa, and so experienced, .hat he rendered his horses the swiftest in all Greece. But as neither of these fables seems to account for the goat and hor kids, it has been supposed that they refer to Almathasa and her sister Melissa, who fed Jupiter, during his infancy, * In the latitude of London ; but in the latitude of New England, Capella disappears below the horizon, in the N. N. W., for a few hours, and then reappears in the N. N. E. How may it be known? What are its distance and direction from El Nath, in the horm of Taurus? When docs Capella come to the meridian 3 Describe the star in the east shoulder of Auriga. Describe Theta. IWhat curious coincidence Cºists between the stars in the show.lders of Auriga and those in the shoulders of Orion ? Describe the situation of Del/a. The two stars in the shoulders of Ant?’īga form the base of two tri- angles; please describe them. Hiſhat stars in Auriga, Orion, the Hare, and the Dove are on the same ºne, idiºn 2 (low far is this line of stars west of the solstitial colure: MAP III.] CAMELOPARDALU.S.-THE LYNX. 65 with goat’s milk, and that, as a reward for their kindness, they were placed in the heavems. But there is no reason assigned for their being placed in the arms of Auriga, and the inference is unavoidable, that mythology is in fault on this oint. p Jamieson is of opinion that Auriga is a mere type or scientific symbol of the beautiful fable of Phaeton, because he was the attendant of Phoebus at that re- mote period when Taurus opened the year. CAMELOPARDALU.S. THE CAMELOPARD.—This constellation was made by He- velius out of the unformed stars which lay scattered between Perseus, Auriga, the head of Ursa Major, and the Pole Star. It is situated directly N. of Auriga and the head of the Lynx, and occupies nearly all the space between these and the pole. It contains 58 small stars; the five largest of which are only of the 4th magnitude. The principal star lies in the thigh, and is about 20° from Capella, in a northerly direction. It marks the northern boundary of the temperate zone; being less than one degree S. of the Arctic circle. There are two other stars of the 4th magnitude near the right knee, 120 N. E. of the first mentioned. They may be known by their standing 19 apart and alone. The other stars in this constellation are too small, and too much scattered to invite observation. HISTORY..—The Camelopard is so called from an animal of that name, peculiar to Ethiopia. This animal resembles both the camel and the leopard. Its body is º: like that of the leopard. Its neck is about seven feet long, its fore and hind legs, from the hoof to the second joint, are nearly of the same length; but from the second joint of the legs to the body, the fore legs are so long in coul- parison with the hind ones, that no person could sit upon its back, without in- stantly sliding off as from a horse that stood up on his hind feet. C H A P T E R IV. DIRECTIONS FOR TRACING THE CONSTELLATIONs which ARE on THE MERIDIAN IN FEBRUARY. THE LYNX. THE constellation of the Lynx, like that of the Camelopard, exhibits no very interesting features by which it can be dis- tinguished. It contains only a moderate number of inferior stars, scattered over a large space N. of Gemini, and between Auriga and Ursa Major. The whole number is 44, including Of what was the Camelopard made? Where is it situated? What is the whole num- her of stars? What is the magnitude of the largest? What are the name and position of the principal one? Where are the other principal stars situated? How may they be known? Whence does it derive its name 2 What is the situation of the Lynx? What are the number and magnitude of its stars 3 66 PICTURE OF THE HEAVENS. [FEB. only three that are so large as the 3d magnitude. The largest of these, near the mouth, is in the solstitial colure, 14%o N. of Menkalina, in the E. shoulder of Auriga. The other two prim- cipal stars are in the brush of the tail, 33° 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. HISTORY —This constellation takes its name from a wild beast which is said to be of the genus of the wolf. - GEMINI. -7- THE Twins.—This constellation represents, in a sitting posture, the twin brothers, Castor and Pollux. Gemini is the third sign, but fourth constellation in the order of the Zodiac, and is situated south of the Lynx, be- tween Cancer on the east, and Taurus on the west. The orbit of the earth passes through the centre of the constella- tion. As the earth moves round in her orbit from the first point of Aries to the same point again, the sum, 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 constel- lation 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 sum is then passing, because the feeble lustre of the stars is obscured by the superior effulgence of the SUIIl. ^ When the sun is just entering the outlines of a constellation on the east, its western limit may be seen in the morning twilight, just above the rising sun. So when the sum has arrived at the western limit of a constellation, the eastern part of it may be seen lingering in the evening twilight, just behind the setting sun. Under other circumstances, when the sun is said to be in, or to enter, a particu- lar constellation, it is to be understood that that constellation is not then visible, but that those opposite to it, are. For example: whatever constellation sets with the sun on any day, it is plain that the one opposite to it must be then rising, and continue visible through the night. . Also, whatever constellation rises and sets with the sun to-day, will, six months hence, irise at sun-setting, and set at sum-rising. For example: the sun is in the centre of Gemini about the 6th of Describe the position of the largest. Describe the position of the other two principal stars. What are their distance and direction from the ome in the head? When is its centre on the meridian? Describe the position and appearance of the Twins. What is the relative position of Gemini among the signs and constellations of the Zodiac 3 How is the orbit of the earth situated, with respect to these constellations? How do the sun and earth appear to move through these signs? When does the Sun appear to pass through the constellation Gemini? Do we usually see the constellations while the sun is passing through them? Under what circumstances can we see some part of them? . When the sun is in or entering any constellation, are the opposité constella. tions visible or not? If a constellation rise with the sun to-day, how will it rise siz months hence 2 Give an evample. MAP III.] GEMINI. 67 July, and must rise and set with it on that day; consequently, six months from that time, or about the 4th of January, it will rise in the east, just when the sun is setting in the west, and will come to the meridian at midnight; being them ex- actly opposite to the Sun. Now as the stars gaintſpon the sun at the rate of two hours every month, it follows that the centre of this constellation will,(on the 17th of February, come to the meridian three hours earlier, or at 9 o'clock in the evening. It would be a pleasant exercise for students to propose questions to each other, somewhat like the following:—What zodiacal constellation will rise and set with the sun to-day ? What one will rise at sun-setting 3 What constellation is three hours high at sun-set, and where will it be at 9 o'clock 3 What constel- lation rises two hours before the sun ? How many days or months hence, and at what hour of the evening or morning, and in what part of the sky shall we see the constellation whose centre is now where the sun is ? &c., &c. In solving these and similar questions, it may be remembered that the sun is in the vernal equinox about the 21st of March, from whence it advances through one sign or constellation every succeeding month thereaſter; and that each con- Stellation is one month in advance of the sign of that name: wherefore, reckon' Pisces in March, Aries in April, Taurus in May, and Gemini in June, &c.; be- ginning with each constellation at the 21st, or 22d of the month. Gemini contains 85 stars, including one of the 1st, one of the 2d, four of the 3d, and seven of the 4th magnitudes. It is readily recognised by means of the two principal stars, Cas- tor and Pollua', of the 1st and 2d magnitudes, in the head of the Twins, about 40 apart. There being only 11 minutes’ difference in the transit of these two stars over the meridian, they may both be consid- ered as culminating at 9 o'clock about the 24th of February. Castor, in the head of Castor, is a star of the 1st magnitude, 4}o N. W. of Pollux, and is the northernmost and the bright- est of the two. Polluar, is a star of the 2d magnitude, in the head of Pollux, 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.” 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 variation 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. Bradly and Maskelyne ſound that the line joining the two stars which form Castor was, at all times of the year, parallel to the line joining Castor and Pollux; and that both of the former move around a common centre between them, in If a constellation come to the meridian at midnight to-day, how long before it will come to the meridian at 9 o'clock; in the evening 2 If the constellation. Gemini come to tº meridian at midnight, on the 4th of January, when will it culminate at 9 o'clock? What is the number of stars in Gemini? By what means is it readily recognised? When do these stars culminate? Describe Càstor. Describe Pollux. For what pur- pose is it observed at sea? Is the brightness of these two stars always the same? Who ascribes this variableness to Castor, and for what reason? 68 PICTURE OF THE HEAVENS. I FEB orbits nearly circular, as two balls attached to a rod would do, iſ suspended by a String affixed to the centre of gravity between then, “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 as- tronomy. 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 dis. tinguish the ſeet of the twins. The brightest of these is Alhena, 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 Castor’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 parallel with them, there is another row of three stars. about 6° apart, which mark the knees. There are, in this constellation, two other remarkable parallel rows, lying at right angles with the former; one, leading from the head to the foot of Castor, the brightest star being in the middle, and in 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 belcw it, in the knee. Wasat is in the ecliptic, and very near the centre of the constellation. The two stars, Mu and Tejat; in the northern ſoot, are also very near the ecliptic : Tejat is a small star of between the 4th and 5th magnitudes, 29 W. of Mu, and deserves to be noticed because it marks the 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, 239 W. of Tejat, is a star of only the 5th magni- tude, but rendered memorable as being the star which served for many years to determine the position of the planet Herschel, after its first discovery. Thus as we pursue the study of the stars, we shall find continually new and more wonderful developments to engage our feelings and reward our labour. We shall have the peculiar satisſaction of reading the same volume that was spread out to the patriarchs and poets of other ages, of admiring what they admired, and of being led as they were led, to look upon these lofty mansions of being as hav. ing, above them all, a common Father with ourselves, “who ruleth in the armies of heaven, and bringeth forth their hosts by number.” 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 sin- gular. They were educated at Pallena, and aſterwards embarked with Jason in the celebrated contest ſor the golden fleece, at Colchis; on which occasion .# 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 petasus, on whose top glittered a star. Among the ancients, and especially among the Romans, there prevailed a superstition that Castor and Pollux often appeared at the head of their armies, and led on their troops to battle and to victory. “Castor and Pollux, first in martial force, One bold on foot, and one renown'd for horse. Fair Leda's twins in time to stars decreed, & One ſought on ſoot, one curb’d the fiery steed.”— Virgil, “Castor alert to taine the foaming steed, * And Pollux strong to deal the manly deed,”--Martial. The brothers cleared the Hellespont and the neighbouring seas from pirates, after their return from Colchis; ſrom which circumstance they have ever since been regarded as the ſriends' 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 innumediately the tempest ceased, and the sea was calm. Describe the stars which mark the fect of the Twins. Specify the stars in each. How is this rov' situated with respect to Orion 2 Describe the second row of stars in this constellatºon. Are there yet other rows in this constellation ? Describe them. What is the position of Wasat 2. Two other stars are very yea) the ecliptic; mention them. Jescribe the position of Tejat. Glee a description ºf the star Propus. MAP III.] CANIS MINOR. 69 From this circumstance, the sailors inferred, that whenever both fires appeared in the sky, it would be fair weather: but when only one appeared, there would be storms. St. Paul, aſter being wrecked on the island of Melita, embarked for Rome “in a ship whose sign was Castor and Polluºr;” so formed, no doubt, in accordance with the popular belieſ 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 and 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 Tyndarus. They became enamoured 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 himself 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 himself of immortality; wherefore, Jupiter permitted Castor, who had been slain, to share the immortality of Pollux; and consequently, as long as the one was upon earth, so long was the other detained in the infernal regions, and they alternately lived and died every day. Jupiter also ſurther rewarded their fraternal attachment by changing them both into a constellation under the name of Gemini, Twins, which, it is strangely pretended, never 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. Castor and Pollux were worshipped both by the Greeks and Romans, who sacrificed white lambs upon their altars. In the Hebrew Zodiac, the constella- tion of the Twins reſers to the tribe of Benjamin. CANIS MINOR. THE LITTLE Dog.—This small constellation is situated about 5° N. of the equinoctial, 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 of the 1st magnitude, and is about 40 S. E. of the next bright- est, marked Gomelza, which is of the 2d magnitude. These two stars resemble the two in the head of the Twins. Procyon, in the Little Dog, is 230 S. of Pollux in Gemini, and Gomelza is about the same distance S. of Castor. A great number of geometrical figures may be formed of the principal stars in the vicinity of the Little Dog. For ex- ample; Procyon is 23° S. of Pollux, and 26° E. of Betelguese, and forms with them a large right angled triangle. Again : Procyon is equidistant from Betelguese and Sirius, and forms with them an equilateral triangle whose sides are each about 26°. If a straight line, connecting Procyon and Sirius, be produced 239 farther, it will point out Phaet, in the Dove. Describe the situation of Canis Minor. What is its whole number of stars? What is the magnitude of its principal ones? What is the brightest one called, and how is it situateſ, What other stars do Procyon and Gomelza resemble? What are the distance and direction of Procyon from Pollux? Of Gomelza from Castorm What are their distance and direction from Castor and Pollux? What kind of figures may be formed of the 8tars in the neighbourhood of the J,ittle Dog A Give some cyamples, *0 PICTURE OF THE HEAVENS. |FEB. Procyon is often taken for the name of the Little Dog, or for the Whole constellation, as Sirius is for the greater one; hence it is common to refer to either of these constellations by the name of its principal star. Procyon comes to the me- ridian $3 minutes after Sirius, on the 24th of February; although it rises, in this latitude, about half an hour before it. For this reason, it was called Procyon, from two Greek words which signify (Ante Canis) “before the dog.” “Canicula, fourteen thy stars; but far Above them all, illustrious through the skies, Beams Procyon ; justly by Greece thus calléd The bright jorerunner of the greater Dog.” History.-The Little Dog, according to Greek fable, is one of Orion's hounds. Some suppose it 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 Maera, which belonged to Icarus, and discovered to his daughter Erigone the place of his burial. Others, again, Say it is one of Actaeon’s hounds that devoured their master, after Diana had transformed him into a Stag, to pre- vent, as she said, his betraying her. “This said, the man began to disappear By slow degrees, and ended in a deer. Transform'd at length, he flies away in haste, And wonders why he flies so fast. But as by chance, within a neighbºring brook, He saw his branching horns, and alter'd look, Wretched Actaeon 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 the ileetest of the pack that press'd Close at his heels, and sprung before the rest, Had fasten’d 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 grovelling on the ground.” It is most probable, however, that the Egyptians were the inventors of this con- stellation; and as it always rises a little before the Dog-star, which, at a particu: lar season, they so much dreaded, it is properly represented as a little watchful creature, giving notice like a faithful sentinel of the other's approach, * It is not difficult to deduce the moral of this fable...The selfishness and caprice of human friendship furnish daily illustrations of it. While the good man, the philan- thropist, 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 couſi not shake the will of their benefactor, he is straightway pursued, like Ac- taeon, by his own hounds; and, like Actaeon, he is “torm to the ground” by the fangs that fed upon his bounty.-L. Q. C. L. What name is usually given to the Little Dog" When does Procyon rise and culmi- nate, with respect to the Dog-star? What name, for this reason, was given to this constellation ? MAP III.] MONOCEROS—CANIS MAJOR. 71 MON OCEROS. THE UNICORN.—This is a modern constellation, which was made out of the unformed stars of the ancients that lay scat- tered 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. It contains 31 small stars, of which the seven principal ones are of only the 4th magnitude. Three of these are situated in the head, 39 or 40 apart, forming a straight line N. E. and S. W. about 90 E. of Betelguese in Orion’s shoul- der, and about the same distance S. of Alhena 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 particu- lar 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 the rock in Caffraria; and thence conjectures that such an animal, instead of being fabulous, 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. CANIS MAJOR. THE GREAT Dog.—This interesting constellation is situa- ted southward and eastward of Orion, and is universally known º the brilliance of its principal star, Sirius, which is apparently the largest and brightest in the heavens. It glows in the winter hemisphere with a lustre which is unequalled 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. What stars compose the constellation Monoceros? How is this constellation situ- ated, and when is it on the meridian! What is the whole number of its stars? What lº, he magnitude of its principal ones? Describe those in the head. Describe the po. Sition and appearance of Canis Major. What is its appearance in the winterº what 1S its distancé from the earth º to be, and how is it compared with that of the 9ther stars? How long would it take a cannon-bail to pass over this distance in what time Would sound reach Sirius from the earth? 72 PICTURE OF THE HEAVENS. |FEB. It may be shown in the same manner, that a ray of light, which occupies only 8 minutes and 13 seconds in coming tô us from the sun, which is at the rate of nearly two hundred thousand miles a second, would be 3 years and 82 days in passing through the vast space that lies between Sirius and the carth. Conse- quently, were it blotted from the heavens, its light would continue visible to us for a period of 3 years and 82 days after it had ceased to be. If the 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? In the remote ages of the world, when every man was his own astronomer, the rising and setting of Sirius, or the Dog- star, as it is called, was watched with deep and various so- licitude. The ancient Thebans, who first cultivated astro- nomy in Egypt, determined the length of the year by the ſº of its risings. The Egyptians watched its rising with mingled apprehensions of hope and fear; as it was ominous to them of agricultural prosperity or blighting drought. It foretold to them the rising of the Nile, which they called Siris, and admonished them when to sow. The Romans were accustomed yearly, to sacrifice a dog to Sirius to render him propitious in his influence upon their herds and fields. The eastern nations generally believed the rising of Sirius would be productive of great heat on the earth. Thus Virgil:— “Tum steriles exurere Sirius agros : Ardebant herba’, et victum seges agra megabat.” “Parched was the grass, and blighted was the corm: * Nor 'scape the beasts; for Sirius, from on high, With pestilential heat infects the sky.” Accordingly, to that season of the year when Sirius rose with the sun and seemed to blend its own influence with the heat of that luminary, fbe ancients gave the name of Dog- days, (Dies Caniculares). At that remote period the Dog- days commenced 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 11th of August, being one day less than the ancients reckoned. 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 time 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. g ºf: $. How long is light in coming from Sirius to the earth? Suppose this star were now to be blotted from the heavens, hono long before its twinkling would ečpire? How was the rising of Sirius regarded in the remote ages of the world? What iisc was made of it by the ancient. Thelyans? How did the Egyptians regard it, and for what reason? What did it for:te) to them? What did the Romans offer in sacrifice to Sirius annually? Why?. How was it regarded by the eastern natiºns generally? What season of tho year did the ancients call Dog-days 2 When did these begin, and how long did they last? At present, when do they begin and ent!" Haye Our Dog-days any reference to the Dog-star? * MAP III.] CAN IS MAJOR. 73 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 preces- sion at the equinoxes. This enables us to determine with approximate accu- racy, the dates of many events of antiquity, which cannot be well determined by other records. We do not know, for instance, in what precise period of the world Hesiod flourished. Yet he tells us, in his Opera et Dies, lib. ii. v. 185, that. Arcturus in his time rose heliacally, 60 days after the winter solstice, which, ` then was in the 9th degree of Aquarius, or 39° beyond its present position. Now 39° 50}^*=2794 years since the time of Hesiod, which corresponds very nearly with history. When a star rose at sun-setting, or set at sun-rising, it was called the Achroni- cal rising or setting. When a planet or star appeared above the horizon just r before the sun, in the morning, 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 magnitude are seen rising and setting when the sum is 12° below the horizon; stars of the 2d magnitude require the sun's depression to be 13°; stars of the 3d magnitude, 14°, and so on, allowing one degree for each magnitude. 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 poetical rising and set. ting. They served to mark the times of religious ceremonies, the seasons al- lotted to the several departments of husbandry, and the overflowing of ºn Nile The student may be perplexed to understand how the Dog-star, which he seldom sees till mid-winter, should be associated 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, as by night; but on account of the superior splendour of the sun, we cannot see them. Sirius is situated nearly S. of Alhena, in the feet of the Twins, and about as far S. of the equinoctial as Alhena is N. of it. . It is about 100 E. of the Hare, and 26° S. of Be. telguese 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 direction of the Three Stars in the belt of Orion. Its distance from them is about 23°. It comes to the meri- dian at 9 o'clock on the 11th of February. Mirzam, in the foot of the Dog, is a star of the 2d magni- tude, 53° W. of Sirius. A little above, and 40 or 50 to the left, there are three stars of the 3d and 4th magnitudes, form- ing a triangular figure somewhat resembling a dog’s head. What is meant by the Achronical rising and setting of the stars 2 IWhat, by their Pſel?acal rising and setting 2 By whom were the terms thus applied, and what were these risings and settings called Ž II hat did they serve 2 Explain how it is, that the Dog-star, which is seldom seen till mid-winter, should be associated with the most ſervirl heat of sun-nner. Are there as many stars over our head in the daytime as in the night? Describe the situation of Sirius. What is its position with regard to Be- telguese and Procyon, and in connexion with them what figure does it form 3 With What other stars does it form a similar triangle What is the appearance of these two triangles taken together? How else is Sirius pointed out? Describe the position and magnitude of Mirzam, What stars mark the head of the Dog? 74 PICTURE OF THE HEAVENS, |MAR. f 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. Wesem 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 30 apart, and 129 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 ; all of which are easily traced out by the aid of the map. History-Manilius, a Latin poet who flourished in the Augustan age, wrote an admirable poem, in five books, upon the fixed stars in which he thus speaks of this constellation:— “All others he excels; no fairer light Ascends the skies, none sets so clear and bright.” But EUDosíA best describes it :— “Next shimes the Dog with sixty-ſour distinct; Fam’d ſor pre-eminence in envied song, * Theme of from cric and Virgilian lays: His fierce mouth flames with dreaded Sirius ; Three of his stars retire with feeble beans.” According to some mythologists, this constellation represents one of Orion's hounds, which was placed in the sky, near this celebrated huntsman. Others say it received its name in honour of the dog given by Aurora to Cephalus, which surpassed in speed all the animals of his species. Cephalus, it is said at. tempted to prove this by running him against a fox, which, at that time, was thought to be the ſleetest of all animals. After they had rum together a long time without either of them obtaining the victory, it is said that Jupiter was so i. gratified at the fleetness of the dog that * assigned him a place in the 1 ea VenS. But the name and ſorrm of this constellation are, no doudt, derived from the Iºgyptians, who, carefully watched its rising, and by it judged of the swelling of the Nile, which they called Siris, and, in their hieroglyphical manner of writing, since it was as 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 dawn, the overflowing of the Nile immediately ſollowed. §. it warned them, like a faithful dog, to escape from the region of the inun- ation, C H A P T E R V . DIRECTIONS FOR TRACING THE CONSTELLATIONS WHICH ARE ON THE MERIDIAN IN MARCH. ARGO NAVIS. THE SHIP ARgo.—This constellation occupies a large space in the southern hemisphere, though but a small part of it can Which is the brightest of these, and what remarkable circumstance in its history? How has it appeared since its return? Describe the situation and magnitude of Wesent What stars mark the hinder feet?...What is the number of visible stars in this con- stellation 7 Describe the constellation Argo Navis? MAP III.] ARGO NAWIS. yºf M 5 be seen in the United States. It is situated S. E. of Canis Major, and may be known by the stars in the prow and deck of the ship. If a straight line joining Betelguese and Sirius, be produ- ced 180 to the southeast, it will point out Naos, a star of the 2d magnitude, in the rowlock of the ship. This star is in the S. E. corner of the Egyptian X., and of the large equi- lateral triangle made by itself with Sirius and the Dove. When on the meridian, it is seen from this latitude about 8° above the southern horizon. It comes to the meridian on the 3d of March, about half an hour after Procyon, and continues visible but a few hours. Gamma, in the middle of the ship, is a star of the 2d mag- nitude, about 7o S. of Naos, and just skims above the south- ern horizon for a few minutes, and then sinks beneath it. The principal star in this constellation is called, after one of the pilots, Canopus; it is of the 1st magnitude, 36° nearly S. of Sirius, and comes to the meridian 17 minutes after it; but having about 539 of S. declination, it cannot be seen in the United States. The same is true of Miaplacidus, a star of the 1st magnitude in the oars of the ship, about 25° E. of Canopus, and 619 S. of Alphard, in the heart of Hydra. An observer in the northern hemisphere, can sce the stars as many degrees south of the equinoctual in the southen n hemisphere, as his own latitude lacks of 90°, and no inore. Markeb, is a star of the 3d magnitude, in the prow of the ship, and may be seen from this latitude, 16° S. E. of Sirius, and about 100 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., 39 and 40 apart. This constellation contains 64 stars, of which, two are of the 1st magnitude, four of the 2d, and mime of the 3d. Most of these are too low down to be seen in the United States. IIISTORY..—This constellation is intended to perpetuate the memory of the famous ship which carried Jason and his 54 companions to Colchis, when they resolved upon the perilous expedition of recovering the golden ſleece The de- rivation of the word Angolias been often disputed Some derive it from Argos, Supposing that this was the name of the person who first proposed the expedi- tion, and built the ship. Others maintain th t it was built at Argos, whence its name. Cicero calls it Argo, because it carried G1 cc ſuns cominorily called Ar- gives. Diodorus derives the word from , which signifies such ſt Ptoletny says, but not truly, that Hercules built the ship and called tº Argo, a ter a son of Jason, who bore the same matue. This slup had filty oars, and being thus pro- pelled must have fallen far short of the bulk of the su allest shºp eraſt used by Where is it situated? ... Pont out the situation of Naos, in the ship” When may it to Seen in this latituden When is it on the moralian 7 Describe the position and magnú- tude of Gamma. What are the situation and name of the principal Star in this constel- lation? Why can it not be seen in the United States? Is any other considerable star in the ship similarly situated? Describe Markeb. How may this star he known What is the muniºber of visible stars in this constellation? What is the magnitude of its prin- Clpal ones? 76 PICTURE OF THE HEAVENS. [MAR moderms. 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 ſorest of Dondoma by Minerva, which had the power of giving oracles to the Argonauts. This ship was the first, it is said, that ever ventured on the sea. Aſter the expe- dition was finished, and Jason had returned in triumph, he ordered her to be flº ashore at the isthmus of Corinth, and consecrated to Neptune, the god of le Sea, Sir Isaac Newton endeavours to settle the period of this expedition at about 30 ears before the destruction of Troy; and 43 years after the death of Solomon. r. Bryant, lowever, rejects the history of the Argonautic expedition as a mere fiction of the Greeks, and supposes that this group of stars, which the poets de- nominate Argo Navis, refers to Noah’s ark and the deluge, and that the fable of the Argonautic expedition, is founded on certain Egyptian traditions that related to the preservation of Noah and his family during the flood. CAN CER. THE CRAB, is now the fifth constellation and fourth sign of the Zodiac. It is situated in the ecliptic, between Leo on the E. and Gemini on the W. It contains 83 stars, of which, one is of the 3d, and seven of the 4th magnitude. Some place the first-mentioned star in the same class with the other seven, and consider none larger than the 4th magnitude. Beta, is a star of the 3d or 4th magnitude, in the south- western claw, 100 N. E. of Procyon, 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. Acubens, is a star of similar brightness, in the southeastern claw, 100 N. E. of Beta, and nearly in a straight line with it and Procyon. An imaginary line drawn from Capella through Pollux, will point out Acubens, at the distance of 249 from Pollux. It may be otherwise distinguished by its standing between two very small stars close by it in the same claw. Tegmine, the last in the back, appears to be a small star, of between the 5th and 6th magnitudes, 839 in a northerly direction from Beta. It is a treble star, and to be distinctly seen, requires very favourable circumstances. Two of them are so near together that it requires a telescopic power of 300 to separate them. About 70 northeasterly from Tegmine, is a nebulous cluster of very minute stars, in the crest of Cancer, suffi- ciently 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. of each. It may otherwise be discovered by means of two conspicuous stars What is the relative position of Cancer among the signs and constellations of the Zodiac! How is it situated? What are the number and magnitude of its stars? Where is Beta situated, and how may it be known a Which way from Procyon and Acubens ; Describe Acubens. What are its distance and direction from Pollux? How may it be otherwise known? Describe Tegmine. There is a remarkable cluster in this con. stellation-describe its position. How may it otherwise be discovereſ,” MAP mi.] CAN CER. 77 of the 4th magnitude lying one on either side of it, at the dis- tance of about 29, called the northern and southern Aselli. By some of the Orientalists, this cluster was denominated Praesepe, the Manger, a contrivance which their fancy fitted up for the accommodation of the Aselli or Asses; and it is so called º modern astronomers. The appearance of this nebula to the unassisted eye, is not unlike the nucleus of a comet, and it was repeatedly mistaken for the comet of 1832, which, in the month of November, passed in its neighbour- hood. - The southern Asellus, marked Delta, is situated in the line of the ecliptic and in connexion with Wasat and Tejat, marks the course of the earth’s orbit for a space of 36° from the solstitial colure. There are several other double and nebulous stars in this constellation, most of which are too small to be seen; and in- deed, the whole constellation is less remarkable for the bril- liancy of its stars than any other in the Zodiac. The sun arrives at the sign Cancer about the 21st of June, but does not reach the constellation until the 23d of July. The mean right ascension of Cancer is 1289. It is conse- quently on the meridian the 3d of March. A few degrees S. of Cancer, and about 17° E. of Procyon, are four stars of the 4th magnitude, 3° or 4° apart, which mark the head of Hydra. This constella- tion will be described on Map III. The beginning of the sign Cancer (not the constellation) is called the Tropic of Cancer, and when the sun arrives at this point, it has reached its utmost litait of north declination, where it seems to remain stationary a few days, before it begins to decline again to the south. This stationary attitude of the sun is called the summer solstice; from two Latin words signifying the sum’s standing still. The distance from the first point of Cancer to the equinoctial, which at present, is 23° 273', is called the obliquity of the ecliptic. . It is a remarkable and well as: certained fact, that this is continually growing less and less. The tropics are slowly and steadily * the equinoctial, at the rate of about half a second every year; so that the sun does not now come so far north of the equator in suminer, nor decline so far south in winter, as it must have done at the creation, by nearly a degree. History.—In the Zodiacs of Esme, and Dendera, and in most of the astrological remains of Egypt, a Scarabaeus, or Beetle, is used as the symbol of this sign; but in Sir William Jones's Oriental Zodiac, and in soune others ſound in India, we meet with the figure of a crab. As the Hindoos, in all probability, derived their knowledge of the stars from the Chaldeans, it is supposed that the figure of the crab, in this place, is more ancient than the Beetle. In some eastern representations of this sign, two animals, like asses, are ſound in this division of the Zodiac ; and as the Chaldaic name for the ass may be translated muddiness, it is supposed to allude to the discolouring of he Nile, which river was rising when the sun entered Cancer. The Greeks, in copying this sign, have placed two asses as the appropriate symbol of it, which still re- What is the manne of this cluster? What is its appearance to the naked eye, and for What has it been mistaken? How is the star callcd the southern Asellus, situated, with respect to the ecliptic What other stars in this cºnste'?ation 2. At what time does the sun enter the sign Cancer? At what time the constellation 2 If here is the tropic of Cancer situated 2 When the sun reaches this point what is said of its de- clination ? What is this stationary attitude of the sun called 2 What is the obliquity of the ecliptic 2 What remarkable fact in respect to this distance? Doey his 2.jäix tº stability of the tropics. 7% 78 PICTURE OF TſIE FILAVENS. LAPRIL. tnain. They explain their reason, however, for adopting this figure, by saying that these are the animals that assisted Jupiter in his victory over the giants, I}opuis accounts for the origin of the asses in the following words:--lie Can- cer, où sout les étoiles appellees les anes, forme l’impreinte du pavillon d’ls. sachar que Jacob assimile à l'ane. Mythologists give different accounts of the origin of this constellation. The prevailing opinion is, that while Hercules was engaged in his famous contest with the dread ſul Lernaean monster, Juno, envious of the ſame of his achieve- ments, sent a sea-crab to bite and annoy the hero's feet, but the crab being soon despatched, the goddess to reward its services, placed it among the constella- tionS. “The Scorpion's claws here clasp a wide extent, And here the Crab’s in lesser clasps are bent.” C H A P T E R W I. DIRECTIONS FOR TRACING THE CONSTELLATIONS WHICH ARE ON THE MERIDIAN IN APRIL. LEO. THE LION.—This is one of the most brilliant constellations in the winter hemisphere, and contains an unusual number of very bright stars. It is situated next E. of Cancer, and directly S. of Leo Minor and the Great Bear. The Hindoo Astronomer, Varaha, says, “Certainly the southern solstice was once in the middle of Asleha (Leo); the northern in the first degree of Dhan- ishta” (Aquarius). Since that time, the solstitial, as well as the equinoctial points, have gone backwards on the ecliptic 759. This divided by 50}”, gives 5373 years; which carry us back to the year of the world 464. Sir W. Jones, says, that Varaha lived when the solstices werc in the first degrees of Cancer and Capricorn; or about 400 years before the Christian era. Leo is the fifth sign, and the siarth constellation of the Zo- diac. The mean right ascension of this extensive group is 1509, or 10 hours. Its centre is therefore on the meridian the 6th 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 two are of the 1st magnitude, two of the 2d, six of the 3d, and fifteen of the 4th. - “Two splendid stars of highest dignity, Two of the second class the Lion boasts, And justly figures the fierce sunliner’s rage.’ The principal star in this constellation is of the 1st mag- nitude, situated in the breast of the animal, and named Re- gulus, from the illustrious Roman consul of that name. What is the general appearance of the constellation Leo'ſ Where is it situated? what is the relative order among the signs and constellations of the Zodiac." What is . the right ascension of Leo, and when is its centre on the meridian 2. When do the outlines of the figure come to the meridian What number of visible stars does it con- tain, and how large are the principal ones? What is the name of the first star in tho sonstellation, and whenco is it derived? MAP IV.] |LEO. 79 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 magnitude about 20 S. of it, and one of the 3d mag- nitude 50 N. of it, which will serve to point it out. Regulus is the brightest star in the constellation, except Denebola, in the tail, 25° E. of it. Great use is made of Re- gulus by nautical men, for determining their longitude at sea. Its latitude, or distance from the ecliptic, is less than #9; but its declimation, or distance from the equinoctial is nearly 132 N.; so that its meridian altitude will be just equal to that of the sum on the 19th of August. Its right ascension is very nearly 1509. It therefore culminates about 9 O C. ock on the 6th of April. - When Regulus is on the meridian, Castor and Pollux are seen about 40° N. W. of it, and 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 tri- angle whose vertex is at Regulus. 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, de- scribe the blade. Al Gieba, is a bright star of the 2d magnitude, situated in the shoulder, 49 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 towards the west; and it is the first in the blade of the sickle. Adhafera, is a star of the 3d magnitude, situated in the neck, 40 N. of Al Gieba, and may be known by a very mi- nute star just below it. This is the second star in the blade of the sickle. 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 magnitude, situated in the head, is 24° S.W. of Ras al Asad, and a little within the curve of the sickle. About midway Describe the situation of Regulus. What other stars serve to point it out? What is Its comparative brightness? What use is made of it in nautical astronomy 3 What are its latitude and declination? On what day will Regulus culminate at 9 o'clock in the evening? When is it on the meridian, with what stars does it form a large triangle, and in what direction are they from it? What are the name and position of the next considerable star in its vicinity? What stars form the blade of the sickle? Where in Al Gleba situated, and how may it be distinguished? What is the position of Adhafers and how may it be known? Describe thosltuation of Ras al Asad. * 8() PICTURE OF THE FIEAVENS. [APRIL. between these, and a little to the E., is a very small star, hardly visible to the naked eye. Lambda, situated in the mouth, is a star of the 4th magni- tude, 3}o S. W. of Epsilon, and the last in the sickle’s point. ICappa, situated in the nose, is another star of the same magnitude, and about as far from Lambda as Epsilon. Epsilon and Kappa are about 5%9 apart, and form the longest side of a triangle, whose vertex is in Kappa. Zozma, situated in the back of the Lion, is a star of the 2d magnitude, 18° N. E. of Regulus, and midway between it and Coma Berenices, a fine cluster of small stars, 180 N. E. of Zozma. Theta, situated in the thigh, is another star of the 3d mag- nitude, 59 directly S. of Zozma, and so nearly on the same meridian that it culminates but one minute after it. This star makes a right angled triangle with Zozma on the N. and Denebola on the E., the right angle being at Theta. Nearly in a straight line with Zozma, and Theta, and South of them, are three or four smaller stars, 40 or 59 apart, which mark one of the legs. Denebola, is a bright star of the 1st magnitude, in the brush of the tail, 10° S. E. of Zozma, and may be distin- guished by its great brilliancy. It is 59 W. of the equinoc- tial colure, and comes to the meridian 1 hour and 41 minutes after Regulus, on the 3d of May; when its meridian altitude is the same as the sun’s at 12 o'clock the next day. When Denebola is on the meridian, Regulus is seen 25° W., of it, and Phad, in the square of Ursa Major, bears 39° N. of it. It forms, with these two, a largé right angled triangle ; the right angle being at Denebola. It is so nearly on the salue meridian with Phad that it culminates only four minutes before it. Denebola is 35% o W. of Arcturus, and about the same dis- tance N. W. of Spica Virginis, 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 forms of a Rhom- bus: called by some, the DIAMOND OF VIRGO. A line drawn from Denebola through Regulus, and continued 7° or 89 further in the same direction, will point out Xi and Omicron, of the 3d and 4th magni. tudes, situated in the fore claws, and about 3° apart. What star is next? Dºscribe the position of Lambda? What are the situation and magnitude of Kappa! What is the distange between Epsilon and Kappa, Describe the position of Zozman. What are the magnitude and position of Theta;. What geometri- cal figure may be formed with this star, Zozma and Dºmebola 3, What stars in this neighbourhood mark one of the legs of Leo? Describe Denebolag. How far is it from the equinoctial colure, and when does it come to the micridian? ... When Denebola is on the meridian, what geometrical Jigure does it form, in conncavior. with Régulus and Phad 2 With what other star is it nearly on the stone meridian 2 What is the position of Denebola in regard to Arcturus and Spica Virginis, and what figure does it form with them? With what other stars does Denebola form a similar figure?, What large geometrica figure is formed by these two triangles? What stars point out those in the jore claws 7 MAP IV.] - L.F.O. 81 There are a number of other stars of the 3d and 4th magnitudes in this con- stellation, 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 neighbourhood. History.—According to Greek ſable, this Lion represcnts the formidable ani, mal which infested the forests of Nemasa. It was slain by Hercules, and placed by Jupiter among the stars in commelnoration of the dreadful conſiict. Some writers have applied the story of the twelve labours of Hercules to the progress of the sum through the twelve signs of the ecliptic ; and as the colubat of that celebrated hero with the Lion was his first labour, they have placed Leo as the §: sign. The figure of the Lion was, however, on the Egyptian charts long efore the invention of the ſabies of Hercules. 'It would Seein, Inoreover, ac- cording to the ſable itself, that Hercules, who represented the sun, actually slew the Neniaean Lion, because Leo was already a zodiacal sign. In hieroglyphical writing, the Lion was an emblem of violence and fury; and the representation of this animal in the Zodiac, signified the intense heat occa. sioned by the sum when it entered that part of the ecliptic. The Egyptians were much annoyed by lions during the heat of summer, as they at that season, left the desert, and hunted the banks of the Nile, which had then reached its greatest elevation. It was thereſore 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 Egyp- tian Zodiacs. The overflowing of the Nile, which was regularly and anxiously expected every year by the Egyptians, took place when the sun was in this sign. They therefore paid more attention to it, it is to be presumed, than to any other. This was the principal reason, Mr. Green supposes, why Leo stands first in the Zodiacs of Dendera. The circular zodiac, mentioned in our account of Aries, and which adorned the ceiling in one of the inner rooms in the famous temple in that city, was brought away en masse in 1821, and removed to Paris. On its arrival at the Louvre, it was purchased by the king for 150,000 francs, and, after being exhibited there for a year, was placed in one of the halls of the library, where it is now to be seen in apparently perfect preservation. This most interesting relic of astrology, after being cut away from the ruins where it was found, is about one ſoot thick, and cight feet square. The rock of which it is composed, is sandstone. On the face of this stone, appears a large square, enclosing a circle ſour feet in diame- ter, in which are arranged in an irregular spiral line, the zodiacal constellations, commeneing with the sign Leo. On each side of this spiral line are placed a great variety of figures. These are supposed to represent other constellations though they bear no analogy, in form, to those which we now have. Many of these figures are accompanied with hieroglyphics, which probably express their names. The commentator of Champollion, from whom we have derived many interesting facts in relation to them, has furnished merely a general history of their origin and purpose, but does not add particulars. Copies of these drawings and characters, have been exhibited in this country, and the wonderful conclu- sions that have been drawn from them, have excited much astonishment. º Compared with our present planispheres, or with stellar phenomena, it abounds with contradictory and irrelevant matter. So far from proving what was strenu- jusly maintained by infidel writers, soon after its discovery, that the Greeks took from it the model of their zodiac, which they have transmitted to us, it seems to demonstrate directly the reverse. The twelve sigms, it is true, are there, but they are not in their proper places. Cancer is between Leo and the pole; Virgo bears no proportion to the rest; some of the signs are placed double; they are all out of the ecliptic, and by no means occupy those regular and equal portious of space which Egyptian astronomers are said to have exactly measured by means of their clepsydra. The figures, without what may be termed the zodiacal circle, could never have included the same stars in the heavens which are now circumscribed by the figures of the constellations. Professor Green is of opinion, that the small apartinent in the ruins of Dendera, which was mysteriously ceiled with this zo: diac, was used for the purposes of judicial astrology, and that the sculptured figures upon it were employed in horoscopical predictions, and in that casting of nativities ſor which the Egyptians were so ſamous. Why is the position of Regulus and Denchola often referred to? - 82 PIC'TURE OF THE HEAVENS. LAPRIL. In the Hebrew Zodiac, Leo is assigned to Judah, on whose standard, according to all traditions, a Lion is painted. This is clearly intimated in numerous passa- es of the Hebrew writings: Ex.—“Judah is a Lion's whelp; he stoopeth down e croucheth as a Lion ; and as an old Lion; who shall Youse him up 'P' Gen. xlix. 9. “The Lion of the tribe of Judah hath prevailed.” Rev. v. 5. LEO MINOR. . . *. THE LITTLE LION.—This constellation was formed by Hevelius, out of the Stellae informes, or unformed stars of the ancients, which lay scattered between the Zodiacal con- stellation Leo, on the S. and Ursa Major, on the N. Its mean right ascension is the same with that of Regulus, and it comes to the meridian at the same time on the 6th of April. The modern constellations, or those which have been added to our celestial maps since the adoption of the Greek notation, in 1603, are referred to by the letters of the English alphabet, instead of the Greek. This is the case in regard to #: Minor, and all other constellations whose origin is subsequent to that period. . . - Leo Minor contains 53 stars, including only one of the 3d magnitude, and 5 of the 4th. The Fº star is situated in the body of the animal, 13° N. of Gamma Leonis,* in a straight line with Phad, and may be known by a group of smaller stars, a little above it on the N. W. It ſorms an equilateral triangle with Gamma and Delta Leonis, the vertex bein in Leo Minor. This star is marked with the letter l, in modern catalogues, an being the principal representative of the constellation, is itself sometimes called the Little Lion : 8° E. of this star (the Little Lion) are two stars of the 4th mag- nitude, in the last paw of Ursa Major, and about 10° N. W. of it, are two other stars of the 3d magnitude, in the first hind paw. “The Sinaller Lion now succeeds; a cohort Of fifty stars attend his steps; And three, to sight unarm’d, invisible.” SEXT ANS. THE SExTANT, called also URANIA’s SExTANT, f is a modern constellation that Hevelius made out of the unformed stars of the ancients, which lay scattered between the Lion, on the N., and Hydra, on the S. It contains 41 very small stars, including only one as large * Leon is is the genitive, or possessive case of Leo, and Cam?na Leomis means the Gamma of Leo. Thus also the principal star in Aries is marked Alpha Arietis, mean- ing the Alpha of Aries, &c. - + Urania was one of the muses, and daughter of Jupiter and Mnemosyne. She pre- sided over astronomy. She was represented as a young Virgin, dressed in an azure- coloured robe, crowned with stars, bolding a robe in her hands, and having many mathematical instruments about her. What is the origin of Leo Minor, and how is it situated? What is Its mean right as- cension? When is it on the meridian? What are the number and magnitude of lis stars? What is the position of the principal star in this constellation, and how may it be known What figure does it form ºth some other stars 7 - What letter represents this star, and what else is it called 2, What relukº do we find in this constellation? What are the origin and position of the Sextant? How many stars does it contain? . * MAP tv.1 HYDRA AND THE CUP. 83 as the 4th magnitude. This is situated very near the equi- noctial, 13° S. of Regulus, and comes to the meridian about the same time on the 6th of April. The other stars in this constellation are too small to engage attention. A few of the largest of them may be traced out from the map. History.—A sextant, in mathematics, is the sixth part of a circle, or an arch comprehending 60 degrees. But the teru, is more particularly used to denote an astronomical instrument well known to mariners. Its use is the sanie as that of the quadrant; namely, to measure the angular distance, and take the altitude of the sun, moon, planets, and fixed staš It is indispensable to the mariner in finding the latitude and longitude at and should be in the hands of every surveyor and practical engineer. It may serve the purpose of a theodolite, in measuring inaccessible heights and distânces. It may gratify the young pupil to know, that by means of such an instrument, well adjusted, and with a clear eye and a steady hand, he could readily tell, within a few hundred yards, how far north or south of the equator he was, and that from any quarter of the world, known or unknown. This constellation is So called, on account of a supposed resemblance to this instrument. HYDRA AND THE CUP. Hydra, THE WATER SERPENT, is an extensive constella- tion, winding from E. to W. in a serpentine direction, over a space of more than 100 degrees in length. It lies south of Cancer, Leo, and Virgo, and reaches almost from Canis Mi- nor to Libra. It contains sixty stars, including one of the 2d magnitude, three of the 3d, and twelve of the 4th. Alphard, or Cor Hydrae, in the heart, is a lone star of the 2d magnitude, 23° S. S. W. of Regulus, and comes to the meridian at the same time with Lambda, in the point of the sickle, about 20 minutes before 9 o'clock on the 1st of April. There is no other considerable star near it, for which it can be mistaken. An imaginary line drawn from Gamma Leonis º Regulus, will point out Cor Hydrºe, at the distance Of 239. The head of Hydra may be distinguished by means of four stars of the 4th magnitude, 2$o and 49 apart, situated 60 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 69 directly S. of Acubens, and culminates at the same time. * . When Alphard is on the meridian, Alkes, of the 4th mag- nitude, situated in the bottom of the Cup, may be seen 249 What is the position of the largest one? Describe the situation and extent of the constellation Hydra. What are the number and magnitude of its stars? Describe the osition and magnitude of Alphard, What are the distance and direction of Cor Hy- Yaº from Gamma Leonis? How may the head of Hydra be distinguished A How māy the three upper stars in this cluster be known? Which stars form a beautiful little triangle? Hów is Alkes situated, and when may it be seen? S4 PICTURE OF THE HEAVENS. LAPRIL. S. E. of it, and is distinguished by its forming an equilateral triangle with Beta and Gamma, stars of the same magnitude, 6° S, and E. of it. , Alkes is common both to Hydra and the Cup. Beta, on the S., is in Hydra, and Gamma, on the N. E., is near the middle of the Cup. A line drawn from Zozma, through Theta Leonis, and continued 38% o directly S. will reach Beta; it is therefore on the same meridian, and will culminate at the same time on the 23d of April. The Cup itself, called also the Crater, may be easily dis- tinguished by means of six stars of the 4th magnitude, form- ing a beautiful crescent, or semicircle, opening to the W. The centre of this group is about 150 below the equinoctial, and directly S. of the hinder feet of Leo. The crescent form of the stars in the Cup is so striking and well defined, when the moon is absent, that no other description is necessary to point them out. Its centre comes to the meridian about two hours after Alphard, on the same evening; and consequently, it culminates at 9 o'clock, one month after Alphard does. The remainder of the stars in this constellation may be easily traced by aid of the map. When the head of Hydra is on the meridian, its other ex- tremity is many degrees below the horizon, so that its whole length cannot be traced out in the heavens until its centre, or the Cup, is on the meridian. - * —“Near the equator rolls The sparkling Hydra, proudly eminent To drink the Galaay’s reſulgent sea ; Nearly a fourth of the encircling curve Which girds the ecliptic, his vast folds involve; Yet ten the number of his stars diffused * O'er the long track of his enormous spires: Chief beams his heart, sure of the second rank, But emulous to gain the first.”—Eudosia. . HISTORY..—The astrologers of the east, in dividing the celestial nosts into vari. ous compartments, assigned a popular and allegorical meaning to each. Thus the sign Leo, which passes the meridian about midnight, when the sun is in Pisces, was called the House of the 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 hermisphere, symbolized the moon’s course: hence the Nodes are called the Dragon’s head and tail, to this day. The hydra was a terrible monster, which, according to mythologists, inſested the neighbourhood of the lake Lerna, in the Peloponnesus. It had a hundred heads, according to Diodorus; fifty, according to Simonides; and nine, accord- ing to the more commonly received opinion of Apollodorus, Hyginus, and others, As soon as one of these heads was cut off, two immediately grew up if the wound was not stopped by fire. - If Alkes be situated in the Cup, why is it also included in Hydra? How are the other two stars that make a triangle with Alkes, situated How is Beta situated With respect to Zozima and Theta Leonis? When is Beta on the meridian? How may the Cup be distinguished 3 How is the centre of this É. situated with respect to Leo and the equinoctial? What single circumstance is sufficient to designate the stars in the Cup? When is it on the meridian When the head of Hydra is On the meridian, Where is the other extremity of the constellation? When the sun enters the sign Cancer, at the summer sol- size, he discontinues his progress towards the north pole, and a, ins to return towards the south pole. This retrograde mo- tion was fitly represented by a Crab, which is said to go back- wards. The sun enters this sign about the 22d of June. The heat which usually follows in the next month, was represented by the Lion ; an animal remarkable for its fierce- ness, and which at this season was frequently impelled by thirst, to leave the sandy desert, and make its appearance on the banks of the Nile. The sum 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 ob- serve an equilibrium or balance. The sign was therefore represented under the symbol of a pair of Scales. Autumn, which produces fruit in great abundance, brings with it a variety of diseases, and on this account was repre- sented 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. Aquarius, or the Water-Bearer, is represented by the figure of a man pouring out water from an urn, an emblem of the dreary and uncomfortable season of winter. The last of the zodiacal constellations was Pisces, or a couple of fishes, tied back to back, representing the fishing season. The severity of winter is over; the flocks do not afford sustenance, 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 }. celestial narch; 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; What sign was represented under the figure of a Crab, and why? When does the *um enter this sign 2. What animal represented the heat of summer, and why? When does the sun enter the sixth sign, and how is this season represented? Why was the sign, which the sum enters at the autumnal equinox represented under the symbol of a Balance? Why were the autumnal signs, Scorpio and Sagittarius, represented as they are 3, What does the Goat represent? What is signified by the Water-Bearer? What do the Fishes represent? 13% F50 ORIGIN OF THF. Lioms 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 Chal- dean constellations, and substituted such images in their place as had a more special reference to their own history. The Romans, also, pursued the same course with regard to their history; and hence the contradictory accounts that have de- scended to later times. Some, moreover, with a desire to divest the science of the stars of its pagan jargon and profanity, have been induced to alter both the names and figures of the constellations. In doing this, they have committed the opposite fault; that of blending them with things sacred. The “venerable Bede,” for example, instead of the profane names and figures of the twelve constellations of the Zodiac, substituted those of the twelve apostles. Julius Schillerius, following his example, çompleted the reformation in 1627, by giving Scripture names to all the constellations in the heavens. Weigelius, too, a celebrated professor of mathematics in the university of Jena, made a new order of constellations, by converting the firma- ment into a COELUM HERALDICUM, in which he introduced the arms of all the princes of Europe. But astronomers, gene- rally, never approved of these innovations; and for ourselves, we had as lief the sages and heroes of antiquity should con- tinue to enjoy their fancied honours in the sky, as to see their places supplied by the princes of Europe. 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 not embraced in the old con- stellations, and hence arose that mixture of ancient and mod- ern names which we meet with in modern catalogues. * The order of the signs is thus described by Dr. Watts :- The Ram, the Bull, the heavenly Twins And next the Crab, the Lion shines, The Virgin, and the Scales; The Scorpion, Archer, and Sea-Goat, The Man that holds the JWater-Pot, And Fish, with glittering tails. Similar to this are the Latin verses:– Sunt, aries, taurus, gemini, cancer, leo, virgo, . Libraque, scorpius, arciténerºs, Caper, ampho?'a, pisces. Why have attempts been made to change the names and figures of the ancient con- stellations? What fault has been committed in doing this? What did the venerable Bede substitute for the profane names and figures of the twelve constellations of the Zodiacº Who followed his example, and to what extent? What other change was attempted, and by whom , , Have astronomers generally approved of these innova- tions : What was the number of the old constéïations? hence is the mixture of ancient and modern names which we meet with in modern catalogues? CONSTELLATIONS, 151 Astronomers divide the heavens into three parts, called the northern and southern hemispheres, and the Zodiac. In the northern hemisphere, astronomers usually reckon thirty-four constellations; in the Zodiac twelve, and in the southern hemisphere forty-seven ; making, in all, ninety-three. Besides these, there are a few of inferior note, recently formed, which are not considered sufficiently important to be particularly described. About the year 1603, John Bayer, a native of Germany, invented the convenient system of denoting the stars in each constellation by the letters of the Greek alphabet, applying to the largest star the first letter of the alphabet; to the next largest the second letter, and so on to the last. Where there are more stars in the constellation than there are Greek let- ters, the remainder are denoted by the letters of the Roman alphabet, and sometimes by figures. By this system of no- tation, it is now as easy to refer to any particular star in the heavens, as to any particular house in a populous city, by its street and number. - * Before this practice was adopted, it was customary to de- note the stars by referring thern to their respective situations in the figure of the constellation to which they severally be- longed, 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 and maps, are, purely, a fanciful invention—answering many convenient ends, however, for purposes of reference and classification, as they enable us to designate with facility any particular star, or cluster of stars; though these clusters very rarely, if ever, represent the real figures of the object whose names they bear. And yet it is somewhat remarkable that the name of “Great Bear,” for instance, should have been given to the very same constellation by a nation of American aborigines, (the Iro- quois,) and by the most ancient Arabs of Asia, when there never had been any communication between them I Among other nations, also, between whom there exists no evidence of any intercourse, we find the Zodiac divided into the same number of constellations, and these distinguished by nearly the same names, representing the twelve months, or seasons of the year. The history of this whimsical personification of the stars carries us back to the earliest times, and introduces us, as we have seen, to the languages and customs, the religion and How do astronomers usually divide the heavens, and what is the number of con: stellations in each division? What convenient system of notation has been invented for denoting the stars in each constellation? Who invented this system 3 Before this method was introduced, what was the practice? 152 NUMBER, DISTANCE, AND poetry, the sciences and arts, the tastes, talents, and peculiar genius, of the early nations of the earth. The ancient Atlan- tides and Ethiopians, the Egyptian priests, the magi of Per- sia, the shepherds of Chaldea, the Bramins of India, the man- darins of China, the Phoenician navigators, the philosophers of Greece, and the wandering Arabs, have all added more or less to these curious absurdities and ingenious inven- tions, and have thus registered among the stars, as in a sort of album, some memorial of themselves and of the times in which they lived. 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 chromology, geography, and languages, are here preserved in imperishable characters. The adven- tures 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— “ISnowest thou the ordinances of heaven 2 Canst thou bind the sweet influences of the PLEIADEs, or loose the bands of ORION ? Canst thou bring forth MAzzAROTH in his season, or canst thou guide ARCTURUs with his sons 7” Here, too, are consecrated the lyre of Orpheus, and the ship of the Ar- gonauts; and, in the same firmament, glitter the mariner's compass and the telescope of Herschel. C H A P T E R X. I W. NUMBER, DISTANCE, AND ECONOMY of THE STARs. THE first conjecture in relation to the distance of the fixed stars, is, that they are all placed at an equal distance from the observer, upon the visible surface of an immense concave vault, which rests upon the circular boundary of the world, and which we call the Firmament. We can with the unassisted eye, form no estimate of their respective distances; nor has the telescope yet enabled us to arrive at any exact results on this subject, although it has re- vealed to us many millions of stars that are as far removed What is the first conjecture which we form in relation to the distances of the fixed stars? What means have we for ascertaining their number and distanco ) ECONOMY OF THE STARS. 153 beyond those which are barely visible to the naked eye, as thése are from us. Viewed through the telescope, the hea- vens become quite another spectacle—not only to the under- standing, but to the senses. New worlds burst upon the sight, and old ones expand to a thousand times their former dimen- sions. Several of those little stars which but feebly twinkle on the unassisted eye, become immense globes, with land and water, mountains and valleys, encompassed by atmos: pheres, enlightened by moons, and diversified by day and oight, summer and winter. & Beyond these are other suns, giving light and life to other systems, not a thousand, or two thousand merely, but multi- plied without end, and ranged all around us, at immense dis- tances 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. 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 heyond the utmost boundaries of human vision, than a drop of water to the ocean ; and, iſ 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 an eminent divine of the present century,”) not to look on our earth, as the universe of God, but as a single, insignificant atom of it; that it is only one of the many mansions which the Supreme Being has created for the accommodation of his worshippers; and that he may now be at work in regions more distant than geome- try ever measured, creating worlds more manifold than num- bers ever reckoned, displaying his goodness, and spreading over all, the intimate visitations of his care. The immense distance at which the nearest stars are known to be placed, proves that they are bodies of a prodigious size, not in ſerior to our sun, and that they shine, not by reflected rays, but by their own native light. It is therefore concluded, with good reason, that every fixed star is a sun, no less spacious than ours, surrounded by a retinue of planetary worlds, which * Chalmers. How do the heavcns appear through the telescope A What are beyond those little Stars Which are scarcely visible to the naked eye How many stars are visible through the telescope? What proportion may this vast assemblage of suns and worlds bear to what lies beyond the utmost boundaries of human vision? How should we learn from this to regard our own earth What does the immense distance of the stars prove in regard to their magnitude and light? 154 NUMBER, DISTANCE, AND revolve around it as a centre, and derive from it light and heat, and the agreeable vicissitudes of day and night. These vast globes of light, then, could never have been de- signed merely to diversify the voids of infinite space, nor to shed a few glimmering rays on our far distant world, for the amusement of a few astronomers, who, but for the most pow- erful telescopes, had never seen the ten thousandth part of them, ... We may therefore rationally conclude, that wherever the All-wise Creator has exerted his creative power, there also he has placed intelligent beings to adore his goodness. Hipparchus, the father of astronomy, first made a catalogue of the fixed stars. It contained 1022. The accuracy with which the places of these were recorded, has conferred essential benefit upon the science, and has enabled us to solve many celestial phenomena and problems of chronology, which other- wise had been difficult. During the 18th century, upwards of 100,000 were catalogued by the various astronomers of Europe, and their position in the heavens determined with an exactness that seldom varied a second ſrom the truth; insomuch that it has been justly remarked, that “there is scarcely a star to be seen in the heavens, whose place and situation is not better known than that of most cities and towns upon the earth.” But the stargazers of our times are not idle. Professor Bessell of Konigs- berg, observed in three years, it is asserted, between 30,000 and 40,000 stars, comprehended within a zone of 15° on each side of the equator; but even this great number is but a small portion of the whole number which lie within the limit of the zone which he examined. To procure a more complete survey, the academy of Berlin proposed that this same zome should be parcelled out among twenty-four observers, and that each should confine himself to an hour of right ascension, and examine it in iminute detail. This plan was adopted; and the 18th lfour was confided to Professor Inghirami, of Florence, and examined with so much care, that the ſº of 75 U00 stars in it, have been determined. Pro- ſessor M. Slruve, of the I)orpat university, has examined in person, 120,000 stars, of which 800 (double ones) were before unknown to science. The labours of Sir Wm. Iſerschel were chiefly devoted to exploring the sys- tems of nebulae and double stars that lic, ſor the most part, beyond the reach of ordinary telescopes. No ſewer than two thousand five hundred nebulae were observed by this indefatigable astronomer, whose places have been computed from his observations, reduced to a common epoch, and arranged into a cata- logue in order of their right ascension, by his sister Miss CARolin E HERSCHEL, a larly so justly celebrated in Europe for her astronomical knowledge and dis. coveries, but whose name, strange as it is, is seldom mentioned in this country. Be it remembered, nevertheless, for her ſame, that she discovered two of the satellites of the planet which bears her brother’s maine, besides a multitude of COIIletS. - The greatest possible ingenuity and pains have been taken by astronomers to determine, at least, the approximate dis- tance 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 distan- ces from the earth, it is because they have not the requisite data. The solution of the problem, if they had the data, would not be more difficult than to compute the relative dis- What conclusion may be drawn from this fact as to their great design? What pains have astronomers taken to find the distance of the stars, and what result have they come toº. For what reason have they failed to calculate their distance? Is the prob- lem a difficult one? - - EconoMy of THE STARs. 155 tances of the planets—a thing which any school-boy 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 diame- ter of the earth’s orbit, which, in round numbers, is 190 millions of miles, and endeavour, 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 appre- hension of the pupil, if he does not shrink from the illustra- tion, through an idle fear that it is beyond his capacity. For example; suppose that, with an instrument construct- ed for the purpose, we should this night take the precise bear- ing or angular direction from us of some star in the northern hemisphere, and note it down with the most perfect exact- ness, and, having waited just six months, when the earth shall have arrived at the opposite point of its orbit, 190 mill- ions 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 our travelling so great a distance one side of it. Now it is evident, that if it changes its apparent position at all, the quantity of the change will bear some proportion to the distance gone over ; that is, the nearer the star, the greater the angle; and the more remote the star, the less the angle. It is to be observed, that the angle thus found, is called the star's Annual Par- allaar. But it is found by the most eminent astronomers of the age, and the most perfect instruments ever made, that this parallax does not exceed the four thousandth part of a de- gree, or a single second ; so that, if the whole great orbit of the earth were lighted up into a globe of fire 600 millions of miles in circumference, it would be seen from the nearest star only as a twinkling atom; and to an observer placed at this distance, our sun, with its whole retinue of planetary worlds, would occupy a space scarcely exceeding the thickness of a spider’s web.” If the nearest of the fixed stars are placed at * A just idea of the import of this term, will impart a force and sublimity to an ex- pression of St.James, which no power of words could in prove. . It is said, Chapter I, verse 17., of Him fºcum whom cometh down every gool and perſect gift, that there is “ova en rapaxxx; n n +pºrn; azraa tºwagº.” Literally, There is “neither par. allaº, nor shadow ºf change:" As if the apostle had said—Peradventure, that in tra: velling millions aid millions of niiles through the regions of imamensity, there may be a sensible parallax to some of the fixed stars ; yet, as to the Father of Lights, view % tºp whatever point of his Empire we may, he is without paralia, or shadow of C/28/29'6 What measure is (mployed in estimating the distances of the fixed stars? How is it used? What is ti,e angle thus found called? What is the greatest magnitude of the annual parallax? . 156 NUMBER, DISTANCE, AND such inconceivable distances in the regions of space, with what line shall we measure the distance of those which are a thousand or a million of times as much farther from them, as these are from us. 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: : So 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 0.000004848.1368= Nat. Sine of 1/7. Is to 1.0000000000000–Nat. Sine of 90°. - So is 95,273,868.867748554=Earth’s distance from the sun, To 19,651,627,683,449=Star’s distance from the sun. In this calculation we have supposed the earth to be placed at the mean dis- tance of 24,047 of its own seini-diameters, or 95,273,868.867748554 miles from the sun, which makes the star's distance a very little less than twenty billions of miles. Dr. Herschel says that Sirius cannot be nearer than 100,000 times the diameter of the earth’s orbit, or 19 007,788.800 000 of miles. Biot, who either takes the earth’s distance greater than he lays it down in his Traite’ Element aire d’Astronomie Physique, or has made an errour in figures, makes the distance 20086,868,036,404. Dr. Brewster makes it 20,159,665.000 miles. A mean of these counputations, is 20 billions; that is, 20 millions of mill- ions of miles, to a parallax of it’ Astronourers are generally agreed in the opinion that the annual parallax of the stars is lºss than l’, and consequently that the nearest of them is placed at a much greater distance ſtom us, than these calculations make it. It was, how- over, announced during the last year, that M. D’Assas, a French astronomer had sa’isfactorily established the annual parallax of Keid, (a small star 8° N. o Gamina Eridani.) to be 2'', that of I’igel, in Orion to be 1”. 43. arid that of Sirius to be l’’. 24. If these results may be relied on, Keid is but 10 billions, Rigel but 14 billions, and Sirius 16 billions of miles from the earth. This latter distance is, however, so great that, if Sirius were to fall towards the earth at the rate of a million of miles a day, it would take it ſorty three thousand, three hundred years to reach the earth; or, if the Almighty were now to blot it out of the heavens, its brilliance would continue undinninished in our hemisphere ſor the space of three years. The most brilliant stars, till recently, were supposed to be situated nearest the earth, but later observations prove that this opinion is not well founded, since some of the smaller stars appear to have, not only a greater annual parallax, but an absolute motion in space, much greater than those of the brightest class. What conclusion may be drawn from this fact in regard to the distances of the ſixed stars? If the annual parallax of a star were known, by what simple rule could yºu computº its listance? If we allow the annual parallax of the perest star to be 1’’, what will its distance be? What is a mean of the calculations of different astron- ontérº, for a para’law of 1° 2 What recent observations indicate a greater parallac to some of the stars 2 If the parallac of Sirius be l’’.24, what will be its distance 2 Hoto 'ong would it require, pºssing through this distance, at the rate of a million of 77.3/ey a day, to reach the earth, and how long would its light continue, undiminished £9 us, were it to be blotted from the heavcms? What has been supposed to be the rela- tivo distance of the most brilliant stars from the earth 7 What do later observations }}rove, in regard to this opinion 7 ECONOMY OF THE STARS, 157 . It has been computed that the light of Sirius, although twenty thousand million times less than that of our Sun, is, nevertheless, three hundred and twenty-four times greater than that of a star of the sixth magnitude. If we suppose the two stars to be really of the same size, it is easy to show that the star of the sixth magnitude is fifty-seven and one third times farther from us than Sirius is, because light diminishes as the square of the distance of the luminous body increases. By the same reasoning it may be shown, that iſ Sirius were placed where the sun is, it would appear to us to be ſour times as large as the Sun, and give four times as much light and heat. It is by no means unreasonable to suppose, that many of the fixed stars exceed a million of miles in diameter. - We may pretty safely affirm, then, that stars of the sixth magnitude, are not less than 900 millions of millions of miles distant from us; or a million of times farther from us than the planet Saturn, which is scarcely visible to the naked eye. But the human mind, in its present state, can no more appre- ciate such distances than it can inſinity; for if our earth, which moves at more than the inconceivable velocity of a mill- ion and a half of miles a day, were to be hurried from its orbit, and to take the same rapid flight over this immense tract, it would not traverse it in sixteen hundred thousand years; and every ray of light, although it moves at the rate of one hundred and ninety-three thousand miles in a single second of time, is more than one hundred and seventy years in com- ing from the star to us. But what is even this, compared with that measureless ex- tent which the discoveries of the telescope indicate 2 Ac- cording to Dr. Herschel, the light of some of the nebulae, just perceptible through his 40 feet telescope, must have been a million of ages in coming to the earth; and should any of them be now destroyed, they would continue to be perceptible for a million of ages to come. Dr. Herschel inſorins us, that the glass which he used, would separate stars at 497 times the distance of Sirius, It is one of the wonders of creation that any phenomena of bodies at suuh an immense distance from us should be perceptible by human sight; but it is a part of the Divine Maker's plan, that although they do not act physically upon us, yet they should so far be objects of our perception, as Suppose the light of Sirius to he twenty thousand million times less than that of Our Sun, how would it compare with that of a star of the sixu, magnitude? If we Suppose the two stars to be of the same size, how much farther off is the star of the Sixth magnitude, than Sirius is Suppose Sirius to be placed where our Sun is, how 30guld its apparent magnitude, and its light and heat compare with those of the sun ? What may we generally affirm of the distance of stars of the sixth magnitude? 'Can the human mind appreciate such distances? What illustrations can you give to show their immensity? What is this distance compared with that of the telescopic stars, and the nebulae? Why are we able to see bodies at so great a distance? 158 NUMBER, DISTANCE, AND 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 reasonable to conclude, that those ex- pressions in the Mosaic history of Creation, which relates to the creation of the fixed stars, are not to be understood as referring to the time when they were brought into existence, as if they had been created about the same time with our earth; but as simply declaring the fact, that, at whatever pe- riod in duration they were created, they derived their eacist- ence from God.” “That the stars here mentioned,” (Gen. i. 16.) says a dis- tinguished commentator,” “were the planets of our system, and not the fixed stars, seems a just inference from the fact, that after mentioning them, Moses immediately subjoins, “And Elohim set them in the firmament of the heaven to give light upon the earth, and to rule over the day and over the might;’ evidently alluding to Venus and Jupiter, which are alternately our morning and evening stars, and which ‘give light upon \he earth,’ far surpassing in brilliancy any of the fixed stars.” However vast the universe now appears; however numerous the worlds which may exist within its boundless range, the language of Scripture, and Scripture alone, is sufficiently comprehensive and sublinie, to express all the emotions which maturally 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 are authentic and divine. We have hitherto described the stars as being immoveable 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 re- trograde; and that many of them have dark spots upon their surface, and turn on their axes, like the sun. A remarkable change appears to be gradually taking place in the relative distances of the stars from each other in the constellation Hercules. The stars in this region appear to be spreading farther and farther apart, while those in the opposite point of the heavens seem to close nearer and nearer together in the same mammer as when walking through a * S. Turner, F. S. A. R. A. S. L., 1832. - With these facts heſore us, what miny we reasonably conclude with regard to the expressions in the Mosaic history which relate to the creation of the fixed stars 2 What is the opinion of Mr. 'Turner in regard to the stars herº mentionell? To what is the expression, “To rule over the d, y and over the night,” supposed to allude? Give some account of the real motions of the fixed stars. What remarkable changes are taking place in the constellation Hercules? £CONOMY OF THE STARS. 159 forest, the trees towards which we advance, appear to be constantly separating, while the distance between those which we leave behind, is gradually contracting. From this appearance it is concluded, that the Sur, with all its retinue of planetary worlds, is moving through the re- gions of the universe, towards some distant centre, or around some wide circumference, at the rate of sixty or seventy thousand miles an hour; and that it is therefore highly prob- able, if not absolutely certain, that we shall never occupy that portion of absolute space, through which we are at this moment passing, during all the succeeding ages of eternity.” The author of the CHRISTIAN PHILosoph ER endeavours 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 pro- vince of creation to another, for six thousand years, and will continue the same rapid course for a thousand millions years to come; it is highly probable, if not absolutely certain, that, at the end of this vast tour, he would have advanced no far- ther than the ‘suburbs of creation,’—and that all the magnifi- cent systems of material and intellectual beings he had sur- veyed, during his rapid flight, and for such a length of ages, bear no more oroportion to the whole empire of Omnipotence than the smallest grain of sand does to all the particles of rºatter contained in ten thousand worlds.” Were a seraph, in prosecuting the tour of creation in the manner now stated, ever to arrive at a limit beyond which no farther displays of the Divinity could be perceived, the thought would overwhelm his faculties with unutterable emo- tions; he would feel that he had now, in some measure, comprehended all the plans and operations of Omnipotence, and that no farther manifestation of the Divine glory remain- ed to be explored. But we may rest assured that this can never happen in the case of any created intelligence. There is moreover an argument derivable from the 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 nutmber of stars be finite and occupy only a part of space, the outward stars would be continually attracted * Professor Bessel does not fall in with this prevailing opinion. What conclusion is drawn from this appearance, Shall we them prºbably ever 9CCupy that portion of space through which we are now passing, againi What illus- tration does the author of the Christian Philosopher give in order to convey some idea of the boundless extent of the umiverse? Were a scraph ever to arrive at a limit beyond which no farther displays of the divine glory could be perceived, how would the idea affect him? Is it probable that such a place exists in the universe, or within the scope of any created intelligence 7 160 FALLING, OR Shooting STARs. * -- to those within, and in time would unite in one. But if the number be infinite, and they occupy an infinite space, all parts would be nearly in equilibrio, and con- sequently each fired 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 seems almost afraid lest he should be overlooked amidst the im- mensity of beings that must needs be under the superintend- ence of God; or that any finite mortal should exclaim, when contemplating the heavens—“What is man, that THOU art mindful of him P C H A P T E R X W II. FALLING, OR SHOOTING STARs. THE phenomenon of shooting stars, as it is called, is com- mon 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 sun, and that their return to certain places might be calculated with as much certainty and exactness as that of any of the Čomets. Dr. Burmey, of Gosport, kept a record of all that he ob- served in the course of several years. The number which he noticed in 1819, was 121, and in 1820, he saw 131. Pro- fessor Green 1s conſident that a much larger number are anr- nually seen in the United States. Signior Baccaria supposed, they were occasioned by elec- tricity, and thinks this opinion is confirmed by the following: observations. About an hour after sunset, he and some friends, that were with him, observed a falling star, directing its course directly towards them, and apparently growing larger and larger, but just before it reached them it disap- Where does the phenomenon of falling, or shooting stars occur? What is there to excite our admiration in this phenomenon ) is this interesting phenomenon well un- dcrºstood What are the different opinions in regard to them 3 Fow many shooting stars did Dr. Burney observe in the years 1819 and 1820? ...Is it probable that a much larger number is seen every year in the United States?, What did Baccaria suppose they were occasioned by, and what observations did he make to strengthen his opinion? FALLING, OR SHOOTING STARs. \61 peared. On vanishing, their faces, hands, and clothes, with the earth, and all the neighbouring objects, became suddenly illuminated with a diffused and lambent light. It was attend- ed with no noise. During their surprise at this appearance, a servant informed them, that he had seen a light shine Sud- denly in the garden, and especially upon the streams which he was throwing to water it. The Signior also observed a quantity of electric matter col- dect about his kite, which had very much the appearance of a falling star. Sometimes he saw a kind of halo accompanying the kite, as it changed its place, leaving some glimmering of light in the place it had quitted. Shooting stars have been supposed by those meteorologists who refer them to electricity or luminous gas, to prognosticate changes in the weather, such as rain, wind, &c.; and there is, perhaps, some truth in this opinion. The duration of the brilliant tract which they leave behind them, in their motion £hrough the air, will probably be found to be longer or shorter, according as watery vapour abounds in the atmosphere. The motion that this phenomenon betokens high winds, is of great antiquity. , Virgil, in the first book of his Georgics, expresses the same idea:— “Saepe e iam stellas vento impendente widebis Praecipites cqºlo labi; ... per umbram Flaunmaruin longos a tergo albescere tractus. And oſt, before tempestuous winds arise, The seeming stars all headlong from the skies, And shooting through the darkness, gild the night With sweeping glories and long trails of light.” The number of shooting stars, observed in a single night, though variable, is commonly very small. There are, how- £ver, 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 other. As early as the year 472, in the month of November, a phenomenon of this kind took place near Constantinople. As Theophanes relates, “The sky appeared to be on file,” with the corruscations of the flying meteors. A shower of stars, exactly similar took place in Canada, between the 3d and 4th of July, 1814, and another at Montreal, in November, 1819. In all these cases, a residuum, or black dust, was deposited upon the surface of the waters, and upon the roofs of buildings, and other objects. In the year 1810, “inflamed sub- Stances,” it is said, fell into and around lake Van, in Armenia, which stained the water of a blood colour, and cleft the earth in various places. On the 5th of What was the appearance upon streams of water? What did he observe at this time about his kite? What connexion are they supposed to have with meteorologvº What circumstance may we probably find to confirm this idea? Is this motion of very ancient, or of modern date? What is, usually, the number of shooting stars observed in a single might? When, and where, occurred the first instance, on record, of their falling in great numbers? Mention some other instances. What remarkable vestigs toas left by these meteoric showers 2 4% 14” 162 FALLING, OR SHOOTING STARs. September, 1819, a like phenomenon was seen in Moravia. History furnisłſes many more instances of meteoric showers, depositing a red dust, in some places, So plentiful as to adulit of chymical analysis. The commissioner, (Mr. Andrew Ellicott,) who was sent out by Cur government to fix the boundary between the Spanish. possessions in North America and the United States, witness— ed a very extraordinary flight of shooting stars, which filled the whole atmosphere from Cape Florida to the West India Islands. This grand phenomenon took place the 12th of November, 1799, and is thus described:—“I was called up,” says Mr. Ellicott, “about 3 o'clock in the morning, to see the shooting stars, as they are called. The phenomenon was grand and awful. The whole heavens appeared as if illu- minated with skyrockets, which disappeared only by the light. of the sun, after daybreak. The meteors, which at any one- instant of time, appeared as mumerous as the stars, flew ine all possible directions except from the earth, towards which, they all inclined more or less, and some of them descended; perpendicularly over the vessel we were in, so that I was ins constant expectation of their falling on us.” Mr. Ellicott further states that his thermometer which had been at 80° Fahr. for the four days preceding, fell to 56°, about 4 o’clock, A. M., and that nearly at the same time, the wind changed from the south to the northwest, from whence it blew with great violence for three days without intermission. These same appearances were observed, the same might, at Santa Fe de Bogota, Cumama, Quito, and Peru, in South America ; and as far north as Labrador and Greenland, ex- tending to Weimar in Germany, being thus visible over an extent on the globe of 649 of latitude, and 949 of longitude. The celebrated Humboldt, accompanied by M. Bompland, then in S. America, thus speaks of the phenomenon:—"Towards the morning of the 13th of No. venuber, 1799, we witnessed a most extraordinary scene of shooting meteors. Thousands of botides, and falling stars succeeded each other during four hours. Their direction was very regular from north to south. From the beginning of the phenomenon there was not a space in the firmament, equal in extent to three diameters of the moon, which was not filled, every instant, with bolides or falling stars, All the meteors left luminous traces, or phosphorescent bands behind them, which lasted seven or eight seconds.” This phenomenon was witnessed by the Capuchin missionarv at San Fer- nando de Afiura, a village situated in lat. 7°53' 12", amidst the savannahs of the province of Varinas; by the Franciscan monks stationed near the cataracts of the Oronoco, and at Marca, on the banks of the Rio Negro, lat. 2° 40' long. 70° 21', and in the west of Brazil, as far as the equator itself; and also at the city of Porto Cabello, lat. 109 6' 52', in French Guiana, Popayan, Quito, and Peru. It is somewhat surprising that the same appearances, observed in places so widely separated, almid the vast and lonely deserts of South America, should have been seen, the same might, in the United States, in Labrador, in Greenland, and at Itterstadt, near Weimar, in Germany Recite instances of a similar kind, in which a red dust has been deposited. Describe the phenomenon of shooting stars described by Mr. Ellicott, in 1799. Describe the same phenomenon as seen, in Soºth America, by Humboldt and others. In what other Tarts of the earth, was 4t witnessed, and by whom FALLING, OR SHOOTING STARs. 163 * * 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 Cayamburo, so great a number of falling stars, that the mountain 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. Trancis, when it was perceived that the blaze on the horizon was caused by fiery meteors, which ran along the Sky in all directions, at the altitude of 12 or 13 degrees.” But the most sublime phºnomenon of shooting stars, of which the world has furnished any record, was witnessed £hroughout the United States on the morning of the 13th of JNovember, 1833. The entire extent of this astonishing exhibition has not been precisely ascertained, but it covered no inconsiderable portion of the earth’s surface. It has been traced from the ongitude 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, any where in Europe, nor in South America, nor in any part of the Pacific ocean yet heard ſtom. - Every where, within the limits abovementioned, the first appearance was that of fireworks of the most imposing grandeur, covering the entire vault of heaven with myriads of fireballs, resembling skyrockets. Their corruscations were bright, gleaming and incessant, and they fell thick as the flakes in the early snows of December. To the splen- dours of this celestial exhibition, the most brilliant skyröckets and fireworks of art, bear less relation than the twinkling of the most tiny star, to the broad glare of the sun. The whole heavens seemed in motion, and suggested to some the awful grandeur of the image employed in the apocalypse, upon the opening of the sixth seal, when “the stars of heaven fell unto the earth, even as a fig-tree casteth her untimely figs, when she is shaken of a mighty wind.” . One of the most remarkable circumstances attending this display was, that the meteors all seemed to emanate from one and the same point, a little southeast of the zenith. Following the arch of the sky, they ran along with immense velocity, Describe another phenomenon of a similar kind, seen in South America about thirty years before. When occurred the most sublime phenomenon of shooting stars of Which the world has any record? How extensively was it witnessed? What was the first appearance of the phenomenon? What scene in the apocalypse, did it sug- É. § Some? From What point did the meteors appear to emanate?. Describe their * 164 FALLING, OR SHOOTING STARs. describing in some instances, an arc of 300 or 400 in a few seconds. On more attentive inspection it was seen, that the meteors exhibited three distinct varieties; the first, consisting of phosphoric limes, apparently described by a point; the second, of large fireballs, that at intervals darted along the sky, leav- ing luminous trains, which occasionally remained in view for a number of minutes, and, in some cases, for half an hour or more ; the third, of undefined luminous bodies, which remain- ed nearly stationary in the heavens for a long time. Those of the first variety were the most numerous, and resembled a shower of fiery snow driven with inconceivable velocity to the north of west. The second kind appeared more like falling stars—a spectacle which was contemplated by the more unemlightened beholders with great amazement and terrour. The trains which they left, were commonly white, but sometimes were tinged with various prismatic colours, of great beauty. These fireballs were occasionally of enormous size. Dr. Smith, of North Carolina, describes one which appeared larg— er than the full moon rising.” “I was,” says he, “startled by the splendid light in which the surrounding scene was exhibited, rendering even small objects quite visible.” The same ball, or a similar one, seen at New Haven, passed off in a northwest direction, and exploded a little northward of the star Capella, leaving, just behind the place of explosion, a train of peculiar beauty. The line of direction was at first nearly straight; but it soon began to contract in length, to dilate in breadth, and to assume the figure of a serpent scROL- LING itself up, until it appeared like a luminous cloud of va- pour, floating gracefully in the air, where it remained in full view for several-minutes. 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 * If this body were at the distance of 110 miles, from the observer, it must have had a diameter of one mile ; if at the distance of 11 miles, its diameter was 528 feet ; and if only one mile off, it milst have been 48 feet in diameter. These considerations leave no doubt, that many of the meteors were bodies of large size. What other appearances were observed upon more attentive inspection? Give a more particular account of the first van icty. Of the second. What do we know in regard to the size of these ſireballs? How does Dr. Smith describe one seen by him in North Carolina? What Was the *. Of the same or a similar ball, as seen at New Haven? What was there peculiar in the course, and final disappearance of it? Suppose this meteor was 110 miles distant from the place of ohservation, what mºunt have been its diameter 2 What, if it were 11 miles distant 2 What, if only one mile 2 Mention some examples of the third variety of meteors FALLING, or SHOOTING STARS. 165 settled towards the horizon, until it disappeared. At Niagara Falls, a large, luminous body, shaped like a square table, was seen near the zenith, reniaining for some time almost stationary, emitting large streams of light. The point from which the meteors; seemed to emanate, was observed by those who fixed its position among the stars, to be in the constellation Leo; and, according to their concur- rent 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 east- ward, but accompanied the stars in their apparent progress westward. . A remarkable change of weather from warm to cold, ac- companied the meteoric shower, or immediately followed it. In all parts of the United States, this change was remarkable for its suddenness and intensity. In many places, the day preceding had been unusually warm for the season, but, be- fore the next morning, a severe frost ensued, umparalleled, for the time of year. In attempting to explain these mysterious phenomena, it is argued, in the first place, that the meteors had their origin beyond the limits of our atmosphere; that they of course did not belong to this earth, but to the regions of space exte- TIOr to lt. *- The reason on which ſhis conclusion is founded is this:—All bodies near the earth, including the atmosphere itself, have a common motion with the earth around its axis ſtom west to east ; but the radiant point, that indicated the source from which the ineteors einamated, followed the course of the stars from east to west; therefore, it was independent of the earth’s rotation, and consequently, at a great distance from it, and beyond the limits of the atmos- phere. The height of the meteoric cloud, or radiant point, above the earth’s surface was, according to the inean average of Professor Olmsted’s observa- tions, not less than 223S miles. That the meteors were constituted of very light, combus- tible materials, seems to be evident, from their exhibiting the actual phenomena of combustion, they being consumed, or converted 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 quantity of matter been considerable, with so prodigious a velocity, they would have had sufficient momentum to dash them upon the earth; where the most disastrous consequences might have followed. - In what constellation was the point from which the meteors seemed to radiate? What changes were obseryed in the weather during or soon after this phenomenon? In attempting to account for these phenomena, what hypothesis has been advanced in regard to the place where the neteors had their origin? What is the reasoning by which this hypothesis is sustained 3 How high was the meteoric cloud supposed io 5e above the earth 2 What do we know in regard to the substance of which the meteors were composed? What might have been the consequences, if their quantity of matter had been considerable? 166 FALLING, OR SHOOTING STARs. The momentum of even light bodies of such size, and in such numbers, trav. ersing the atmosphere with such astonishing velocity, must have produced ex- tensive deraugements in the atmospheric equilibrium. Cold air from the upper regions would be brought down to the earth; the portions of air incumbent over districts of country, remote from each other, being mutually displaced, Wruld exchange places, the air of the warm latitudes be transſerred to colder, 2nd that of cold latitudes, to warmer regions. 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 appear- ances, is electricity. But no known properties of electricity are adequate to account for the production of the meteors, for the motions, or for the trains which they, in many instances, left behind them. Others, again, have referred their proximate cause to magnetism, and to phosphoretted hydrogen ; both of which, however, seem to be utterly insufficient, so far as their properties are known, to account for so unusual a phe- Il O]] le]] OI). Professor Olmsted, of Yale College, who has taken much pains to collect facts, and to establish a permanent theory for the periodical recurrence of such phenomena, came to the conclusion, that— The meteors of November 13th, 1833, emanated from a nebulous body, which was then pursuing its way along with the earth around the sum ; that this body continues to re- volve around the sum, in an elliptical orbit—but little in- clined to the plane of the ecliptic, and having its aphelion Tear the orbit of the earth; and finally, that the body has a period of nearly sia, months, and that its perihelion is a little below the orbit of Mercury. - This theory, at least accommodates itself to the remarkable fact, that almost all the phenomena of this description, which are known to have happened, have occurred in the two opposite months of April and November. A similar exhibition of meteors to that of November, 1833, was observed on the same day of the week, April 20th, 1803, at Richmond, in Virginia, Stockbridge, Massachusetts, and at Halifax, in British Amer- ica. Another was witnessed in the autumn of 1818, in the North sea, when, in the language of the observers, “all the surrounding atmosphere was enveloped in one expansive sea of fire, exhibiting the appearance of another Moscow in flames.” *- Exactly one year previous to the great phenomenon of 1833, namely, on the 12th of November, 1832, a similar me- IWhat effect must the momentum of even light bodies of such size, moving with such velocity, have had upon the atºnosphere 2 Mention some hypotheses which have been proposed to account for these meteors. To what conclusion did Professor Olmsted, after a long investigation, come, in regard to them? To what remarkable facts in such phenomena, is this theory adapted? At what other corresponding periods have similar phenomena been observed 7 FALLING, OR SHOOTING STARs. 167 * teoric display was seen near Mocha, on the Red sea, by Capt. Hammond and crew, of the ship Restitution. A gentleman in South Carolina, thus describes the effect of the phenomenon of 1833, upon his ignorant blacks:—“I was suddenly awakened by the most distressing cries that ever ſell on my ears. Shrieks of horrour, a.d cries of mercy, I could hear from most of the negroes of three plantations, amount- ing in all to about six or eight hundred. While earnestly listening for the cause, I heard a ſaint voice near the door calling my name; I arose, and taking my sword, stood at the door. At this moinent, I heard the same Yoice still beseeching me to rise, and saying, ‘O ! my God, the world is on fire P I then opened the door, and it is difficult to say which excited me Inost—the awfulness of the scene, or the distréssed cries of the negroes ; upwards of one hundred lay prostrate on the ground—some speechless, and some with the bitterest cries, but inost with their hands raised, imploring God to save the world and them. The scene was truly awful; for never did rain fall inuch thicker, than the meteors fell towards the earth ; east, west, north, and South, it was the same !” Since the preceding went to press, the Author has been po- litely furnished, by Professor Olmsted, with the accom- panying communication. “I am happy to hear that you propose to stereotype your ‘Geography of the Heavens.’ It has done much, I believe, to diffuse a popular knowledge of astronomy, and I am pleased that your efforts are rewarded by an ex- tended patronage. “Were I now to express my views on the subject (Me- teoric Showers) in as condensed a form as possible, I should state them in some such terms as the following: The mete- oric showers which have occurred for several years past on or about the 13th of November, are characterized by four peculiarities, which distinguished 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, they mostly appear to radiate from a common centre, that is, were their paths in the heavens traced backwards, 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 every where at , nearly the same time of night, namely, from three to four o'clock—a time 168 FALLING, OR SHOOTING STARs. about half way from midnight to sunrise. The meteors are inferred to consist of combustible matter, because they are seen to take fire and burn in the atmosphere. They are known to be very light, because, although they fall towards the earth with immense velocity, few, if any, ever reach the earth, but are arrested by the air, like a wad fired from a piece of artillery. Some of them are inferred to be bodies of comparatively great size, amounting in di- ameter to several hundred feet, at least, because they are seen under so large an angle, while they are at a great dis- tance from the spectator. Innumerable small bodies thus, consisting of extremely light, thin, combustible matter, existing together in space far beyond the limits of the at- mosphere, are believed to compose a body of immense extent, which has been called ‘the nebulour body.” Only the skirts or extreme portions of this are brought down to the earth, while the entire extent occupies many thousand, 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 periodic time of the nebulous body is either nearly a year, or half a year. Various reasons have in- duced the belief that half a year is the true period; but this point is considered as somewhat doubtful. The 20tli- acal light, a ſaint light that appears at different seasons of the year, either immediately preceding the morning or following the evening twilight, ascending ſron the sun in a triangular form, is with some degree of probability. thought to be the nebulour body itself, although the exist- ence of such a body, revolving in the solar system, was inferred to be the cause of the meteoric showers, before any connexion of it with the zodiacal light was even thought of.” GENERAL PHENOMENA OF THE SOLAR SYSTEM. 169 G E N E R A L P H E N O M E N A. of THE SOLAR, SYSTEM. C H A P T E R X W I I I. OUR attention has hitherto been directed to those bodies which we see scattered every where throughout the whole celestial concave. These bodies, as has been shown, twinkle with a reddish and variable light, and appear to have always the same position with regard to each other. We know that their number is very great, and that their distance from us is immeasurable. We are also acquainted with their comparative brightness and their situation. In a word, we have before us their few visible appearances, to which our knowledge of them is well nigh limited ; al- most all our reasonings in regard to them being founded on comparatively few and uncertain analogies. Accord- ingly our chief business, thus far, has been to detail their number, to destribe their brightness and positions, and to give the names by which they have been designated. There now remain to be considered certain other ce- lestial bodies, all of which, from their remarkable appear- ance and changes, and some of them from their intimate connection with the comfort, convenience, and even ex- istence of man, must have always attracted especial ob- servation, and been objects of the most intense contemplation and the deepest intetest. Most of these bodies are situ- ated 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 conspicuous among the bodies which give light by might, and from her soft and silvery brightness, so pleasing to behold; re- To what particulars is our knowledge of the fixed stars, those heavenly bodies which we have heretofore been considering, well nigh confined Where are the bodies which now remain to be considered, situated? Which of them are the most important? 15 170 GENERAL PHENOMENA markable 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. The partial or total obscuration of these two 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. 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 towards 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. The Moon sometimes is not seen at all; and then, when she first becomes visible, appears in the west, not far from the setting Sun, with a slen- der crescent form ; every night she 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. The Sun, if his motions be attentively observed, will be found to have another motion, opposite to his apparent diurnal motion from east to west. This may be perceived distinct- ly, 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 revo- lution in the heavens. These are the most obvious pheno- mena exhibited by these two bodies. 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. 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 Describe the most obvious phenomena of the Sun and Moon. Describe the most obvious phenomena of the planets. OF THE SOLAR SYSTEM. 171 places in the concave itself. Sometimes they are station- ary; sometimes they appear to be moving from west to east, and sometimes to be going back again from east to west; being seen at sunset sometimes in the east, and sometimes in the west, and always apparently changing their position with regard to the earth, each other, and the other heaven- ly bodies. From their wandering as it were, in this man- ner, through the heavens, they were called by the Greeks TXavnrat, planets, which signifies wanderers. There also sometimes appear in the heavens, bodies of a very extraordinary aspect, which continue visible for a con- siderable period, and then disappear from our view; and noth- ing more is seen of them, it may be for years, when they again present themselves, and take their place among the bodies of the celestial 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, when they shine with their greatest brilliancy. As they recede from the Sun, they gradually lose their splendour, resume their ſaint and nebulous appear- ance, and their train diminishes, until they entirely disap- pear. 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 the Greeks countai, comets, which signifies 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 different theories were adopted to ac- count for these celestial appearances. The Egyptians, Chaldeans, Indians, and Chinese, early possessed many astro- nomical facts, many observations of important phenomena, and many rules and methods of astronomical calculation; and it has been imagined, that they had the ruins of a great system of astromotnical science, which, in the earliest ages of the world, had been carried to a great degree of perfection, and that while the principles and explanations of the phenomena were lost, the isolated, unconnected facts, rules of calculation, and phenomena themselves, remain- ed. Thus, the Chinese, who, it is generally agreed, possess the oldest authen- tic observations on record, have recorded in their annals, a conjunction of five planets at the same time, which happened 2461 years before Christ, or 100 years before the flood. By mathematical calculation, it is ascertained that this conjunction really occurred at that time. The first observation of a solar eclipse of which the world has any knowledge, was made by 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 Whence do they derive their name, Describe the comets. . Whence is their name derived A. What oriental nations early possessed rvany important astronomical facts, observations, and rules 2 Whence is it supposed that they obtained them 3 172 GENERAL PHENOMENA emperor was so irritated against the great officers of state ſor neglecting to pre. dict the eclipse, that he caused them to be put to death.*. The astronomical epoch of the Chinese, according to Bailly, commenced with Fohi, 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 antedilu- viari astronomy was preserved and transmitted, it is said that the columns on which it was registered lave survived the deluge, and that those of Egypt are only copies which have become originals, now that the others have been for. gotien. The Indians, also, profess to have u:any celestial observations of a very early date. The Chaldeans have been justly celebrated in all ages for their astronounical observations. When Alexander took Babylon, his precep- tor, Callisihemes, found a series of Chaldean observations, male in that city, and extending back with little interruption, through a period of 1903 years pre- ceding that event. This would carry us back to at least 2234 years beſore the birth of Christ, or to about the time of the dispersion of mankind by the con- ſusion of tongues. Though it be conceded, that upon this whole period in the history of the science, the obscurity of very reuote antiquity must necessari. ly rest, still it will remain evident that the plenomena of the heavenly bodies had been observed with great atteiition, and had been a subject of no ordinary interest, - But however numerous or inſportant were the observations of oriental an- tiquity, they were never reduced to the shape and symmetry of a regular SYSf ell). *i. Greeks, in all probability, derived many notions in regard to this sci- ence, and many facts and observations, from lºgypt, the great ſountain of an- cient learning and wisdom, and many were the speculations and hypotheses of their philosophers. In the fabulous period of Grecian history, Atlas, Her- cules, Linus, and Orpheus, are ulentioned as persons distinguished for their knowledge of astronomy, and ſor the improve ificnts which they made in the science. But in regard to this period, little is known with certainty, and it must be considered, as it is termed, fabulous, The first of the Greek philosophers who taught Astrono- my, was Thales, of Miletus. He flourished about 640 years before the Christian era. Then followed Anaximan- der, Anaximenes, Anaxagoras, Pythagoras, Plato.—Some of the doctrines maintained by these philosophers were, that the Earth was round, that it had two motions, a diurnal mo- tion 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, &c.; that her eclipses were caused by the Earth’s shadow, that the planets were not designed merely to adorn our heavens, that they were worlds of themselves, and that the fixed stars were centres of distant systems. Some of them, however, maintained, that the Earth was flat, and others, that though round, it was at rest in the centre of the universe. - - When that distinguished school of philosophy was estab- lished at Alexandria, in Egypt, by the muniſicence of the * It is well known that the Chinese have, from time immemorial, considered Solar Eclipses and Cºnjunctions of the planets, as prognostics of importance to the Empire, and that they have bect Eredicted us a matter of State policy. Give some instances. I l'ere these facts, however, reduced to a science 2. Whence, is it probable, that the Greeks derived their first motions of astronomy? What is the name of the first of the Greek, philosophers who taught astronomy? At what time did he flourish . What Greek philosophers after him, taught upon the same subject A Men- tion some of the doctrines which they maintained. . OF THE SOLAR SYSTEM. 173 sovereigns to whom that portion of Alexander’s empire had fallen, astronomy received a new impulse. It was now, in the second century after Christ, that the first complete sys- tem or treatise of astronomy, of which we have any know- ledge, was formed. All before had been unconnected and incomplete. Ptolemy, with the opinions of all antiquity, and of all the philosophers who had preceded him, spread out before him, composed a work in thirteen books, called the Meyaxn Xuvragus, or Great System. Rejecting the doc- trine of Pythagoras, who taught that the Sun was the centre of the universe, and that the Earth had a diurnal motion on its axis and an annual motion around the Sun, as contrary to the evidence of the senses, Ptolemy endeavoured to ac- count for the celestial phenomena, by supposing the Earth to be the centre of the universe, and all the heavenly bodies to revolve around it. He seems to have entertained an idea in regard to the supposition, that the Earth revolved on its axis, similar to one which some entertain even at the pre- sent day. “If,” says he, “there were any motion of the Earth common to it and all other heavenly bodies, it would certainly precede them all by the excess of its mass being so great ; and animals and a certain portion of heavy bodies would be leſt behind, riding upon the air, and the Earth itself would very soon be completely carried out of the heavens.” e In explaining the celestial phenomena, however, upon his hypothesis, he met with a difficulty in the apparently stationary attitude and retrograde two- tions which he saw the planets sometimes have. To explain this, however, he supposed the planets to revolve in small circles which he called epis cycles, which were, at the same time, carried around the Earth in larger circles, which he called deferents, or carrying circles. In ſollowing out his theory and applying it to the explanation of different phenomiena, it became necessary to add new epicycles, and to have recourse to other expedients, until the system became unwieldy, cum brous, and complicated. This theory, although astronomical observations continued to be made, and some distinguished astrouomers appeared from time to time, was the prevailing theory until the middle of the 15th century. It was not, however, altrays received with implicit confidence; nor were its difficulties always entirely unappreciated. Alphonso X, king of Castile, who ſlourished 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 creation of the world, I could have given hitn good advice.” He did not, however, mean any impiety or irreverence, except what was directed against the system of Ptolemy. e º About the middle of the 15th century, Copernicus, a native of Thorn in Prussia, conceiving a passionate attach- ment to the study of astronomy, quitted the profession of When was the first complete system of Astronomy written, and by whom In how many books was it comprised, and what was tho work called 3 What was the system of Ptolemy IIow did Ptolemy explain the stations and retrogradations of the plancts & . How long was the system of Ptolemy the prevailing system 2 Has it always received with implicit confidence 2 Who established a new System of Astronomy about the gºdle of the 15th century? 174 - GENERAL PHENOMENA medicine, and devoted himselſ, with the most intense ardour, to the study of this science. “His mind,” it is said, “had long been imbued with the idea that simplicity and harmony should characterize the arrangements of the planetary sys- tem. In the complication and disorder which, he saw, reigned in the hypothesis of Ptolemy, he perceived insuper- able objections to its being considered as a representation of nature.” - In the opinions of the Egyptian sages, in those of Pytha- goras, Philolaus, Aristarchus and Nicetas, he recognised his own earliest conviction that the Earth was not the centre of the universe. His attention was much occupied with the speculation of Martinus Capella, who placed the Sun be- tween Mars and the Moon, and made Mercury and Venus revolve around him as a centre, and with the system of Ap- pollonius Pergoeus, who made all the planets revolve around the Sun, while the Sun and Moon were carried around the Earth in the centre of the universe. The examination, however, of these hypotheses, gradual- ly expelled the difficulties with which the subject was beset, and after the labour of more than thirty years, he was per- mitted to see the true system of the universe. The Sun he considered as immoveable, in the centre of the system, while the earth revolved around him, between the orbits of Venus and Mars, and produced by its rotation about its axis all the diurnal phenomena of the celestial sphere. The other planets he considered as revolving about the Sun, in orbits exterior to that of the Earth. (See the Relative Po- sition of the Planets’ Orbits, Plate I. of the Atlas.) Thus, the stations and retrogradations of the planets were the necessary consequence of their own motions, combin- ed with that of the Earth about the Sun. He said that “by long observation, he discovered, that if the motions of the planets be compared with that of the Earth, and be esti- mated according to the times in which they perform their revolutions, not only their several appearances would fol- low from this hypothesis, but that it would so connect the order of the planets, their orbits, magnitudes, and distances, and even the apparent motion of the fixed stars, that it would be impossible to remove one of these bodies out of its place without disordering the rest, and even the whole of the uni- verse also.” - Soon after the death of Copernicus, arose Tycho Brahe, What led him to doubt the system of Ptolemy How long was he employed in the ex amination of different hypotheses before he came to a satisfactory result 7 What, was the system of Copernicus? What distinguished, astronomer, soon after the time of Co- pernicus, enriched astronomy with many valuable observations ! . OF THE SOLAR SYSTEM. 175 born at Knudstorp, in Norway, in 1546. Such was the distinction which he had attained as an astronomer, that when dissatisfied with his residence in Denmark, he had re- solved to remove, the king of Denmark, learning his inten- tions, detained him in the kingdom, by presenting him with the canonry of Rothschild, with an income of 2000 crowns per annum. He added to this sum a pension of 1000 crowns, gave him the island of Huen, and established for him an ob- servatory at an expense of about 200,000 crowns. Here Tycho continued, for twenty-one years, to enrich astronomy with his observations. His observations upon the Moon were important, and upon the planets, numerous and precise, and have formed the data of the present generalizations in astronomy. He, however, rejected the system of Coperni- cus; considering the Earth as immoveable in the centre 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 as simple as that of Copernicus, and involved the absurdity of making the Sun, planets, &c. revolve around a body com- paratively insignificant. Near the close of the 15th century, arose two men, who wrought most important changes in the science, Kepler, and Galileo, the former a German, the latter an Italian. Previous to Kepler, all investigations proceeded upon the supposition that the planets moved in circular orbits, which had been a source of much error. This supposition Kepler showed to be false. He discovered that their orbits were ellipses. The orbits of their secondaries or moons he also found to be the same curve. He next determined the di- mensions of the orbits of the planets, and found to what their velocities in their motions through their orbits, and the times of their revolutions, were proportioned; all truths of the greatest importance to the science. 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 What inducements did the king of Denmark offer him to remain in the kingdom? How long did he continue to make observations in his observatory in the island of Huen? How were the heavenly bodies arranged, in his system A What absurdity did it involve What two illustrious astronomers made several very important discoveries soon after the tim? § º Braheº What were the discoveries of Kepler? What were the discoveries of {lllièO , 176 GENERAL PHENOMENA were discovered revolving about Jupiter; and Venus, as Copernicus had predicted, was seen exhibiting all the differ- ent phases of the Moon, waxing and waning as she does, through various forms. Many minute stars, not visible to the naked eye, were descried in the milky-way ; and the largest fixed stars, instead of being magnified, appeared to be small brilliant points, an incontrovertible argument in fa- vour of their immense distance from us. All his discoveries served to confirm the Copernican theory, and to show the absurdity of the hypothesis of Ptolemy. Although the general arrangement and motions of the planetary bodies, together with the figure of their orbits, had been thus determined, the force or power which car- ries them around in their orbits, was as yet unknown. The discovery of this was reserved for the illustrious New- ton.” By reflecting on the nature of gravity—that power which causes bodies to descend towards the centre of the earth—since it does not sensibly diminish at the greatest dis- tance from the centre of the earth to which we can attain, be- ing as powerful on the loftiest mountains as it is in the deep- est caverns, he was led to imagine that it might extend to the Moon, and that it might be the power which kept her in her orbit, and caused her to revolve around the Earth. He was next led to suppose that perhaps the same power carried the primary planets around the Sun. By a series of calculations, he was enabled at length to establish the fact, that the same force which determines the fall of an apple to the Earth, car- ries the moons in their orbits around the planets, and the planets and comets in their orbits around the Sun. - To recapitulate briefly : the system, (not hypothesis, for much of it has been established by mathematical demonstra- tion,) by which we are now enabled to explain with a beauti- ful simplicity the different phenomena of the Sun, planets, moons, and comets, is, that the Sun is the central body in the system ; that the planets and comets move round him in elliptical orbits, whose planes are more or less inclined to each other, with velocities bearing to each otherſ a cer- tain ascertained relation, and in times related to their dis- tances; that the moons, or secondaries, revolve in like man- ner, about their primaries, and at the same time accompany º T}. scover, of Newton was in some measure anticipated by Copernicus, Kepler, al) (1 HOOKę. * The orbits or paths of the planets were discovered by tracing the course of the planets by means of the fixed stars. What was the º of Newton How was he led to make it?, Recapitulate bliefly the system by which we are enabled to explain the different celestial phenomena. OF THE. SOLAR SYSTEM. 177 them in their motion around the Sun; all meanwhile revol- ving on axes of their own ; and that these revolutions in their orbits, are produced by the mysterious power of attraction. The particular mode in which this system is applied to the explanation of the different phenomena, will be exhibited as we proceed to consider, one by one, the several bodies above mentioned. These bodies, thus arranged and thus revolving, consti- tute what is termed the solar system. The planets have been divided into two classes, primaries and secondaries. The latter are also termed moons, and sometimes satellites. The primaries are those which revolve about the Sun, as a centre. The secondaries are those which revolve about the primaries. There have been discovered eleven prima- ries; namely, Mercury, Venus, the Earth, Mars, Vesta, Juno, Ceres, Pallas, Jupiter, Saturn, and Herschel; of which, Mercury is the nearest to the Sun, and the others follow, in the order in which they are named. Vesta, Juno, Ceres, and Pallas, were discovered by means of the telescope, and, because they are very small, compared with the others, are called asteroids. There have been discovered, eighteen secondaries. Of these, the Earth has one, Jupiter four, Saturn seven, and Herschel six. All these, except our Moon, as well as the asteroids, are invisible to the naked eye. Plate 1, of the Atlas, “exhibits a plan of the Solar System,” comprising the relative magnitudes of the Sun and Planets; their comparative distances from the Sun, and from each other; the position of their orbits, with respect to each other, the Earth, and the Sun ; together with many other particulars which are explained on the map. There, the first and most prominent object which claims attentijn, is the representation of the Sun’s circumference, with its deep radiations, bounding the upper margin of the map. It is apparent, however, that this segment is hardly one sixth of the whole circumference of which it is a part. Were the map suſliciently large to adulit the entire orb of the Sun, even upon so diminutive a scale as there represented, we should then see the Sun and Planets in their just proportions—the diameter of the former being 112 times the diameter of the Earth. It was intended, originally, to represent the Earth upon a scale of one inch in diameter, and the other bodies in that proportion; but it was ſound that it would increase the map to 4 times its size ; and hence it because necessary to assiume a scale of half ath inch for the Earth's diameter, which tuakes that of the Sun #6 inches, and the other bodies, as represented upon the map, The relative position of the Planets’ Orbits is also represented, on a scale as large as the she t would permit. Their relative distances from the Sun as a centre, atid from each other, are there shown correctly : But had we wished to enlarge the diurension:s of i hest orbits, so that they would exactly corres- Yonil with the scale to which we have drawn the planets, the map must have een nearly 4 miles in length. Iſenice, says Sir Johil IIerschel, “the idea that What is meant by the Solar System 3 Into what two classes have the planets been di- vided A Deſine a primary planet. Define a secondary planet. How many primary plan- ets have been diseovered? What are their names, and what the order of their distance from the sun,” Which of them were discovered by means of the telescope? Why are these termed asteroids? . How many secondaries have been discovered 3 . How are they distributed among the primaries 7 Which of the primaries and secondaries are invisible to the naked eyei 178 THE SUN. we can convey correct notions on this subject, by drawing circles on paper, is out of the question.” . To illustrate this.-Let us suppose ourselves standing on an extended plane, or field of ice, and that a globe 4 feet 8 inches in diameter is placed in the Centre of the plane, to represent the Sun. Having cut out of the map, the dark circles representing the planets, we may proceed to arrange them in their respective orbits, about the Sun, as fellows : - First, we should take Mercury, about the size of a small currant, and place it on the circumference of a circle 194 feet from the Sun ; this circle would represent the orbit of Mercury, in the proper ratio of its magnitude. Next, We should take Venus, about the size of a rather small cherry, and place it on a circle 362 feet from the Sun, to represent the orbit of Venus: Then would come the Earth, about the size of a cherry, revolving in an orbit 500 feet ſrom the Sun:—After the Earth, we should place Mars, about the size of a cranber- ry, on a circle 762 feet from the Sun:—Neglecting the Asteroids, soune of which would not be larger than a pin’s head, we should place Jupiter, hardly equal to a moderate sized melon, on a circle at the distance of half a mile (2601 feet) from the Sun;–Saturn, somewhat less, on a cirle nearly a mile (4769 feet) from the Sun; and last of all, we should place Iſerschel, about the size of a peach, on the circurnference of a circle nearly 2 miles (959) feet) from the Sun To imitate the motions of the planets, in the abovementioned orbits, Mercu- ry must describe its own diameter in 41 seconds; Venus, in 4 minutes 14 seconds; the Earth, in 7 minutes; Mars, in 4 minutes 48 seconds; Jupiter, in 2 hours 56 minutes; Saturn, in 3 hours 13 minutes; and Herschel, in 2 hours 16 minutes. Many other interesting subjects are embraced in Plate 1; but they are either explained on the map, or in the following Chapters, to which they res- pectively relate. A C H A P T E R XIX. THE SUN. The sun is a vast globe, in the centre of the solar system, dispensing light and heat to all the planets, and govern- ing all their motions. t tº 9 it is the great parent of vegetable life, giving warmth to the seasons, and colour to the landscape. Its rays are the cause of various vicissitudes on the surface of the earth and in the atmosphere. By their agency, all winds are pro- duced, and the waters of the sea are made to circulate in vapour through the air, and irrigate the land, producing springs and rivers. ſº The Sun is by far the largest of the heavenly bodies whose dimensions have been ascertained. Its diameter is something more than 887 thousand miles. Consequently, it contains a volume of matter equal to fourteen hundred thou- sand globes of the size of the Earth. Of a body so vast in its dimensions, the human mind, with all its efforts, can Mention some of the effects produced by the Sun. What is its magnitude, coºpºeſ with that of the other heavenly bodies whose dimensions have been estimated 7 What is its diameter 3 Fiow much larger is the Sun than the Earth? THE SUN. 179 form no adequate conception. The whole distance between the Earth and the Moon would not suffice to embrace one third of its diameter. Here let the student reſer to Plate I. where the Relative Magnitudes of the Sun and Planets are exhibited. Let him compare the segment of the Sun’s circumference, as there represented, with the entire circumference of the Earth. They are both drawn upon the same scale. The segiment of the Sun’s circumference, since it is almost a straight line, inust be a very Sinall part of what the whole circumference would be, were it represented entire. Let the student understand this diagram, and he will be in some measure able to con- ceive how like a mere point the Earth is, compared with the Sun, and to forum in his unind some image of the vast magnitude of the latter. Were the Sun a hollow sphere, perforated with a thousand openings to admit the twinkling of the luminous atmosphere around it—and were a globe as large as the Earth placed at its centre, with a satellite as large as our Moon, and at the same distance from it as she is from the earth, there would be present to the eye of a spectator on the interior globe, a universe as splendid as that which now appears to the un- instructed eye—a universe as large and extensive as the whole creation was conceived to be, in the infancy of astron- omy. The next thing which fills the mind with wonder, is the distance at which so great a body must be placed, to occupy, apparently, so small a space in the firmament. The Sun’s mean distance from the Earth, is twelve thousand times the Earth’s diameter, or a little more than 95 millions of miles. We may derive some faint conception of such a distance, by considering that the swiftest steamboats, which ply our waters at the rate of 200 miles a day, would not traverse it in thirteen hundred years; and, that a cannon ball, flying night and day, at the rate of 16 miles a minute, would not reach it in eleven years. The Sun, when viewed through a telescope, presents the appearance of an enormous globe of fire, frequently in a state of violent agitation or ebullition; dark spots of irregu- lar form, rarely visible to the naked eye, sometimes pass over his disc, from east to west, in the period of nearly fourteen days. These spots are usually surrounded by a penumbra, and that, by a margin of light, more brilliant than that of the Sun. A spot when first seen on the eastern edge of the Sun, appears like a line which progressively extends in breadth, till it reaches the middle, when it begins to contract, What is the whole distance between the Earth and the Moon, compared with the di- ameter of the Sun?, Give some illustration to enable us to conceive of the magnitude of e Sun, What is the distance of the Sun from the Earth A Give some illustration to en; able us to conceive of the distance. What is the appearance of the Sun when viewed through a telescope A, In what time do the spots seen on the Sun pass across the disc? In what direction do they move Describe their appearance. £80 THE SUN. A. and ultimately disappears, at the western edge. In some rare instances, the same spots re-appear on the east side, and are permanent for two or three revolutions. But, as a general thing, the spots on the Sun are neither permanent nor uniform. Sometimes several small ones unite into a large one ; and, again, a large one separates into numer- ous small ones. Some continue several days, weeks, and even months, together; while others appear and disappear, in the course of a few hours. Those spots that are formed gradually, are, for the most part, as gradually dissolved; whilst those that are suddenly formed, generally vanish as quickly. - It is the general opinion, that spots on the Sun were first discovered by Galileo, in the beginning of the year 1611 ; though Scheiner, Harriot, and Fabricius, observed them about the same time. During a period of 18 years from this time, the Sun was never found entirely clear of spots, excepting a few days in December, 1624; at other times, there were frequently seen, twenty or thirty at a time, and in 1625, upwards of fiſty were seen at once. From 1650, to 1670, scarcely any spots were to be seen ; and, from 1676, to 1684, the orb of the Sun presented an un- spotted disc. Since the beginning of the eighteenth cen- tury, 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 ſtom the earth, corresponds to 462 miles; and a circle of this diameter (containing there. fore nearly 220,000 square miles) is the least space which can be distinctly dis- cerned on the Sun as a visible area, even by the most powerful glasses. Spots have been observed, however, whose linear diameter has been more than 44,000 miles; and, iſ some records are to be trusted, of even still greater €Xtent. DR. DICK, in a letter to the author, says, “I have ſor many years examined the Solar spots with considerable trainuteness, and have several times seen spots which were not less than the one twenty-fiſth part of the Sun's diameter, which would make them about 22, 192 miles in diameter, yet they were visible neither to the naked eye, nor through an opera glass, Inagnifying about three times. And, therefore, if any spots have been visible to the naked eye—which we must believe, unless we refuse respectable testimony—they could not have been much less than 50,000 miles in diameter.” The apparent motion of these spots over the Sun's sur- face, is continually varying in its direction. Sometimes they seem to move across it in Straight lines, at others in curve lines. ... These phenomena may be familiarly illustra- ted in the following manner. Do the same spots ever re-appear on the east side? Are the spots generally permanent and uniform 3 Describe their irregularities?, Who, is it generally supposed, first discover- ed spots on the Sun? Who else observed them about the same time What was the breadth of the one seen by Dr. Herschel in 1799 Jn what direction do the spots on the Sun appear to move? - * The sun. 18i Let E E represent the ecliptic; N S, its north and south poles, M the point where the spot enters, and mi the point where it leaves the Sun's disc. At the end of November, and the beginning of December, the spot will º LO move downwards, across the Sun's disc, from left to right, describing the straight lines M. m, Fig. 1; soon after this period, these lines begin graſſually to be inflected towards the north, till about the end of February, Q, the begin- ning of March, when they describe the curve lines represented in Fig. 2. After the beginning of March, the curvature decreases, till the latter end of May, or . the beginning of June, when they again describe straight, lines tending up- wards, as in Fig. 3. By and by these straight lines begin to be inſected down- wards, till about the beginning of September, when they take the form of a curve, having its convex side towards the south pole of the Sun, as in Fig. 4. Fig. 3, Fig. 4. ar - As these phenomena are repeated every year, in the same order, and belong to all the spots that have been per- ceived upon the Sun's disc, it is concluded, with good rea- son, (that these spots adhere to the surface of the Sun, and revolve with it, upon an axis, inclined a little to the plane of the ecliptic.) 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 se- conds; but during that time, the spot has, in fact(gone through one revolution, together with an arc, equal to that described by the Sun, in his orbit, in the same time, which reduces the time of the Sun’s actual rotation on his axis, to 25 days, 9 hours, and 36 minutes The part of the sun’s disc not occupied by spots, is far from being uniformly bright. Its ground is finely mottled with an appearance of minute, dark dots, or pores, which, , Illustrate these phenomena by diagrams. What conclusions have been drawn from these phenomena 3. What is the apparent time occupied by a spot in revolving from any particular §. of the Sun's disc to the same point again? What is the actual time oes Čupied by the *f; of the spot, and of course by the Sun on its axis 182 THE SUN. attentively watched, are found to be in a constant state of change. . (What the physical organization of the Sun may be, is a question which astronomy, in its present state, cannot solve. It seems, however, to be surrounded by an ocean of inex. haustible flame, with dark spots of enormous size, now and then floating upon its surface. From these phenomena,(Sirº W. Herschel supposed the Sun to be a solid, dark body, sur- rounded by a vast atmosphere, almost always filled with luminous clouds, occasionally opening and disclosing the dark mass within.) The speculations of Laplace were dif. ferent. . . He imagined the solar orb to be a mass of fire, and the violent effervescences 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. & Among all the conflicting theories that have been ad- Vanced, 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 substance, 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. Herschel supposes that the density of the lu- minous clouds need not be greater than that of our Aurora Borealis, to produce the effects with which we are ac- quainted. * The similarity of the Sun, to the other globes of the sys- tem, in its supposed solidity, atmosphere, surface diversified with mountains and vallies, and rotation upon its axis, has led to the conjecture that it is inhabited, like the planets, by beings whose organs are adapted to their peculiar circum- stances. Such was the opinion of the late Dr. Herschel, ) who observed it unremittingly, with the most powerful tele- scopes, for a period of fifteen years. Such, too, was the opinion of Dr. Elliott, who attributes to it the most delight- ful scenery; and, as the light of the Sun is eternal, so, he Have we been able to determine what the physical organization of the Sun is 3. What was the theory of Sir W. Herschel in regard to this subject What was that of Lêplace? What is the prevailing theory 2, What circumstances have led to the conjecture that the Sun is inhabited? What was the opinion of Dr. Herschel Qn this point? How long had he observed it unremittingly, and with the most powerful telescopes 7 What was the opinion of Dr. Elliott upon the same point / MERCURY. - 183 \ imagined, were its seasons. Henge, he infers that this imminary offers one of the most blissful habitations for Intel- ligent beings of which we can conceive. MERCURY. 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 only (2984 miles. Its bulk therefore is about 18} times less than that of the Earth. It would require more º millions of such globes to com- pose a body equal to the Sun. IIere the student should refer to the diagrams, exhibiting the relative magni- tudes and distances of the Sun and planets, Plate I. And whenever this sub- ject recurs in the course of this work, the student should recur to the figures Öf this plate, until he is able to form in his unind distinct conceptions of the relative magnitudes and distances of all the planets. The Sun and planets being spheres, or nearly so, their relative bulks are estituated by cºmparing the cubes of their diameters?, thus, the diameter of Mercury being 2984 iniles, and that of the earth 7924; their bulks are as the cube of 2984, to the cube of 7924, or as 1 to 188, nearly. It 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 distance of nearly 37 millions of miles. The length of Mercury's year, therefore, is equal to about three of our months. S. The rotation of a planet on its axis, constitutes its day; its revolution about the Sun constitutes its year. Mercury is not only the most dense of all the planets, but receives from the Sun seven times as much light and heat as the Earth. The truth of this estimate, of course, depends upon the supposition that the intensity of solar light and heat at the planets, varies inversely as the squares of their distances from the Sun. - 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- What is the distance of Mercury from the Sunn ...What is its magnitude compared with that of the other planets? What is its diameter How many such bodies would it re- quire to compose a body equal, to the Sun. How are the retative bulks of the plane's es- timated? ...In what direction does it revolve, on its axis, and what time does it occupy in the revolution?...In how long time does it, perform its revolution about the Sun? What is its mean distance from the Sun ?, What, then, is the length of its year, compared with ours; Wh it measures a planet's day 2, What measures its year 2 ...What is the density of Mºrcury, compared with that of the other planets? ... [How much light and heat does it re- § ſºmº with §§§ º what §§ does the truth of this estimate epend , iſ this were really the fact in regard to the planets, w * against their being inhabited 3 & planets, would it be any argument 184 MERCURY, wise Creator has attempered every dwelling place in his empire to the physical constitution of the beings which he has placed in it. • *. Frolin a variety of ſacts which have been observed in relation to the produc. tion of caloric, it does not appear probable, that the degree of heat on the sur- face of the different planets depends on their respective distances from the Sun. It is inore 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 different situations which they occupy in the soiar system, ; and that these different quantities 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 of the planets. On this hypothesis, which is corroborated by a great variety of facts and experiuments, there may be no more sensible heat experienced on the planet Mercury, that on the surface of líerschel, which is fiſty times farther reuloved frou the Sun. 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 splendour of its beams. Its enlightened hemisphere being thus always turn- ed 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. 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 in its southern hemisphere, one of which was 10% miles high :—nearly three times as high as Chimborazo, in South America. - . It is worthy of observation, that the highest mountains which have been dis. covered in Mercury, Venus, the Moon, and perhaps we may add the Earth, are all situated in their southern hemispheres. During a few days in March and April, August and Sep- tember, Mercury may be seen for several minutes, in the morning 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 On what does the degree of heat at the different planets probably depend ? Why have astronomers been able to make but couniaratively few discoveries, respecting Mºr- cury What is its appearance when viewed through a telescope of considerable magnity- ing power What circumstances prove that it is an opaque body, shining only with the }: it of the sunº llow was the rotation ºf Mercury on its axis determingd, and by whom? lat did he discover on its surface? What was the altitude of the highest mountain which Jhe saw In which hemisphere are the highest mountains which have been isc.vered in Mercury, Venus, and the Moon, situated 2 Does the same fact exist in ºregard to the Earth? During what months may Mercury be seen for a few days, and in what parts of the day? Why is it visible at these times, and not utothers? MERCURY. • 185 distance that it ever departs from the Sun, on either side, varies from 16°12', to 28° 48', 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 denouiuated its aphelion, and the least its perihelion. On the diagrain, exhibiting the Relative Position of the Planets' Orbits, [Plate I.] these onts are represented by little dots in the orbits at the extremities of the right ines which uleet thern ; the Perihelion points being above the Ecliptic, the Aphelion points below it. 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 face of the Sun, but at all other times, either a little above, or a little below it. - Being commonly immersed in the Sun's rays in the evening, and thus continuing invisible till it emerges from them in the morning, it appeared to the ancients like two distinct stars. A long series of observations was requisite, before they recognised the identity of the star which was seen to recede from the Sun in the morning with that which approached it in the evening. But as the one was never seen until the other disappeared, both were at last found to be the same planet, which thus oscillated on each side of the Sun. Mercury's oscillation from west to east, or from east to west, is really accomplished in just half the time of its revo- lution, which is about 44 days; but as the Earth, in the mean- time, follows the Sun in the same direction, the apparent elongations will be prolonged to between 55 and 65 days. The passage of Mercury over the Sun’s disc, is deno- minated a Transit. This would happen in every revo- lution, if the orbit lay in the same plane with the orbit of the Earth. But it does not ; it cuts the Earth’s orbit in two opposite points, as the ecliptic does the equator, but at an angle three times less. See diagram, Relative Position of the Planets’ Orbits, and their Inclination to the Plane of the Ecliptic. [Plate I.] The dark lines denote sections in the planes of the planets' orbits. The dotted lines continued from the dark lines denote the inclination of the orbits to the plane of the Ecliptic, which inclina- tion is marked in figures on them. Let the student fancy as many circular pieces of paper, intersecting each other at the several angles of inclination What are the greatest distances which it departs from the Sun, on either side 7 What is the Eſongation of a planet 2 What is its Aphelion 2 JWhat is its Perihelion ? In what direction does Alercury revolve about the Sun ? What is the figure of its orbit? De- scribe its apparent motion, as seen from the Earth. How did it appear to the ancients : What was the cause of this appearance How were these apparently two distinct stars at last found to be but one What is the actual period of each elongation of Mercury? What the apparent period? What is the cause of this difference?... What does the expres- sion, transit of * Why does it not make a transit at every revolution? RS6 . - MERCURY. marked on this diagram, and he will be enabled to understand more easily what is meant by the inclination of the planets' orbits. It will be perceived on the diagram, that the inclination of Mercury’s orbit to the plane of the ecliptic is 79.9". - These points of intersection are called the Nodes of the orbit. Mercury’s ascending node is in the 16th degree of Taurus; its descending node in the 16th degree of Scorpio. As the Earth passes these nodes in November and May, the transits of Mercury must happen, for many ages to come, in one of these months. * * The following is a list of all the Transits of Mercury from the time the first was observed fly Gassendi, November 6, 1631, to the end of the present cem- tury. 16:21 Nov. 6. 1707 May 5. 1776 Nov. 2. 1835 Nov. 7. 1644 Nov. 6. 17 10 Nov. 6. 1782 Nov. 12. 1845 May 8. J651 Nov. 2, i.1723 Nov. 9. 17S6 May 3. t848 Nov. 9. 1661 May 3. 1736 Nov. 10. 1789. Nov. 5. 1861 Nov. 11. 1604 Nov. 4. 1740 Nov. 2. 1799 May 7. 1868 Nov. 4. 1974. May 6. 1743 Nov. 4. . 1802 Nov. 8. 1878 May 6. 1677 Nov. 7. 1753 May 5. 1815 Nov. 1 1. 1881 Nov. 7. 16:10 Nov. 9. 1736 Nov. 6. 1S22 Nov. 4. 1891 May 9. 1697 Nov. 2. 1769 Nov. 9. 1832 May 5, 1894 Nov. 10. By comparing the mean motion of any of the planets with the mean motion of the Earth, we may, in like manner, deterinine the periods in which these bodies will return to the same points of their orbit, and the same positions with respect to the Sun. The knowledge of these periods will enable us to determine the hour when the planets rise, set, and pass the meridian, and in general, all the phenomena dependent upon the relative position of the Earth, the planet, and the Suri ; for at the end of one of these periods they commence again, and all recur in the same order. We have, only to find a number of sidereal years, in which the planet completes exactly, or very nearly, a certain number of revolutions; that is, to find such a nuumber of planetary revolutions, as, when taken together, shall be exactly equal to one, or any number of re- volutions of the Earth. In the case of Mercury, this ratio will be, as 87.969 is to 365.256. Whence we find, that, . . . - - 7 periodical revolutions of the Earth, are equal to 29 of Mercury: 13 periodical revolutions of the Earth, are equal to 54 of Mercury: 33 periodical revolutions of the Earth, are equal to 137 of Mercury: 46 periodical revolutions of the Earth, are equal to 191 of Mercury. Therefore, transils of Mercury, at the saune node, triay happen at intervals of 7, 13, 33, 46, &c. years. Transits of Venus, as well as eclipses of the Sun and Moon, are calculated upon the salne principle. The sidereal revolution of a planet respects its absolute motion ; and is measured by the time the planet takes to revolve from any fixed star to the same star again. - - The synodical revolution of a planet respects its relative motion ; and is measured by the time that a planet occupies in conting back to the same posi- tion with respect to the Eartli and the Sun. * The sidereal revolution of Mercury, is 87d. 23h. 15am. 44s. Its synodical re- volution is found by dividing the whole circumference of 360° by its relative motion in respect to the Earth. Thus, the mean daily inotion of Mercury is What are the points where the orbits of the planets intersect the orbit of the Earth call- ed? Where is \{ercury's ascending mode? Where is its descending node 1 in what months must the transit of \}ercury occur for many ages to come 3 §y must they occur in these months II:/ºu can we determine the periods in which the pancts will return. to the same points of their orbits, and the same positions in respect to the Sun ? Why fs it useful to know these perituſ's 2, S are the method of making the computation. What will the ratio be in the case of Mercury 2 State the ratio between the periodi- cal revolutions of the Earth and Mercury. At wha' intervals then may transits of Mercury at the same node happen 2 Upon what principle are transits of Venus, and eclipses of the Sun and Moor, calculated 2 What is the sidereal revolution of a §: 2. What is the synodical revolution ? What is the time qf the sidereal revo- ution of Mercatºry 2 State the method of computing the time of the synodical revo. ltation. Compute the syriodical revolution of Mercury. - • VENUS. 187 14732”.555; that of the Earth is 3548’’.318; and their difference is 11184” .237, being Mercury's relative ſpotion, or what it gains on the Earth every day. Now by simple proportion, 11184’’.237 is to 1 day, as 360° is to 1156. 21h. 3", 25”, the period of a synodical revolution of Mercury. The absolute motion of Mercury in its orbit, is 109,757 miles an hour; that of the Earth, is 68,288 miles: the difference, 41,469 miles, is the mean relative motion of Mercury, with respect to the Earth. VENUS. THERE are but few persons who have not observed a beau- tiful star in the west, a little after sunset, called the evening star. This 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 sometimes on the east side of him, and sometimes on the west, thus continually oscillating backwards and for- wards between certain limits. 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 dis- cover any sensible change in its position; but after a few days, we perceive that it has fallen considerably behind the Sun, and that it continues to depart farther and farther from him, setting later and later every evening, until the distance between it and the Sun, is equal to a little more than half the space from the horizon to the zenith, or about 46°. It now begins to return towards 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 final- ly sets with the Sun, and is lost in the splendour of his light. - A few days after the phenomena we have now described, What is the rate per hour of the absolute motion of Mercury in its orbit? Qf the Earth? What is the mean relative motion of Alençury with respect to the Earth A What beautiful star sometimes appears in the west a little after sunset? What is the comparative dis- tauce of Venus from the Sun A. What is its comparative brightness?...In what direction is its apparent motion? Why is it neverseen at midnight, nor in opposition to the Sun? At what times is it visible? How long after sunset is it when we first behold it in the west ? Describe its changes of position. - 188 VENUS. We perceive, in the morning, near the eastern horizon, a bright star which was not visible before. This also is Venus, which is now called the morning star. It departs farther and farther from the Sun, rising a little earlier every day, until it is seen about 46° west of him, where it appears stationary for a few days; then it resumes its course towards the Sun, appearing later and later every morning, until it rises with the Sun, and we cease to behold it. In a few days, the evening star again appears in the west, very near the setting-sun, and the same phenomena are again exhibited. Such are the visible appearances of Venus. Venus revolves about the Sun from west to east in 2243 days, at the distance of abont 68 millions of miles, moving in her orbit at the rate of 80 thousand miles an hour. She turns around on her axis once in 23 hours, 21 minutes, and 7 seconds. Thus her day is about 25 minutes shorter than ours, while her year is equal to 7% of our months, or 32 weeks. The mean distance of the Earth from the Sun is estimated at 95 millions of miles, and that of Venus being 68 millions, the diameter of the Sun, as seen from Venus, will be to his diameter as seen from the Earth, as 95 to 68, and the surface of his disc as the square of 95 to the square of 68, that is, as 9025 to 4626, or as 2 to 1 nearly. The intensity of light and heat being inversely as the squares of their distances from the Sun, Venus receives twice as much light and heat as the Earth. Her orbit 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 being abuut 23° from the Sun, and Venus 46°, the orbit of Venus must be outside of the orbit of Mercury. - The true diameter of Venus is 7621 miles; but her ap- parent diameter and brightness are constantly varying, ac- cording to her distance from the Earth. When Venus and the Earth are on the same side of the Sun, her distance In what direction, and in what time, does Venus revolve about the Sun ?, What is her distance from the Sun ? What is the rate per hour of her motion in her orbit 7 In what time does she revolve on her axis How are the lengths of her day and year, compared with those of the Earth 3 How much ºf: does the Sun appear at Venus than he does at the Earth How much more light and heat does she receive from him, than the Earth? How much farther is Venus from the Sun than Mercury On which side of the qrbit of Mercury must her orbit be? What is her, true diameter 3 . In what proportion do her ap- parent diameter and brightness constantly vary? What is her distance from the Earth when they are both on the same side of the Sun ? venus. 189 from the Earth is only 26 millions of miles; when they are on opposite sides of the Sun, her distance is 164 millions of miles. Were the whole of her enlightened hemisphere turned towards us, when she is nearest, she would exhibit a light and brilliancy twenty-five times greater than she generally does, and appear like a small brilliant moon; but, # that time, her dark hemisphere is turned towards the arth. When Venus approaches nearest to the Earth, her apparent, or observed diameter, is 61’’.2; when most remote, it is only 9’’.6 : now 61”.2–3–9".6 = 63, her.ce when nearest the Earth her apparent diameter is 6; times greater than when most distant, and surface of her disc (C#)*, or nearly 41 times greater. In this work, the apparent size of the heavenly bodies is estituated from the apparent surface of their discs, which is always proportional to the squares of their apparent diauieters, When Venus’ right ascensión is less than that of the Sun, she rises before him ; when greater, she appears after his setting. She continues alternately morning and evening star, for a period of 292 days, each time. To those who are but little acquainted with astronomy, it will seem strange, at first, that Venus should apparently continue longer on the east or west side of the Sun, than the whole time of her periodical revolution around him. But it will be easily understood, when it is considered, that while Venus moves around the Sun, at the rate of about 1° 36' of angular motion per day, the Earth follows at the rate of 59'; so that Venus actually gains on the Earth, only 37' in a day. - - Now it is evident that both planets will appear to keep on the same side of the Sun, until Venus has gained half her orbit, or 180° in advance of the Earth; and this, at a mean rate, will require 292 days, since 292X37–10804", or 180° nearly. Mercury and Venus are called Inferior” planets, because their orbits are within the Earth’s orbit, or between it and the Sun. The other planets are denominated Superior, because their orbits are without or beyond the orbit of the * In almost all works on Astronomy, Mercury and Venus are denominated inferior planets, and the others, superior. Bat as these terms are employed, not to express the relative size of the lº but to indicate their situation with respect to the Earth, it would be better to adopt the terms interror and evterior. What is it when they are on opposite sides of the Sun ? Which hemisphere is turned towards the Earth when she is nearest to us? Were her enlightened hemisphere turne towards us at that time, how, would her light and brilliancy be compared with that which she generally exhibits, and what would be her appearance What is the length of her apparent diameter when shº is nearest to the Earth & What is it when she is most remote & How is the apparent size of a heavenly body estimated in this work 2. In what circumstances does. Venus rise before, and in what set after, the Sun ?, How long does she continue, each time, alternately morning and evening star 3, Why does she ap- i. longer qm the east or west side of the Sun than the whole time of her periodical revo- ution around him? Why are Mercury and Venus called Inferior planets? Why are the other planets termed Superior planets? 190 VENUS. Earth. [Plate 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 in con- junction on the same side of the Sun. In the former case, the planet is said to be in its inferior conjunction, and in the #. case, in its superior conjunction; as in the following gure. CONJUNCTION AND OPPOSITION OF THE PLANETS. Fig. 5. *%. gºv - , sº Jºs The period of Venus' synodical revolution is ſound in the same manner as that of Mercury; mainely, by dividing the whole circumference of ber orbit by her mean relative motion in a day. Thus, Venus' absolute mean dail motion is 1° 36' 7’’.8, the Earth's is 59’ 8’’.3, and their difference 36'59’’.5. Divide 360° by 36' 59’’.5, and it gives 583.920, or nearly 584 days, for Venus’ synodical revolution, or the period in which she is twice in conjunc- tion with the Earth. Venus passes from her inferior to her superior conjunction in about 292 days. At her inferior conjunction, she is 26 millions of miles from the Earth; at her superior conjunc- tion, 164 millions of miles. How often, in every synodical revolution, will each of these planets be in conjunction on the same side of the Sun that the Earth is How often on the opposite side 2 Ex- plain this. What names distinguish these two species of conjunction,) How is the 80/- 'nodical revolution of Venus found 2 Make the calculation. , How long is she in pass: # from her inferior to her superior conjunction? How far is she from the Earth at her inferior conjunction? How far at her superior 3 * VENUS. 191 It might be expected that her brilliancy would be propor- tionally increased, in the one case, and diminished, in the other; and so it would be, were it not that her enlightened hemisphere is turned more and more from us, as she ap- proaches the Earth, and comes more and more into view as she recedes from it. It is to this cause aione that we must attribute the uniformity of her splendour as it usually ap- pears to the naked eye. Mercury and Venus present to us, successively, the various shapes and appearances of the Moon ; waxing and waning through different phases, from the beautiful crescent to the full rounded orb. This faet shows, that they revolve around the Sun, and between the Sun and the Earth. Let the pupil endeavour to explain these phases on any other supposition, and he will be convinced that the system of Ptolemy is erroneous, while that of Copernicus is confirmed. It should be remarked, however, that Venus is never seen when she is entire- ly fuli, except once or twice in a century, when she passes directly over the Sun's disc. At every other conjunction, she is either behind the Sun, or so near him as to be hidden by the splendour of his light.” The diagrain on the next page will better illustrate the various appearances of Venus, as she moves around the Sun, than any description of Llein could do. From her inferior to her superior conjunction, Venus ap- pears on the west side of the Sun, and is then our morning star; from her superior to her inferior conjunction she ap- pears on the east side of the Sun, and is then our evening Star. * The eminent astronomer, THOMAS Dick, LL.D., well known in this country as the author of the Christian Philosopher, Philosophy of a Future State, &c., in a review of this remark, observes—" This ought not to be laid down as a general truth. About the year 1813, I made a #. variety of observations on Venus in the dily time, by an equatorial instrument, and found, that she could be seen when only 1° 27' from the Sun's margin, and consequently may be seen at the moment of her superior conjunction, when her geo: centric liltitude, ut that time, equals or ºvceeds 1,43'. I have some ſalut expectations of being able to see Venus, in the course of two or three duys, ut her superior conjunction, if the weather be favourable.”—March 3, 1834. , Why is not her brilliancy proportionably increased in the former case, and diminished in the lutter?...What appearancº's do Mercury and Venus present to us at different times? \) hitt supposition is necessary for the explanation of these phases What system do they tend to refute?, What system do they confirm A How of en is V, nus seen when she is entirely full? Why is she not seen at the full oftener?, in what part of her or- bit does Venus appear on the west side of the Sun in what on the easin in what parts is she, alternately, morning and evening star? § APPEARANCES OF VENUS As SHE MOVES AROUND THE SUN. Fig. 6. º Superior Conjunction. 772 # Inferior Conjunction. VENUS. 193 Like Mercury, she sometimes seems, to be stationary. Her apparent motion, like his, is sometimes rapid ; at one time, direct, and at another, retrograde; vibrating alternate- ly backwards and forwards, from west to east, and from east to west. These vibrations appear to extend from 45° to 47°, , on each side of the Sun. Consequently she never appears in the eastern horizon, more than three hours before sunrise, nor continues longer in the western horizon, after Sun- set. Any star or planet, therefore, however brilliant it unay appear, which is secn earlier or later than this, cannot be Venus. In passing from her western to her eastern elongation, her motion is from west to east, in the order of the signs; it is thence called direct motion. In passing from her eastern to her westerm elongation, her motion with respect to the Earth, is from east to west, contrary to the order of the signs; it is thence denominated retrograde motion. Her motion appears quickest about the time of her conjunctions; and she seems stationary, at her elongations. She is bright- est about 36 days before and after her inferior conjunction, when her light is so great as to project a visible shadow in the might, and sometimes she is visible even at noon-day. In the following fixure, the outer circle represents the Earth's orbit, and the inner circle, that of Venus, while she moves around the Sun, in the order of the letters a, b, c, d, &c. When Venus is at a, she is in her inſerior conjunction, between the Earth and Stun ; and is in a situation similar to that of the Moon at her change, being then invisible, because her dark helmisphere is towards the Earth. At c, she appears half enlightened to the Earth, like the Moon in her first quarter; at d, she appears alırıost full, her enlightened side being tºen aluost directly towards the Earth; at e, she is in her superior conjunc. tion, and would appear quite ſull, were she no!, directly behind the Sun, or so near him as to be lidden by the splendour of his light ; at f she appears to be on the decrease; and at g, only half enlightened, like the Moon in her last quarter: at a, she disappears again between the Earth and the Sun. In tuoving from g to c, she seems to go backwards in the heavens, because she moves contrary to the order of the signs. In turning the arc of the circle ſroun retrograde to direct motion, or from direct to retrograde, she appears nearly stationary for a few days; because, in the former case, she is going almost directly from the Earth, and in the latter, coming towards it. As she describes a much larger portion of her orbit in going from c to g, than from g to c, she appears unuch longer direct than retrograde. At a mean rate, her re- trogradations are accomplished in 42 days. Describe hor apparent motion. How far on each side of the Sun do the vibrations of Venus extend? What then is the longest time before sunrise that she appears in the eastern horizon & What the longest time after sunset thqt she appears in the west- ern ? What is the direction of her motion while she passes from her western to her east- ern elongation Why is it called direct motion? What is, its direction as she passes from her eastern to her western elongation? Why is it called retrograde When is her apparent motion quickest ?, When does she appear stationary? When is she brightest 7 How great is her light at this time? * 194 VENUS. DIRECT AND RETROGRADE MOTION. Fig. 7. woulow 1924,Q- If the orbit of Venus lay exactly in the plane of the Earth’s orbit, she would pass centrally across the Sun’s disc, like a dark round spot, at every inferior conjunction; but as one half of her orbit lies about 34° above the ecliptic, and the other half as far below it, she will always pass the Sun a very little above or below it, except when her in- ferior conjunction happens in, or near, one of her nodes ; in which case she will make a transit. [Relative position of the Planet’s Orbits, Plate I—Plane of Venus—Inclina- tion 3° 23'.] - . This phenomenon, therefore, is of very rare occurrence: it can happen only twice in a century; because it is only twice in that time that any number of complete revolutions of Venus, are just or nearly equal to a certain number of the Earth’s revolutions. The principle which was illustrated in predicting the transits of Mercury, applies equally well to those of Venus ; that is, we must find such sets of numbers, (representing complete revolutions of the Earth and Venus,) as shall be to each other in the ratio of their periodical times, or as 365,256 is to 224.7. Thus; the motion of Venus, in the Julian years, is 2106591’’.52; that of the Earth for the same period being 129627”.45, the ratio will be Why does not Venus pass centrally across the Sun's disc at every inferior conjunction? In what circumstances will she make a transii, across the sung How often can this phe- momenon happen? Why can it not happen oftener n State the method of predicting the transits of Venus, VENUS. - 195 $. ######1.”.}}. As the two terms of this fraction cannot be reduced by a oommon divisor, we must multiply them by such numbers as will māke one a multiple of the other; accordingly, 13 times the denominator will be hearly equal to 8 times the numerator ; and 475 times the denoulinator will equal 291 tiunes the nulnerator. *. By combining these two periods and their multiples by addition, and sub- traction, we shall obtain the period of all the transits that have evºhappened. "Thus ; 291–8×7 =235, another period; and 291—6XS=243, adº period, and so on. Whence we find that, .* 8 periodical revolutions of the Earth, are equal to 13 of Venus. 235 periodical revolutions of the Earth, are equal to 382 of Venus. 243 periodical revolutions of the Earth, are equal to 395 of Venus. 251 periodical revolutions of the Earth, are equal to 408 of Venus. 291 periodical revolutions of the Earth, are equal to 475 of Venus. Hence a transit of Venus may happen at the same node, after an interval of 8 years; but if it do not happei, then, it cannot take place again, at the same node, in less than 235 years. The orbit of Venus crosses the ecliptic near the middle of Gemini and Sagittarius; and these points imark the po- sition of her nodes. At present, her ascending node is in the 14th degree of "Gemini, and her descending node, in the same degree of Sagittarius. The Earth passes her ascending node in the beginning of December, and her descending mode, in the beginning of June, Hence, the transits of Venus, for ages to come, will happen in December and June. 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 time of the next transit at the same mode, which will accordingly happen in 1874. There will be another at the same node in 1882, * This phenomenon was first witnessed by Horrox, a young gentleman about 21 years •of age, living in an obscure village 15 miles north of Liverpool. The tables of Kepler, con- structed upon the observations of Tycho Brahe, indicated a transit of Venus in 1631, but none was observed. Horrox, without much assistance from books and instruments, set himself to inquire into the error of the tables, and found that such a phenomenon, might be expected to happen in 1639. He repeated his calculations during this interval, with all the carefulness and enthusiasm of a scholar ambitious of being the first to predict and observe a celestial phenomenon, which, from the creation of the world, had never been witnessed. Qonfident of the result, he communicated his expected triumph to a confi- dential friend residing in Manchester, and desired him to watch for the event, and to take observations. So anxious was t ſorrow not to fail of witnessing it himself, that he com- menced his observations the day before it was expected, and resumed them at the rising of the Sun on the morrow. B; it the very h ºr when his calculations led him to expect *the visible appearance of Venus upon the Sun's disc, w is tilso the appointed hour for the public wºn ship of God on the Sabbath. The delay of a few minutes might deprive jhim forever of an opportunity of observing the transit. If its very commencement were not noticed, clouds might intervene, and conceal it until the Sun º set: and nearly a -century and a half would elapse before another opportunity would occur. He had been waiting for the event with the most ardºnt anticipation for eight years, and the result pro- misud much benefit to the science N twithstanding all thºs, Horrow twice suspend- ed his observations, and twice repaired to the House of God, the Great Author of the #. worlds he delighted to contemplate. When his duty was thus performed, and he had returned to his chamber the second time, his love of science was gratified with full ‘success ; and he saw what no mortal eye had observed before - lf any thing can add interest to this incident, it is the modesty with which the young astronomer apologizes to the world, for suspending his observations at all. “I observed it,” says he, “from sunrise till nine o'clock, again a little before ten, and lastly at noon, and from one to two o'clock; the rest of the day being devoted to higher “duties, which might not be neglected for these pastimes.” - After how long an in erval many a transit of Venus happen tigain at the same mode 2 ..If it do not happen then, how long a period must elapse before it will occur again .dºt the same node?' Where does the orbit of Venus cross the ecliptic, and where are her nodes?, In, what months, for ages to come, will the transits of Venus happen, and ‘why? At which node, and when, did the first transit of Venus ever known to have been observed, take place 3 When will the next two transits occur 196 VENUS. eight years afterwards. It is not more certain that this phe- nomenon will recur, than that the event itself will engross the attention of all the astronomers then living upon the Earth. It will be anticipated, and provided for, and observ- ed, in every inhabited quarter of the globe, with an inten- sity of solicitude which no natural phenomena, since the creation, has ever excited. The reason why a transit of Venus should excite so great an interest, is, because it may be expected to solve an im- portant 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 a universal standard of astronomical measure. Another consideration will render the observation of this transit pe- culiarly favourable; and that is, astronomers will be supplied with better instruments, and more accurate means of obser- vation, than on any former occasion. So important, says Sir John Herschel, have these observaſions appeared to astronomers, that at the last transit of Venus, in 1769, expeditions were fitted out, on the most efficient scale, by the British, French, Russian, and other governments, to the remotest corners of the globe, for the express purpose of making them. The celebrated expedition of Captain Cook to Otaheite, was one of them. The general result of all the observations made on this most memorable occasion, gives 8".5776 for the Sun's horizontal parallax. 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.) The inclination of the axis of Venus to the plane of her orbit, though not precisely known, is commonly estimated at WZ59; which is ( more than three times as great as the inclination of the Earth’s axis to the plane of the ecliptic. The north pole of Venus' axis inclines towards the 20th degree of Aquarius; the Earth’s towards the beginning of Cancer; consequently, the northern parts of Venus have{summer in the signs where those of the Earth have winter, and vice versa. The declination of the Sun on each side of her equator, must be equal to the inclination of her axis; and if this ex- tends to 75°, her tropics are only 15° from her poles, and ..her polar circles 15° from her equator) It follows, also, that Why will the next transit excite a very great and universal interest? Unon what do the phen ingna of the seasons of each of the planets depend What is the estimated inclina- tion of the axis of Venus to the plane of her orbit How does this inclination compare with that of the Earth's axis to the plane of the eclipticº What seasons have the north- ern parts of Venus, when those of the Earth, have winter How do we know this? To what must the declimation of the Sun on each side of her equator be equal How far are ber tropics from her poles, and her polar circles from her equator? VENUS. 197 the Sun must change his declination more in one day at Venus, than (in five days on the Earth; and consequently, that he never shines vertically on the same places for two days in spiccession. This may perhaps be providentially ordered, to prevent the too great effect of the Sun's heat, which, on the supposition that it is in inverse proportion to the square of the distance, is twice as great on this planet as it is on the Earth. At each pole, the Sun continues half a year* without set- ting in summer, and as long without rising in winter; con- sequently, the polar inhabitants of Venus, like those of the earth, have only (one day and one night in the year; with this difference, that the polar days and nights of 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 winters in that zone will be almost twice as jong as the summers. - TELESCOPIC APPEARANCES OF VENUS. Fig. 8. ºft||| sºft.* gº .* *= When viewed through a good telescope, Venus exhibits not only all the moon-like phases of Mercury, but also a va- riety of inequalities on her surface; dark spots, and brilliant shades, hills, and valleys, and elevated mountains.) But (on account of the great density of her atmosphere, these in- * That is, half of Venus' year, or 16 weeks. How much more must the Sun change his declination in one day at Venus than on the Farth Why, perhaps, is this so ordered 7 lºſow many º and nights have her polar inhabitants during the year Flow long are these days and nights, compared with those of our polar inhabitants How many, and what seasons, has Venus, between her polar circles? ...What is the length of the winters in this zone, compared with that of the sum- mers & What appearances, besides her moon-like phases, does Venus exhibit when seen through a good º 198 THE EARTH. equalities are perceived with more difficulty than those up- on the other planets. - * The mountains of Venus, like those of Mercury and the Moon, are highest in the º 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 (10 to 22 miles X. The observations of Dr. Herschel do not indicate so great an altitude ; and he thinks, that in general they are considerably overrated. He estimates the diame ter of Venus at 8,049 miles; making her bulk more than, one sixth larger than that of the Earth.) Several eminent. astronomers affirm, that they have repéatedly seen Venus. attended by a satellite, and they have given circumstantiał 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 astro- nomers deny the existence of such a bodyS.because it was: not seen with Venus on the Sun’s disc, at the transits of 1761, and 1769. ) f THE EARTH. THE Earth is the place from which all our observations. of the heavenly bodies must necessarily be made. The ap- parent motions of these bodies being very considerably af- fected by her figure, motions, and dimensions, these hold an important place in astronomical science. It will there- fore be proper to consider, first, some of the methods by which they have been determined. If, standing on the sea-shore, in a clear day, we view a ship leaving the coast, in any direction, the hull or body of the vessel first disappears; afterwards the rigging, and lastly, the top of the mast vanishes from our sight. Those on board the ship, observe that the coast first sinks below the horizon, then the buildings, and lastly the tallest spires of the city * 1st, 22.05 miles; 2d, 18.97 miles; 3d, 11.44 miles; 4th, 10.84 miles. Why is it more difficult to perceive the inequalities on her surface than those on the other planets \ . In which hemisphere are her mountains highest ? What does M. Schroer ter make the altitude ºf some of the highest l is this estimate confirmed by the observa- tions of Dr. Herschel How long is the diameter of Venus, according to Herschel's es- timate How much larger, then, must she be than the Earth Q Some astronomers aſhrm. that they have seen Venus attended by a satellite, why ſlo others deny the existence of such a body ? Why is, it important, in an astronomical view, to be acquainted with the figure, dimensions, and motions of the Earth A Mention some of the proofs of the con- vexity of its surface? - THE EARTH. 199 - which they are leaving. Now these phenomena are evi- dently caused by the convexity of the water which is be- tween the eye and the object; for, were the surface of the sea merely an extended plain, the largest objects would be visible the longest, and the smallest disappear first. CONVEXITY OF THE EARTH. Fig. 9. Again : navigators have sailed quite around the Earth, and thus proved its convexity. Ferdinand Magellan, a Portuguese, was the first who carried this enterprise into execution. He eubarked from Seville, in Spain, and directed his course towards the west. After a long voyage, he descried the continent of Aumerica. Not finding an opening to enable liiin to continue his course in a westerly direction, he sailed along the coast towards the south, till, couting to its sou- thern extreunity, he sailed around il, and ſonnd himself in the great Southern Ocean. He then resumed his course towards the west. After soune time he arrived at the Molucca Islands, in the Eastern Hemisphere; and sailing con- tinually, Iowards the west, he made Europe ſrom the east; arriving at the place from which he set out." - - The next who circumnavigated the Earth, was Sir Francis Drake, who sail- ed from Plymouth. December 13, 1577, with five sinall vessels, and arrived at the same place, September 26, 1580. Since that time, the circumnavigation of the Earth has been performed by Cavendish, Cordes, Noort, Sharien, Here- mites, Dampier, Woodes, Rogers, Schovten. Roggewin, Lord Anson, Byron, Carteret, Wallis, Bougainville, Cook, King, Clerk, Vancouver, and unany others. These navigators, by sailing in a westerly direction, al- lowance being made for promontories, &c. arrived at the country they sailed from. Hence, the Earth must he either cylindrical or globular. It cannot be cylindrical, because, if so, the meridian distances would all be equal to each other, which is contrary to observation. The figure of the Earth is, therefore, spherical. - - The convexity of the Earth, north and south, is proved by the altitude of the pole, and of the circumpolar stars, *— * Magellan sailed from Seville, in Spain, August 10, 1519, in the ship called the Victo- ry, accompanied by four other vessels In Aºi 1521, he was killed in a skirmish with the natives, at the island of Sebut, or Zebu, sometimes called Matan, one of the l hilip- pines. One of his vessels, however, arrived at St. Lucar, near Seville, September 7, 1522. Who first sailed around the Earth 2 Describe briefly his voyage. Who meat cir- cumnavigated the Earth 2. Describe his voyage. Mention the games ºf some of those who have since accºmplished this enterprise. What may we infer from these facts in regard to the figure of the Earth? How is the convexity of her surface proved? 200 "THE EARTH. which is found uniformly to increase as we approach them, while the inclination to the horizon, of the circles described: by all the stars, gradually diminishes. While proceeding. in a southerly direction, the reverse of this takes place. The altitude of the pole, and of the circumpolar stars, con- tinually decreases; and all the stars describe circles whose inclination to the horizon increases with the distance. Whence we derive this general truth : The altitude of one pole, and the depression of the other, at any place on the Earth's surface, is equal to the latitude of that place. Another proof of the convexity of the earth’s surface is, that the higher the eye is raised, the farther is the view ex- tended. An observer may see the setting sun from the top, of a house, or any considerable eminence, after he has ceasa. ed to be visible to those below. • The curvature of the Earth for one mile is 8 inches; and this curvaturg. increases with the square of the distance. Frou, this general law, it will be, easy to calculate the distance at which any object whose height is given, may; be seen, or to determine the height of an object when the distance is known. 1st. To find the height of the object when the distance is given. RULE. Find the square of the distance in miles, and take two thirds of that, number for the height in feet. - Ex. l.-How high must the eye of an observer be raised, to see the surface. of the ocean, at the distance of three miles 3 Ams. The square of 3 ft., is 9. ſt., and # of 9 ft. is 6 ft. Ex. 2. Suppose a person can just see the top of a spire over an extended plain of ten miles, how high is the steeple 7 Ans. The square of 10 is 100, and 3 of 100, is 663, feet. 2. To find the distance, when the height is given. -- RULE. Increase the height in feel one half, and extract the square root, for. the distance, in miles. Ex, 1.—How far can a person see the surface of a plain, whose eye is ele- wated six feet above if q Ams. 6, increased by its half, is 9, and the square root of 9 is 3; the distance is then 3 miles. Ex. 2.--To what distance can a person see a light-house whose height is 96 feet from the level of the ocean 3 Mns. 96 increased by its half, is 144, and the square root of 144 is 12; the distance is therefore 12 miles. 3. To find the curvature of the Earth when it exceeds a mile. RULE. Multiply the square of the distance by .000 i26. Although it appears from the preceding facts, that the Earth is spherical, yet it is not a perfect sphere. If it were, the length of the degrees of latitude, from the equator to the poles, would be uniformly the same ; but it has been found, by the most careful measurement, that as we go from the equator towards the poles, the length increases with the lati- tude. º These measurements have been made by the most eminent mathematicians, of different countries, and in various places, from the equator to the arctic To what is the convezily proportional 2 State the rule, deduced frºm this fact, for finding the height of an object, when its distance from us is given. State the Yule for finding the distance when the height is given. State the rule for finding, the curvature of the Earth when the distance eaceeds a mile, Is the figure of the Éaº an exact sphere Were the Earth a pººl sphere, how would the length of the degrees. of latitude be, compared with each other? How are they, in fact? THE EARTH. 201 wº" circle. They have found that a degree of latitude at the arctic circle-was mine sixteenths of a mile longer than a degree at the equator, and that the ratio of increase ſor the interniediate degrees was nearly as the squares of the sines of the latitude. Thus the theory of Sir Isaac Newton was confirqied, that the body of the Earth was unore routitled and convex between the tropics, ..but considerably flattened towards the poles. Places o * Length of a degree ~ f ofº, Latitude. in English miles. Observers. Peru Equator. | 6S. 732 Bouguer. *Pennsylvania 39°12' N. 6S. 896 Mason and J)ixon. Italy 43 01 - 6S. 90S Boscovieh and Lennaire. France 46 69.034 Delaubre and Mechain. England 5| 20' 54}'' 69. 146 - Mudge. Sweden Gö 20 10 6). 292 Swainberg. These measurements prove the Earth to be an oblate º longest or equatorial diameter is 7924 miles, and polar diameter, 7898 miles. The mean diameter is, therefore, about 7912, and their difference 26 miles. The French Academy have determined that the mean diameter of the Earth, from the 45th degree of north latitude, to the opposite degree of south latitude, is accurately 7912 miles. If the Earth were an exact sphere, its diameter Fig. 10. might be delerinined by its curvature, from a single A. B measurement. Thus, in 1he adjoining figure, we have =- A B equal to l tºile, and B IX equal to 8 inches, to AP find A E, or I; E, which does not sensibly differ from A E, since B I) is only 8 inches. Now it is a propo- sition of Euclid, (B. 3, prop. 36,) 1.liat, when from a point without a circle, two lines be drawn, one cutt.ng and the other touching it, the touching line (B A) is a mean proportional between the cutting line (B E) and that part of it (B I)) without the circle. , - B D : B A :: B A : B E or A E very nearly. That is, 1 mile being equal to 63360 inches, Aº 8 : 63300 : : 63.360 : 50lSl 1:0 inches, or 7920 miles. This is very nearly what the inost elaborate calculations make the Earth's equatorial diarneter. The Earth, considered as a planet, occupies a favoured rank in the Solar System. It pleased the All-wise Crea- tor to assign its position among the heavenly bodies, where nearly all the sister planets are visible to the naked eye. § is situated next to Venus, and is the third planet from the NC Ulſ). To the scholar who for the first time takes up a book on astronomy, it will 'no doubt seein strange to find the Earth classed with the heavenly bodies. What is the length of a degree at the Arctic circle, compared goith a degree at the equator, as fort” d by the measurements ºf tº ſerent mathemat c axis 2 Phat have thet.fºrund to be the ratio ºf increase, for the intermediate degrees 2 Hijiº theory do these facts cºnfirm 2 What is the length of the Earth's equatorial diameter, as found by these Ineºsurements? What, her polar diamet,ºr What is the difference between the two What is hºr mºm diameter? What havs the French academy determined to be the ºxact mean diameter from the 45th degree of north latitudº to the opposite degree of south latitude? I'lust, a 'e ſhe methgil ºf finding the diamºter of the 'Earth Jºrdºn her Cºrvátº e, oº, the s?!?posit or th ºf her ſigure is an exact sphere. What is the length of her diameter as thus found 2 How is this, compared with the equatorial diameter, gº found by the most elaborate calculations? What is the position of the Earth in the Solar System? 202 THE EARTH, For what can appear more unlike, than the Earth, with her vast and seemingly immeasurable extent, and the stars, which appear but as points The Earth is dark and opaque, the celestial bodies are brilliant. We perceive in it no motion ; while in them we observe a continual change of place, as we view them at different hours of the day or night, or at different seasons of the year. It moves round the Sun, from west to east, in 365 days, 5 hours, 48 minutes, and 48 seconds; and turns, the same way, on its axis, in 23 hours, 56 minutes, and 4 seconds. The former is called its annual motion, and causes the vicissitudes of the seasons. The latter is called its diurnal motion, and produces the succession of day and night. The Earth’s mean distance from the Sun is about 95 millions of miles. It consequently moves in its orbit at the mean rate of 68 thousand miles an hour. Its equatorial di- ameter being 7924 miles, it turns on its axis at the rate of 1040 miles an hour. - Thus, the earth on which we stand, and which has serv- ed for ages as the unshaken foundation of the firmest struc- tures, is every moment turning swiftly on its centre, and, at the same time, moving onwards with great rapidity through the empty space. This compound motion is to be understood of the whole earth, with all that it holds within its substance, or sustains upon its surface—of the solid mass beneath, of the ocean which flows around it, of the air that rests upon it, and of the clouds which float above it in the air. That the Earth, in common with all the planets, revolves around the Sun as a centre, is a fact which rests upon the clearest demonstrations of philosophy. That it revolves, like them, upon its own axis, is a truth which every rising and setting sun illustrates, and which very many phenomena concur to establish. Either the Earth moves around its axis every day, or the whole universe moves around it in the same time. There is no third opinion, that can be formed on this point. Either the Earth must revolve on its axis every 24 hours, to pro- duce the alternate succession of day and might, or the Sun, Moon, planets, comets, fixed stars, and the whole frame of the universe itself, must move around the Earth, in the same time. To suppose the latter case to be the fact, would be to cast a reflection on the wisdom of the Supreme Architect, whose laws are universal harmony. As well might the beetle, that in a moment turns on its ball, imagine the heav- What revolutions does it perform, and in what direction? What is the time º: in. each of these revolutions By what terms are these revolutions distinguished, and what. important effects do they produce? What is the Earth's mean distance from the Sun?, {}}. is the mean rate of its motion in its orbit per hour ! What is the rate of its revolu- tion on its axis per hour? What are the proofs, that it performs these two revolutions?. THE EARTH, 203 ens and the Earth had made a revolution in the same instant. It is evident, that in proportion to the distance of the ce- lestial bodies from the Earth, must, on this supposition, be the rapidity of their movements. The Sun, then, would move at the rate of more than four hundred thousand miles in a minute ; the nearest stars, at the inconceivable velocity of 1400 millions of miles in a second; and the most distant luminaries, with a degree of swiftness which no numbers could express, and all this, to save the little globe we tread upon, from turning safely on its axis once in 24 hours. The idea of the heavens revolving about the Earth, is en- cumbered with innumerable other difficulties. We will mention only one more. It is estimated on good authority, that there are visible, by means of glasses, no less than one hundred millions of stars, scattered at all possible distances in the heavens above, beneath, and around us. Now, is it in the least degree probable, that the velocities of all these bodies should be so regulated, that, though describing circles so very different in dimensions, they should complete their revolutions in exactly the same time. In short, there is no more reason to suppose that the heav- ens revolve around the Earth, than there is to suppose that they revolve around each of the other planets, separately, and at the same time; since the same apparent revolution is common to them all, for they all appear to revolve upon their axis, in different periods. The rotation of the Earth determines the length of the day, and may be regarded as one of the most important el- ements in astronomical science. It serves as a universal measure of time, and forms the standard of comparison for the revolutions of the celestial bodies, for all ages, past and to come. Theory and observation concur in proving, that among the innumerable vicissitudes that prevail throughout creation, the period of the Earth’s diurnal rotation is immu- table. * The Earth performs one complete revolution on its axis in 23 hours, 56 minutes, and 4.09 seconds, of solar time. This is called a sidereal day, because, in that time, the stars appear to complete one revolution around the Earth. But, as the Earth advances almost a degree eastward in its orbit, in the time that it turns eastward around its axis, it is plain that just one rotation never brings the same me- ridian around from the Sun to the Sun again; so that the Earth requires as much more than one complete revolution § important purposes does the period of the Earth's rotation serve 7 What is a si- dereal day? What is a solar day 7 - 204 - THE EARTH. on its axis to complete a solar day, as it has gone forward in that time. Hence in every natural or solar day, the Earth performs one complete revolution on its axis, and the 365th part of another revolution. Consequently, in 365 days, the Earth turns 366 times around its axis. And as every revolution of the Earth on its axis completes a side- real day, there must be 366 sidereal days in a year. And, generally, since the rotation of any planet about its axis is the length of a sidereal day at that planet, the number of sidereal days will always exceed the number of solar days, by one, let that number be what it may, one revolution be: ing always lost in the course of an annual revolution. This difference between the sidereal and solar days may be il- lustrated by referring to a watch or clock. When both hands set out together, at 12 o'clock for instance, the minute hand must travel more than a whole circle before it will overtake the hour hand, that is, before they will come into conjunction again. In the same manner, if a man travel around the Earth eastwardly, no matter in what time, he will reckon one day ºmore, on his arrival at the place whence he set out, than they do who remain at rest; while the man who travels arround the Earth westwardly will have one day less. From which it is manifest, that, if two persons start from the same place at the same time, but go in contrary directions, the one travelling eastward and the other westward, and each goes completely around the globe, although they should both arrive again at the very same hour at the same place from which they set out, yet they will disagree two whole days in their reckoning. Should the day of their return, to the man who travelled westwardly, be Monday, to the man who travelled eastwardly, it would be Wednesday; while to those who remained at the place itself, it would be Tuesday. Nor is it necessary, in order to produce the gain or loss of a day, that the journey, be perſon med either on the equa- tor, or on any parallel of latitude ; it is sufficient for the purpose, that all the meridians of the Earth be passed through, eastward or westward. The time, also, occupied in the journey, is equally unimportant ; the gain or loss of a day being the same, whether the Earth be travelled around in 24 years, or in as many hours. What part of a second revolution does the Earth complete in every solar day ? How many times, then, does it turn on its axis in 365 days How many sidereal days are there in a year?. On any planet, what is the number of the sidereal º compared with the number of the solar; illustrate the difference between the sidereal,and solar days by re- ferring to a watch or clock. Illustrate it by referring to two travellers going around the globe, one eastwardly and the other westwardly. - THE FARTH. 205 It is also evident, that if the Earth turned around its axis but once in a year, and if the revolution was performed the same way as its revolution around the Sun, there would be perpetual day on one side of it, and perpetual night on the other.) From these facts the pupil will readily comprehend the principles involved in a curious problem which appeared a few years ago : It was gravely report- ed by an Aujerican ship, that, in sailiug over the ocean, it clauced to find siz Sundays in February. The fact was insisted on, and a solution deulanded. There is nothing absurd in this.-The uran who travels arounfil the ſºarth east- wardry, will see the Sun go down a little earlier every succeeding day, than if he had remained at rest ; or earlier than they do who live aſ the place from which he set out. The ſasſer he travels towards the rising sun, the sooner will it appear above the horizon in the ſuorning, and so much sooner will it set in the evening. What he illus gains in limé, will bear the same proportion to a solar clay, as the distance travelled does to the circuit crence of the Earth. —As the globe is 360 degrees in circuiuſer ence, the Sun will appear to Inove over one twenty-fourth part of its surface, or 14°, every hour, which is 4 minutes ſo one degree.—Consequently, the Sun will rise, coule to the uleri- dian, and set, 4 minutes. sooner, at a place 19 east of us, than it will with us; at the distance of 28 the Sun will rise and set 8 minutes sooner; at the dis- tance of 39, 12 minutes sooner, audi so on. - - Now the unan who travels oue degree to the east, the first day, will have the Sun on his meridian 4 unnutes sooner than we (lo who are at rest ; and the second day, 8 minutes sooner, and on the third day, 12 uninutes sooner, and so on , each successive day being coupleted 4 minutes earlier than the preced- ing, until he arrives again at the place frou which he started ; when this con- tinual gain of 4 trainules a day will have amounted to a whole (lay in advance of our time ; he having seen the Sun rise and set once more than we have. Consequently, the day on which he arrives al houſe, what cver day of the week it inay be, is one day in advance of ours, and he must needs live that day over again, by calling the next day by the same name, in on der to tuake the accounts hartrionize. If this should be the last day of February in a bissextile year, it would also be the same day of the week that the first was, and be six times repeated ; and if it should happen on Sunday, he would, under these cil cuurstances, have six Sundays in February. Again :--Whereas the man who travels at ſlie rate of one degree ſo the east, will have all his days 4 minutes shorter than ours, so, ou the contrary, the man who travels at the same rate towards the west, will have all his days 4 minutes longer than ours. When he has finished the circuit of the Earth, and arrive i at the place from which he first set-out, he will have seen the Sun rise and set once less than we have. Consequently, the day he gets home will be one day after the time at that place : for which reason, iſ he arrives at home on Saturday, according to his own account, he will liave to call the next day Monday; Sunday having gone by before he reached home. Thus, on whatever day of the week January should end, in counich years, he would find the same day repeated ouly three times in February. lf January ended on Sunday, he would, under these circumstances, find only three Sundays in February. The Earth’s motion about its axis being perfectly equa- ble and uniform in every part of its annual revolution, the sidereal days are always of the same length, but the solar or natural days vary very considerably at different times of the year. This variation is owing to two distinct causes: the If the Earth revolved on its axis but once a year, and in the same direction as it revolves around the Sun, what would be the consequence as it regards day and night? It was gravely reported some years ago by an American ship, that in sailing over, the ocean, it ſound sia Sundays in February; please explain, this....Why are the sidereal days always of the same length , What are the causes of the difference in the length of the solar days? - 18 206 THE EARTH. inclination of the Earth’s axis to its orbit, and the inequality of its motion around the Sun.) From these two causes it is, that the time shown by a well regulated clock and that of a true sun-dial are scarcely ever the same. The difference between them, which sometimes amounts to 16+ minutes, is called the Equation of Time, or the equation of solar days. The difference between mean and apparent time, or, in other words, be- tween Equinoctial and Ecliptic time, may be further shown by Figure 11, which represents the circles of the sphere. Let it be first premised, that equinoctical time is clock time; and that ecliptic time is solar or apparent time. It appears, that from Aries to Cancer, the sun in the ecliptic coines to the meridian lefore the equinoctial sum ; from Cancer to Libra, after it; from Libra to Capricorn, before it; and from Capricorn to Aries, wºler it. If we notice what months the Sun is in these several quarters, we shall find, that from the 25th of December to the 16th of April, and ſrom the 16th of June to the 1st of Septeinber, the clock is faster than the sun-dial ; and that, from the 16th of April to the 16th of June, and from the 1st of September to the 25th of December, the sun-dual is faster than the clock. EQUATION OF TIME. S It is a universal fact, that, while mone of the planets are perfect spheres, none of their orbits are perfect circles, The planets all revolve about the Sun, in ellipses of different degrees of eccentricity; having the Sun, not in the centre of the ellipse, but in one of its foci. What is meant by the expression, equation of time?...Illustrate the difference between mean and apparent time by reference to Fig. 11. What is the figure of the orbits of the planets? In what point of the orbits is the Sun situated? --- THE EARTH. 207 The figure A D B E is an ellipse. The line A B is called the transverse axis, and the line drawn through the imiddle of this line, and per- pendicular to it, is the conjugate axis. The point C, the middle of the transverse axis, is the centre of the ellipse. The points F and f. equally distant from C, are called the foci. C F, the distance from the centre to one of the foci, is called the eccentricity. The orbits of the planets being ellipses, having the Sun in one of the foci, if A D B E be the orbit of a planet, with the Sun in the focus F, when the planet is at the point A, it will be in its peri- helion, or nearest the Sun; and when at the point B in its aphelion, or at its greatest distance from the Sun. The difference in these distances is evident- ly equal to Ff that is, equal to twice the eccentricity of its orbit. In every re- volution, a planet passes through its perihelion and aphelion. The eccentri. city of the iºarth's orbit is about one and a half unillions of uniles ; herice she is three millions of imiles nearer the Sun in her perihelion, than in her aphe- lion. - Now as the Sun remains fixed in the lower focus of the Earth’s orbit, it is easy to perceive that a line, passing centrally through the Sun at right angles with the longer axis of the orbit, will divide it into two unequal segments. Precisely thus it is divided by the equinoctial. (That portion of the Earth’s orbit which lies above the Sun, or north of the equinoctial, contains about 184 degrees; while that portion of it which lies below the Sun, or south of the equinoctial, contains only 176 degrees, This fact shows why the Sun continues about 8 days longer on the north side of the equator in summer, than it does on the south side in winter. The exact calculation, for the year 1830, is as follows: º d. h. m. From the vernal equinox to the summer solstice, -92 21 19 . h. m. Froin the summer solstice to the autumnal equinox, -93 14 l ; 183, 11, 19. Froun the autumnal equinox to the winter solstice, -S9 17 17 & d. h. in. Froin the winter solstice to the vernal equinox, =S9 1 13 S 178, 18, 30. Difference in ſavour of the north side, - 7, 16, 49. NThe points of the Earth’s orbit which º to its greatest and least distances from the Sun, are called, the former the Apogee, and the latter the Perigee two Greek words, the former of which signifies from the Earth, and the latter about the Earth. These points are also designated by the common name of Apsides, [See these points represented, Plate I.] The Earth being in its perihelion about the the 1st of Janu- ary, and in its aphelion the 1st of July, we are three millions of miles nearer the Sun in winter than in midsummer. The reason why we have not, as might be expected, the hottest weather when the Earth is nearest the Sun, is, because the —s- What is the cecentricity of an orbit 2 How many times is a planet in its aphe- lion, and how nany in its perihelion, in every revolution 2 Hºrw match farther is it from the Swn in the former case than in the latter 2 In which focus of the Earth's orbit is the Sun ? How does the equinoctial divide the Earth's orbit 2 Why does the Sun remain longer on the north side of the equator in summer, than it does on the south side in winter IWhat are the Earth's Apogee and Perigee 2. By what common name are these two points designated 2 When is the Earth in its Perihelion ? When in its Aphelion 2 Are we nearer the Sun in summer than in winter? How much nearer are we in winter than in summer Why do we not have the hottest weathêr when ye are nearest the Sun? 208 • THE MOON, Sun, at that time, having retreated to the southern tropic, shines so obliquely on the northern hemisphere, that its rays have scarcely half the effect of the summer Sun; and con- tinuing but a short time above the horizon, less heat is ac- cumulated by day than is dissipated by night. As the Earth performs its annual revolution around the Sun, the position of its axis remains invariably the same; always pointing to the North Pole of the heavens, and al- ways maintaining the same inclination to its orbit. This seems to be providentially ordered for the benefit of man- kind. If the axis of the Earth always pointed to the centre of its orbit, all external objects would appear to whirl about our heads in an inexplicable maze) . Nothing would appear permanent. The mariner could no longer direct his course by the stars, and every index in nature would mislead us. THE MOON. THERE is no object within the scope of astronomical ob- servation which affords greater variety of interesting inves- tigation than the various phases and motions of the Moon. From them the astronomer ascertains the form of the Earth, the vicissitudes of the tides, the causes of eclipses and oc- cultations, the distance of the Sun, and, consequently, the magnitude of the solar system. These phenomena, which are perfectly obvious to the unassisted eye, served as a stand- ard of measurement to all nations, until the advancement of science taught them the advantages of solar time. It is to these phenomena that the navigator is indebted for that precision of knowledge which guides him with well grounded conſidence 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 U1S6S. When the Moon, after having been in conjunction with the Sun, emerges from his rays, she first appears in the evening, a little after sun-set, like a fine luminous crescent, with its convex side towards the Sun. If we observe her As the Earth revolves about the Sun, what is the position of its axis Should its axis always pºint to the centre of its orbit, how would external objects appear to us? What important purposes does the Moon serve to the astronomer A . Of what importance are her phenomena to the navigator What nations used to ussemble at the time of the new or of the full Moon, to express their gratitude for her benefits 2 Describe the apparent motion of the Moon, and her phases. THE MOON. 209 the next evening, we find her about 13° farther east of the Sun than on the preceding evening, and her crescent of light sensibly augmented. Repeating these observations, we per- ceive that she departs farther and farther from the Sun, as her enlightened surface comes more and more into view, un- til she arrives at her first quarter, and comes to the meridian at sun-set. She has then finished half her course from the new to the full, and half her enlightened hemisphere is turn- ed towards the Earth. After her first quarter, she appears more and more gib- bows, 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. In the first half of her orbit she appears to pass over our heads through the upper hemisphere; she now descends be- low the eastern horizon to pass through that part of her or- bit which lies in the lower hemisphere. After her full she wanes through the same changes of ap- 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-sun. For the next two or three days she is lost to our view, rising and setting in conjunction 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 con- junction, it was turned to the east; it is now turned towards the west. These different appearances of the Moou are called her phases. . . They prove that she shines not by any light of her own ; if she did, being globular, we should al- ways see her a round full orb like the Sun. The Moon is a satellite to the Earth, about which she re- volves in an elliptical orbit) in 29 days, 12 hours, 44 min- utes, and 3 seconds: the time which elapses between one new moon and another. This is called her synodic revo- lution. Her revolution from any fixed star to the same star again, is called her periodic or siderial revolution. It is accomplished in 27 days, 7 hours, 43 minutes, and 11+ sec- onds; but in this time, the Earth has advanced nearly as many degrees in her orbit; consequently the Moon, at the How is it known that the Moon does not shine by her own light? About what does the Moon revolve, and what is the figure of her orbit? . What is the time of her revolution from one new Moon to another "What is this revolution denominated? What is her pe. riodic or sidereal º ! In what time is this accomplished A 210 THE MOON. end of one complete revolution, must go as many degrees farther, before she will come again into the same position with respect to the Sun and the Earth. The Moon is the nearest of all the heavenly bodies, bein about 30 times the Jameſe of the Earth, or 240,000 miles, distant from us. Her mean daily motion, in her orbit, is nearly 14 times as great as the Earth's); since she not only accompanies the Earth around the Sun every year, but, in the meantime, performs nearly 13 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 nean rate, no less than 13° 10' 35" in a day; yet this is to be understood as angular motion —inotion in a Sumall orbit, and therefore einbracing a great number of degrees, and but colnparatively few iniles. As the Moon, while revolving about the Earth, is carried with it at the same time around the Sun, her path is ex- tremely irregular, and very different from what it seems to be. . Like a point in the wheel of a carriage, moving over a convex road, the Moon will describe a succession of epicycloidal curves, which are always concave towards the i. not very unlike their presentation in the following gure. THE Moon’s Motion. Fig. 12. w" V. §W. % §§ sº º \ ** To what is the difference of time in those two revolutions owing? How great is the distance of the Moon from the Earth, compared with thut of the other heavenly bodies? What is her distance from us What is her motion in her orbit, compared with the Earth's How muny times does she revolve around the Earth, every year? The §. rent motion of the Moon is greater in her orbit than that of any other heavenly body; 38 it to be understood that she passes,through a correspondent space 2 Describe Moon's path. ‘I’HE MOON, 211 Let A d b B represent a portion of the Earth's orbit; and a b c d e the lunar orbit. When the Earth is at b, the new Moon is at ſt; and while the Earth is moving from b to its position as represented in the figure, the Moon has moved through half her orbit, from a to c, where she is full ; so while the Earth is moving from its present position to d, the \loon drºscribes the other half of her orbit ſtom c to e, where she is again ill conjunction. The Moon, though apparently as large as the Sun, is the (smallest of all the heavenly bodies, that are visible to the naked eye. Her diameter is but 2162 miles; consequently {her surface is 13 times less than that of the Earth, and her bulk 49 times less) It would require (70 millions of such bodies to equal the volume of the Sun'. The reason why she appears as large as the Sun, when, in truth, she is so much less, is because she is 400 times nearer to us than the Sun; The Moon revolves once on her axis exactly in the time that she performs her revolution around the Earth. This is evident(from her always presenting the same side to the Earthy for iſ she had no rotation upon an axis, every part of her surface would be presented to a spectator on the Earth, in the course of her synodical revolution. It follows, then, that there is but ône day and night in her year, con- taining, both together; 29 days, 12 hours, 44 minutes, and 3 seconds. As the Moon turns on her axis only as she moves around the Earth, it is plain that the inhabitants of one half of the lunar world are totally deprived of the sight of the Earth, unless they travel to the opposite hemisphere. This we may presume they will do, were it only to view so sublime a spectacle ; for it is certain that from the Moon the Earth tappears ten times larger than any other body in the universe. As the Moon enlightens the Earth, by reflecting the light of the Sun, so likewise the Earth illuminates the Moon, ex- hibiting to her the same phases that she does to us, only in a contrary 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 splendour when the Sun is absent ; it therefore enjoys suc- cessively two weeks of illumination from the Sun, and two What is her magnitude, compared with that of the other heavenly bodies 7 What is her diameter How great are her surface and her bulk, comi-ured with those of the Earth? How many such bodies would it require to equal the volume of the Sun ? Why does she appear as large as the Sun, when in reality she is so much less A What is the time of her revolution on her axis, compared with thºt of her revolution around the Earth How is this proved 3. How many days and nights then has she in the course of her, synodical re- volution What is the length of both united? Describe the phenomena of the Earth as seen by the inhabitants of the Moon. - 212 THE MOON. weeks of earth-light from the Earth. The other side of the Moon has alternately a fortnight's light, and a fortnight's darkness. 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 Qurs: As the full Moon always happens when the Moon is di- rectly opposite the Sun, all the full Moons in our winter, must happen when the Moon is on the north side of the equi- noctial, because then the Sun is on the south side of it; con- sequently, at the north pole of the Earth, there will be a fortnight’s moon-iight and a fortnight's darkness by turns, for a period of six months, and the same will be the fact du- ring the Sun’s absence the other six months, at the south ole. p The Moon's axis being inclined only about 13° to her orbit, she can have no sensible diversity of seasons; from which we may infer, that her atmosphere is mild and uni- form. The quantity of light which we derive from the Moon when full, is at least 300 thousand times less than that of the Sun." ' When viewed through a good telescope, the Moon' pre- sents a most wonderful and interesting aspect. Besides the large dark spots, which are visible to the naked eye, we perceive extensive valleys, shelving rocks, and long ridges of elevated mountains, projecting their shadows on the plains below. Single mountains occasionally rise to a great height, while circular hollows, more than three miles deep, seem excavated in the plains. Her mountain scenery'bears a striking resemblance to the towering sublimity and terrific ruggedness of the Alpine re- * This is Mons. Bouquer’s inference, from his experiments, as stated by La Place, in his work, p. 42. The result of Dr. Wollaston's computations was different, Professor Leslie makes the light of the Moon 150,000 times less than that of the Sun: it was former- ly reckoned 100,000 times less. As the Earth revolves on its axis, how do its continents, seas, and islands, appear to the lunar inhabit ºnts For what purposes may these spots serve to the lunarians? What are the periods of the Miodn's presence and absence to the polar inhabitants : . Explain, this. Why cannot the Moon have any sensible diversity of seasons 7. What then ; we inſer to be the character of her atmosphere? What is the quantity of light which she affords when full, compared with that of the Sun ? Describe the appearance of the Moon when seen through a good telescope. What mountains of the Earth does hor mountain scenery resemble 7 THE MOON. 213 gions, or of the Appenines, after which some of her moun- tains have been named, and of the Cordilleras of our own continent. Huge masses of rock rising precipitously from the plains, liſt their peaked summits to an innense height in the air, while shapeless crags hang over their projecting sides, and seem on the eve of being precipitated into the tremendous chasm below. Around the base of these frightful eminences, are strewed numerous loose and unconnected fragments, which time seems to have detached from their parent mass ; and when we examine the rents and ravines which accompany the overhanging cliffs, the beholder expects every moment that they are to be torn from their base, and that the process of destructive separation which he had only contemplated in its effects, is about to be exhibited before him in all its reality. The range of mountains called the Appenines, which tra- verses a portion of the Moon's disc from north-east to south- west, and of which some parts are visible to the naked eye, rise with a precipitous and craggy front from the level of the Mare Imbrium, or Sea of showers.” In this extensive range are several ridges whose summits have a perpendicu- lar elevation of four miles, and more ; and though they often descend to a much lower level, they present an inac- sessible barrier on the north-east, while on the south-west they sink in gentle declivity to the plains. - There is one remarkable feature in the Moon's surface which bears no analogy to any thing observable on the Earth. This is the circular cavities which appear in every part of her disc. *Some of these immense caverns are nearly four miles deep, and forty miles in diameter. They are most numerous in the south-western part. As they reflect the Sun's rays more copiously, they render this part of her surface more brilliant than any other. They present to us nearly the same appearance as our Earth might be sup- posed to present to the Moon, if all our great lakes and seas were dried up. The number of remarkable spots on the Moon, whose latitude and longitude have been accurately determined, Jexceeds 200. The number of seas and lakes, as they were Yormerly considered, whose length and breadth are known, * The name of a lunar spot. Describe the appearance of her m 'unſains. (in what part of her disc is that range of mountains called the Appenines, situated 3 ſloscribe it. What remarkable feature in the Moon's surface, bears no analogy to any thing observable on the Earth's sufice? Describe their appearance. What is the number of remarkable spots in the Moon's surface, whose latitude and longitude have been accurately determined What is the number of seas and lakes, as they were formerly considered, whose dimensions are known? 214 the MOON. * is between 20 and 30; while the number of peaks and mountains, whose perpendicular elevation varies from a fourth of a mile to five miles in height, and whose bases are from one to seventy miles in length, is not less than one hundred and fifty.* ‘Graphical views of these natural appearances, accompanied with minute and familiar descriptions, constitute what is called Selenography, from two Greek words, which mean the same thing in regard to the Moon, as Geog- raphy does in regard to the Earth. An idea of some of these scenes may be formed by con- ceiving a plain of about 100 miles in circumference, encircled by a range of mountains, of various forms, three miles in perpendicular height, and having a mountain near the centre, whose top reaches a mile and a half above the level of the plain. From the top of this central mountain, the whole plain, with all its scenery, would be distinctly visible, and the view would be bounded only by a lofty amphitheatre of mountains, rearing their summits to the sky, The bright spots of the Moon are the mountainous regions; while the dark spots are the plains, or more level parts of her surface. There may be rivers or small lakes on this planet; but it is generally thought, by astrono- mers of the present day, that there are no seas or large col- lections of water, as was formerly supposed. Some of these mountains and deep valleys are visible to the naked eye ; and many more are visible through a telescope of but moderate powers. A telescope which magnifies only 100 times, will show a spot on the Moon's surface, whose diameter is 1223 yards; and one which magnifies a thousand times, will enable us to perceive any enlightened object on her surface whose di- mensions are only 122 yards, which does not much exceed the dimensions of some of our public edifices, as for instance, the Capitol at Washington, or St. Paul’s Cathedral. Pro- fessor Frauenhofer, of Munich, recently announced that he had discovered a lunar edifice, resernbling a fortification, together with several lines of road. The celebrated as- tronomer Schroeter, conjectures the existence of a great * Brewster's Selenography. . The best maps of the Moon hitherto published, are those by Schroeter; but the most curious and complete representation of the telescopic and na- túral appearances of the Moon, is to be seen on Russel's Lunar Globe. See also Seleno- graphia, by C. Blunt. What is the number of peaks and mountains whose perpendicular elevation varies from a fourth of a mile to five miles, and whose buses are from one to seventy miles in length? What is Se'enog, a phy Ž Give an illustration to enable us to form some idea of some of these scenes. Which spots are the ſnountainous regions, and which the plains? Do as- tronomers now suppose, as they did formerly, that there are large collections of water on the Moon's surface? Are any of her mountains and valleys visible to the naked eye? How small a spot on the Moon's surface can be seen by a telescope which magnifies 100 times? How small an enlightened object can be seen by one which magnifies 1000 times? Mention any public edifices which are of nearly the same dimensions, EC Li PSES. 215 city on the east side of the Moon, a little north of her equator, an extensive canal in another place, and fields of vegeta- ion in another. SOLAR AND LUNAR. ECLIPSES. Of all the phenomena of the heavens, there are none which engage the attention of mankind more than eclipses yf the Sun and Moon; and to those who are unacquainted with astronomy, nothing appears more wonderful than the accuracy with which they can be predicted. In the early ages of antiquity they were regarded as alarming devia- tions from the established laws of nature, presaging great public calamities, and other tokens of the divine displeasure. In China, the prediction and observance of eclipses are made a matter of state policy, in order to operate upon the fears of the ignorant, and impose on them a superstitious regard for the occult wisdoin of their rulers. In Mexico, the natives fast and aſilict themselves, during eclipses, under an apprehen- sion that the great spirit is in deep sufferance. Soule of the northern tribes of Indians have imagined that the Moon had been wounded in a quarrel ; and others, that she was about to be swallowed by a huge fish. It was by availing himself of these superstitious notions, that Columbus, when shipwrecked on the island of Jamaica, extricated himself and crew from a most embarrassing condition. Being driven to great distress for want of provisions, and the natives refusing him any assistance, when all hope seein- ed to be cut off, he bethought himself of their superstition in regard to eclipses. Having assembled the principal unen of the island, he remonstrated against their inhumanity, as being offensive to the Great Spirit; and told them that a great plague was even ready to fall upon them, and as a token of it, they would that night see the Moon hide her face in anger, and put on a dreadfully dark and theatening aspect. This artifice had the desired eſfect; for the eclipse had no sooner begun, than the frightened barbarians came running with all kinds of provisions, and throwing themselves at the feet of Columbus, implored his forgiveness.--Almagest, Vol. I. 55 c. v. 2. An eclipse of the Sun takes place, when the dark body of the Moon, passing directly between the Earth and the Sun, intercepts his light. This can happen only at the in- stant of new Moon, or when the Moon is in conjunction ; for it is only then that she passes between us and the Sun. An eclipse of the Moon takes place when the dark body of the Earth, coming between her and the Sun, intercepts his light, and throws a shadow on the Moon. This can happen only at the time of full Moon, or when the Moon is in oppo- sition ; for it is only then that the Earth is between her and the Sun. As every planet belonging to the solar system, both pri- How were eclipses regarded in the early ages of antiquity To what purpose do the rulers of China make their prediction and observance subservient 2 How do the natives of Melvico demean themselves during an eclipse 2 Why do they do this 2 What notions have some of the northerm tribes of Indians entertained with regard to eclipses of the Moon & Relate the anecdote of Columbus extricating himself and his crew from distress, by availing himself of the superstitious motions of the na- tives of Jamaica in regard to eclipses. What causes eclipses of the Sun? What causes eclipses of the Moon? * 216 ECLIPSES, mary and secondary, derives its light from the Sun, it must cast a shadow towards that part of the heavens which is op- posite to the Sun. . This shadow is of course nothing but a privation of light in the space hid from the Sun by the opaque body, and will always be proportioned to the mag- nitude of the Sun and planet. If the Sun and planet were both of the same magnitude, 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. If the planet were larger than the Sun, the shadow would continually diverge, and grow larger and larger; but as the Sun is much larger than any of the planets, the shadows which they cast must converge to a point in the form pf a cone; the length of which will be proportional to the size and distance of the planet from the Sun. 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 primary planets cau eclipse another. The shadow of any plauet which is accoupanied by satellites, may, on certain occasions, cclipse its satellites; l; tıt it is not loug enough to eclipse any Other body. The shadow of a satellite, or Moon, may also, on certain occa- Sions, fall on the primary, and eclipse it. When the Sun is at his greatest distance from the Earth, and the Moon at her least distance, her shadow is suffi- ciently long to reach the Earth, and extend 19,000 miles beyond. When the Sun is at his least distance from the Earth, and the Moon at her greatest, her shadow will not reach the Earth’s surface by 20,000 miles. So that when the Sun and Moon are at their mean distances, the cone of the Moon's shadow will terminate a little before it reaches the Earth's surface. In the former case, iſ a conjunction take place when the centre of the Moon comes in a direct line between the centres 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 Fig. 13. In consequence of the Earth’s motion during the eclipse, this circular area becomes a continued belt over the earth's surface; being, at the broadest, In what direction does every planet of the solar system cast a shadow 7 What is this shadow, and to what is it proportional \, if the Sun and planet were both of the same magnitude, what would be the form of the shadow, and its diameter 2 ºf the planet were larger than the Sun, what would be the form of the shadow ºut as the Sun is much larger than any of the planets, what must be the form of their shadows, and to what are they proportional Why can no one of the prºnary planets ectºpsc another ? Eir- plaim how, on certain occasions, they may eclipse their satellites, and om others be eclipsed by them. When the Sun is at his ſtreatest distance from the Earth, and the Moon at her ieast distance, how far will her shadow extend A When the Sun is at his least distance and the Moon at her greatest ? When the Sun and Moon are both at their onean distances ! In the first case, in what gircumstances will the Moon's shadow fall centrally on the Earth, and what will be its figure and diameter 3 How will the Sun ap- pear to all places lying within this dark spot 2 Describe the effect of the Earth's motion, dvºring the eclipse, upon this circular (, ; ca. EcLIPSEs. 217 175 miles wide. This belt is, however, rarely so broad, and often dwindles to a mere nominal line, without total darkness. - In March, this line extends itself from S. W. to N. E., and in September, from N. W. to S. E. In June, the central line is a curve, going first to the N. E., and then to the S. E.; in December, on the contrary, first to the S. E., and then to the N. E. To all places within 2000 uniles, at least, of the central line, the eclipse will be visible ; and the nearer the place of obser- vation is to the line, the larger will be the eclipse. In winter, if the central trace be but a little northward of the equator, and in Summer, if it be 25° N. latitude, the eclipse will be visible all over the northern hemisphere. As a general rule, though liable to imany, Inodifications, we may observe, that places from 200 to 250 miles from the central line, will be 11 digits eclipsed; from thence to 500 miles, 10 digits; and so on, diminishing one digit .n about 250 miles. ECLIPSES OF THE SUN. Fig. 13. If, in either of the other cases, a con- =\ s & e 2 : . Jºš junction take place when the Moon's 'º-º centre is directly between the centres \***** of the Sun and Earth, as before, the Moon will then be too distant to cover the entire face of the Sun, and there will be seen, all around her dark body, a slender ring of dazzling light. This may be illustrated by the adjoining fig- ure. Suppose C D to represent a part of the Earth’s orbit, and the Moon’s shadow to termi- nate at the vertex V. The small space between e f will represent the breadth of the luminous ring which will be visible all around the dark ody of the Moon. Stich was the eclipse of February 12, 1831, which passed over the southern states from S. W. to N. E. It was the only annular eclipse ever visible in the United States. Along the path of this eclipse, the luminous ring remained perfect and unbroken for the space of two min- utes. The next annular eclipse which will be visible to any, considerable portion of the Uni. ted States, will take place Sept. 18th, 1838. Jº- From the most elaborate calculations, compar- ed with a long series of observations, the length of the Moon's shadow in eclipses, and her dis- tance ſroun the Sun at the same time, vary with- c...” in the limits of the following table : C In either of the other cases, the same circumstances occurring as before, what will be the appearance of the Sun ? Why does not the Moon, in this case, cause a total eclipse} When did the only eclipse of this cind, ever visible in the United States, happen? How long did the luminows ring, along its path, remain unbroken 2 When will the next annular eclipse, * to any considerable portion of the United States, happen? 218 . ECLIPSES, Distance in miles. Length of shadow in Length Distance in Length of shadow, * * * Semidiaineters. | in miles. | Semidianaeters. Dist. of Moon. | - Least | 57.760X3956= 228,499 55.902X3956= | 221, 148 Mean 5S,728.23956= 232.328 60 238×30.56= 238,300 Greatest | 59.730s& 3956= 236.392 | 63.S62×3956= | 252,638 Thus it appears that the length of the cone of the Moon's shadow, in eclipses, varies from 228,499 to 236,292 miles; being 7.793 miles longer in the one case, than in the other. The inequality of her distances from the Earth is much greater; they vary from 221,148 to 252,638 miles, making a difference of 31,490 miles. Although a central eclipse of the Sun can never be total to any spot on the Earth more than 175 miles broad; yet the space over which the Sun will be more or less partially eclipsed, is nearly 5000 miles broad. The section of the Moon’s shadow, or her penumbra, at the Earth's sur- face, in cclipses, is far from being always circular. If the conjunction hap- pen when the centre of the Moon is a little above or a little below the line joining the centres of the Earth and Sun, as is most frequently the case, the shadow will be projected obliquely over the Earth’s surface, and thus cover a much larger space. To produce a partial eclipse, it is not necessary that the shadow should reach the Earth ; it is sufficient that the apparent distance between the Sun and Moon be not greater than the sum of their semidiameters. If the Moon performed her revolution in the same path in which the Sun appears to move; in other words, if her orbit lay exactly in the plane of the Earth’s orbit, the Sun would be eclipsed at the time of every new Moon, and the Moon at the time of every full. But one half of the Moon’s orbit lies about 5° on the north side of the ecliptic, and the other half as far on the south side of it; and, consequently, the Moon's orbit only crosses the Earth’s orbit in two opposite points, called the Moon's nodes. - When the Moon is in one of these points, or nearly so, at the time of mew Moon, the Sun will be eclipsed. When she is in one of them, or nearly so, at the time of full Moon, the Moon will be eclipsed. But at all other new Moons, the Moon either passes above or below the Sun, as seen from the Earth; and, at all other full Moons, she either passes above or below the Earth’s shadow ; and consequent- ly there can be no eclipse. . What are the limits between which the Moon’s shadow varies in eclipses? What is the difference between these two limits 2 What are the liºn its of her distances from the Earlh 2 What is the diffe, ence between them. & What is the greatest breadth of any spot on the Earth's surface, to which a gentral eclipse of the Sun can be totall What is the breadth of the greatest space over which the Sun can be more or less partially eclipsed? Is the penumbra of the Moon at the Earth's surface in eclipses always circular 2. In what circumstances will the shadow be projected obliquely over the Earth's swiface 2 lMust the shadow reach the Earth, to produce a partial eclipse 2 What is the great- est apparent distance between the Sun and Moºn, within which such a result will take place? Why is not the Sun eclipsed at the time of every new Moon, and the Moon at every full? . In what circumstances will an eclipse of the Sun, and in what an eclipso of the Moon, happen? ECLIPSES. 319 If the Moon be eacactly in one of her nodes at the time of her change, the Sun will be centrally eclipsed. If she be 13° from her mode at the time of her change, the Sun will appear at the equator to be about 11 digits eclipsed. If she be 3° from her node at the time of her change, the Sun will be 10 digits eclipsed, and so on ; a digit being the twelfth part of the Sun's diameter. But when the Moon is about 18° from her node, she will just touch the outer edge of the Sun, at the time of her change, without producing any eclipse. These are called the ecliptic limits. Between these limits, an eclipse is doubtful, and requires a more exact calcula- tion. - The mean ecliptic limit for the Sun is 16:9 on each side of the node; the mean ecliptic limit ſor the Moon is 103.9 on each side of the node. In the former case, then, there are 33° about each node, making, in all, 66° out of 360°, in which eclipses of the Šstm Inay happen: in the latter case, there are 21° about each node, making, in all, 42° out of 360° in which eclipses of the Moon usually occur. The proportion of the solar, to the lunar eclipses, therefore, is as 66 to 42, or as 11 to 7. Yet, there are more visible eclipses of the Moon, at any given place, than of the Sun; because a lunar eclipse is visible to a whole hemisphere, a solar eclipse only to a small portion of it. 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. * Eclipses of the Sun always begin on his western edge, and end on his eastern ; but all eclipses of the Moon com- mence on her eastern edge, and end on her western. If the Moon, at the time of her opposition, be exactly in her node, she will pass through the centre of the Earth’s shadow, and be totally eclipsed. If, at the time of her opposition, she be within 6° of her node, she will still pass through the Earth’s shadow, though not centrally, and be totally eclipsed: but if she be 12° from her node, she will only just touch the Earth’s shadow, and pass it without being eclipsed. The duration of lunar eclipses, therefore, depends upon the difference between the diameter of the Moon and that section of the Earth’s shadow In what circumstances is the Sun centrally eclipsed? What is the ratio between the Moon's distance from her node, and the number of digits that the Sun is eclipsed? What are these limits called A Will there always be oclipses when the Moon is within these limits 7 What is the ecºpfsc lix, it for the Saty, 2 HWhat is iſ for the Moon 2 Viſhat number of degrees, ther, are there abºut each node, and how many out of 360°, in which solar eclipses can happen 2 Hºw many in ºphich lunar eclipses usually hop- pen 2 What then is the prºpºrtion of the solar to the lunar eclipses 2 II'hy then are there more colipses of the Moon visible at any given place than of the Sur, 2 What is the greatest possible duration of the annular appearance of a solar eclipse? What is the greatest possible duration of a total solar cclipse to any part of the world? What is the greatest duration of a total lunar eclipse On which side of the Sun do solar eclipses always begin, and on which do they end? On which side of the Moon do lunar eclipses always begin, and on which do they end? In what circumstances is time Moon totally eclipsed? Beyond what distance from her node, if she be, will she only touch the Earth’s shadow, and uot be eclipsed? On what then does the duration of lunar eclipses depend? * 220 ECLIPSES. through which she passes. . When an eclipse of the Moon is both total and central, its duration is the longest possible, amounting nearly to 4 hours : É. . duration of all eclipses not central, varies with her distance from the node. . * ECLIPSES OF THE MOON, Fig. 15. 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 as great as the distance of the Moon; exceeding it in the same ratio that the diameter of the Earth does the diame- ter of the Moon, which is as 3.663 to 1. The length of the Earth’s shadow, and its diameter at | Diameter | Length of the distance of the Moon, are subject to the variations of the the shad- exhibited in the following table. * shadow. ow in ms. § Moon at the apogee 5,232 & Sun at the perigee Moon at her mean distance 5,762 842,217 Moon at the perigee 6,202 S Moon at the apogee 5,270 Sun at his mean distance { Moon at her mean distance 5,799 856,597 Moon at the perigee 6,329 Moon at the apogee 5,306 Sun at the apogee Moon at her mean distancel 5,836 871,262 Moon at the perigee 6,365 The first column of figures expresses the diameter of the Earth's shadow at the Moon : and as the diameter of the Moon is only 2162 miles, it is evident that it can always be comprehended by the shadow, which is unore than twice as broad as the disc of the Moon. The time which elapses between two successive changes of the Moon is called a Lunation, which, at a mean rate, is about 294 days. If 12 lunar months were exactly equal to the 12 solar months, the Moon's modes would always occupy the same points in the ecliptic, and all eclipses would happen in the same months 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, In what circumstances is the dºtration of the litmar eclipse the longest possible 2 What is the length of the greatest duration of a lunar eclipse 2 . With no/hat does the duration of celipses, not central, rary 2 What is the diamoter of the Earth's shadow at the distance of the Miodn What is the length of the Earth's shadow What is their ratio to each other Between what limits does the length of the Earth's shadow, and Žts diameter at the distance of the Moon, vary 2 Iſhat is the breadth of the Earth's shadoºp compared with that of the disc of the Moon 2 What is a lunation? How many days ; a lunation embrace? Why do not all eclipses happen in the same months of ge year ECLIPSES. 221 but has not quite accomplished her revolution around the Sun : the consequence is, that the Moon's nodes fall back ln the ecliptic at the rate of about 194° annually ; so that the eclipses happen sooner every year by about 19 days. As the Moon passes from one of her nodes to the other in 173 days, there is just this period between two succes- sive 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 1989 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 period of eclipses, if any couplete number of lunations were finished without a remainder. But this never happens ; ſor 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 perforin 18 annual revolutions alid 2:2:29 of another, while the Moon would perſorm 230 lunations, and S5° of another, before the mode would come around to the Sairie point of the ecliptic again : SG iliat the Sun would then be 138° from the node, and the Moon 859 from the Sun. But after 223 lunations, or 18 years, 11 days,” 7 hours, 42 minutes, and 31 seconds, the Stan, Moon, aud Earth, will return so nearly in the same position with respect to each other, that there will be a regular return of the same eclipses for many ages. This grand period was discovered by the Chaldeans, and by them called Saros. If, therefore, to the ſnean time of any eclipse, either of the Sun or Moon, we add the Chaldean period of 18 years and 11 days, we shall have the return of the same eclipse. This mode of predict- ing eclipses will hold good for a thousand years. In this period there are usually 70 eclipses; 41 of the Sun, and 29 of the Moon. The number of eclipses in any one year, cannot be less than two, nor more than seven. In the former case, they will both be of the Sun ; and in the latter, there will be five of the Sun, and two of the Moon—those of the Moon will be total. There are sometimes six; but the usual number is four: two of the Sun, and two of the Moon. The cause of this variety is thus accounted for. Although the Sun usually passes by both modes only once in a year, he may pass the same mode again a little before the end of the year. In consequence of the retrograde motion * If there are four leap years in this interval, add 11 days ; but if there are five, add only ten days. How far do the Moon's modes fall back in the ecliptic annually, and how much sooner do the eclipses happen every year in what time does the Moon pass from ome of her nodes to the other ? What is the length of the time which elapses between two successive eclipses of the Sun or the Vioon After there have been eciipses at one node, in what time may we be sure that there will be eclipses at the other In what time do the Moon's rºotles comple'e a bickward enroºt'ien around the ecliptic 2 Iiſhy is there not always a regillar period of eclipses in this time 2 If the Sun and Moon should both start Jrom a line of conjunction with e ºther mode, how many revolutions would the Swn. ſperform, and how many lunations the Moon, befºre the mode would cºme around to the same point agitim 2 After how many lunations with the Sun, Moton, and Earth, 7'etatiºn so nearly to the same pusilion with respect to each other, that there will be a regular return of the same eclipses for many ages 2 ſi hat ration discovered this grand period, and what did they call it 2 M'hat is the mode of predicting eclipses, with which this fact furnishes its 2 How many eclipses are there wisually in this pe. riod? What is the least, and what the greatest number of eclipses, in any one year? In the former case, what eclipses will they be? What, in the latter? What is the usual number of eclipses in the year, and what eclipses are they 7 Please explain the cause of 19* this variety. 222. MARS. of the Moon’s modes, he will come to either of them 173 days after passing the other. He may, therefore, return to the same mode in about 346 days, 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, six in all. And, since 12 lunations, or 354 days from the first eclipse in the beginning of the year, leave room for another new Moon before the close of the year, and sincé this new Moon may fall within the ecliptic limit, it is possible for the Sun to be eclipsed again. Thus there may be seven eclipses in the same year. Again: when the Moon changes in either of her nodes, she cannot come within the lunar ecliptic limit at the next full, (though iſ she be full in one of her nodes, she lilay come into the solar ecliptic limit at her next change.) and six months afterwards, she will change near the other node ; thus mak- ing only two eclipses, The following is a list of all the solar eclipses that will be visible in Europe and America during the remainder of the present century. To those which will be visible in New-England, the number of digits is annexed. Year. Month Day & hour. |Digits || Year. Month |Day and Hour. Digits 1834, Nov. 30 1 22 P. M. 10}o 1S69, Aug. || 7 5 21 A. M. 10} 1836, May 15 7 25 A. M. 8 1870, Dec. 22 6 0 A, M. 183S, Sept. 18 3 27 P. M. 11 1873, May 26 3 0 A. M. 1841, July 18 10 0 A. M. 1874, Oct. 10 4 0 A. M. 1842, July & Q Q Mer. || 1 1875, Sept. 29 5 56 A. M. 11% 1844, Dec. 9 3 46 P. M. |2th 1876, Mar. 25 4 11 P. M. 33 1845, May | 6 4 55 A. M. # 1878, July 29 456 P. M. 7# , 1846, Apr. 25 11 15 A. M. 6; 1879, July 19 2 0 A. M. 1847, Oct. 9 1 0 A. M. 1880, Dec. 31 7 30 A. M. 5} 1848, Mar. 5 750 A. M. 6; 1882, May 17 l 0 A. M. 1851, July 28 7 48 A. M. 33 1885, Mar. 16 0 35 A. M. | 6 1854, May 26 426 P. M. i 1886, Aug. 29 6 30 A. M. $58, Mar. 15 6 14 A. M. l; 1887, Aug. 18 10 0 P. M. 1859, July 29 5 32 P. M. 2; 1890, June 17 3 0 A. M. 1860, July 18 7 23 A. M. 6; 1891, June | 6 0 0 Mer. - 1861, Dec. 31 7 30 A. M. 4} . 1892, Oct. 20 0 19 P. M. 8: 1863, May 17 1 0 P. M. 1895, Mar. 26 4 0 A. M. 1865, Oct. 19 9 10 A. M. 3# 1896, Aug. 9 0 0 Mer. 1866, Oct. S 11 12 A. M | 0 1897, July 29 9 8 A. M. 44 1867, Mar. 6 3 A. M 1899, June | 8 0 0 Mer. 1868, Feb. 23 10 0 A. M. 1900, May 28 8 9 A. M. | 11 The eclipses of 1838, 1854, 1869, 1875, and 1900, will be very large. In those of 1845, 1858, 1861, 1873, 1875, als, 1880, the Sun will rise dºsed In that of 1844, the Sun will set eclipsed. Those of 1838, 1854, and 1875, will be annular. The scholar can continue this table, or extend it backwards, § adding or subtracting the Chaldean period of 18 years, 11 days, 7 hours, minutes, and 31 seconds. - MARS. 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. Mars appears to the naked eye, of a fine ruddy com- plexion ; resembling, in colour, and apparent magnitude, the star Antares, or Aldebaran, near which it frequently passes.) It exhibits its greatest brilliancy (about the time What is the position of Mars in the solar system 7 Describe its appearance to the na- ked eye. When does it exhibit its greatest brilliancy * - MARS. 223 that it rises when the Sun sets, and sets when the Sun rises;) because it is then nearest the Earth. It is least brilliaft when it rises and sets with the Sun; for then it is five times farther removed from us than in the former case. (Its distance from the Earth at its nearest approach is about 50 millions of miles. Its greatest distance from us is about 240 millions of miles: In the fortner case, it appears nearly 25 times larger than 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 all the planets from the Earth, whether they be interior or exterior plancts, varies łº the limits of the diameters of their orbits; for when a planet is in that point of its orbit which is nearest the Earth, it is evidently nearer by the whole diameter of its orbit, than when it is in the opposite point, on the other side of its orbit. The apparent diaméter of the planet will also vary for the saine reason, and to the saine degree: 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. This proves not only that its orbit is eacterior to the Earth’s orbit; but that it is an opaque body shining only by the re- flection of the Sun) The motion of Mars through the constellations of the zodiac is but little more than half as great as that of the Earth 3 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 conclude that two months hence it will be in the next &onstellation; four months hence, in the next ; six months, in the next, and so on. Mars performs his revolution around the Sun in 1 year and 104 months, at the distance of 145 millions of miles; moving in its orbit at the mean rate of 55 thousand miles an hour.) Its diurnal rotation on its axis is performed in #24 hours, 39 minutes, and 214 seconds; which makes its day about 44 minutes longer than ours, Why is it most brilliant at this time? What are its least and greatest distances from us 3 How much larger does it appear in the former case than in the latter 3 H"ithin what limi s does the distance of all the planets from the Earth vary 2 With what does the apparent diameter of a planet vary 2 What moon-like phases has Mars? What does the fact, that it never assumes the crescent form at its conjunction, prove, in regard to its situation 7 How do we know it to be opaque * What is the rate of:ts motion through the constellations of the zodiac, compared with that of the Earth 3 How long is it in passing over one sign 3 At what rate per day is this? How, then, if we know in what constellation it is at any one time, may we determine in what constellation it will be at any subsequent time? lm what time does it perform its revolution around the Sun ? What is its distance from the Sun ? What is the mean rate of its motion in its or- bit per hour ! In what time does it perform its revolution on its axis 3 What, then, is the length of its day, compared with that of the Earth - 224 MARs. Its mean sidereal revolution is performed in 686.9796458 solar days; or º; days, 23 hours, 30 minutes, 41.4 seconds. Its synodical revolution is P. in 779.936 solar days; or in 779 days, 22 hours, 27 minutes, and Sec OIAC.S., * ~. & J ‘Its form is that of an oblate spheroid, whose polar diame- ter is to its equatorial, as 15 is to 16, nearly. Its mean diameter is 4222 miles.) Its bulk, therefore, * times less than that of the Earth ; and being 50 milličns of miles farther from the Sun, it receives from him only half as much light and heat.) - $ The inclination of its axis to the plane of its orbit, is about (283°. Consequently, its seasons must be very similar to those 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 mights, 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 Heyschel.) To a spectator on this planetſ the Earth will appear al- ternately, 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 240,000 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 open 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's & The progress of Mauš in the heavens, and indeed of all the superior pla- néts, will, like Mercury and Venus, sometimes appear direct, sometimes retrograde, and sometimes he will seem stationary. When a superior planet first becomes visible in the morning, west of the Sun, a little aſter its conjunction, its motion is direct, and also most rapid. When it is first seen east of the Sun, in the evening, soon aſter its opposition, its motion is rº retrograde. These retrograde movements and stations, as they appear to a In what time does, it perform its mean sidereal revolution ? In what time, its sy. nodical revolution 2 What are its form and dimensions? What, then, is its bulk, com- R}; with the Earth's, and how much less light, and heat does it receive from the Sun? hat is the inclination of its axis to the plane of its orbit? How are its seasons, compa- red with those of the Earth In what particulars is there a greater analogy between Mars and the Earth, than between the Earth and any other planet in the solar system What must be the appearance of the Earth to a spectator at Mars? What is the greatest dis- tance from the Earth at which our Moon will appear to him to be? Why may we rea- ;% conclude that Mars has no satellite 2 Describe the progress of Mars through € /26& 130??.S. MARS, 225 spectator from the Earth, are common to all the planets, and demonstrate the truth of the Copernican system. The telescopic phenomena of Mars afford peculiar in- terest 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 bril- liant. Dr. Herschel supposes that they are produced by the reflection of the Sun’s light from the frozen regions, and that the melting of these masses of polar ice is the cause of the variation in their magnitude and *"...], He was the more confirmed in these opinions by observ- ing, that aſter the exposure of 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 darkness during eight months, had considerably in- creased. He observed, farther, that when this spot was most lu- minous, 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. TELESCOPIC APPEARANCES OF MARS. Fig. 16. A {The extraordinary height and 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 colourless transparent me- dium, its colour inclines to red, in proportion to the density of the medium, and the space through which it has travelled. Thus the Sun, Moon, and stars, appear of a reddish colour II hat system, do these retrograde movements and stations, common to all the pla- mets as seen from the Earth, serve to establish 2 What are the telescopic phenomena of Mars? How does Dr. Herschel account for them 3 How may the remarkable redness of the light of Mars be accounted for? 226 THS ASTEROIDS, when near the horizon; and every luminous object, seen through a mist, is of a ruddy hue. This phenoumenon may be thus explained –The momentum of the red, or least reſrangible rays, being greater than that of the violet, or most refran- gible rays, the former will nake their way through the resisting medium, while the latter are either reflected or absorbed. The colour of the beam, therefore, when it reaches the eye, must partake of the colour of the least refrangible rays, and this colour 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 pro- portion of its violet rays, and consequently then be red. Dr. Brewster sup- poses that the difference of colour among the other planets, and even the i. stars, is owing to the different heights and densities of their atmos- pheres. * - THE ASTEROIDS, OR TELESCOPIC PLANETS. AscenDING higher in the solar system, we find, between the orbits of Mars and Jupiter, a cluster of four small plan- ets, which present a variety of anomalies that distinguish them from all the older planets of the system. Their names are Vesta, Juno, Ceres, and Pallas. They were all dis- covered about the beginning of the present century. The dates of their discovery, and the names of their discoverers, are as follows: Ceres, January 1, 1801, by M. Piazzi, of Palermo. Pallas, March 28, 1802, by M. Olbers, of Bremen. Juno, September 1, 1804, by M. Harding, of Bremen. Vesta, March 29, 1807, by M. Olbers, of Bremen. The scientific Bode* entertained the opinion, that the plane- tary distances, above Mercury, formed a geometrical series, each exterior orbit being double the distance of its next interior one, from the Sun ; a fact which obtains with re- markable exactness between Jupiter, Saturn, and Herschel. But this law seemed to be interrupted between Mars and Jupiter. Hence he inferred, that there was a planet want- ing in that interval ; which is now happily supplied by the discovery of the four star-form planets, occupying the very space where the unexplained vacancy presented a strong objection to his theory. * According to him, the distances of the planets may be expressed mearly as follows: the Earth's distance from the Sun being 10. Mercury == 4: Asteroids 4––3X28 = 28 Venus 4-4-3Xl = 7|Jupiter 4––3X2 = 52 The Earth 4-H 32.2 = 10}Saturn 4–H3X25 = 100 Mars 4-H 3X22 = 16 Herschol 4–H3X2 i = 196 . Comparing these values with the actual mean distances of the planets from the Sun, we cannot but remark the near agreement, and can scal cely besitate 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, and of the reason for that law.—Brinks ley's Elements, p. 89. ...What new planets have been discovered within the present century? Where are they situated ) . What are the dates of their discovery, and the names of their discoverers? Why did Bode infer that there was a planet wanting between Mars and Irºnitor? THE ASTEROIDS, 227 These bodies are much smaller in size than the older planets—they all revolve at nearly the same distances from the Sun, and perform their revolutions in nearly the same periods,--their orbits are much more eccentric, and have a much greater inclination to the ecliptic,+and what is altogether singular, except in the case of comets—all cross each other; so that there is even a possibility that two of these bodies, may, some titne, in the course of their revolu- tions, 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 all the other three, in two opposite points. The student should here refer to the Figures, Plate I. of the Atlas, and veri. fy such of these particulars as are there represented. It would be well for the teacher to require him to observe particularly the positions of their orbits, and to state their different degrees of inclination to the pianc of the ecliptic. From these and other circumstances, many eminent as- tronomers are of opinion, that these four planets are the fragments of a large celestial body which once revolved between Mars and Jupiter, and which burst asunder by some tremendous convulsion, or some external violence. The discovery of Ceres by Piazzi, on the first day of the present century, drew the attention of all the astronomers of the age to that region of the sky, and every inch of it was minutely explored. The consequence was, that, in the year following, Dr. Olbers, of Bremen, announced to the world the discovery of Pallas, situated not many degrees from Ceres, and very much resembling it in size. From this discovery, Dr. Olbers first conceived the idea 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 neighbourhood, or else, having diverged from the same point, “they ought to have two common points of reunion, or two modes in opposite regions of the heavens through which all the planetary fragments must sooner or later pass.” One of these nodes he found to be, in the constellation Virgo, and the opposite one, in the Whale; and it is a re- markable coincidence that it was in the neighbourhood of In what partigulars do these new planets differ from the older planets? How is it pos- sible that two of them should over come into collision How is it that Vesta is sometimes farther from the Sun than either Ceres, Pallas, or Juno, when her mean distance is many millions of miles less than theirs? What is the position of her orbit with regard to their orbits 3, What theory in regard to the origin of these planets have some astronomers de- rived from these and some other circumstances? Who first conceived this idea How came he to have this idea 2. Where did he imagine other fragments might be found? In what constellations did he find these nodes to he? 228 THE ASTEROIDS, the latter constellation that Mr. Harding discovered the planet Juno. In order therefore to detect the remaining fragments, if any existed, Dr. Olbers examined, three times every year, all the small stars in Virgo, and the Whale; and it was actually in the constellation Virgo, that he dis- covered the planet Vesta. Some astronomers think it not unlikely that other fragments of a similar description may hereafter be discovered. Dr. Brewster attributes the fall of meteoric stones to the smaller fragments of these bodies happening to come within the sphere of the Earth’s at- traction. - Meteoric stones, or what are generally termed aerolites, are stones which soinetimes ſall from the upper regions of the atmosphere, upon the Earth. The substance of which they are composed, is, for the most part, metallic ; but the ore of which it cousists is not to be found in the same constituent roportions in any known substance upon the Earth. Their fall is general- ſ. preceded by a lulliuous appearance, a hissing noise, and a loud explo- sion ; aud, when ſound in, unediately aſter their descent, they are always hot, and usually covered with a black crust, indicating a state of exterior fusion. . Their size varies from that of small fragments of inconsiderable weight, to that of the most ponderous masses. They have been found to weigh from 300 pounds to several tons ; and they lave descended to the Earth with a ſorce sufficient to bury them unany ſeet under the surface. . Some have supposed that they are projected from volcanoes in the Moon ; others, that they proceed Iron volcanoes on the Earth ; while others imagine that they are generated in the regions of the atmosphere ; but the truth, probably, is not yet ascertained. In some instances, these stones have penetrated through the roofs of houses, and proved destructive to the inhabitants. lf we carefully compute the ſorce of gravity in the Moon, we shall find, that iſ a body were projected from her surface with a luomentum that would cause it to Inove at the rate of 8,200 ſeet in the first second of time, and in the direction of a line joining the centres of the Earth and Moon, it would not ſall again to the surface of the Moon ; but would become a sa- tellite to the Earth. Such an impulse might, indeed, cause it, even aſter many revolutions, to fall to the Earth. . The fall, therefore, of these stones, from the air, may be accounted for in this manner. Mr. IIarte calculates, that even a velocity of 6000 feet in a second, would be sufficient to carry a body projected from the surface of the Moon beyond the power of her attraction. If so, a projectile ſorce three times greater than that of a cannon, would carry a body ſrom the Moon beyond the point of equal attraction, and cause it to reach the Earth. A ſorce equal to this is often exerted by our volcanoes, and by subterranean steam. Hence, there is no iuripossibility in the supposition of their coming ſrom the Moon ; but yet I think the theory of aerial consolidation the more plausible. Vesta appears, however, like a star of the 5th or 6th magnitude, shining with a pure steady radiance, and is the only one of the asteroids which can be discerned by the naked eye. * Where were Juno and Vesta actually found? How did Dr. Olbers discover Vesta ? To what does Dr. Brewster attribute the fall of meteoric stones What is meant by the eacpression, meteoric stones 2 Of what substance are they composed ?. In what 7:é- spect do they differ from any metallic substances known on the Earth 2, What indi- cations generally precede their fall 2. In what state are they found to be after rheir descent 2 What is their magnitude 2 What theories have been adopted to accou??? jor their origin 2. Ea:plain how it is not impossible that they may come from the Moom. Describe the appearance of Vesta. ‘THE ASTEROIDS. 229 JUNO, the next planet in order after Vesta, revolves around the Sun in 4 years, 4} months, at the mean distance of 254 millions of miles, moving in her orbit at the rate of 41 thousand miles an hour. Her diameter is estimated at 1393 miles. This would make her magnitude 183 times less than the Earth's. The light and heat which she receives from the Sun is seven times less than that received by the Earth. The eccentricity of her orbit is so great, that her great- est distance from the Sun is nearly double her least distance; so that, when she is in her perihelion, she is nearer the Sun by 130 millions of miles, than when she is in her aphelion. This great eccentricity has a corresponding effect upon her rate of motion; for being so much nearer, and there- fore so much more powerfully attracted by the Sun at one time than at another, she moves through that half of her orbit which is nearest the Sun, in one half of the time that she occupies in completing the other half. According to Schroeter, the diameter of Juno is 1425 miles; and she is *Surrounded by an at noosphere inore dense than that of any of the other Aplanets. Schroeter also remarks, that the variation in her brilliancy is chiefly owing to certain changes in the density of her atmosphere; at the same time lie Illinks it not improbable that these changes may arise froun a diurnal revolution on her axis. CEREs, the planet next in order after Juno, revolves about the Sun in 4 years, 7} months, at the mean distance of 263; millions of miles, moving in her orbit at the rate of 41 thousand miles an hour. Her diameter is estimated at 1582 miles, which makes her magnitude 125 times less than the Earth’s. The intensity of the light and heat which she re- ceives from the Sun, is about 7+ times less than that of those received by the Earth. Ceres shines with a ruddy colour, and appears to be only about the size of a star of the 8th magnitude. Consequent- ly she is never seen by the naked eye. She is surrounded by a species of cloudy or nebulous light, which gives her What is the planet next in order after Vesta \,. In what time does she complete her re- volution around the Sun ? What is her mean distance from him 2 What the rate of her motion per hour? What is the length of her diameter How much less, then, is her magnitude, than that of the Earth? How much light and heat does she receive from the Sun, compared with those received by the Earth How much greater is her greatest dis- tance from the Sun, than her least distance How much less time does she occupy in moving through that half of her orbit which is nearest tº the Sun, than she does in mo- ving through that half which is farthest from him 2 What is her diameter according to Schroeter 2 According to the same astronomer, what is the density of her atmos- There, compared with that of the other planets 2 To what does he attribute the ca- riation in her brilliancy 2. What is the next planet in order after Juno In what time does she complete her revolution about the Sun ?, What is her mean distance from him 3 What is the rate of her motion per hour? What is her diameter? How great is her mag: nitude, compared with that of the Earth? What is the intensity of the light, and heat which she receives from the Sun, compared with that of those received by the Earth 3 Describe her appearance. 230 JUPITER. somewhat the appearance of a comet, forming, according to Schroeter, an atmosphere 675 miles in height. Ceres, as has been said, was the first discovered of the asteroids. At her discovery, astronouners congratulated themselves upon the harmony of the system being restored. They had long wanted a planet to fill up the great void between Mars and Jupiter, in order to make the system couplete in their own eyes; but I he successive discoveries of Pallas and Juno again introduced confusion, and presented a difficulty which they were unable to solve, till Dr. Olbers suggested the idea that these small anomalous bodies were merely the fraginents of a larger planet, which had been exploded by some mighty convulsion. A mong the inost able and decided advocates of this hypothesis, is Dr. Brewster, of Edinburgh. PALLAs, the next planet in order after Ceres, performs her revolution around the Sun in 4 years, 73 months, at the mean distance of 264 millions of miles, moving in her orbit at the rate of 41 thousand miles an hour. Her diameter is estimated at 2025 miles, which is but little less than that of our Moon. It is a singular and very remarkable pheno- menon in the solar system, that two planets, (Ceres and Pallas,) nearly of the same size, should be situated at equal distances from the Sun, revolve about him in the same period, and in orbits that intersect each other. The dif- ference in the respective distances of Ceres and Pallas is less than a million of miles. The difference in their side- real revolutions, according to some astronomers, is but a single day ! - - The calculation of the latitude and longitude of the asteroids, is a labour of extreme difficulty, requiring more than 400 equations to reduce their anomalous perturbations to the true place. This arises from the want of auxiliary tables, and ſrom the fact that the elements of the star-ſorin planets, are very imperfectly determined. Whether any of the asteroids has a ro- tation omits axis, remains to be ascertained. * c. JUPITER, JUPITER is the largest of all the planets belonging to the solar system. It may be readily distinguished from the fixed stars, by its peculiar splendour and magnitude; ap- pearing to the naked eye almost as resplendent as Venus, although it is more than seven times her distance from the Sun. How high, according to Schroeter, is the atmosphere formed by this nebulous light º' Why did astronomers congratulaſe themselves at the discovery of this planet 2. What again introduced confusion and difficulty into their system 2 . How were they at length enabled to solve the difficulty 2 What planet is the next in order after Ceres? In what time does she complete her revolution around the Sun ? What is her mean dis- tance from him What is the rate of her motion in her orbit per hour?...What is her di- ameter How, greatis it compared with the diameter of the Moon? What is the differ- ence between the respective distances of Ceres and Pallas from the Sun ? What is the difference between the times of their sidereal revolutions? Why is the calculation of the latitude and longitude of the asteroids a labour of extreme difficulty? Have any of the asteroids rotations on their aves? Which is the largest planet of the solar system? How may Jupiter be readily distinguished from the fixed stars? How much farther is he from the Sun than Venus? JUPITER. 231 When his right ascension is less than that of the Sun, he is our morning star, and appears in the eastern hemi- sphere before the Sun rises; when greater, he is our evening star, and lingers in the western hēmisphere after the Sun sets. Nothing can be easier than to trace Jupiter among the constellations of the zodiac ; for in whatever constellation he is seen to-day, one year hence he will be seen equally advanced in the neart 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 constel- lation. The exact mean motion of Jupiter in its orbit, is about one twelfth of a degree in a day; which almounts to only 30°20′ 32” in a year. For 12 years to come, he will, at a mean rate, pass through the constellations of the zodiac, as follows: 1834 | Aries. 1838 Leo. | 1842 | Sagittarius. 1835 | Taurus. | 1839 Virgo. 1843 || Capricornus. 1836 Gemini. 1840 | Libra. 1844 || Aquarius. 1837 | Cancer. 1841 | Scorpio. | 1845 || Pisces. Jupiter is the next planet in the solar system above the asteroids, and performs his annual revolution around the Sun in nearly 12 of our years, at the mean distance of 495 millions of miles; moving in his orbit at the rate of 30,000 miles an hour. The exact period of Jupiter’s sidereal revolution is 11 years, 10 months, 17 days, 14 hours, 21 nuinutes, 25% seconds. His exact mean distance from the Sun is 495 533,837 iniles ; consequently, the exact rate of his motion in his orbit, is 29.94.3 miles per hour. He revolves on an axis, which is 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 5 hours long. His form is that of an oblate spheroid, whose polar diame- ter is to its equatorial, as 13 to 14. He is therefore consid- erably 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 a universal law that the equatorial parts of every body, revolving on an axis, will be swollen -s In what case is he our morning star, and in what our evening? How may he be traced among the constellations Q, the Zodiac In what constellation will he be, each year, for twelve yea’s to C me?...What is his pºsition in the solar system A What is his mean dis. tance from the Sun? What is the rate per hour of his motiou in his orbit? What is the eaact period of his sidereal evolution 2 fiſhat is his exact mean distance from the Sun ?., What the étact rate per hour of his motion in his orbit 2 What is the posi- tion of his axis with respect to the plane of his orbit? How many days and nights does his year contain } How long are they, each? What is his form? What is the ratio be. tween his polar and equatorial diameters? What is the cause of his being more flattened at the poles than any of the other planets 3 - 232 JUPITER. out, in proportion to the density of the body, and the rapidi- ty of its motion. The difference between the polar and equatorial diameters of Jupiter, exceeds 6000 miles. The difference between the polar and equatorial di- ameters of the Earth, is only 26 miles. Jupiter, even on the most careless view through a good telescope, appears to be oval; the longer diameter being parallel to the direction of his belts, which are also parallel to the ecliptic. By this rapid whirl on his axis, his equatorial inhabitants are carried around at the rate of 26,554 miles an hour; which is 1600 miles farther than the equatorial inhabitants of the Earth are carried, by its diurnal motion, in twenty- four hours. The true mean diameter of Jupiter is 86.255 miles; which is nearly 11 times greater than the Earth’s. His volume is therefore about thirteen hundred miles larger than that of the Earth, (Compare his magnitude with that of the Earth. Plate 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 conies to the meridian at midnight, which never happens in the case of an interior planet. This proves that Jupiter revolves in an orbit which is eacterior to that of the Earth. As the variety in the seasons of a planet, and in the length of its days and nights, depends upon the inclination of its axis to the plane of its orbit, and as the axis of Jupiter has no inclination, there can be no difference in his seasons, on the same parallels of latitude, nor any variation in the length of his days and nights. It is not to be understood, however, that one uniform season prevails from his equator to his poles; but that the same parallels of latitude on each side of his equator, uniformly enjoy the same season, what- ever 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 kindly ordered by the beneficent Creator ; for had his axis been inclined to his orbit, like that of the Earth, his polar winters would have been alternately a dreadful night of sia years darkness. I ſhat is the difference betwcen his polar and equatorial diameters ? IWhat does Jais form appear to be, through a good telescope 2 What is the direction of his longer diameter 2. At what rate per hour are his equatorial inhabitants carried by his motion on his axis How much farther is this than the equatorial inlıubitants of the Earth are carried in 24 hours ? What is Jupiter's true mean diameter 7 How much greater is it than the Earth's What is his volume, compared with the Earth's What is the degree of light and heat which he receives from the sun, compared with that re- ceived by the Earth n How do we know that Jup ter’s orb "t is eaterior to that of the Earth? What is the arrangement of Jupiter's seasons, and of his days and nights? Had his axis been inclined to the plane of his orbit, like that of our Earth, how long would his polar nights have been 7 - JUPITER. 233 TELESCOPIC APPEARANCES OF JUPITER. Jupiter when viewed 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 paraliel not only to each other, but, in general, to his equator, which is also nearly parallel to the ecliptic. They are subject, however, to considerable variation, both in breadth and number. Sometimes eight have been seen at once; sometimes only one, but more usually three. Dr. Herschel once perceived his whole disc covered with small belts. Sometimes these belts continue for months at a time with little or no variation, and sometimes a new belt has been seen to form in a few hours. Sometimes they are interrupted in their length; and at other times, they appear to spread in width, and run into each other, until their breadth exceeds 5,000 miles. 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 variable appearances, but little is known. They are generally supposed to be nothing more than atmospherical phenomena, resulting from, or combined with, the rapid mo- tion 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 opertings in the attuosphere of the planet, while others imagine that they are of a more perumanent nature, and are the unarks of great physical revolutious, which are perpetually agitating and changing the surface of the planet. The first of these opiniotis sufficiently explains the variations in the form and magnitude of the spots, and the parallelism of the belts. The spot first observed by Cassini, in 1665, which has both disappeared and re-appeared in the same form and position for the space of 43 years, could not possibly be occasioned by any atmospherical variations, but seems evidently to be connected with the surface of the planet. The form of the Describe Jupiter's appearance, as seen through a telescope. What is supposed to be the cause of these phenomena? Relate some of the different opinions entertained by &Sł?'Orºomzers or this subject. - 20% 234 JUPITER, belt, according to some astronomers, may be accounted for by supposing: that the atmosphere reflects more light than the body of the planet, and that the clonds which float in it, being thrown into parallel strata by the . rapidity of its diurnal motion, form regular interstices, through Wilſº a F6. , seen its opaque body, or any of the permanent spots which unay come within, n he range of the opening. Jupiter is also attended by four satellites or moons, some. of which are visible to him every hour of the night; exhib- iting, on a small scale and in short periods, most of the phe- nomena of the solar system. When viewed through a tele- scope, these satellites present a most interesting and beau- tiful appearance. The first satellite, or that nearest the planet, is 259,000 miles distant from its centre, and revolves. around it in 423 hours; and appears, at the surface of Jupi- ter, four times larger than our Moon does to us. His second; satellite, being both smaller and farther distant, appears: about the size of ours; the third, somewhat less; and thes fourth, which is more than a million of miles from him, and takes 164 days to revolve around him, appears only about one: third the diameter of our Moon. These satellites suffer frequent eclipses from passing: through Jupiter’s shadow, in the same manner as our Moon is eclipsed in passing through the Earth’s shadow. The three nearest satellites fall into his shadow, and are eclips- ed, in every revolution ; but the orbit of the fourth is so much inclined, that it passes by its opposition to him, two years in six, without falling into his shadow. By means of these eclipses, astronomers have not only discovered that light is 8 minutes and 13 seconds in coming to us from the Sun, but are also enabled to determine the longitude of pla- ces on the Earth with greater facility and exactness than by any other methods yet known. It was long since found, by the most careſul observations, that when the Earth is in that part of her orbit which is nearest to Jupiter, the eclipses . appear to happen 8' 13’’ sooner than the tables predict; and when in that part of her or bit which is farthest from him, 8' 13" later than the tables predict; making a total difference in time, of 16' 26"’. From the . mean of 6000 eclipses observed by Delambre, this disagreement between . observation and calculation, was satisfactorily settled at 8' 13’’, while both were considered equally correct. Now when the eclipses happen sooner - than the tables, Jupiter is at his nearest approach to the Earth—when later, at his greatest distance ; so that the difference in his distances from the Earth, in the two cases, is the whole diameter of the Earth's orbit, or about 190 millions of miles. Iſence, it is concluded that liglit is not instantane- How many satellites has Jupiter? How often are they visible to him 3 What is the distance from him of his first or nearest satellite What is the time of its revolution? What is its apparent magnitude at the surface of Jupiter, compared, with the magnitude of the Moon, as seen oy us? What are the apparent magnitudes of his other stºtellites, as seen at his surfage, compared with that of the Moon as seen at the Earth.3 What is the distance of his fourth satellite from him What is the time of its revolution? (low often are his three nearest, satellites, eclipsed ? How often his fourth? Why is it not eclipsed as often as the others ? What important purposes have these eclipses served to astronomers? State the method by which the progressive motion of light, and the time which it occupies in coming to us from the Swn, were discovered. SATURN. 235 ous, but that it occupies 16/26’’ in passing across the Earth's orbit, or 8'13' in coming from the Sun to the Earth; being nearly 12 inillions of miles a minute. The revolutions of the satellites about Jupiter are pre- cisely similar to the revolutions of the planets about the Sun. In this respect they are an epitome of the solar sys- tem, exhibiting, on a smaller scale, the various changes that take place among the planetary worlds. Jupiter, when seen from his nearest satellite, appears a thousand times larger than our Moon does to us, exhibiting, on a scale of inconceivable magnificence, the varying forms of a crescent, a half moon, a gibbous phase, and a full moon, every 42 hours. The apparent diameters of Jupiter's satellites, their unean distances from #aiſm, and their periodical revolutions, are exhibited in the ſollowing table. App. | Satellites. Revolution. Diain. | Mean Dist. * First, 1d. 18h, 28m. 1, 667 259.0 |0 Second, 3, 13 14 1, 189 41 4 000. Third, 7 3 43 1. 0.50 647,000 Fourth, 16 16 32 | 0, 550 | 1,164,000 SATURN. Saturn is situated between the orbits of Jupiter and Her- schel, and is the most remote planet from the Earth of any that are visible to the naked eye. It may be easily distin- guished from the fixed stars by its pale, feeble, and steady light. It resembles the star Fomalhaut, both in colour and size, differing from it only in the steadiness and uniformity of its light. From the slowness of its motion in its orbit, the pupil, throughout the period of his whole life, may trace its appa- rent course among the stars, without any danger of mistake. Having once found when it enters a particular constella- tion, he may easily remember where he is to look for it in any subsequent year; because, at a mean rate, it is just 2+ years in passing over a single sign or constellation. Saturn’s mean daily motion among the stars is only about 2", the thirtieth part of a degree. Saturn entered the constellation Virgo about the beginning of 1833, and continued in it until the middle of the year 1835, when he passed into Li- - -- . In what respect are Jupiter's satellites an epitome of the solar system What is Jupi- ter's appearance, as seen from his nearest satellite? What are the diameters, mean dis- ºces, and times ºf the revolution of his satellites ?, Where, in the solar system, is Saturn situated . How may it be distinguished from the fixed stars what stir does it resemble? In what respects is it like it, and in what is it differenſ from it? How may his Place among the stars be readily found? What is about the rate of his mean daily mo: tion among the stars?. When did Saturn enter, the constellation Virgo, and how long 3. #.§ in tº 2 What constellation did he enter newt, and how long will hº 236 SATURN. bra. He will, continue in that constellation until 1838; and so on; occu- É. about 2% years in each constellation, or nearly 30 years in one revo- Ul L}() (). The mean distance of Saturn from the Sun is nearly double that of Jupiter, being about 909 millions of miles, His diameter is about 82,000 miles ; his volume therefore is eleven hundred times greater than the Earth’s. Moving in his orbit at the rate of 22,000 miles an hour, he requires 291 years to complete 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. The surface of Saturn, like that of Jupiter, is diversified with belts and dark spots. Dr. Herschel sometimes per- ceived five belts on his surface ; three of which were dark, and two bright. The dark belts have a yellowish tinge, and generally cover a broader zone of the planet than those of Jupiter. To the inhabitants of Saturn, the Sun appears 90 times less than he appears to the Earth; and they receive from him only one ninetieth part as much light and heat. But it is computed that even the mimetieth part of the Sun’s light exceeds the illuminating power of 3,000 full moons, which would be abundantly sufficient for all the purposes of life. The telescopic appearance of Saturn is unparalleled. It is even more interesting than #|Jupiter, with all his moons |and belts. That which emi- |nently distinguishes this |planet from every other in |the system, is a magnificent #|{zone or ring, encircling it §|with perpetual light. §: The light of the ring is É'more brilliant than the pla- How long time does he occupy in passing through each Coºl stellation, and what is the length of his year 2 What is his distance from the Sun ? How much greater is this than jºitoi's disiance? What is his diameterº. How much greater is his vºlume than tº of the Earth What is the rate per hour of his motion in his orbit 3, In what time is his diurnal motion on his axis performed How many of his own days does his year con- tin, and how many of ours?' 'What is the appearance ºf his surface to us? How many j; ; ). He schºl perceive on his surface? Describe them, How much less loes the Sun appear to the iniº of Saturn than to us? What degree of light, and heuſ: ājjīom the sum, compared with that received by the Earth? To the light of §§ many fall moons is this degree of light equal? Describe the telescooic appearance. of Saturn ? SATURN. 237 net itself. It turns around its centre of motion in the same time that Saturn turns on its axis. When viewed with a good telescope, it is ſound to consist of two concentric rings, divided by a dark band. By the laws of mechanics, it is impossible that the body of the rings. should retain its position by the adhesion of the particles alone ; iſ unust ne- cessarily revolve with a velocity that will generate centrifugal ſorce suſfi- cient to balance the attraction of Saturn. Observation confirms the truth of these principles, showing that the rings rotate about the planet in 10% hours, which is considerably less than the time a satellite would take to re- Volve about it at ille same distance. Their plane is inclined to the ecliptic in an angle of 319. In consequence of this obliquity of position, they al- Ways appear elliptical to us, but with an eccentricity so variable as to ap- pear, or casionally, like a straight line drawn across the planet ; in which case they are visible only by the aid of snperior instruments. Such was their position in April. 1833; for the Sun was then passing from their south to their north side. The rings intersect the ecliptic in two opposite points, SATURN’s RINGs. Fig. 19. & II. -T- ſlº se—" ºyſ sºmºmº-º-º-º-º: ſº ** Why should ape judge, previous to observation, that these rings must revolve arrowid him 2 Does observation conſºry, this opizzjon 2 In ºphat wºme do the rings revolte about the p'aneſ 2 Is this a grea er or less time than a satellite at the same dis- tance would require to epo we about it 2. Ji'hy do the rings always appear ellirtical to us?. To what eatent does the eccentricity of the rings vary & What is the posi- fion of the rings with regard to the ecliptic? 238 SATURN. which may be called their nodes. These points are in longitude 1709, and 350 degrees. When, therefore, Saturn is in either of these points. his rings will be invisible to us. On the contrary, when his longitude is 80°, or 260°, the rings inay be seen to the greatest alvantage. As the crlges of the rings will present the unselves to the Sun twice in each revolution of the planet, it is obvious that the disappearance of the un will occur once in about 15 years ; subject, however, to the variation dependent on the position of the Earth at that time. The precoding diagrams are a very good representation of the form and position of the rings as they apprºar to a spectator during one complete revolu- tion of Saturn through the signs of the ecliptic. By reference to the figure. it will be scein, that when Saturn is in either of the first six signs, the Sun shines on the south side of the rings; and that while he is in either of the last six signs, upon their north side. The following are the dates during the ensuing revolutions of the planet, when its mean heliorenſric longitude is such that the rings will (if the Earth be favourably situated) either be invisible, or seen to the greatest advan- tage. 1833 April. 200 of Virgo. Invisible. 18 8 July. | 20° of Scorpio. North side illuminated. 1S47 I) ec. 20° of Aquarius. Invisible. - 1855 April. 209 of Geulini. South side illuminated. 1863 Nov. 200 of Virgo. Invisible. The distance between Saturn and his inner ring, is only 21,000 miles; being less than a tenth part of the distance of our Moon from the Earth. The breadth of the dark band, or the interval between the rings, is hardly 3,000 miles.— The breadth of the inner ring is 20,000 miles. Being only about the same distance from Saturn, it will present to his inhabitants a luminous zone, arching the whole concave vault from one hemisphere to the other with a broad girdle of light. The most obvious use of this double ring is, to reflect light upon the planet in the absence of the Sun ; what other purposes it may be intended to subserve, is to us unknown. The sun, as has been shown, illuminates one side of it during 15 years, or one half of the period of the planet’s revolution ; and, during the next 15 years, the other side is enlightened in its turn. Twice in the course of 30 years, there is a short interval of time when neither side is enlightened, and when, of course it ceases to be visible ;-namely, at the time when the Sun ceases to shine on one side, and is about to shine on the What is the lon” iºude of these modes 2 In what position of Saturn, then, will the rings be invisible to us, and in that position will they be seen to the best advantage 2 IIow often will the disapped rance of the rings occur? Explain this. In what signs quill the planet bººth,” the Sun shines on the South side of the rings, and in what on the north side & What is the distance between Saturn and his inner ring How great is this, compared with the distance of our Moon from the Earth? What is the distance be- twcen the two rings. What is the breadth of the inner ring 3 What must be its appear. ance at Saturn ? ...What is the most obvious use of this double ring How long a time does the Sun enlightºn each side of it alternately How often, and in what circumstan- ces, is neither side enlightened, and the ring, of course, invisible 7 SATURN. 239 other.” It revolves around its axis, and consequently, around Saturn, in 104° hours, which is at the rate of a thou- sand miles in a minute, or 58 times swifter than the revolu- tion of the Earth's equator. When viewed from the middle zone of the planet, in the absence of the Sun, the rings will appear like vast luminous arches, extending along the canopy of heaven, from the eastern to the western horizon, exceeding in breadth a hun- dred times the apparent diameter of our Moon. Besides the rings, Saturn is attended by seven satellites, which revolve about him at different periods and distances, and reciprocally reflect the Sun’s rays on each other and on the planet. The rings and moons illuminate the nights of Saturn ; the moons and Saturn enlighten the rings, and the planet and rings reflect the Sun’s beams on the satel- lites. The fourth of these satellites (in the order of their distance) was first discovered by Huygens, on the 25th of March, 1655, a...d, in honour of the discoverer, was called the Huigenian Satellitc. This satellite, being the largest of all, is seen without much diſficulty. , Cassini discovered the 1st, 2d, 3d, and 5th satellites, between October, 1671, and March, 1684. Dr. Herschel discovered the 6th and 7th in 1789. These are nearer to Saturn than any of the rest, though, to avoid confusion, they are named in the order of their discovery. The sixth and seventh are the smallest of the whole ; the first and second are the next smallest; the third is greater than the first and second ; the fourth is the largest of them all ; and the fifth surpasses the rest in brightness. Their respective distances from their primary, vary from half the distance of our Moon, to two millions of miles. Their periodic revolutions vary from 1 day to 79 days. The orbits of the six inner satellites, that is, the 1st, 2d, 3d, 4th, 6th, and 7th, all lie in the plane of Saturn’s rings, and revolve around their outer edge; while the 5th satellite de- viates so far from the plane of the lings, as sometimes to be seen through the opening between them and the planet. Iaplace imagines that the accumulation of matter at Saturn's equator re- tains the orbits of the first six satellites in the plane of the equator, in the same manner as it relains the rings in that plane. It has been satisfactorily ascertained, that Saturn has a greater accuuuulation of matter about his * This happens, as we have already shown, when Saturn is either in the 20th degree of Pisces, or the 20th degree of Virgo. When he is between these points, or in the 20th de- ree either of Gemini or of Sagittarius, his ring appears most open to us, and more in the orm of an oval, whose longest diameter is to the shortest as 9 to 4. ... In what time does the ring complete its revolution on its axis, and, of course, around the planet What is the rate per minute of its motion How rapid is this, compared with the motion of the Earth’s equator A . What would be the appearance of the rings, if viewed from the middle zone of the planet, in the absence of the Sun A. How many moons as Saturn ? How are Saturn, his rings and satellites, severally, enlightened 3 IWhat are the dates of their discovery, and the names of their discovereºs 2 . What are their comparative magnitudes, distances, and times of revolution 3 What is the position of their orbits with respect to the rings of Saturn ? What does Laplace imagine retains the orbits ºf Saturn's Jīrst sia, satellites in the plane of his equator 2 240 SATURN, equator, and consequently that he is more flattened at the poles, than Jupi- ter, though the velocity of the equatorial parts of the former is unuch less than that of the latter. This is sufficiently accounted for by the fact, that the rings of Saturn lie in the plane of his equator, and act unore powerfully upon those parts of his surface than upon any other ; and thus, while they aid in diminishing the gravity of these paris, also aid the centrifugal force in flattening the poles of the planet. Indeed, had Saſurn never revolved upon his axis, the action of the rings would, of itself, have been sufficient to give hiin the forum of an oblate spheroid. & The theory of the satellites of Saturn is less perfect than that of the satellites of Jupiter. The difficulty of observing their eclipses, and of measuring their elongations from their primary, have prevented astronomers from determining, with their usual precision, their mean distances and revo- lutions. - We may remark, with the Christian Philosopher, that there is no planet in the solar system, whose firmament presents such a variety of splendid and magnificent objects as that of Saturn. The various aspects of the seven moons, one rising above the horizon, while another is setting, and a third approach- ing to the meridian ; one entering into an eclipse, and an- other emerging from one ; one appearing as a crescent, and another with a gibbous phase ; and sometimes the whole of them shining in the same hemisphere, in one bright as- semblage . The majestic motion of the rings, at one time illuminating the sky with their splendour, and eclipsing the stars; at another, casting a deep shade over certain regions of the planet, and unveiling to view the wonders of the starry firmament, are scenes worthy of the majesty of the Divine Being to unfold, and of rational creatures to con- template. Such displays of Wisdom and Omnipotence, lead us to conclude that the numerous splendid objects connected with this planet, were not created merely to shed their lustre on naked rocks and barren sands; but that an immense popu- lation of intelligent beings is placed in those regions, to enjoy the bounty, and adore the goodness, of their great Creator. + The following table exhibits the apparent and mean distances of the satellites from their primary, aud the times of their periodical revolution. Their dis- tances in miles were couputed ſron their observed micrometer distances; the diameter of Saturn's equator being considered equal to 80,000 miles. Why are astronomers less, acquainted with the mean distances and revolutions of Şa- turn's satel ites, than with those of Jupiter 3 Describe the firmament of Saturn, as illu- minated by his rings and satellites. HERSCHEL. 241 Satel- Periodic Distance in Distance in lites. revolution. diauieters. miles. I 0d. 22h. 38, n. 1.540 - 123,200 2 l 8 53 1976 158,080 3 1 2} 18 2.447 195,720 4 2 17 45 3. 134 . 250,720 5 4 T 12 25 4 377 350 160 6 15 22 41 I0. 143 81].400 7 79 7 55 20 577 2.366. 160 HERSCHEL. Herschel is the most distant planet from the Sun that has vet been discovered. 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. As it moves over but one degree of its orbit in 85 days, It will be seven years in passing over one sign or constella- tion. At present,” its mean right ascension is 332+9, and its declination 154° S. It is therefore in the tail of Capri- corn, making a small triangle with Deneb and Delta Algedi. When first seen by Dr. Herschel, in 1781, it was in the foot of Gemini ; so that it has not yet completed two thirds of a revolution since it was first discovered to be a planet. It is remarkable that this body was observed as far back as 1690. It was seen three times by Flainstead, once by Bradley, once by Mayer, and eleven times by Leinonnier, who registered it among the stars; but not one of them suspected it to be a planet. The inequalities in the motions of Jupiter and Saturn, which could not be accounted for from the mutual attrac- tions 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 confirmed March 13th, 1781; when Dr. Herschel dis- covered the motions of this body, and thus proved it to be a planet. Herschel is attended by six moons or satellites, which revolve about him in different periods, and at various dis- * Beginning of the year 1834. What is the relative distance of the planet Herschel from the Sun ? What is its appear- ance to the naked eye, in what circumstances can it be seen 3 What is the rate of its motion in its orbit 3 What is its present position 3 What was its position when first dis- covered to be a planet How much, them, of its revolution has been completed, since it was first discovered 3 At how early a date was this body observed in the heavems? Who observed it, before it was discovered to be a planet 2 How many times was it seem by them, respectively? What did they consider it to be 2. What led astronomers to suppose that there existed another planet £º Saturn? When and by whom was Herschel discovered to be a planet? How many moons has it 2 242 HERSCHEL. tances. Four of them were discovered by Dr. Herschel, and two by his sister, Miss Caroline Herschel. It is possi- ble that others remain yet to be discovered. Herschel’s mean distance from the Sun is 1828 millions of miles; more than twice the mean distance of Saturn. His .sidereal revolution is performed in 84 years and 1 month, and his motion in his orbit is 15,600 miles an hour. He is supposed to have a rotation on his axis, in common with the other planets; but astronomers have not yet been able to obtain any occular proof of such a motion. His diameter is estimated at 34,000 miles; which would make his volume more than 80 times larger than the Earth's. To his inhabitants, the Sun appears only the 3+g 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 sº part of the Sun’s light ex- ceeds the illuminating power of 800 full Moons. This add- ed to the light they must receive from their six satellites, will render their days and mights far from cheerless. Such was the celestial system with which our Earth was associated at its creation, distinct from the rest of the starry hosts. Whatever may be the comparative antiquity of our globe, and the myriads of radiant bodies which nightly gem the immense vault above us, it is most reasonable to conclude, that the Sun, Earth, and planets, differ little in the date of their origin. - This fact, at least, seems to be philosophically certain, that all the bodies which compose our solar system must have been placed at one and the same time in that arrange- ment, and in those positions in which we now behold them ; because all maintain their present stations, and motions, and distances, by their mutual action on each other. Neither could be where it is, nor move as it does, nor appear as we see it, unless they were all coexistent. The presence of each is essential to the system—the Sun to them, they to the Sun, and all to each other. This fact is a strong indication that their formation was simultaneous. By whom were Herschel's satellites discovered? What is the distance of Herschel's orbit from the Sun ? How much greater is this distance than that of Saturn? in what time is his sidereal revolution performed 2 What is the rate per hour of his motion in his orijit A Hus he a rotation on his axis 3 What is his diameter estimated to be How much larger would this make his volume than the Earth How much less does the Sun prºpear to be to the inhabitants of Hersch l, than he does to us 2 What degree of light and heat do they receive from him, compared with that received by the Earth A To the light ºf how mºny full moons is this degree of light equal 3. What reason have we to suppose t the different bodies of the solar system were created at the same time? COMETS. - 243 COMETS. Comets, whether viewed as ephemeral meteors, or as substantial bodies, forming a part of the Solar system, are objects of no ordinary interest. When, with uninstructed gaze, we look upwards, to the clear sky of evening, and behold, among the multitudes of heavenly bodies, one, blazing with its long train of light, and rushing onward towards the centre of our system, we insensibly shrink back as if in the presence of a supernatu- ral 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 sence of that power which could create and set in motion such bodies. Comets are distinguished from the other heavenly bodies, by their appearance and motion. The appearance of the planets is globular, and their motion around the Sun is near- ly in the same plane, and from west to east; but the comets have a variety of forms, and their orbits are not confined to any particular 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 opposite sides of the same hoop, be extended, so that is shall be long and narrow, it will then represent the orbit of a coinet. The Sun is always in one of the foci of the comet’s orbit. There is, however, a practical difficulty of a peculiar nature which em- barrasses the solution of the question as to the form of the couletary orbits. It so lappens that the only part of the course of a connet which can ever be visible, is a portion throughout which the ellipse, the parabola, and hy- perbola, so closely reseum ble each other, that 'tio observations can be obtain- ed with sufficietit accuracy to enable tus to utistinguish theni. In fact, the ob- served path of any coulet, while visible, may belong either to an ellipse, pa- rabola, or hyperbola. r 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 appearance. These two parts constitute the body, and, in many instances, the whole of the comet. ..What feelings does the contemplation of comets naturally excite? How are comets distinguished from the other heavenly bodies? Describe their appearance, and motion. § three parts may comets be considered to be composed 3 Describe these parts severally, 244 COMETS. Most of them, however, are attended by a long train, called the tail : though some are without 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 vapour. Nothing is known with certainty of the composition of these bodies. The envelope appears to be nothing more than vapour, becoming more luminous and transparent when approaching the Sun. As the comets pass between us and the fixed stars, their envelopes and tails are so thin, that stars of very small magnitudes may be seen through them. Some comets, having no nucleus, are transparent throughout their whole extent. 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 cf vapour, or less condensed at the centre. By others it is maintained that the nucleus is sometimes solid and opaque. It seems probable, however, that there are three classes of comets; viz.: 1st. Those which have no nucleus, being transparent throughout their whole ex- tent ; 2d. Those which nave a transparent nucleus; and, 3d. Those having a nucleus which is solid and opaque. A comet, when at a distance from the Sun, viewed through a good telescope, has the appearance of a dense vapour surrounding the nucleus, and sometimes flowing far into the regions of space. As it approaches the Sun, its light becomes more or 111aut, till it reaches its perihelion, when its light is more dazzling than that of any other celes- tial body, the Sun excepted. In this part of its orbit are seen to the best advantage the phenomena of this wonderful body, which has, from remote antiquity, been the spectre of alarm and terrour. 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 centre of the comet. The tail of the comet of 1744, formed near- ly a quarter of a circle ; that of 1689 was curved like a Have all comets these three parts? What apparent differences may be perceived in the composition of different comúts , , Into what classes, with reference to their composi; tion, may comets be divided . Describe the different appearances of comets at diff rent distances from the Sun. In what part of their orbit are their phenomena seen to the best advantuge? What is usually the direction of the luminous train What was the direc- tion of the tail of the comet of 1744? Of that of 1689 " . COMETS. 245 Turkish sabre. Sometimes the same comet has several tails. That of 1744 had, at one time, no less than sia, which appeared and disappeared in a few days. The comet of 1823 had, for several days, two tails; one ex- tending towards the Sun, and the other in the opposite direction. - • Comets, in passing among and near the planets, are materially drawn aside from their courses, and in some cases have their orbits entirely changed. This is remarka- bly true in regard to Jupiter, which seems by some strange fatality to be constantly in their way, and to serve as a per- petual stumbling block to them. “The remarkable comet of 1770, which was found by Lexell to revolve in a ſuoderate ellipse, it a period of about five years, actually got entangled annoug the satellites of Jupiter, and thrown out of iis orbit by the attrac- tions of that planet,” and has not been leard of since.—Herschel, p. 310. By this extraordinary reneontre, the inotions of Jupiter’s saiellites suffer- ed not the least perceptible derangement;—a sufficient proof of the aeriforin mature of the coinet’s mass. 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 mo- tiºn of the Earth or the Moon. The observations of philosophers upon comets, have as yet detected nothing of their nature. Tycho Brahe and Appian supposed their tails to be produced by the rays of the Sun, transmitted through the nucleus, which they sup- posed to be transparent, and to operate as a lens. Kepler thought they were occasioned by the atmosphere of the comet, driven off by the impulse of the Sun’s rays. This opinion, with some modification, was also maintained by Euler. Sir Isaac Newton conjectured, that they were a thin vapour, rising from the heated nucleus, as smoke as- cends from the Earth ; while Dr. Hamilton supposed them to be streams of electricity. “That the luminous part of a cornet,” says Sir John Herschel, “is some- thing in the nature of a smoke, fog, or cloud, suspended in a transparent atnuosphere, is evident from a fact which has been often noticed, viz. that How many tails had the comet of 1744 at one time, and how long did they continue to appear How many had that of 1823, and what was their direction? When comets pass near planets, how does the attraction of the planets affect them in regard to what play met is this remarkably true? Mention an example of cornets being so affected. What fact connected with this case proves the aeriform nature of the comet’s mass 2 How is it clear from observation that comets contain very little matter? What were the opi- pions of Tycho Brahe, Appian, Kepler, Euler, Sir Isaac Newton, and Dr. Hamilton, in regard to the tails of comets What roas the opinion of Sir John Herschel, and on tohat founded ? 21% 246 . COMETS, the portion of the tail where it comes up to, and surrounds the head, is yet separated ſrom it by an interval less luminous ; as we often see one layer of clouds laid over another with a considerable clear space between theiu.” And again—“It follows that these can only be regarded as great masses of thin vapour, susceptible of being penetrated through their whole substance by the sunbeams.” Comets have always been considered by the ignorant and superstitious, as the harbingers of war, pestilence, and fam- ine. Nor has this Öpinion been, even to this day, confined to the unlearned. It was once universal. And when we examine the dimensions and appearances of some of these bodies, we cease to wonder that they produced universal alarm. According to the testimony of the early writers, a comet which could be 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 Ro- mans, the comet was believed to be his metamorphosed soul, armed with fire and vengeance. This comet is again mentioned as appearing in 1106, and then resembling the Sun in brightness, being of a great size, and having an im- mense tail. In the year 1402, a comet was seen, so brilliant as to be discerned at noon-day. In 1456 a large comet made its appearance. It spread a wider terrour than was ever known before. The be- lief was very general, among all classes, that the comet would destroy the Earth, and that the Day of Judgment was at hand This comet appeared again in the years 1531, 1607, 1682, 1758, and is now approaching the Sun with accelerated velocity. It will pass its perihelion in November, 1835, and every 75% years thereaſier. We now [October, 1835,) see this self same counet, so often expelled the Church of Rome, returning to re- assert his claim to a ſellowship with the solar ſamily. 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 regardless of the present, and anxious only for the future. The Romish Church held at this time unbounded sway over the lives, and fortunes, and consciences of men. To prepare the world for its expected doom, Pope Calixtus III. ordered the Ave Maria to be re- peated three times a day, instead of two. He ordered the church bells to be rung at noon, which was the origin of How have comets been regarded by the ignorant and superstitious * Mention some of the most remarkable comets which have appeared. Describe them seyerally, and relate lſ] ...}} manner they were severally regarded ? What is the periodic time of this ©07??&t COMETS. - 247 that practice, so universal in Christian churches. To the Ave Maria, the prayer was added—“Lord, save us from the Devil, the Turk, and the Comet:” and once, each day, these three obnoxious personages suffered a regular excom- munication. The pope and clergy, exhibiting such fear, it is not a matter of wonder that it became the ruling passion of the multitude. The churches and convents were crowded for confession of sins; and treasures uncounted were poured into the Apostolic chamber. The comet, after suffering some months of daily cursing and excommunication, began to show signs of retreat, and soon disappeared from those eyes in which it found no ſa- vour. Joy and tranquillity soon returned to the faithful sub- jects of the pope, but not so their money and lands. The people, however, became satisfied that their lives, and the safety of the world, had been cheaply purchased. The pope, who had achieved so signal a victory oven the mon- ster of the sky, had checked the progress of the Turk, and kept, for the present, his Satanic majesty at a safe distance; while the Church of Rome, retaining her unbounded wealth, was enabled to continue that influence over her followers, which she retains, in part, to this day. The comet of 16S0 would have been still more alarm- ing than that of 1456, had not science robbed it of its ter- rours, and history pointed to the signal failure of its prede- cessor. This comet was of the largest size, and had a tail whose enormous length was more than minety-six mil- lions of miles. At its greatest distance, it is 13,000 millions of miles from the Sun; and at its nearest approach, only 574,000 miles from his centre ; * or about 130,000 miles from his surface. In that part of its orbit which is nearest the Sun, it flies * In Brewster’s edition of Ferguson, this distance is stated as only 49,000 miles. This is evidently a mistake : for if the comet approached the Suu's centre within 49,000 miles, it would penetrate 390,000 miles below the surface ‘l aking Ferguson's own elements for computing the perihelion distance, the result will be 4:4, 360 miles. The mistake may be accºunted for by suppºsing that the cipher had been onlitted in the copy, and the period pointed off one figure further to the left Yet, with this alteration, it would still be incor- rect ; because the Earth's mean tistance 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 A. Pingré, is as 0.00603 to 1. This multiplied into 35,273.869, gives 574,500 miles for the comets perihelion distance from the Sun's centre; from which, it we sº tract his mºdiameter,'º miles, we shihaº 130,660 mill's, the distance of the come t 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 shall find that the latter is only the 1-166th part of the Earth's distance. Now the square 9ſ 186 is 27,556; and this expresses the number of times that the Sun appears larget to the comet, in the above situation, than it does to the Earth. Saiſire makes it 34,596 times larger. . According to Newton, the velocity is 880,000 miles per hour. More recent discoveries indicate a velocity of 1,240,108 miles per hour. 248 COMETS, with the amazing 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; consequently, it is then exposed to a heat 27,000 times greater than the solar heat at the Earth. This intensity of heat exceeds, several thousand times, that of red-hot iron, and indeed all the degrees of heat that we are able to produce. A simple mass of vapour, 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 are, nevertheless, capable of enduring an inconceivable intensity of both heat and cold. This is the comet which, according to the reveries of Dr. Whiston and others, deluged the world in the time of Noah. Whiston was the friend and successor of Newton : but, anxious 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 punishment. According to his theory, a comet was the awful prison-house in which, as it wheeled from the remotest regions of darkness and cold into the very vicinity of the Sun, hurrying its wretched tenants to the extremes of per- ishing cold and devouring fire, the Almighty was to dispense the severities of his justice. -- Such theories may be ingenious, but they have no basis of facts to rest upon. They more properly belong to the chimeras of Astrology, than to the science of Astronomy. When we are told by philosophers of great caution and high reputation, that the fiery train of the comet, just allud- ed 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, and that another, which appeared soon after, had one 40,000,000 of miles long, and when we consider also the inconceivable 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 phantasies are not peculiar to any age or country. Even in our own times, the beautiful comet of 1811, the most splendid one of modern times, was generally considered among the superstitious, as the dread harbinger What is the degree of heat to which the comet of 1680 is exposed, when in its perihelion compared to that experienced at the Earth 2 ...What is the intensity of such a degree of - heat, compared with that of red-hot iron, or with any degree of heat which we are able to produce? What inference may be derived from this fact in regard to the composition of comets 3 What were the reveries of Dr. Whiston and others in regard to this comet? What facts ought to make us cease to wonder that comets were in #e; ages consider. ed as harbingers of evil? Hºve these phantasies, however, been confined to the darker #. 3 , of what event was the comet of 1811 considered, in our country, to be the har glnger COMETS. 249 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 an- ticipation of Biela’s comet of 1832. The nucleus of the comet of 1811, according to observa- tions made near Boston, was 2,617 miles in diameter, cor- responding 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 the comet, including its envelope, 50,617 miles. It had a very luminous tail, whose greatest length was one hundred million of miles. This comet moved, in its perihelion, with an almost inconceivable velocity— fifteen hundred tiunes greater than that of a ball bursting ſroin the unouth of a cannon. According to Regionoi, tantis, the comet of 1472 moved over an arc of 120° in one day. Brydone observed a comet at Paleriuo in 1770, which pass- ed through 50° of a great circle in the heavens in 24 Hours. Auother coulet, which appeared in 1759, passed over 41 ° in the same time. The conjecture of Dr. Halley therefore seeins highly probable, that if a body of such a size, having any considerable density, and luoving with such a velocity, were to strike our Earth, it would instantly reduce it to chaos, uningling its eleinents in ruin. The transient effect of a comet 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, the consequences would §e awful. A new direction would be given to its rotary motion, and it would revolve around a new axis. The seas, ſorsaking their beds, would be hurried, by their centrifugal ſorce, 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 hu- man industry and genius would be at once destroyed. 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 atten- tion 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 earposed to. After a mature examination, they re- ported,—“We have found that, of 281,000,000 of chances, there is only one unfavourable, there exists but one which can produce a collision between the two bodies.” “Admitting, then,” say they, “ſor a mounent, that the counets which may strike the Earth with their nucleuses, would annihilate the whole human race; the danger of death to each individual, resulting from the ap- * Describe this comet. Give some c.camples of the velocity of conets. Iſ'hat would 27 obab y be the effect upon the Earth, shºw d - comeſ strike' it 2 I ſhat do's Dr. Brew. ster say would be the effect of a comet passing near the Earth 2 But if the Earth 20°re actually to rece' pe. a shock from a compet, what does he say would be the resuls 2 How did the French mathematicians and astronomers find the chances of a collision be- tween the Earth and eomets to stand A Hiſhat, then, on the suppos tion that a stroke of a comet would annihilate the whole human race, is the danger of death to each in- dividual, resulting from the appearance of an unknown comet 250 COMETS. pearance of an unknown comet, would be exactly equal to the risk he would run, if in an urn there was only one single white ball among a total num- ber of 281,000,000 balls, and that his condemnation to death would be the lºable consequence of the while ball being proſluced at the first draw- E" We have before stated that comets, unlike the planets, observe no one direction in their orbits, but approach to, and recede from their great centre of attraction, in every possi- ble direction. Nothing can be more sublime, or better calculated to fill the mind with profound astonishment, than to contemplate the revolution of comets, while in that part of their orbits which comes within the sphere of the tele- scope. Some seem to come up from the immeasurable depths below the ecliptic, and, having doubled the heavens' mighty cape, again plunge downward with their fiery trains, “On the long travel of a thousand years.” Others appear to come down from the zenith of the uni- verse to double their perihelion about the Sun, and then re- ascend far above all human vision. Others are dashing through the solar system in all possi- ble directions, and apparently without any undisturbed or undisturbing path prescribed by him who guides and sus- tains them all. Until within a few years, it was universally believed that the periods of their revolutions must necessarily be of prodi- gious length ; but within a few years, two comets have been discovered, whose revolutions are performed, compa- ratively, within our own neighbourhood. To distinguish them . from the more remote, they are denominated the comets of a short period. The first was discovered in the constella- tion Aquarius, by two French astronomers, in the year 1786. The same comet was again observed by Miss Caro- line Herschel, in the constellation Cygnus, in 1795, and again in 1805. In 1818, Professor Encke determined the dimensions of its orbit, and the period of its sidereal revolu- tion ; for which reason it has been called “Encke's Comet.” This comet performs its revolution around the Sun in about 3 years and 4 months,” in an elliptical orbit which lies wholly within the orbit of Jupiter. Its mean distance from the Sun is 212 millions of miles; the eccentricity of its orbit is 179 º * Owing to the disturbing influences of the surrounding planets, the periodic return of is coinet, like that of allotiners, is liable to be hastened or returded several days. Its ..]eriod varies from about 1203 to 1212 days. What is the direction of comets in their orbits What has been, until within a few years, the universal opinion in regard to the length of the times of their revolution 3 Why does not, the same Qpinion prevail now A What are these two comets denominated? Re- late the history of the discovery qf the first, Why is it called Encke's comet What is e time of the revolution of Encke's comet 2 ...What is the form of its orbit, and what its position with regurd to the orbit of Jupiter?, What is this comet's mean distance from the Sun? What is the eccentricity of its orbit? - coniets. 25i millions of miles; consequently it is(358 millions of miles nearer the Sun in its perihelion, than it is in its aphelion. It was visible throughout the United States in 1825, when it presented a fine appearance. It was also observed at its next return in 1828; but its last return to its perihelion, on the 6th of May, 1832, was invisible in the United States, on account of its great Southern declination. . The second “Comet of a short period,” was observed in 1772; and was seen again in 1805. It was not until its re-appearance in 1826, that astronomers were able to determine the elements of its orbit, and the exact period of its revolution. This was successfully accomplished by M. Biela of Josephstadt; ) hence it is called Biela’s Comet. According to observations made upon it in 1805, by the cele- brated Dr. Olbers, its diameter, including its envelope, is ^42,280 miles. It is a curious fact, that the path of Bie- la's comet passes very near to that of the Earth ; ; so near, that at the moment the centre of the comet is at the point nearest to the Earth’s path, the matter of the comet extends beyond that path, and includes a portion within it. Thus, if the Earth were at 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 the Earth, the Earth would be enveloped in the ne- bulgus atmosphere of the comet. With respect to the effect which might be produced upon our atmosphere by such a circumstance, it is impossible to offer any thing but the most vague conjecture. C Sir John Herschel was able to distinguish stars as minute as the 16th or 17th magnitude through the body of the comet 1 Hence it seems reasonable to infer, that the nebulous matter of which it is composed, must be infinitely more attenuated than our atmosphere; so that for every particle of cometary matter which we should inhale, we should inspire millions of par- ticles of atmospheric air. - & This is the comet which was to come into collision with the Earth, and to blot it out from the Solar System. In re- turning to its perihelion, November 26th, 1832, it was com- puted that it would cross the Earth’s orbit at a distance of How much nearer the Sun, then, is the comet, when in its perihelion than when in its aphelion,? . In what years has this coinet be n seen in the United States A Why was it not visible in the United States at the time of its return in 1832 A. Relate the history of the discovery of the second comet of a short period Why is it called Biela's coinet? What, according to the observations of Dr. Olbers in 1805, was the diameter of Biela's comet, in- cluding the envelope? How near does the path of Bieia's comet lie to that of the Earth? What would be the effect upon our atmosphere should, the nebulous atmosphere of the comet envelope it? What reason have we to suppose that it is more attenuated than our Atmosphere 3. It was predicted that this, comei would come into collision with the Earth.3, what were the grounds of probability that such an event would take place, and why did it not 3 - 252 COMETS. only 18,500 miles. It is evident that if the Earth had been in that part of her orbit at the same time with the comet our atmosphere would have mingled with the atmosphere o the comet, and the two bodies, perhaps, have come in contact. But the comet passed the Earth's orbit on the 29th of Oc- tober, in the 8th degree of Sagittarius, and the Earth did not arrive at that point until the 30th of November, which was 32 days afterwards. - If we multiply the number of hours in 32 days, by 68,000 (the velocity of the Earth per 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 any time, was about 51 millions of miles; its near- est approach to the Sun, was about 83 millions of miles. Its mean distance from the Sun, or half the longest axis of its orbit, is 337 millions of miles. Its eccentricity is(253 mil- lions of miles; consequently, it is '507 millions of miles nearer the Sun in its perihelion than it is in its aphelion, The period of its sidereal revolution is: 2,460 days, pr about 63 years. ". . Although the comets of Encke and Biela are objects of very great inter- est, 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 º them of less interest to physical astronouny than those of longer periods. They do not, like them, rush from the invisible arid inaccessible depths of space, and, after sweeping our system, depart to distances with the con- ception of which the imagination itself is conſounded. They possess none of that grandeur which is connected with whatever appears to break through the fixed order of the universe. It is reserved for the connet of Halley alone to afford the proudest triumph to those powers oſ calculation by which we are enabled to follow it in the depths of space, two thousand Inillions of miles beyond the extreme verge of the solar system ; and, not- withstanding disturbances which render each succeeding period of its return different from the last, to ſoretel that return with precision. The following representation of the entire orbit of Biela’s comet, was obtained from the Astronomer Royal of the Greenwich Observatory. It shows not only the space and position it occupies in the solar system, but the points where its orbit intersects all the planetary orbits through which it passes. By this, it is seen that its perihelion lies between the orbits of the Earth and Venus, while its aphelion extends a little beyond that of Jupiter) What was its nearest approach to the Earth at any time? What its nearest approach to the Sun ? ...What its mean distance, from the Sun ? What its eccentricity 3 What then, is the difference between its perihelion and aphelion distances ! What is the period of its sidereal revolution? Why are the cºmets of Encke and Biela objects of less tºte- Test to physical astronomy than those of longer periods & What is the situation of the orbit of Biela's comet in the solar system 7 Fig. 20- # #s #: S$ # à 5 # # @k> " . # ·. S$ j N, N -- o It \ of| Jupitcr tA Y,s © -- •, # { b # ©L> <3.) 254 - COMETS, This diagram not only exhibits the course of the comet at its last return, but also denotes its future positions on the first day of every year during its next revolution. It is also apparent that it will return to its perihelion again in the ... autumn of 1839, but not so immediately in our vicinity as to be the proper cause of alarm. To be able to predict the Very day and circumstances of the return of such a bodi- less and eccentric wanderer, after the lapse of so many years, evinces"a perſection of the astronomical calculus that may justly challenge our admiration. “The re-appearance of this comet,” says Herschel, “whose return in 1832 was made the subject of elaborate calculations by mathematicians of the first eminence, did not disappoint the expectation of astronomers. It is hardly possible to imagine any thing more striking than the ap- pearance, after the lapse of nearly seven years, of such an all but imperceptible cloud or wisp of vapour, true, however, to its predicted time and place, and obeying laws like those which regulate the planets.” Herschel, whose Observatory is at Slough, England, observed the daily progress of this connet ſrom the 24th of September, until its disappearance, compared its actual position from day to day with its calculuted position, and ſound them to agree within ſour or five iminutes of time in Iight ascen- sion, and within ..}. seconds of declimation: . Its position, them, as repre- sented on a planisphere which the author prépared for his pupils, and af. terwards published, was true to within a less space than one third of its Fº diameter. Like some others that have been º: COInet as no luminous train by which it can be easily recognized by the "faked eye, except when it is very near the sº This is the reason why it was not more generally observed at its late returri. Although this comet is usually denominated “Biela’s comet,” yet it seems that M. Gambart, director of the Observatory at Marseilles, is equally en- titled to the honour of identifying it with the comet of 1772, and of 1S05. He discovered it only 10 days after Biela, and immediately set about calcu- lating its elements from his own observations, which are thought to equal, if they do not surpass, in point of accuracy, those of every other as- trono Oſler, Up to the beginning of the 17th century; no correct no- tions 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 extremities. ; There was nothing, in the ob- servations 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 When will this comet retum again? How much did its actual position, Jrom day to day, as observed by Herschel, differ from its cºlºnºlated position ? Why was it not onºre generally observed at its late return ? What astronomer besides Biélil identi- fied it with the comet of 1772 and 1805? What were the opinions of ºstronomers in tº gard to the paths of comets, up to the beginning of the 17th century? What were Kepler's opinions on this subject - COMETS. 255 system, revolving about the Sun in elliptical orbits that re- turned into themselves. This grand discovery was reserved for one of the most industrious and sagacious astronomers that ever lived—this was lyr. Halley, the contemporary and friend of Newton, When the comet of 1682 made its appearance, he set him- self about observing it with great care, and found there was a wonderful resemblance 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. This is therefore called Halley's comet. It is the very same comet that filled the eastern world with so much consternation in 1456, and became an object of such abhorrence to the church of Rome. Of all the comets which have been observed since the Christian era, only three have had their elements so well determined that astronomers are able to fix the period of their revolution, and to predict the time and circumstances of their appearance. These three are, Encke's, whose last revolution about the Sun was performed in 1212 days; Biela’s, whose period was 2461 days; and Halley’s, which is now accomplishing its broad circuit in about 28,000 days) ‘Encke's and Halley’s will return to their perihelion the present year (1835), and Biela’s in 1839. ... Halley’s comet; true to its predicted time and place, is now (Oct. 1835,) visible in the evening sky. But we behold none of those phenotinena which threw our ancestors of the middle ages into agonies of superstitious terrour, We sce not the come/a hor remuda, magnitudiºnis, 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 counet 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 l,65S,000 000 miles ; consequently it is 3,316,000,000 miles far- ther from the Sun in its aphelion than it is in its perihelion. In the latter case, its distance from hini is only 55.700,000 miles ; but in the former, it is 3,371,700 000 miles Therefore, though its aphelion distance be great, its mean distance is less than that of Herschel ; and great as is the aphelion distance, it is but a very small fraction less than one five-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 mega- Who first discovered the identity of comets , , Relate the manner by which he came to this discovery. How many of all the comets observed since the Christian era, have had their elements so well determined, that astronomers are able to fix the period of their re- volutions, and to predict the time and circumstances of their appearance 1 \\ hat comets are these? In what time, do they accomplish their revolutions? When will they, seve- rally, return to their perihelion 3 What comet is now (Oct. 1835) visible? What are the mean, and the aphelion and perihelion distances of Halley's comet from the Sun ? What part of the distance beyond which the nearest of the flared stars must be pla. ced, is its aphelion distance 2 256 LAW OF UNIVERSAL GRAVITATION. tive and not positive, the nearest of them may be at twice or ten times that distance. The number ºf comets which have been observed since the Christian era, amounts to 700 Scarcely a year has passed without the observaſjon of one or two. And since multitudes of them must escape observation by reason of their traversing that part of the heavens which is above the hôi, zon in the day time, their whole number is probably many thousands? Comets so circumstanced, can only become vii; by the rare coincidence of a .#;". of the Sun-a coincidence which happened, as related by Seneca.it,0 years before Clifist, when a large coinet was actually observed very near the Sun.) But M. Arago rºasons in the following manner, with respect to the num- ber of comets º: number of ascertained coineſs, which, at their least distances, pass within the orbit of Mercury, is thirty. Assuming that the coinets are uniformly distributed throughout the solar system, there will be 117,649 times as uſary coulets included within the orbiſ of Herschel, as there are within the orbit of Mercury. . But as there are 30 within the orbit of Mcreury, there must be 3,529,470 within the orbit of Herschel ! : Of 97 coinets whose elements have been calculated by astronomers, 24 K. between the Sun and the orbit of Mercury ; 33 hetween the orbits of 1ercury and Venus ; 21 between the orbits of Venus and the Earth ; 15 between the orbits of Ceres and Jupiter. “Forty-nine of these comets move from cast to west, and 48 in the opposite direction. ; The total number of distinct coinets, whose p?ths during the visible part of their courseshad been ascertained, up to the year 1832, was one hundred and thirty-seven. : W. 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 maturally arise in the mind, but which sur- pass the limited powers of the human understanding at pre- sent to determine. C H A P T E R X. X. of THE FORCES BY WHICH THE PLANETS ARE RETAINED IN THEIR ORBITS. Having described the real and apparent motions of the bodies which compose the solar system, it may be interest- ing next to show, that these motions, however varied or com- plex they may seem, all result from one simple principle, or law, namely, the - Hyhat is the natºmber of comets which have been observed since the Christian era 2 IWhy must some ºf then escape observation 2 . How great is probably their actual natºmber 2 In what case alom c can comets which travers the horizon in the day time become visible 2 Mention an instance of a comet thus becoming visible 2 What is the reºsoning of MI. Arago in regard to the number of connets & Describe the track among the orbits of the planets, of the 97 conneſs whose tiements have been calculated by astronomers. In what direction do they move & What, wºn to the year 1832, was the whole muºnber of distinct comets, whose path, during the visible part of their course, has been determined 2 By what principle, or law, are the planets ro- ūined in their orbits 7 - - - - LAW OF UNIVERSAL GRAVITATION, 257 LAW OF UNIVERSAL GRAVITATION. It is said, that Sir Isaac Newton, when he was drawing to a close the demonstration of the great truth, that gravity is the cause which keeps the heavenly bodies in their orbits, was so much agitated with the magnitude and importance of the discovery he was about to make, that he was unable to roceed, and desired a friend to finish what the intensity of is feelings did not allow him to do.’ By gravitation is meant, that universal law of attraction, by which every particle of matter in the system has a tendency to every other particle. This attraction, or tendency of bodies towards each other, is in proportion to the quantity of matter they contain. The Earth, being immensely large in comparison with all other substances in its vicinity, destroys the effect of this attrac- tion between smaller bodies, by bringing them all to itself. 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 Earth, also, attracts the Moon, and she in turn at- tracts the Earth. A ball, thrown upwards from the Earth, is brought again to its surface; the Earth’s attraction not only counterbalancing that of the ball, but also producing a motion of the ball towards itself. This disposition, or tendency towards the Earth, is mani- fested in whatever falls, whether it be a pebble from the hand, an apple from a tree, or an avalanche from a moun- tain. All terrestrial bodies, not excepting the waters of the ocean, gravitate towards the centre of the Earth, and it is by the same power that animals on all parts of the globe stand with their feet pointing to its centre. The power of terrestrial gravitation is greatest at the earth’s surface, whence it decreases both upwards and downwards; but not both ways in the same proportion. It decreases upwards as the square of the distance from the Earth’s centre increases; so that at a distance from the centre equal to twice the semi-diameter of the Earth, the gravitating force would be only one fourth of what it is at the surface. But below the surface, it decreases in the direct ratio of the dis- Who discovered this great truth, and how was he affected in view of it? What is meant }. gravitation 3. "To what is it proportioned? Give some example. . How is it known that the attraction of gravitation is reciprocal ? Give some examples to illustrate this principle. Where is the power of terrestrial gravitation, the greatest? From t oint, does the power degrease equally, both upwards and downwards? What is the aw of decrease upwards? Give an example. What is the law of decrease downwards? Give an example. 25% 258 LAW OF UNIVERSAL GRAVITATION. tance from the centre ; so that at a distance of half a semi- diameter from the centre, the gravitating force is but half what it is at the surface. Weight and Gravity, in this case, are synonymous terms. We say a piece of lead weighs a pound, or 16 ounces; but if by any means it could be raised 4000 miles above the surface of the Earth, which is about the distance of the surface from the centre, and consequently equal to two semi-diameters of the Earth above its centre, it would weigh only one fourth of a pound, or four ounces; and if the same weight could be raised to an elevation of 12,000 miles above the surface, or four semi-diameters above the centre of the Earth, it would there weigh only one sixteenth of a pound, or one ounce. The same body, at the centre of the Earth, being equally attracted in every direction, would be without weight; at 1000 miles from the centre it would weigh one fourth of a pound ; at 2000 miles, one half of a pound ; at 3000 miles, three fourths of a pound; and at 4000 miles, or at the sur- face, one pound. It is a universal law of attraction, that its power decreases as the square of the distance increases. The converse of this is also true, viz. The power increases, as the square of the distance decreases. Giving to this law the form of a practical rule, it will stand thus : The gravity of bodies above the surface of the Earth decreases in a dupli- cate ratio, (or as the squares of their distances) in semi-diameters of the earth, Jrom the earth's centre. That is, when the gravity is increasing, multiply the weight by the square of the distance ; but when the gravity is decreasing, divide the weight by the square of the distance. Suppose a body weighs 40 pounds at 2000 miles above the Earth's sur. face, what would it weigh at the surface, estimating the Earth's semi-diameter at 4000 tmiles 4. From the centre to the given height, is 1* 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 the distance of the Moon, (240,000 miles,) what would be its weight. Thus, 4000)240,000(60 semi diameters, the square of which is 3600. As the gravity, in 1his case, is decreasing, diride the weight by the square of the distance, and it will give 3500)256(1-1üth of a pound, or 1 ounce. 2. To find to what height a given weight must be raised to lose a certain portion of its weight. RULE.— Divide the weight at the surface, by the required wcight, and ex- tract the square root of the quotient. Ex. A boy weighs 100 pounds, how high must he be carried to weigh but 4 pounds ! Thus, 100 divided by 4, gives 25, the square root of which is 5 semi-diameters, or 20,000 miles above the Cenſ re. Bodies of equal magnitude do not always contain equal What is the relation between weight and gravity? Illustrate it by some examples. What, ther, is the general law in regard to the increase and decrease of attraction 3 How may this ſay be expressed, in the form of a practical rule 2, Suppºse, for ea:- ample, the semi-diameter of the Earth be es’imated, in round nwinbers, at 4000 miles, and that a body, elevated 2000 miles above its surface, should weigh 40 pounds, what would the same body weigh, if brought to the Earth's surface? Suppose a body which weighs 256 pounds upon the surface of the Earth, he raised to the distance ºf the Moon, what would be its weight at such an elevation ? ['The pupil should be re- %. to give the calculation, as well as the answer, l Bt, what rule can we determine the height to which a body must be raised, in order to its losing a certain portion { its weight?. Give an example. Do bodies of the same magnitude always contain equ quantities of matter? law of UNIVERSAL GRAVITATION. 259 quantities of matter; a ball of cork, of equal bulk with one of lead, contains less matter, because it is more porous. The Sun, though fourteen hundred thousand times larger than the Earth, being much less dense, contains a quantity of matter only 355,000 times as great, and hence attracts the Earth with a force only 355,000 times greater than that with which the Earth attracts the Sun. ( The quantity of matter in the Sun is 780 times greater than that of all the planets and satellites belonging to the Solar System; consequently their whole united force of at- traction is 780 times less upon the Sun, than that of the Sun upon them. - *The Centre of Gracity of a body, is that point in which its whole weight is concentrated, and upon which it would rest, if freely suspended. If two weights, one of ten pounds, the other of one pound, be connected together by a rod eleven feet long, nicely poised on a centre, and then be thrown into a free rotary motion, the heaviest will move in a circle with a radius of one foot, and the lightest will describe a cir- cle with a radius of ten feet : the centre around which they move is their common centre of gravity; See the Figure. Thus the Sun and planets move around an imaginary point as a centre, always preserving an equilibrium. CENTRE OF GRAVITY. Fig. 21. If there were but one body in the universe, provided it were of uniform density, the centre of it would be the centre of gravity towards which all the surrounding portions would uniformly tend, and they would thereby balance each other, Thus the centre of gravity, and the body itself, would for- ever remain at rest. It would neither move up nor down ; there being no other body to draw it in any direction. In this case, the terms up and down would have no meaning, What are the comparative bulks and densities of the Sun and the Earth? How great is the quantity of matter in the Sun?&ompared with that of all the planets belonging to the solar system? What is the centre of gravity of a body ? Give an example. How does this illustration apply to planetary motion if there were but one single body in the uni- verse, where would the centre of gravity be? What motion would ūj; have? What would the terms w? and down, in such case, mean? 260 ATTRACTIVE AND PROJECTILE FORCES. except as applied to the body itself, to express the direction of the surface from the centre. Were the Earth the only body revolving about the Sun, as the Sun’s quantity of matter is 355,000 times as great as that of the Earth, the Sun would revolve in a circle equal only to the three hundred and fifty-five thousandth part of the Earth’s distance from it : but as the planets in their seve- ral orbits vary their positions, the centre of gravity is not always at the same distance from the Sun. The quantity of matter in the Sun so far exceeds that of all the planets together, that were they all on one side of him he would never be more than his own diameter from the common centre of gravity ; the Sun is therefore justly con- sidered as the centre of the º The quantity of matter in the Eärth being about 80 times as great as that of the Moon, their common centre of gravity is 80 times nearer the former than the latter, which is about 3000 miles from the Earth's centre. The secondary planets are governed by the same laws as their primaries, and both together move around a com- mon centre of gravity, - *Every system in the universe is supposed to revolve, in like manner, around one common centre. ATTRACTIVE AND PROJECTILE FORCES. 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 power of attraction, draw all the planets to him, if his attractive force were not counterbalanced by the primi- tive impulse of the planetary bodies to move in straight lines. The attractive power of a body drawing another body towards the centre, is denominated Centripetal force ; and the tendency of a revolving body to fly from the centre in a tangent line, is called the Projectile or Centrifugal force. The joint action of these two central forces gives the planets If the Earth were the only body revolving about the Sun, what would be their relative distances from their common centre of gravity If, instead of the Earth alone, the Earth with all the planets, and satellites of the system were on one side, and the Sun alone on the other, at what distance from their common centre of gravity must the Sun be, to bal- ance them all? Where is the centre of gravity between the Earth and Moon? How do you know this 1. By what laws are the secondary planets governed; and the other systems of the universe? What is meant by all simple motion being rºctilinear? Why does not the Sun, by its great attraction, bring all bodies to its surface?. Explain what is meant by ºireta and centrifugal force. what results from the joint action of these two OFCCS ATTRACTIVE AND PROJECTILE FORCES. 261 a circular motion, and retains them in their orbits as they revolve, the primaries about the Sun, and the secondaries about their primaries/ The degree of the Sun's attractive power at each particu- lar planet, whatever be its distance, is uniformly equal to the centrifugal force of the planet.) The nearer any plan- et is to the Sun, the more strongly is it attracted by him ; the farther any planet is from the Sun, the less is it at- tracted by him ; therefore, those planets which are the near- er to the Sun must move the faster in their orbits, in order thereby to acquire centrifugal 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 centrifugal force, for the weaker attraction of the Sun at those distances." A The discovery of these great truths, by Kepler and New- töm, established the UNIVERSAL LAW OF PLANETARY MOTION ; which may be stated as follows: 1. Every planet moves in its orbit with a velocity vary- ing every instant, in consequence of two forces; one tending to the centre of the Sun, and the other in the direction of a tangent to its orbit, arising from the primitive impulse given at the time it was launched into space. The former is call- ed its Centripetal, the latter, its Centrifugal force. Should the centrifugal force cease, the planet would fall to the Sun by its gravity ; were the Sun not to attract it, it would fly off from its orbit in a straight line. 2. By the time a planet has reached its aphelion, or that point of its orbit which is farthest from the Sun, his attrac- tion has overcome its velocity, and draws it towards him with such an accelerated motion, that it at last overcomes the Sun’s attraction, and shoots past him ; then gradually decreasing in velocity, it arrives at the perihelion, when the Sun’s attraction again prevails. 3. However ponderous or light, large or small, near or remote, the planets may be, their motion is always such that imaginary lines joining their centres to the Sun, pass over equal areas in equal times : and this is true not only with respect to the areas described every hour by the same planet, but the agreement holds, with rigid exactness, be- tween the areas described in the same time, by all the plan- ets and comets belonging to the Solar System. From the foregoing principles, it follows, that the force of gravity, and the centrifugal force, are alºla opposing poveers—each continually acting \ - - To what is the Sun's attractive power at eagh º planet equal?, Explain this ; fully. By whom was the universal law of planetary motion established? Repeat nº law. 262 PRECESSION OF THE EquinoxEs, &c. against the other. Thus, the weight of bodies, on the Earth's equator, is dºminished by the centrifugal force of her diurnal rotation, in the propor- tion of one pound ſor every 290 pounds : that is, had the Earth no mojon on her axis, all bodies on the equator would weigh one two hundred and eighly-ninth part more than they now do. On the contrary, if her diurnal motion were accelerated, the centrifugal force would be proportionally increased, and the weight of bodies at ſhe equator would be, in the same ratio, diminished. Should the Earth revolve upon its axis, with a Velocity which would make the day but 84 minutes long, instead of 24 hours, the centrifugal force would counterbalance that of gravity, and all bodies at the equator would then be absolutely destitute of weight; and if the centriſugal force were further augmented, (the Earth revolving in less time than 84 minutes,) gravitation would be completely overpowered, . fluids and loose substances near the equator would fly off from the Sull face. The weight of bodies, either upon the Earth, or on any other planet having a motion around its axis, depends jointly upon the mass of the planet, and its diurnal Velocity. . A body weighing one pound upon the equator of the Earth, would weigh, if removed to the equator of the Sun, 27.9 lbs. Of Mer. çury, 1.03 lbs. Of Venus, 0.98 lbs. Of the Moon, 3 lb. Of Mars, 3 lb. of Jupiter, 2.716 lbs. Of Saturn, 1.01 lbs, C H A P T E R XXI. PRECESSION OF THE EQUINOXES-OBLIQUITY OF THE ECLIPTIC. 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 the PRECESSION of The EquinoxEs, as it is termed. The equinoxes, as we have learned, are the two opposite points in the Earth’s orbit, where it crosses the equator. The first is in Aries; the other, in Libra. By the preces- sion 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 equinoctial, Spring and Autumn, exactly in the same points, but every year a little behind those of the preceding year. This annual falling back of the equinoctical points, is call- ed by astronomers, with reference to the motion of the heavens, the Precession of the Equinoaces ; but it would bet- ter accord with fact as well as the apprehension of the learn- er, to call it, as it is, the Recession of the Equinoxes: for the equinoctial points do actually recede upon the ecliptic, at the rate of about 50+” of a degree every year. It is the name How is the weight of bodies on the Earth's equator affected by its diurnal rotation? What would be the effect if the diurnal motion of the Earth were accelerated? What would be the consequence if the Earth, revolved about its awis in 84 minutes, or in less time 2 What are the equinoxes 7 What is meant by the precession of the equinoxes Why is it called precession of the equinoxes, and what would be a better term? PRECEsston of THE EQUINOXEs, &c. 263 only, and not the position, of the equinoxes which remains permanent. Wherever the Sun crosses the equinoctial in the spring there is the vernal equinox ; and wherever he crosses it in the autumn there is the autumnal equinox; and these points are constantly moving to the west. Fig. 22. To render this subject fa- miliar, we will suppose two carriage roads, extending quite around the Earth : one, representing the equator, •S. running due east and west; § and the other, representing tº gº the ecliptic, running nearly Ş in the same direction as the § former, yet so as to cross it s wifh a small angle, (say of 23#9,) both at the point LT2 | L- 2– where we now stand, for in- - . stance, and in the ...21 Ežiū7.0Głual exactly opposite ; let there also be another road, to * represent the prime ineridi- R e an, running north aud 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 intersec- tion, not in the road leading directly east, but along that of the ecliptic, which leaves the former a little to the north, and let a person be placed to watch when the carriage coines around again, after having made the circuit of the Earth, and see whether the carriage will cross the equinoctial road again precisely in the same track as when it left the goal, Though the person stood exactly in the fortner track, he need not fear being run over, for the carriage will cross the road 100 rods west of him, that is, 100 rods west of the meridian on which he stood. It is to be observed, that 100 rods on the equator is equal to 504 seconds of a degree. If the carriage still continue to go around the Earth, it will, on completing its second circuit, cross the equinoctial path 200 rods west of the ineridian whence it first set out ; on the third circuit, 300 rods west; on the fourth circuit, 400 rods, and so on, continually. Atter 71; circuits, the point of in- tersection would be one degree west of its place at the commencement of the route. At this rate it would be easy to determine how many complete circuits the carriage must perform before this continual failing back of the intersecting point would have retreated over every degree of the orbit, until it reached again the point from whence it first departed. The application of this illustration will be imanifest, when we consider, further, that, The Sun revolves from one equinox to the same equinox again, in 365d. 5h. 48/47’’.81. This constitutes the natu- ral, or tropical year, because, in this period, one revolution of the seasons is exactly completed. But it is, mean- The equinoctial points are continually moving ; how, them, is their position definel. Give, at length, a familiar illustration by which this subject may be understood. Suppose the carriage continues its circuit around the earth, where would it cross the equinocrial the 2d, 3d, and 4th times, 3-c. 2. After how many circuits would this falling back of the equinoctial points amount to one degree on the ecliptic & In what time does the Sun revolve from one equinox to the same equinox again? What is this period called? 264 PRECESSION OF THE EQUINoxEs, &c. while, 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 back 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 Sun's side- real 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. 10}s. for the length of a sideredl revolution ; or the time in which the Sun revolves from one fixed star to the same star again. - As the Sun describes the whole ecliptic, or 360°, in a trop- ical year, he moves over 59'8" of a degree every day, at a mean rate, which is equal to 50+” of a degree in 20 min- utes and 23 seconds of time; consequently he will arrive at the same equinox or solstice when he is 50+” of a degree short of the same star or fixed poin in the heavens, from which he set out the year before. So that, with respect to the fixed stars, the Sun and equinoctial points fall back, as it were, 1° in 713 years. This will make the stars appear to have gone forward 19, 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 ecliptic, with- out regard to the place of the constellations. Hence it be- comes necessary to have new plates engraed for celes- tial globes and maps, at least once in 50 years, in order to exhibit truly the altered position of the stars. At the pres- ent 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 2140 years. Why is it so called? Does the equinox remain stationary during this period?, What results from this? How long does it take the Sun to pass over the interval through which the equinox has thus retreated? What is the length of a sidereal revolution, and how is it determined What portion of the ecliptic does the Sun describe, at a mean rate, every day ! What portion does it describe in 20 minutes and 23 seconds?. If the Sun and equi- noctial points fall back in the ecliptic 50 1-4" of a degree every year, how many years before this regression will amount to a degree ? ... How will this affect the appearance of the stars What practical inconvenience results from this fact? In what period of time does the precession of the stars amount to 30°, or olic whole s gn PRECESSION OF THE EQUINOXES, &c. 265 MOTION OF THE STARS. Fig. 23. To explain this by a figure; Suppose the Sun to have been in conjunction with a fixed star at S, in the first degree of Taurus, (the second sign of the ecliptic.) 340 years before the birth of our Saviour, or about the 17th year of Alexander the Great; then having made 2140 revolutions through the ecliptic, he would be found again at the end of so many sidercal years at S; but at the ent of so many Julian years, he would be found at J. and at the end of so many tropical years, which would bring it down to the beginning of the present century, he would be found at T, in the first degree of Aries, which has receded from S to T in that time by the precession of the equinoc- tial points Aries and Libra. The arc S T would be equal to the amount of the precession (for precession we must still call it) of the equinox in 2140 years, at the rate of 50,” 23572 of a degree, or 20 minutes and 23 seconds of time annually, as above stated. From the constant retrogradation of the equinoctial points, and with them of all the signs of the ecliptic, it follows that the longitude of the stars must continually increase. The tame 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 Tantrus ; 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 particu- lar time of the year, in the time of Hesiod, Eudoxus, Virgil, Pliny, and others, by no means answers at this time to their descriptions. Explain this by a diagram. How does ſhe retrogradation of the equinoctial points afººt the longitide of the stars? Does the same cause extend to their right ascension and declination also How is this rendered apparent? 266 PRECESSION OF THE EQUINOXEs, &c. Hesiod, in his Opera et Dies, lib. ii. verse 185, says: When from the solstice sixty wintry days Their turns have finish'd, mark, with glitt’ring rays, Tºrom Oceau’s sacred flood, Arcturus rise, Then first to gild the dusky evening skies. But Arcturus now rises acronycally in latitude 37° 45' N. the latitude ( Hesiod, and nearly that of Richmond, in Virginia, about 100 days after tha winter solstice. Supposing Hesiod to be correct, there is a difference of 46. days, arising from the precession of the equinoxes since the days of Hesiod. Now as there is no record extant of the exact period of the world when thiſ poet ſlourished, let us see to what result astronomy will lead us. As the Sun moves through about 39° of the ecliptic in 40 days, the winter Solstice, in the time of IIesiod, was in the 9th degree of Aquarius. Now es timating the precession of the equinoxes at 50}” in a year; we shall have 50}” : 1 year: : 39°: 2791 years since the time of Hesiod; if we substract from this oux present era, 1836, it will give 958 years before Christ. Lempriere, in his Classical Dictionary, says Hesiod lived 907 years before Christ See a similar calculation ſor the time of Thales, page 54. The retrograde movement of the equinoxes, and the an- nual extent of it, were determined by comparing the longitude of the same stars, at different intervals of time. The most careful 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 oc- cupying not less than 25,000 y lars in a single revolution. It has not yet completed one qºzarter of its first circuit in the heavens since the creation. Thus observation has not only determined the abso- lute motion of the equinoctial points, but measured its limit; it has also shown that this motion, like the causes which pro- duce it, is not uniform in itself: but that it is constantly ac- celerated by a slow arithmetical increase of 1" of a degree 1n 4,100 years. —A quantity which, though totally inappre- ciable for short periods of time, becomes sensible after a lapse of ages. For example: The retrogradation of the equinoctial points is now greater by nearly #" than it was in the time of Hipparchus, the first who observed this mo- tion ; consequently, the mean tropical year is shorter now by about 12 seconds than it was then. For, since the retro- gradation of the equinoxes is now every year greater than it was then, the Sun has, each year, a space of nearly #ff less to ſº through in the ecliptic, in order to reach the plane of the equator, Now the Sun is 12 seconds of time in p tssing over #" of space. At present, the equinoctial points move backwards, or from east to west along the path of the ecliptic at the rate of Mention an easample. History does not enable us to fia: the precise age of the world fin which Hesiod flourished; what light does astronomy shed upon his question.” By what means was the retrogradation of the equinoxes determined Whv was it diffi- cu't to determine the cause and extent of this motion 1 Not to specify particular cases, w mat has observation at length.determined, with respect to the limit and wºn for mºſy of this backward movement of the equinoctial points? Give an example. . Why should the tropical year, on this account, be shorter now than it was then l What is the present rate of motion of the equinoctial points? PRECESSION OF THE EQUINOXEs, &c. 267 1° in 713 years, or one whole sign, in 2140 years. Con- tinuing at this rate, they will fall back through the whole of the 12 signs of the ecliptic in 25,680 years, and thus re- turn to the same position among the stars, as in the beginning. But in determining the period of a complete revolution of the equinoctial points, it must be borne in mind that the motion itself is continually increasing ; so that the last quar- ter of the revolution is accomplished several hundred years sooner than the first quarter. Making due allowance for this accelerated progress, the revolution of the equinoxes is com- pleted in 25,000 years; or, more exactly, in 24,992 years. Were the motion of the equinoctial points uniform : that is, did they pass through equal portions of the ecliptic in equal times, they would accomplish their first quarter, or pass through the first three signs of the ecliptic, in 6,250 years. But they are 6,575 years in passing through the first quar- ter; about 218 years less in passing through the second quarter; 218 less in passing through the third, and so on. The immediate consequence of the precession of the equi- noxes, as we have already observed, is a continually pro- gressive increase of longitude in all the heavenly bodies. For the vernal equinox being the initial point of longitude, as well as of right ascension, a retreat of this point on the ecliptic tells upon the longitudes of all alike, whether at rest or in motion, and produces, so far as its amount extends, the appearance of a motion in longitude common to them all, as if the whole heavens had a slow rotation around the poles of the ecliptic in the long period above mentioned, similar to what they have in every twenty-four hours around the poles of the equinoctial. As the Sun loses one day in the year on the stars, by his direct motion in longitude ; so the equi- nox gains one day on them, in 25,000 years, by its retrograde In Otl On. The cause of this motion was unknown, until Newton proved that it was a necessary consequence of the rotation of the Earth, combined with its elliptical figure, and the un- equal attraction of the Sun and Moon on its polar and equa- torial regions. There being more matter about the Earth’s equator than at the poles, the former is more strongly at- tracted than the latter, which causes a slight gyratory or In what time, continuing at the same rate, will they fall back through the twelve signs of the ecliptic." In determining the exact period of a complete revolution of the equinoctial Woints, what important circumstance must be borne in mind Making due allowance for their accelerated progress, in what time is a revolution of the equinoxes completed 2 is this motion as quick in the first quarter of their revolution as in the last? What is the time and difference, of describiug each quarter? What is the immediate consequence of the precession of the equinoxes upon the position of the heavenly bodies 3 Explain how this takes place. How does this resemble the annual loss of a sidereal day by the Sun? What is the cause of this motion? 268 PRECESSION OF THE EQUINOxps, &c. “, wabbling motion of the poles of the Earth around those of the ecliptic, like the pin of a top about its centre of motion, when it spins a little obliquely to the base. 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 centre, keeping constantly at its present distance of nearly 23#3 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 cir- cle. 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 corresponding changes in the apparent diurnal motion of the sphere, and in the aspect which the heaveſis must présent at remote periods of time. ; The effect of such a motion on the aspect of the hea- vens, is seen in the apparent approach of some stars and con- stellations 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 construction of the ear- liest catalogues, this star was 12° from the pole; it is now only 1° 34' from it, and it will approach to within half a degree of it; after which it will again recede, and slowly give place to others, which will succeed it in its proximity to the pole. The pole, as above considered, is to be understood, merely, as the var:- ishing poinſ of the Earth's axis ; or flat point in the concave sphere which is always opposile the terrestrial pole, and which consequently must move as that ulowes. - 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 20diac will appear to sweep the whole circumference of the heavens, in an equinoctial year, a star situated 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 successively, at the least distance from it, when their longitude is 3 signs, or 90°. The posi- *. Admitting this explanation, in what does the procession of the equinoxes really consist? To what point in the heavens will the pole of the Earth be directed, during the revolution ? How must this—affect the diurnal motion and aspect of the heavens, in remote ages" Wherein will the effects of such a motion be particularly visible? Give an instance. When you speak ºf the Pole as in motion, what is to be understood by that term 2 Is the precession of the stars, with respect to the equinoxes, equally apparent in every part of th. heavems? At what longitude do the circumpolar stars approach nearest the pole? PRECESSION OF THE EQUINOXEs, &c. 269 tion of the north polar star in 1836, will be in the 17° of Tau- rus ; when it arrives at the first degree of Cancer, which it will do in about 250 years, it will be at its nearest possible approach to the pole—namely, 29° 55'. . About 2900 years before the commencement of the Christian era, Alpha Dra- conis, the third star in the Dragon’s tail, was in the first de- gree 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 brighest in the northern hemisphere, will occupy the position of a pole star, being then about 5° from º pole ; whereas now its north polar distance is upwards of 51°, The roean average precession from the creation (4004 B. C.) to the year #800, is 49”.51455; consequently the equinoctial points have receded since the creation, 2 s. 1498' 27’’. The longifude of the star Beta Arietis, was, in $830, 31°27′ 28’’: Metam, a famous mathermafician of Athens, who flourished 430 years before Christ, says this star, in his time, was in the vernal equinox. #f he is correct, then 31° 27' 28’’, divided by 2250 years, the elapsed time, will give 50}” for the precession. Something, however, Inust be allowed for the imperfection of the instruments used at that day, and even until the sixteenth century. Since all the stars complete half a revolution about the axis of the ecliptic in about 12,500 years, if the North Star be at its nearest approach to the pole 250 years hence, it will, 12,500 years afterwards, be at its greatest possible distance from it, or about 47° above it :—That is, the star itself will remain immoveable in its present position, but the pole of the Earth will then point as much below the pole of the ecliptic, as now it points above. This will have the effect, apparently, of elevating the present polar star to twice its present altitude, or 47°. Wherefore, at the expiration of half the equinoctial year, that point in the heavens which is now 19 18' north of the zenith of Hartford, will be the place of the north pole, and all those places which are situa- ted 1918' north of Hartford, will then have the present pole of the heavens in their zenith. - OBLIQUITY OF THE ECLIPTIC. The distance between the equinoctial and either tropic, measured on the meridian, is called the Obliquity of the Ecliptic : or, this obliquity may be defined as the angle form- What is the position, at present, of the north polar star, and when will it make its nearest possible approach to the true pole of the heavens 3 At what period has any other star been the polar star? When will the star Lyra, which is more than 50° from it, be the north polar star? What was the mean annual precession from the Crea ion to the year 1800, and how much did it amount to in that period 2. When was Beta Arietis Žn the equinoa;, and what is its longitude now 8 ...When will our present north star be at its least, and when at its greatest distance from the pole? In this case, is it pmeant that the star itself will move, or the pole ln what manner? What, then, must be the ap: parent effect? Illustrate these phenomena by a diagram. What is the obliquity of the ecliptic? 23% 270 OBLIQUITY OF THE ECLIPTIC. ' ed by the intersection of the celestial equator with the eclip- tic. Hitherto, we have considered these great primary circles in the heavens, as never varying their position in space, nor with respect to each other. But it is a retnarkable and well ascertained fact, that both are in a state of constant change. We have seem that the plane of the Earth’s equator. is constantly drawn out of place by the unequal attraction of the Sun and Moon acting in different directions upon the unequal masses of matter at the equator and the poles; whereby the intersection of the equator with the ecliptic is constantly refrograding—thus producing the precession of the equinoves. The displacement of the ecliptic, on the contrary, is pro- duced chiefly by the action of the planets, particularly oſt Jupiter and Venus, on the Earth ; by virtue of which the plane of the Earth’s orbit is drawn nearer to those of these, two planets, and consequently, nearer to the plane of the equinoctial. The tendency of this attraction of the planets, therefore, is to diminish the angle which the plane of the equator makes with that of the ecliptic, bringing the two. planes nearer together; and if the Earth had no motion of rotation, it would, in time, cause the two planes to coincide. But in consequence of the rotary-motion of the Earth, the inclination of these planes to each other remains very nearly the same ; its annual diminution being scarcely more than three fourths of one second of a degree in a year. The obliquity of the ecliptic, at the commencement of the present century, was, according to Boily, 23° 27' 56}'', subject to a yearly diuminution of 0’’.4755. According to Bessel, it was 23° 27' 54".32, with an annual diuri- Ilution of 0’’.46. This dimination, however, is subject to a slight semian- nual variation, from the same causes which produce the displacement of the plane of the ecliptic, in precession. The attraction of the Sun and Moon, also, unites with that of the planets, at certain seasons, to augment the diminution of the obliquity, and at other times, to lessen it. On this account the obliquity itself is subject to a periodical varia- tion; for the attractive power of the Moon, which tends to. produce a change in the obliquity of the ecliptic, is variable, while the diurnal motion of the Earth, which tends to pre- vent the change from taking place, is constant. Hence. the Earth, which is so nicely poised on her centre, bows a In what light have we hitherto considered the great circles of the heavens But what is the fact? . By what cause is the displacemºnt of the equinoctial, or the plane of the Earth's equator, effected? How is the displacement of the plane of the ecliptic effected? If the planetary attraction tends constantly to draw the planes of the equinoctial and ecliptic nearer together, what is to prevent them from coinciding in one and the same plane How much is the distance or angle between them diminished every year? What wgs the ob'iquity of the ecliptic, or the quantity of this angle, at the commencement of the present century? Is the annual diminution of the obliquity subject to any tariation? From what cause 2 What effect has the attraction of the Sun and Moon on this obliquity? *...* OBLIQUITY OF THE ECLIPTIC. 271 little to the influence of the Moon, and rises again, alternate- ly, like the gentle oscillations of a balance. This curious phenomenon, is called Mutaſion. + *- In consequence of the yearly diminution of the obliquity of the ecliptic, the tropics are slowly and steadily approach- ing the equinoctial, at the rate of little more than three fourths of a second every year; so that the Sun does not now come so far north of the equator in summer, nor de- cline so far south in winter, by nearly a degree, as it must Have done at the creation. - - The most obvious effect of this diminution of the obliqui- ty of the ecliptic, is to equalize the length of our days and inights; but it has an effect also to change the position of the stars near the tropics. Those which were formerly situated north of the ecliptic, near the summer solstice, are now found to be still farther north, and farther from the plane of the ecliptic. On the contrary, those which, accord- ing to the testimony of the ancient astronomers, were situ- ated south of the ecliptic, near the summer solstice, have ap- proached this plane, insomuch that some are now either situated within it, or just on the north side of it. Similar changes have taken place with respect to those stars situ- ated near the winter solstice. All the stars, indeed, parti- cipate more or less in this motion, but less, in proportion to their proximity to the equinoctial. It is important, however, to observe, that this diminution will not always continue. A time will arrive when this motion, growing less and less, will at length entirely cease, and the obliquity will, apparently, remain constant for a time; after which it will gradually increase again, and con- tinue to diverge by the same yearly increment as it before had diminished. This alternate decrease and increase will constitute an endless oscillation, comprehended between cer- tain fixed limits. Theory has not yet enabled us to deter- mine precisely what these limits are, but it may be demon- strated from the constitution of our globe, that such limits exist, and that they are very restricted, probably not exceed- ing 2°42'. If we consider the effect of this ever varying attribute in the system of the universe, it may be affirmed What results from this alternate and onnosite influence? . º what token does the Earth show her respect to this influence of the Moon 3 What is this henomenon called? What is the consequence of the yearly diminution of the ol,liquity of the eclinitiº in respect to the position of the tropics, and the declimation of the Sun ? What oth r obvious eflects result from this diminution? How does it affect the declination of the stars near the solstices? Do all the stars partake, more or less in this motion 3 Will this diminution of the obliquity always continue ! What are the limits of its alternate yariation? ...What would be the consequence, in respect to the seasons, should the plane of the ecliptic ever coincide with the plane of the equator - 272 THE TIDES. that the plane of the ecliptic never has coincided with the plane of the equator, and never will coincide with it. Such a coincidence, could it happen, would produce upon the Earth perpetual spring. The method used by astronomers to determine the obli- quity of the ecliptic is, to take half the difference of the greatest and least meridian altitudes of the Sun. The following table exhibits the mean obliquity of the ecliptic for every ten years during the present century. 1800 230 27' 54// .78 1860 23S 27 27// .36 1810 23 27 50 .21 17SO 23 27 22 .79 1820 23 27 45 .64 1SS0 23 27 18 .22 1830 23 27 41 .07 1890 23 27 13 .65 18.10 23 27 36 .50 1900 23 27 9 .08. 1850 23 27 31 .93 1910 23 27 4 .52 C. H. A P T E R XXII. THE TIDES. THE oceans, and all the seas, are observed to be incessant- ly agitated for certain periods of time, first from the east towards the west, and then again from the west towards the east. In this motion, which lasts about six hours, the sea gradually swells; so that entering the mouths of rivers, it drives back the waters towards their source. After a con- tinual flow of six hours, the seas seem to rest for about a quarter of an hour ; they then begin to ebb, or retire back again from west to east for six hours more; and the rivers again resume their natural courses. Then after a seem- ing pause of a quarter of an hour, the seas again begin to flow, as before, and thus alternately. This regular alternate motion of the sea constitutes the tides, of which there are two in something less than twenty-five hours. The ancients considered the ebbing and flowing of the tides as one of the greatest mysteries in nature, and were utterly at a loss to account for them. Galileo and l)eseartes, and particularly Kepler, made some successful advances towards ascertaining the cause ; but Sir Isaac Newton was the first who clearly showed what were the chief agents in producing these motions. The cause of the tides, is the attraction of the Sun and Moon, but chiefly of the Moon, upon the waters of the What is the method used by astronomers for determining the obliquity of the ecliptic? What regular motion is observed in the great body of waters upon the globe.” In what periods of time is this alternate ebbing and flowing accomplished? What is it called? How were these phenomena regarded by the ancients? Who ascertained their true cause 3 What is the cause of the tides? "THE TIDES, 273 ocean. In virtue of gravitation, the Moon, by her attrac- tion, draws, or raises the water towards her; but because the power of attraction diminishes as the squares of the dis- tance increase, the waters on the opposite side of the Earth, are not so much attracted as they are on the side nearest the Moon. • That the Moon, says Sir John Herschel, should, by her attraction, heap up the waſ ers of the ocean under her, seeins to most persons very natural; but that the same cause should, at the same time. heap them up on the oppo- sile side, seeins, to many, palpably absurd. Yet no inting is unore true, nor indeed more evident, when we consider that it is uot by her whole attraction, but by the differences of her attractions at the opposite surfaces and at the centre, that the waſ ers are raised. That the tides are dependent upon some known and determinate laws, is evident from the exact time of high water being previously given in every epheineris, and in many of the cositinou aliuanacks. The Moon coln as every day laſer to the iner idian than on the day preceding, and her exact time is known by calculation; and the tides in any and every place, will be ſound to follow the same rule; happening exactly so lmuch later every day as I he Moon coules later to the ineridian. From this exact conformity to the motions of the Moon, we are induced to look to her as the culse; aid to inter that these pheno.ilena are occasioned principally by the Moon's attraction. g THE TIDES. Fig. 26. fluence from either the Sun or Moon, it is obvious from the principles of gravitation, that the waters in the ocean would be truly spherical; (as represented by Fig. 24;) but daily observation proves that they are in a state of continual agi- tation. If the Earth and Moon were without motion, and the Earth covered all over with water, the attraction of the Moon would raise it up in a heap, in that part of the ocean to which the Moon is vertical, as in Figure 25, and there it would, prob- How does the attraction of the Sun and Moon produce tides upon both sides of the earth at the sºurie time l; it ºf 2s Sir Jºhn iſerscºc.'s result ris tºpoſe this theory & Hoºp is it cºoid it that the tides a “e gºver tº ett hj an iſ as cerſ & ned la 3 & 11 ſtaf cº, inci- d ºce is observel be wee: the pner, dºwn pass... g'e of the Mººn, a 14 the time of /, g/l water 2 IV, at conclusion muty we derine from th’s coincidence 2 if the Earth were at test, and under no influence from the attraction of the Sun or Moon, what shape would the waters assume? Suppose the attractive power of the Moon upon the Earth to be as it is, and neither the Earth or \loop to have any motion, what would be the result? How would this condition of things be affected by the Earth's rotation? 274 THE TIDES. ably, always continue ; but by the rotation of the Earth upon its axis, each part of its surface to which the Moon is vertical is presented to the action of the Moon : wherefore, as the quantity of water on the whole Earth remains the Same, when the waters are elevated on the side of the Earth under the Moon, and on the opposite side also, it is evident they must recede from the intermediate points, and thus the attraction of the Moon produce high water at two opposite places, and low water at two opposite places, on the Earth, at the same time, as represented by Figure 26. This is evident from the figure. The waters cannot rise in one place, without falling in another; and the reſore they must fall as low in the lorizon, at C and D, as they rise in the Zenith and madir, at A and B. Fig. 27. THE TIDES. Fig. 27. A # $/ 2% Nº. It has already been shown, under the article gravitation, that the Earth and Moon would fall towards each other, by the power of their mutual attraction, if there were no centri- fugal force to prevent them ; and that the Moon would ſall as much faster towards the Earth than the Earth would fall towards the Moon, as the quantity of matter in the Earth is greater than the quantity of matter in the Moon. The same law determines also the size of their respective orbits around their common centre of gravity. If follows then, as we have seen, that the Moon does not revolve, strict- ly speaking, around the Earth as a centre, but around a point between them, which is 80 times nearer the Earth than the Moon, and consequently is situ- ated about 3000 miles from the Earth’s centre. It has also been shown, that all bodies moving in circles acquire a centrifugal force proportioned to their respective masses and velocity. From these facts, some philosophers account If the Earth and the Moon mutually attract each other with so much force, what pre- vents their coming together But centrifugal force results only from circular motion, does the Earth then circulate around the M100m to acquire the centrifugal force by which it is kept from falling upon the Moon Ans. The Earth does not circulate around the Moon, but around the common centre of gravity between it and the Mloon. Where is this centre situated, and in what time does the Earth revolve about it? (Ans. The centre of gravity, between the Earth and Moon, is about 3000 miles from the Earth's centre, around which it revolves every lunar month, or as often as the Moon revolves around the Eurth.] From the fact of the Earth's motion, as in the case described, how do some philoso. Thers account for high water on the side of the Earth, opposite to the Moon THE TIDES. 275 « » for high water on the side of the Earth opposite to the Moon, in the following In 2011 GT : As the Earth and Moon move around-their common centre of gravity, that part of the Earth which is at any time turned from the Moon, being about 000 miles farther from the centre of gravity, than the side next the Moon, would have a greater centriſugal force than the side next her. At the Earth's centre, the centrifugal force will balance the attractive force : therefore as much water is thrown off by the centrifugal force on the side which is turned from the Moon, as is raised on the side next her by her attraction. From the universal law, that the force of gravity dimin- ishes as the square of the distance increases, it results, that the attractive power of the Moon decreases in intensity at every step of the descent from the zenith to the nadir ; and consequently that the waters on the zenith, being more at- tracted by the Moon than the Earth is at its centre, move ſaster towards the Moon than the Earth’s centre does: And as the centre of the Earth moves faster towards the Moon than the waters about the nadir do, the waters will be, as it were, left behind, and thus, with respect to the centre, they will be raised. The reason why the Earth and wafers of our globe do not seem to be af. fected equally by the Moon's attraction. is, that the earthy substance of the globe, being firmly unitel, does not yield to any difference of the Moon's at- fractive ſorce; insomuch that its upper and lower surface must move equally fast towards the Moon; whereas the waters, collering together but very light- ly, yield to the different degrees of the Moon's attractive force, at different distances from her. The length of a lunar day, that is, of the interval from one meridian passage of the Moon to another, being, at a mean rate, 24 hours, 48 minutes and 44 seconds, the inter- val between the flux and the reflux of the sea is not, at a mean rate, precisely six hours, but twelve minutes and eleven seconds more, so that the time of high water does not happen at the same hour, but is about 49 minutes later every day. The Earth revolves on its axis in about twenty-four hours; if the Moon, therefore, were stationary, the same part of our globe would return beneath it, and there would be two tides every twenty-four hours; but while the Earth is turning once upon its axis, the Moon has gone forward 13° in her orbit— which takes forty-nine minutes more before the same meri- dian is brought again directly under the Moon. And hence every succeeding day the time of high water will be forty- mine minutes later than the preceding. For example:—Suppose at any place it be high water at 3 o'clock in the afternoon, upon the day of new Moon; the following day it will be high water about 49 uninutes aſter 3; the day after, about 3S uninutes after 4; and so on, How is this phenomenon otherwise explained, by the laws of gravity, merely 7 Are the Earth ind waters of he globe aff-cre ; equal y, by the Mºon's arr ract on 2 ſlºhy not 2 What is the average interval be ween th flux and reflux of the sea? What is the length of a lunar day, and of the interval of the flux and reflux of the sea? How is this daily retardation of the tides accounted for? Give an cample 3 276 THE TIDES. till the next mew Moon. The exact daily mean retardation of the tides is thus determined : w The mean motion of the Moon, in a solar day, is 130. 17639639 The mean inotion of the Sum, in a solar day, in 0 .9S.(; 1722 Now, as 15° is to 60 minutes, so is 129. 1907.4917 to 4S' 44”. It is obvious that the attraction of the Sun must produce upon the waters of the ocean a like effect to that of the Moon, though in a less degree ; for the great mass of the Sun is more than compensated by its immense distance. Nevertheless, its effect is considerable, and it can be shown, that the height of the solar tide is to the height of the lunar tide as 2 to 5. Hence the tides, though constant, are not equal. They are greatest when the Moon is in conjunction with, or in opposition to, the Sun, and least when in quad- rature. For in the former case, the Sun and Moon set to- gether, and the tide will equal the sum of the solar and lunar tides, and in the latter they act against each other, and the tide will be the difference. The former are called Spring Tides; the latter, Neap Tides. The spring tides are highest, when the Sun and Moon are near the equator, and the Moon at her least distance from the Earth. The neap tides are lowest, when the Moon in her first and second quarters is at her greatest distance from the Earth. The general theory of the tides is this: When the Moon is nearest the Earth, her attraction is strong- est, and the tides are the highest ; when she is farthest from the Earth, her attraction is least, and the tides are the lowest. From the above theory, it might be supposed that the tides would be the highest when the Moon was on the meridian. But it is found that in open seas, where the water flows freely, the Moon has generally passed the north or south meridian about three hours, when it is high water. The reason is, that the force by which the Moon raises the tide continues to act, and consequently the waters continue to rise, after she has passed the meridian. - For the same reason, the highest tides, which are pro- duced by the conjunction and opposition of the Sun and Moon, do not happen on the days of the full and change ; neither do the lowest tides happen on the days of their quadratures.—But the greatest spring tides commonly hap- Are the tides uniformly high 2 . When, and on what account do they differ? What are these extreme tides called When are the spring tid: s highest When are the meap titles lowest A Wh'it is the general theory upon this subject 2 Does it necessarily result from this theory, that the tide is highest when the Alqon is on the m-ridium A \º hat reason is assigned for this? YWhat similar fact is accounted for upon the same principle? THE TIDES. 277 pen 14 days after the new and full Moons; and the least meap tides 1; days after the first and third quarters. The Sun and Moon, by reason of the elliptical form of their orbits, are al- ternately nearer to and farther from the Earth. Than their mean distances. In consequence of this, the efficacy of the Sun will fluctuate befween the ex- treules 19 and 21, taking 20 for its unean value, and between 43 and 59 for that of the Moon. Taking into account this cause of difference, the highest spring title will be to the lowest reap as 59–4–21 is to 43–19, or as S0 to 24, or 10 to 3 The relative mean influence is as 51 to 20, or as 5 to 2, nearly.— Iſerschel’s Astr. p. 339. Though the tides, in open seas, are at the highest about three hours after the Moon has passed the meridian, yet the waters in their passage through shoals and channels, and by striking against capes and headlands, are so retarded that, to different places, the tides happen at all distances of the Moon from the meridian ; consequently at all hours of the lunar day. In small collections of water, the Moon acts at the same time on every part ; diminishing the gravity of the whole mass. On this account there are no sensible tides in lakes, they being generally so small that when the Moon is verti- cal, it attracts every part alike ; and by rendering all the waters equally light, no part of them can be raised higher than another. The Mediterranean and Baltic Seas have very small elevations, partly for this reason, and partly be- cause the inlets by which they communicate with the ocean are so narrow, that they cannot, in so short a time, either receive or discharge enough, sensibly to raise or sink their surfaces. Of all the causes of difference in the height of tides at different places, by far the greatest is local situation. In wide-mouthed rivers, opening in the direction of the stream of the tides, and whose channels are growing gradually narrower, the water is accumulated by the contracting banks, until in some instances it rises to the height of 20, 30, and even 50 feet. Air being lighter than water, and the surface of the at- mosphere being nearer to the Moon than the surface of the sea, it cannot be doubted but that the Moon raises much higher tides in the atmosphere than in the sea. According to Sir John IIerschel these tides are, by very delicate ob- servations, rendered not only sensible, but measurable. Upon the supposition that the waters on the surface of the Moon are of What is the comparative fºrce of the solar and Fu mar art raction upon the Earth 2 To what is owing the great difference in the time of high water at places lying under the same me ilium Why are there o tides upon likes, and s mºll collections of water? To what cause, more than to all oth ‘rs. is the different h >igh of tides owing 3 Explain this. Is it probable that time Mijon exerts any influence of attraction on the atmosphere? Why is it probable? gi" the atmospheric tides sufficiently sensible to be appreciated? 278 THE SEASONS. the same specific gravity as our own, we might easily determine the height to which the Earth would raise a lunar tide, by the known principle, that the attraction of one of these bodies on the other’s surface is directly as its quantity of matter, and inversely as its (liaiſleter. By unaking the calculation, we shall find the attractive power of the Earth upon the Moon to be 21.777 times greater than that of the Moon upon the Earth. C H A P T E R X. X. III. “THE SEASONS-DIFFERENT LENGTHS OF THE DAYS AND NIGHTS. The vicissitudes of the seasons and the unequal lengths of the days and mights, are occasioned by the annual revo- lution 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 surface depends mainly, if not entirely, upon its exposure to the Sun’s rays. 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 quantities of heat thus received and imparted in the course of the year, must balance each other at every place, or the equilibrium of temperature would not be supported. Whenever, then, the Sun remains more than twelve hours above the horizon of any place, and less beneath, the gen- eral temperature of that place will be above the mean state; when the reverse takes place, the temperature, 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 declimation, or altitude at noon. About the 20th of March, when the Sun is in the vernal equinox, and con- sequently has no declination, he rises at six in the morning and sets at six in the evening; the day and might 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 hemis- phere the temperature increases, and we pass from spring to mid-summer ; while the reverse of this takes place in the How much greater is the attractive power ºf the Earth upon the Mot m, than that ºf the A10on ºrpon the E . , th 2, Whut occasiºns the vicissitudes of the seasons, and the un- equal lengths of the lays and nights? Upon what does the feuij-erature at different places depend ? Under what circumstances do the same places change their tem; eruttire Aro the quantities of heat, received aud impa ted, every year, always equal at the stume places ! Why is it so hen is the tempt ratitre of a duct: a b ºr, and when is it beivto its mean state Upon what does the continuance of the un alkºve th: horizon of any place, de- pend ? When is the Sun as long above our horizon as below it? During what settson of the year is the temperature increasing? THE SEASONS. 279 soutnern hemisphere. From the 21st of June to the 23d of September, the days and nights again approach to equality, and the excess of temperature in the northern hemisphere above the 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. 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 inhabitants of the southern hemisphere from spring to mid-summer. From the 21st of December to the 20th of March, the cold relaxes as the days grow longer, and we pass from the dreariness of winter to the mildness of spring, when the seasons are com- pleted, 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. 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 experience the rigours of our winter; since it can be demonstrated, that as much heat falls upon the same area from a vertical Sun in 8 hours, as would fall from him, at an angle of 60°, in 16 hours. Now as the Sun’s rays fall most obliquely when the days are shortest, 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 dif- ferent seasons. The reason why we have not the hottest temperature when the days are longest, and the cold- est 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 grad- ually, 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. What, at the same time, takes place in regard to the temperature, in the southern hemisphere? . During what portion of the year is the temperature decreasing? For what reason 3 During what portion of the yeur is the cold increasing Why is it so What change of seasons, then, takes place, in the northern and soutfiern hemisphere 2 What other changes complete the seasons of the year? Whence is it evident that the unequal lengths of the days and nights are not the only, nor perhaps the most efficient cause of the heat of summer, and the cold of winter?, What two causes produce the greatest vicissitudes of heat and cold Why, then, do we not have the hottest weather when the days are longest, and the contrary . - 280 THE SEASONS. IBEGINNING AND LENGTH OF THE SEASONS. h. m. s. Sun enters V3 ſº begins) 1833, Dec 21st, 72546 M. T. Wash. “ ºr (Spring “ ) 1834, March 20,856 38 “ & 3 “ “ 5-c (Summer “ “ June 21st,6 3 9 “ { { “ “ Hº (Autumn “ “ Sept 22d, 1958.21 “ { % “ “ VS (Winter “ j “ Dec. 21, 1321 57 “ { { * d. h. m. s. Sun in the Winter Signs . º * e 80 l 30 52 * “ Spring e tº & te 92 2] G 31 “ “ Stauliner § g & t 93 13 55 22 * “ Aututnin . S9 17 23 26 * north of Equator (spring and Summer) 13 6 l l l 53 “south * { (Winter and Autulum) i.78 18 54 18 I,0ngest north of the equator, g g 7 16 7 35 Length of the tropical year, beginning at the winter solstice 1833, and ending at 365 5 56 | 1 the winter solstice 1834, Mean or average length of the tropical year, 365 5 4S 48 The north pole of the Earth is denominated the elevated pole, because it is always about 234° above a perpendicular to the plane of the equator, and the south pole is denomina- ted the depressed pole, because it is about the same distance below such perpendicular. As the Sun cannot shine on more than one half the Earth’s surface at a time, it is plain, that when the Earth is moving through that portion of its orbit which lies above the Sun, the elevated pole is in the dark. This requires six months, that is, until the Earth arrives at the equinox, when the elevated pole emerges into the light, and the depressed pole is turned away from the Sun for the same period. Consequently, there are six months day and six months night, alternately, at the poles. - When the Sun appears to us to be in one part of the eclip- tic, the Earth, as seen from the Sun, appears in the point di- ametrically opposite. Thus, when the Sun appears in the vernal equinox at the first point of Aries, the Earth is actu- ally in the opposite equinox at Libra. The days and nights are then equal all over the world. - As the Sun appears to move up from the vernal equinox to the summer solstice, the Earth actually moves from the autumnal equinox down to the winter solstice. The days now lengthen in the northern hemisphere, and shorten in the southern. The Sun is now over the north pole, where it is mid-day, and opposite the south pole, where it is mid-night. Why is the north mole denominated the elevated pole? Why is the south pole denomi- nated the depressed pole? Why are there six months day and six month night, alternately, at the poles What is always the relative position of the Sun and lºarth in the ecliptic? Give an example. When do the days lengthen in the northern hemisphere, and shorten in the southern? When is it mid-day at the north pole, and mid-night at the south? THE SEASONS. 281 As the Sun descends from the summer solstice towards the autumnal equinox, the Earth ascends from the winter solstice towards the vernal equinox. The summer days in the northern hemisphere having waxed shorter and shorter, now become again of equal length in both hemispheres. While the Sun appears to move from the autumnal equi- nox down to the winter solstice, the Earth passes up from the vernal equinox to the summer solstice ; the south pole comes into the light, the winter days continually shorten in the northern hemisphere, and the summer days as regularly increase in length in the southern hemisphere. While the Sun appears again to ascend from its winter solstice to the vernal equinox, the Earth descends from the summer solstice to the autumnal equinox. The summer days now shorten in the southern hemisphere, and the win- ter days lengthen in the northern hemisphere. When the Sun passes the vernal equinox, it rises to the arctic or elevated pole, and sets to the antarctic pole. When the Sun arrives at the summer solstice, it is noon at the north pole, and midnight at the south pole. When the Sun passes the autumnal equinox, it sets to the north pole, and rises to the south pole. When the Sun arrives at the win- ter solstice, it is midnight at the north pole, and noon at the south pole ; and when the Sun comes again to the vernal equinox, it closes the day at the south pole, and lights up the morning at the north pole. There would, therefore, be 1864 days during which the Sun would not set at the north pole, and an equal time du- ring which he would not rise at the south pole; and 178% days in which he would not set at the south pole, nor rise at the north pole. At the arctic circle, 23° 27.4% from the pole, the longest day is 24 hours, and goes on increasing as you approach the pole. In latitude 67° 18' it is 30 days; in lat. 69° 30' it is 60 days, &c. (See Table XII.) The same takes place be- tween the antarctic circle and the south pole, with the ex- ception, that the day in the same latitude south is a little shorter, since the Sun is not so long south of the equator, as at the north of it. In this estimate no account is taken of the refraction of the atmosphere, which, as we shall When do the summer days in the northern hemisphere grow shorter and shorter? When do they become of equal length in both hemispheres? When do the winter days shorten in the northern hemisphere, and the summer days lengthen in the southern When do the summer days shorten in the southern hemisphere, and the winter days lengthen in the northern ? When does the sun rise to the north pole, and set to the south When is it noon at the north pole, and mid-night at the south pole? When does the Sun set at the north pole, and rise to the south? When is it midnight at the north pole, and noon at the south 3...What is the length of the day at the north pole? What at the south pole? At the arctic circle Between the antarctic circle and the pole? - * 283 THE SEASONS. see hereafter, increases the length of the day, by making the Sun appear more elevated above the horizon than it real- ly is. THIE SEASONS-UNEQUAL LENGTHS OF DAYS AND NIGHTS. Fig. 28. § § The above cut represents the inclination of the Earth's axis to its orbit in every oue of the twelve signs of the ecliptic, and consequently for each month in the year. The Sun enters the sign Aries, or the vernal equinox, on the 201 h of March. when the Earth's axis inclines neither towards the Sun, nor from it, but sideways to it; so that the Sun then shines cqually upon the Earth from pole to pole, and the days and nights are every where equal, This is the beginning of the astronomical year; it is also the beginning of day at the north pole, which is just coming into light, and the end of day at the south pole, which is just going into darkness. By the Earth's orbitual progress, the Sun appears to enter the second sign, Taurus, on the 20th of April, when the north pole, N. has sensibly advanced into the light, while the south pole, S. has been declining from it; whereby the days become longer than the mights in the Northern Hemisphere, and shorter in the Southern. On the 21st of May, the Sun appears to enter the sign Gemini, when the north pole, N. has advanced considerably further into the light, while the south pole, S. has proportionally declined from it ; the summer days are now waxing longer in the Northern Hemisphere, and the nights shorter. The 21st of June, when the Sun enters the sign Cancer. is the first day of summer, in the astronomical year, and the longest day in the Northern Hemis- here. The north pole now has its greatest inclination to the Sun, the ight of which as is shown by the boundary of light and darkness, in the figure, extends to the uſ most verge of the Arctic Circle; the whole of which is included in the enlightened hemisphere of the Earth, and enjºys, at this season constant day during the complete revolution of the Earth on its axis. The whole of the Northeru Frigid Zone is now in the circle of perpetual illu- minalion. 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 nearer to the poles, and the length of the day, MARVEST MOON. 283 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 Septeuber, the Suu enters Libra, the first of the autumnal signs, when the Earth’s axis, llaving the saune inclitiation as it had in the op- osité sigu. Aries, is turned neither from the Sun. inor towards it, but oblique- y to it, so that the Sun again now shines equally upon the whole of the Earth's suriace from pole to pole. The days and niglits are once inore of equal length throughout the wol lºt. - On the 23rl of ()ctober, the Sun enters the sign Scorpio ; the days visibly decrease in length in the Northern Heulisphere, and increase in the South- © 1 (1. On the 22d of November, the Sun enters the sign Sagittarius, the last of the autuurial signs, at which time the boundary of light and darkness is at a considerable distance from the north pole, while the soutli pole has pro- portionally advanced into the light : the length of the day continues to increase in the Southern Heiriispliere, and to lecrease in the Norther n. On the 21st of Deceuiber, which is the period of the winter solstice, the Sun enters the sign Capricorn. At this tune, 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 illumination. It is now that the Southern Heurlispliere enjoys all those advantages with which the Northern Hemisphere was favoured on the 21st of June; while the Northern Heulis- # in its turn, undergoes the dreariness of winter, with short days and long nights. C H A P T E R X X I V. HARVEST MOON.—HORIZON TAL MOON. The daily progress of the Moon in her orbit, from west to 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 takes place, especially about the time of harvest, when the full Moon rises to us for several nights together, only from 18 to 25 minutes later in one day, than on that immediately preceding. From the benefit which her light affords, in lengthening out the day, when the hus- bandmen are gathering in the fruits of the Earth, the full moon, under these circumstances, has acquired the name of Harvest Moon. , It is believed that this fact was observed by persons engaged in agriculture, at a ultic li earlier period than that in which it was noticed by astronouners. The fortner ascribed it to the goodness of the Deity; not doubting but that he had so ordered it for their advantage. About the equator, the Moon rises throughout the year with nearly the equal intervals of 48# minutes; and there the harvest moon is unknown. "What is the mean difference of time in the daily rising of the Moon? Under what cir- ;"; RS ; & º; ; º * Whence the nume of Harvest goriº. By whorº was this phenomenon first observed, and to wha: did they attributg tt? Why is the Harvest Moon unknown at the equator; 284 HARWEST MOON. At the polar circles, the autumnal full Moon, from her first to her third quarter, rises as the Sun sets; and at the poles, where the Sun is absent during one half of the year, the winter full Moons, from the first to the third quarter, shine constantly without setting. By this, it is not meant that the Moon continues full from her first to her third quarter; but that she never sets to the North Polar regions, when, at this season of the year, she is within 90° of that point in her orbit where she is at her ſull. In other words: as the Sun illuupines the south pole during one half of its yearly revolution, so the Moon, being opposite to the Sun at her ſull, Imust illumine the opposite pole, during half of her revolution about the Earth. The phenomenon of the harvest Moon Inay be thus exem- plified by means of the giobc : - - Rectify the globe to the latitude of the place, put a patch or piece of wa- fer in the ecliptic, on the point Aries, and mark every 129 preceding and ſollowing that point, to the number of ten or twelve Inarks on each side of it; bring the equinoctial point marked by the waſer 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 horizon, and observe the hours passed over by the index; the intervals of time between the marks couning to the horizon, will show the diurnal difference of time between the Moon's rising. If these marks be brought to the western edge of the horizon in the same manner, it will show the diurnal difference between the Moon's setting. From this problem it will also appear, that, when there is the least difference between the times of the Moon's rising, there will be the greatest difference between the times of her setting, and the contrary. The reason why you mark every 129 is, that the Moon gains 120 11’ on the apparent course of the Sun every day, and these marks serve to denote the place of the Moon from day to day. It is true, this process sup- poses that the Moon revolves in the plane of the ecliptic, which is not the case; yet her orbit so nearly coincides with the ecliptic, (differing only 5°9′ from it,) that they may, for the convenience of iſlustration, be consid- ered as coinciding ; that is, we may take the ecliptic for the representative of the Moon’s orbit. 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 Moon's orbit lying sometimes more oblique to the horizon than at others. In the latitude of London, for ex- ample, as much of the ecliptic rises about Pisces and Aries in two hours as the Moon goes through in six days; there- fore while the Moom is in these signs, she differs but two hours in rising for six days together; that is, one day with another, she rises about 20 minutes later every day than on the preceding. The parts or signs of the ecliptic which rise with the smallest angles, set with the greatest , and those which rise with the greatest, set with the least. And whenever this angle is least, a greater portion of the ecliptic rises in equal times than when the angle is larger. Therefore, when the How is it at the polar circles, and the poles 3 What is meant by the full Moon's shining from the first to the third quarter 2 How may the phenomenon be eaempli- Jied by means of the artificial g/obe & Why do you mark every 12° of the ecliptic in this problem 2 What does this process of illustration suppose, which is not true, and why is it adopted? To what is the different lengths of the lunar might, in different latitudes, owing 3 Give an example. . How do those parts of the ecliptic set, which rise yith the smallest angles, and the contrary 1 & MARVEST MOON, 285. Moon is in those signs which rise or set with the smallest angles, she rises or sets with the least difference of time; but when she is in those signs which rise or set with the greatest angles, she rises or sets with the greatest differ- enee of time. Let the globe, for example, be rectified to the latitude of New York, 40°42' 40", with Cancer on the meridian, and Libra rising in the east. In this position, the ecliptic lias a luigh elevation, 111aking an augle with the ho- rizon of 72}9. But let the globe he turned half round on its axis, till Capricorn comes to the ineridian, and Aries rises in the east. 1 hen the et:Hiptic will have a low elevation above the liquizoli, Inaking an angle with it of only 25%9. This angle is 47° less than the for iller angle, and is equal to the distance between the tropics. In northern latitudes, the smallest angle made by the ecliptic and horizon, is when Aries rises; at which time Libra sets; the greatest is, when Libra rises and Aries sets. The ecliptic rises fastest about Aries, and slowest about Libra. Though Pisces and Aries make an angle of only 25+9 with the horizon when they rise, to those who live in the latitude of New York, yet the same signs, when they set, make an angle of 72.4°. 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 opposite signs, Virgo and Libra, the daily difference of her rising is al- most four times as great, being about one hour and a quarter. - 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 lise, for a week togeth- er, very near the time of sun-set.—The former of these is called the Harvest Moon, and the latter, the Hunter’s Moon. Although there can be but two full Moons in the year that rise with so little variation of time, yet the phenomenon of the Moon’s rising for a week together so nearly at the same time, occurs every month, in some part of her course or the other. In Winter, the signs Pisces and Aries rise about noon ; hence the rising of the Moo.1 is not then regarded hor perceived. In Spring, these signs rise with the S : n, because he is then in them ; and as the Moon changes while passing through the salue sign with the Sun, it must then be the change, and hence invisible, What results from this in regard to the Moon IIow may this be illustrated on the globe & In nurthern littitudes, what signs rise and set with the least angles What with the greates!! What parts Qi ſhe ecliptic rise fastest, and which slowest A. Give an ex- ample. What is the daily difference of the Moon's rising and setting, in these signs, in the latitude of New York? How many full Moous in a year, which rise with so little dif: erence of time? Why are not these phenomena observed in the same signs, in Win- ter, Spring, and Summer ? 2S6 HORIZONTAL MOON. In Summer, they rise about midnight, when the Moon is in her third quar- ter. On account of her rising so late, and giving but little light, her rising passes unobserved. To the inhabitants at the equator, the north and south poles appear in the horizon; and therefore the ecliptic makes the same angle southward with the horizon when Aries rises, as it does northward when Libra rises; consequently the Moon rises and sets not only with angles nearly equal, but at equal intervals of time, all the year round: Hence, there is no harvest Moon at the equator. The farther any place is from the equator, if it be not beyond the polar circles, the angle which the ecliptic makes with the horizon gradually diminishes when Pisces and Aries rise. Although in northern latitudes, the autumnal full Moons are in Pisces, and Aries; yet in southern latitudes it is just the reverse, because the seasons are so:—for Virgo and Libra rise at as small angles with the horizon in southern latitudes, as Pisces and Aries do in the northern ; and there- fore the harvest Moons are just as regular on one side of the equator as on the other. At the polar circles, the full Moon neither rises in summer, nor sets in winter. For the winter full Moon being as high in the ecliptic as the summer Sun, she must continue, while passing through the northern signs, above the horizon ; and the summer full Moon being as low in the ecliptic as the winter Sun, can no more rise, when passing through the southern signs, than he does. THE HORIZONTAL Moon.--The great apparent magnitude of the Moon, and indeed of the Sun, at rising and setting, is a phenomenon which has greatly embarrassed almost all who have endeavoured to account for it. According to the ordinary laws of vision, they should appear to be least when nearest the liorizon, being then farthest from the eye; and yet the reverse of this is found to be true. The apparent diameter of the Moon, when viewed in the horizon by the naked eye, is two or three times larger than when at the altitude of thirty or forty degrees; and yet when measured by an instrument her diameter is not increased at all. Both the Sun and the Moon subtend a greater angle when on the meridi. an, than they do in the horizon, because they are then actually nearer the place of the spectator, by the whole semi-diameter of the Earth. Explain why there is no Harvest Moon at the equator. The farthor any place is from the equator, how is the angle lyetween the celiptic and the horizon, when Pisces and Aries rise? Do the Harvest Moons happen as regularly, and in the same months, on the south side of the cquator, as on the north & Why does not the ſull Moon rise in summer, nor set in winter, to the inliabitants of the polar circles? According to the ordinary laws of vision, how ought the magnitudes of the Sun and Moon to appear, when they are near- est the horizon 2 What is the fact? How much larger does the Moon appear to the naked eye, when in the horizon, than when at the altitude of thirty, or forty degrees? Where, in reality, do the Swn and Moom subtend the largest angle 2 ""hy is it 80? REFRACTION: 287 This apparent luclease of magnitude in the horizontal Moon, is chiefly an optical illusion, produced by the concav- ity of the heavens appearing to the eye to be a less portion of a spherical surface than a hemisphere. The eye is ac- customed to estimate the distance between any two objects in the heavens by the quantity of sky that appears to lie be- tween them; as upon the Earth we estimate it by the quan- tity of ground that lies between them. Now when the Sun or Moon is just emerging above the eastern horizon, or sinking beneath the western, the distance of the intervening landscape over which they are seen, contributes, together with the refraction of the atmosphere, to exaggerate our estimate of their real magnitudes. C H A P T E R X. X. V. REFRACTION.—TWILIGHT. The rays of light in passing out of one medium into ano- ther of a different density, deviate from a straight course ; and if the density of the latter medium continually increase, the rays of light in passing through it, will deviate more and more from a right line towards a curve, in passing to the eye of an observer. From this cause all the heavenly bodies, except when in the zenith, appear higher than they really are. This bending of the rays of light, giving to the heaven- ly bodies an apparent elevation above their true places, is called Refraction. It is in consequence of the refracting power of the atmos- phere that all heavenly bodies are seen for a short time be- Jore they rise in the horizon, and also after they have sunk below it. At some periods of the year the Sun appears 5 minutes longer, morning and evening, and about 34 minutes longer every day, at a mean rate, than he would do were there no refraction. The average amount of refraction for an object half way between the horizon and the zenith, or at an apparent altitude of 45°, ºs but one sixtieth of a degree, a quantity hardly sensible to the naked eye; but at the visi- ble horizon it amounts to 33% of a degree, which is rather How is the apparent, increase of magnitude in the horizontal Moon, accounted for a How are the rays of light aſtected in passing out of one medium into another, of a differ- ent density ? How, if the density of the laſter medium continually increase ? What as- tronomical phenomenon results from this cause? What is this bending of the rays of light out of their course called? What effect does refract on have upon the apparent rising and setti g of the heavenly hotlies low much longer do we see the Sun, morning and ºvening, than we should, if there were no refraction What is the average amouni of refraction for an object half way between the horizon and the zenith? What is it at the horizon A 288 REFRACTION. more than the greatest apparent diameter of either the Sun or the Moon. Hence it follows, that when we see the lower edge of the Sun or Moon just apparently resting on the borizon, their whole disc is in reality below it, and would be entirely out of sight and concealed by the convexity of the Earth, but for the bending, which the rays of light have undergone in their passage through the air to the observer’s eye. The following general notions of its amount, and law of variations, should be borne in mind : - 1. In the zenith there is no refraction ; a celestial object, situated directly over head, is seen in its true position, as if there were no atmosphere. q 2. In descending from the zenith to the horizon, the refrac- tion continually increases; objects near the horizon appear- ing more elevated by it than those of a higher altitude. 3. The rate of its increase is nearly in proportion to the apparent angular distance of the object from the zenith. But this rule, which is not far from the truth, at moderate zenith distances, ceases to give correct results in the vicinity of the horizon, where the law becomes much more compli- cated in its expression. The effects of reſraction Inust be familiar to every person who has seen a walking stick partially plunged into a liver, or other collection of water. While the stick is held upright, if appears straight, as usual, because there is no reſraction in this position ; but if it be ever so little inclined, the re- fraction takes place, and the stick appears bent; if the inclination be in- creased, the reſraction is also increased. Another easy and ſamiliar illustration of the effect of refraction may be thus obtained :-Put any simall object, as a piece of money, into an empty basin, as near the centre as possible, and retire to such a distance as just to lose sight of the object. Let an assistant then pour water in ſhe basin, and the object will soon appear. Retire again till it is no longer seen ; let more water be added, and it will again appear. . The experiment may be re- peated till the basin is ſull. The edge of the basin inay be supposed to represent the horizon ; ſhe wa'er, the attnosphere; and ſhe piece of unoney, the Sun, or other object wi.ich is thus made to appear by the power of re- fraction, when otherwise it would be tuvisible. It follows from this, that one obvious eſfect of refraction must be to shorten the duration of night and darkness, by prolonging the apparent stay of the Sun and Moon above the horizon. But even after they appear to have set, the in- fluence of the atmosphere still continues to send us a portion of their light; not, indeed, by direct transmission, but by reflection :-for as long as the Sun continues to illuminate What interesting facts result from this truth? What is the first general law of atmos- pheric refraction What is the second general law What is ſhe third Mention 4 familiar instance of rejº action often set m in water. Mięte ion some fºr "gº cºpéri- 7tent, to il ustrate reſ’ ticº on, (tºd shºw pts (j p ico', (ºn 10, tº stºry n tº {’. How doos this principle affici the duration'of nocinnafºkiess, By whilſt principle is it that the atmosphere sends us a portion of the solar light, for a considerable tule before the Sun rises, and after it has set? REFRACTION. 285 any portion of the aculosphere which is above the horizon, the light from this portion is reflected to the Earth, and it is this that causes twilight. In the morning, when the Sun arrives at 18° below the horizon, his rays pass over our heads into the higher region of the atmosphere, and are thence reflected, or as it were, bent down to the Earth. The day is then said to dawn, and the light gradually increases until the Sun appears above the horizon : this is called Morning Twilight, or Aurora, which the heathens personified as a goddess. They assigned to her the office of opening the Gates of the East, to intro- duce the chariot of Apollo or Phatbus. In the evening, after sunset, the rays of the Sun continue to illuminate the atmosphere, till he sinks 18° below the horizon, and a similar effect, called the Evening Twilight; is produced, only in an inverse progression, for the twilight now gradually becomes fainter till it is lost in dark night. The quantity of reflection and the duration of twilight are much influenced by the changes which are perpetually tak- ing place with respect to the heat and cold, the dryness of moisture, &c. of the atmosphere. The height of the atmos- phere, also, has an influence in determining the duration of twilight: Thus in winter, when the air is condensed with cold, and the atmosphere upon that account lower, the twi- light will be shorter; and in summer, when the limits of the atmosphere are extended by the rarefaction and dilation of the air of which it consists, the duration of the twilight will be longer. And for the same reason, the morning twilight, (the air being at that time condensed and contracted by the cold of the preceding night,) will be shorter than the even- ing twilight, when the air is more dilated and expanded. It is entirely owing to the reflecting power of the atmos- phere that the heavens appear bright in the day time. For without such a power, only that part of the heavens would be luminous in which the Sun is placed ; and, if we should turn our backs to the Sun, the whole heavens would appear as dark as in the night, and the stars, even at noon day, would be seen as clear as in the nocturnal sky. In regions of the Earth situated towards the poles, the Sun, during their summer months, is never more than 18° below the horizon ; consequently their twilight continues , What is Twilight 2. How is it occasioned? How is the Evening Twilight produced? By what are the quantity of reflection, and the duration of twilight, considerably influ- emced , Why, is twilight shorter in winter? Why longer in summer? Why is the morn- ing twilight shorer than the evening twilight? To what is it entirely owing, that the heavens appear bright in the day time? How would the heavens appear, if it were not for this power? What are the duration and advantages of twilight in high latitudes? 290 AURORA. BOREALIS. during the whole night. . The same cause has a tendency to diminish the gloom of the long polar mights; for as far north as in lat. 84° 324 the Sun even when at the winter solstice approaches to within 18° of the horizon, and affords a short twilight once in 24 hours, and the pole itself is left in total darkness not more than 80 days. There is still another cause which has a tendency to di- minish the length of the polar mights, the extraordinary refraction occasioned by the extreme density of the air in those regions. This is so great, as to bring the Sun above the horizon some days before it should appear, according to calculation. A remarkable phenomenon of this kind was observed by the Dutch navi. gators who wintered in Nova Zembla, in the year 1596. After enduring a continual night of three months, they were agreeably surprised to find that the Sun began to rise seventeen days sooner than according to computation The observed altitude of the pole, at the place, (says Dr. Smith,) being only 76°, it is impossible to account for the phenomenon, otherwise, than by sup- posing an extraordinary refraction of the Sun’s rays. Kepler computes that the Sun was almost 5° below the horizon when he first appeared ; and con- jºy, that the refraction of his rays was about 10 times greater than With uS, C H A P T E R X. X W I. . . . . . "ex" - AUROR A BOREALIS, . The sublime and beautiful phenomena presented by the Aurora Borealis, or Northern Lights, as they are called, have been in all ages a source of admiration and wonder alike to the peasant and the philosopher. In the regions of the north, they are regarded by the ignorant with supersti- tious dread, as harbingers of evil; while all agree in placing them among the unexplained wonders of nature. These lights, or meteoric coruscations, are more brilliant in the arctic regions, appearing mostly in the winter season and in frosty weather. They commonly appear at twilight near the horizon, and sometimes continue in that state for several hours without any sensible motion; after which they send forth streams of stronger light, shooting with great velocity up to the zenith, emulating, not unfrequently, the lightning in vividness, and the rainbow in colouring; and again, silently rising in a compact majestic arch of steady Relate a remarkable phenomenon of this kind. How are the phenomena of the Au- rora, Borealis regarded by the ignorant? In what do all agree, respecting them? Where are these appearances most frequent and brilliant? Describe the times and manner of their appearance. - AURORA BOREALIS. 291 white light, apparently durable and immoveable, and yet so evanescent, that while the beholder looks upon it, it is gone. At other times, they cover the whole hemisphere with their flickering and fantastic coruscations. On these oc- casions their motions are amazingly quick, and they aston- ish the spectator with rapid changes of form. They break out in places where none were seen before, skimming brisk- ly along the heavens; then they are suddenly extinguished, leaving behind a uniform dusky track, which, again, is bril- liantly illuminated in the same manner, and as suddenly left a dull blank. Some mights they assume the appearance of vast columns; exhibiting on one side tints of the deepest yellow, and on the other, melting away till they become un- distinguishable from the surrounding sky. They have gen- erally a strong tremulous motion from end to end, which continues till the whole vanishes. Maupertuis relates, that in Lapland, “the sky was some- times tinged with so deep a red that the constellation Orion looked as though it were dipped in blood, and that the peo- ple fancied they saw armies engaged, fiery chariots, and a thousand prodigies.” Gmelin relates, that, “in Siberia, on the confines of the icy sea, the spectral forms appear like rushing armies; and that the hissing crackling noises of those aerial fire-works so terrify the dogs and the hunters, that they fall prostrate on the ground, and will not move while the raging host is passing.” Iſerguelen describes “the night, between Iceland and the Ferro Islands, as brilliant as the day,”—the heavens being on fire with flames of red and white light, changing to col- umns and arches, and at length confounded in a brilliant chaos of comes, pyramids, radii, sheaves, arrows, and globes of fire. - But the evidence of Capt. Parry is of more value tha that of the earlier travellers, as he examined the pheno- mena under the most favourable circumstances, during a period of twenty-seven consecutive months, and because his observations are uninfluenced by imagination. He speaks of the shifting figures, the spires and pyramids, the majestic arches, and the sparkling bands and stars which appeared within the arctic circle, as surpassing his powers of descrip- tion. They are indeed sufficient to enlist the superstitious feelings of any people not fortified by religion and philosophy. . Describe their appearance in Lapland as related by Maupertuis, and its effect upon the inhabitants. Describe its appearance between Iceland and the Ferro Islands, as related b Kerguelen. Whose testimony, on this subject is of more value than that of former travel- lers? Why? How does he describe the scomes he witnessed during the polar nights 292 AURORA BOREALIS. The colours of the polar lights, are of various tints. The Tays or beams are steel gray, yellowish gray, pea green, celandine green, gold yellow, violet blue, purple, sometimes rose red, crimson red, blood red, greenish red, orange red, and lake red. The arches are sometimes nearly black, pass- ing into violet blue, gray, gold yellow, or white bounded by an edge of yellow. The lustre of these lights varies in kind as well as intensity. Sometimes it is pearly, some- times imperfectly vitreous, sometimes metallic. Its degree of intensity varies from a very ſaint radiance to a light near- ly equalling that of the Moon. 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 vapours ascending from the Earth into the polar atmosphere, and there ignited by electricity. Dr. Halley objects to this hypothesis, that the cause was in- adequate to produce the effect. He was of opinion that the poles of the Earth were in some way connected with the au- rora; that the Earth was hollow, having within it a mag- netic sphere, and that the magnetic effluvia, in passing from the north to the south, might become visible in the northern hemisphere. - . That the aurora borealis is, to some extent, a magnetical phenomenon, is thought, even by others, to be pretty clearly established by the following considerations. 1. It has been observed, that when the aurora appears near the northern horizon in the form of an arch, the middle of it is not in the direction of the true north, but in that of the magnetic needle at the place of observation; and that when the arch rises towards the zenith, it constantly crosses the heavens at right angles, not to the true magnetic meri- dian. 2. When the beams of the aurora shoot up so as to pass the zenith, which is sometimes the case, the point of their convergence is in the direction of the prolongation of the dipping needle at the place of observation. 3. It has also been observed, that during the appearance of an active and brilliant aurora, the magnetic needle of ten becomes restless, varies sometimes several degrees, and does not resume its former position until after several hours. From these facts, it has been generally inferred that the Describe the colours of the Aurora light. What is one of the earliest theories advanced to explain this phenomenon? How did Dr. Halley propose to account for it? What ob- servations have led pretty generally to the conclusion, º: the northern lights are to some extent a magmotical pheiomenon? & PATRALLAX OF THE HEAVENLY BODIES. 293 aurora is in some way connected with the magnetism of the Earth ; and that the simultaneous appearance of the meteor, and the disturbance of the needle, are either rela- ted as cause and effect, or as the common result of some more general and unknown cause. Dr. Young, in his lec- tures, is very certain that the phenomenon in question is in- timately connected with electro-magnetism, and ascribes the light of the aurora to the illuminated agency of electri- city 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 imagnetism may be induced by electricity, and the electric spark has been drawn from the lmagnet. Sir John Herschel also attributes the appearance of the aurora to the agency of electricity. This wonderful agent, says he, which we see in intense activity in lightning, and in a feebler and more diffused form traversing the upper regions of the atmosphere in the northern lights, is present, probably, in immense abundance in every form of matter which surrounds us, but becomes sensible, only when dis- turbed by excitements of peculiar kinds. C H A P T E R X. X W II. PARALLAX OF THE HEAVEN LY BODIES. Parallax is the difference between the altitude of any celestial object, seen from the Earth’s surface, and the alti- tude of the same object, seen at the same time from the Earth’s centre; or, it is the angle under which the semi- diameter of the Earth would appear, as seen from the object. The true place of a celestial body, is that point of the heavens in which it would be seen by an eye placed at the centre of the Earth. The apparent place is that point of the heavens where the body is seen from the surface of the Earth. The parallax of a heavenly body is greatest, when in the horizon; and is called the horizontal parallaw. Parallax decreases, as the body ascends toward the zenith, at which place it is nothing. The nearer a heavenly body is to the Earth, the greater What is the opinion of Dr. Young in regard to their cause What consideration 'mgy be adduced in Jarther support of the electro-magnetic theory? To what does Sir John Herschel ascribe the aurora! What are his observations upon the s. bject? What 1S Jºlinx: What is the true place of a celestial body What is the apparent place? Where is the parallax of †avenly body the groatest ? What is this parallax called? ot 294 PARALLAX OF THE HEAVENLY BODIE3. is its parallax ; hence the Moon has the greatest parallax of all the heavenly bodies, while the fixed stars, from their immense distance, have no parallax ;* the semi-diameter of the Earth, at such a distance, being no more than a point. As the effect of parallax on a heavenly body, is to depress it below its true place, it must necessarily affect its right ascension 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 al- ways 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 substracts the refraction, to and from the Sun's observed altitude, in order to obtain the true altitude, and thence the latitude. - The principles of parallax are of great importance to as- tronomy, as they enable us to determine the distances of the heavenly bodies from the Earth, the magnitudes of the planets, and the dimessions of their orbits. The Sun's horizontal parallax being accurately known, the Earth’s distance from the Sun becomes known; and the Earth’s distance from the Sun being known, that of all the planets may be known also, because we know the exact periods of their sidereal revolutions, and according to the third law of Kepler, the squares of the times of their revolu- tions are proportional to the cubes of their mean distances. Hence, the first great desideratum in astronomy, where measure and magnitude are concerned, is the determination of the true parallax. At the late council of astronomers, assembled in Lon- don, from the most learned nations in Europe, the Sun’s mean horizontal parallax was settled, as the result of their united observations, at 0° 0' 8".5776.-Now the value of radius, expressed likewise in seconds, is 206264/.8; and this divided by 8".5776, gives 24047 for the distance of the Sun from the Earth, in semidiarmeters of the latter. If we take the equatorial semidiameter of the Earth as sanction- ed by the same tribunal, at (7924+2=) 3962 miles, we shall have 24047X3962–95,273,869 miles for the Sun's true distance. - - * See Chapter XIV, on the number and distance of the Stars. How does the parallax of a body vary, with its altitude? How is it affected by dis- tance 2 Giye an example, What, then, are the necessary effects of parallax on the ap- earance of a heavenly body ? How, them, can we obtain the true altitude of the Sun or oon 3 Do parallaº; and refraction affect the altitude alike 2 Give an €3 ample. Why are the principles of parallax of great importance to astronomy? If the Sun's paral- lax he known. how may the distances of all the planets be known also 7 What inference may be derived from this in regard to the iurportance of parallax PROBLEMS. 295 Both the principle and the calculation of this element may be illustrated by a reference to the diagram on Plate I, of the Atlas: "Thus—the parallactic angle AES = 8/.5776: is to the Earth’s semidiameter as = 3962 miles: : as radius =206264.7/8: is to the distance ES = 95,273,869 miles, as hefore. - Again: The mean horizontal parallax of the Moon is 0°57' 11", or 3431". In this problem, the parallactic angle AMS is 0° 57' 11" = 3431’’; and 3431”: is to 3962 miles:: as 206264".8: is 238,161 miles, for the Moon’s mean dis- tance from the Earth MS.—See Chapter on the Number and Distance of the Stars. C H A P T E R XI. P R O B L E M S A N D TA B L E S, PROBLEM I. To convert DEGREES, &c. INTO TIME. RULE 1.-Divide the degrees by 15, for hours; and mul- tiply the remainder, if any, by 4, for minutes. 2. Divide the odd minutes and seconds in the same man- ner by 15 for minutes, seconds, &c. and multiply each re- mainder by 4, for the next lower denomination. ExAMPLE 1.-Convert 32° 34'45" into time. Thus, 32° -- 15 = 2h. Sº 34 -i- 15 = 2 16// 45 -- 15 = 3 Ans. 32°34'45"— 2h. 10' 197 the time. ExAMPLE 2.—If it is 12 o'clock at this place, what is the time 20° east of us 2 Thus, fifteen in 20°, once, and five over ; the once is 1 hour, and the 5 multiplied by 4, gives 20 minutes: the time is them 1 hour and 20 minutes past 12. ExAMPLE 3.-The longitude of Hartford is 72° 50' west of Greenwich ; what time is it at Greenwich when it is 12 o'clock at Hartford 2 Ans. 4 h. 51 min. 20 sec. - ExAMPLE 4.—When it is 12 o'clock at Greenwich, what is the time at Hartford 7 Ans. 7h. 8m. 40 sec. A. M. NoTE-Table VIII, is designed to facilitate calculations of this kind. The degrees being placed in one column, and the corresponding time in another, 296 PROBLEMs. it needs no explanation, except to observe that degrees in the left hand columns may be considered as so many minutes, instead of degrees; in which case, the corresponding time in the adjoining column, must be read as minutes and seconds, instead of hours and minutes. In like manner, the degrees in the left hand column may be read as seconds, and the correspond- ing time, as seconds and thirds. ExAMPLE.--Find, by the table, the time corresponding to 32° 34' 45”. Thus: Against 32° is 2 h. 8 min. {{ ºA f { { 16 sec. “ 45” “ 3 Answer as above, 2h. 10m. 19's. PROBLEM II. To convert TIME INTO DEGREEs, &c. RuLE.—Multiply the hours by 15, and to the product add one fourth of the minutes, seconds, &c., observing that eve- ry minute of time makes +8, and every second of time, 4/. ExAMPLE 1.-In 2 hours, 10 minutes, and 19 seconds, how many degrees 2 - T hus: 2 h. 10 m. 19 s. 15 * 309 Add 10 quarters, or + of the min. 2 30’ Add 19 quarters, or + of the sec. 4 4.5// Ans. 32° 34'ſ 45// This problem is readily solved by means of Table IX, without the labour of calculation : . Thus : 2 hours =30° 10 minutes = 2 30’ 19 seconds = 4 45’’ Ans. 32O 34’ 45.” Ex. 2.--When it is 12 o'clock at Hartford, it is 4 hours, 51 minutes, and 20 seconds past moon at Greenwich ; how many degrees is Hartford west of Greenwich 3 Thus: 15 times 4 is 60—added to + of 51, is 72° 45'', and this increased by + of 20, is 72° 50.' Ans. Ex. 3.-A Liverpool packet, after sailing several days from New York, finds the time by the Sun 2 hours and 40 minutes later than by the ship's chronometer: how far has the ship progressed on her way ? Ex. 4.—A vessel leaves Boston, and having been tossed about in foul weather for some days, finds, that when it is 12 o'clock by the Sun, it is only 11 o’clock and 50 minutes by the watch; is the vessel east or west of Boston ; and how many degrees 7 - Ex. 5.—The moment of greatest darkness during the an- PROBLEMS. 297 nular eclipse of 1831, took place at New Haven, 10 minutes after 1 o'clock. A gentleman reports that it happened pre- cisely at 1, where he observed it; and another, that it was 5 minutes after 1 where he saw it : Quere. How far east or west were these gentlemen from each other, and how many degrees from New Haven 7 PROBLEM III. To FIND what STARS ARE ON THE MERIDIAN AT NINE o’cLOCK *Y IN THE E WENING OF ANY GIVEN DAY. RULE.—Look for the given day of the month, at the bot- tom of the maps, and all the stars having the same degree of right ascension will be on the meridian at that time. ExAMPLE 1.--What stars will be on the meridian at 9 o'clock, the 19th of January 2 ~º-e Solution.—On Plate III. I find that the principal stars standing over against the 19th of January, are Rigel and Capella. Ex. 2.—What stars are on the meridian the 20th of De- cember 7 Ans. Menkar and Algol. PROBLEM IV. ANY STAR BEING GIVEN, To FIND when IT culminATEs. RULE.—Find the star's right ascension in the table, or by the map, (on the equinoctial,) and the day of the month at the top or bottom of the map will be the day on which it culminates at 9 o'clock. IXAMPLE 1.-At what time is the bright star Sirius on the meridian 2 Solution.--I find by the table, and by the map, that the right ascension of Sirius is 6 hours and about 38 minutes; and the time corresponding to this, at the bottom of the map, is the 11th of February. Ex. 2–At what time is Alpheratz, in the head of Andro- meda, on the meridian 3 Ans. The 9th of November. PROBLEM V. THE RIGHT ASCENSION AND DECLINATION OF A PLANET BEING GIY JN, TO FIND ITS PLACE ON THE MAP. RULE.-Find the right ascension and declination of the * on the map, and that will be its place for the given ay. 29S PROBLEMS. ExAMPLE 1.-Venus’s right ascension on the 1st of Jan- uary, 1833, was 21 hours, 30 minutes, and her declination 16#9 south; required her situation on the map 7 Solution.—On the right hand of the Plate II. I count off 16#9 from the equinoctial, on the marginal scale south, and from that point, 30 minutes to the left, or just half the dis- tance between the XXI, and XXII. meridian of right as- cension, and find that Venus, that day, is within two degrees of Delta Capricorni, near the constellation Aquarius, in the zodiac. NoTE,--It is to be remembered, that the planets will always be found within the limits of the zodiac, as represented in the maps. By means of Table VII, the pupil can find at any time the situations of all the visible planets, on the nuaps; and this will enable, him to determine their position in the heavens, without a chance of mistake. By this means, too, he can draw for himself the path of the planets from month to month, and trace their course among the stars. This is a pleasant and useful exercise, and is practised extensively in some academies. The pupil draws the map in the first place, or such a portion of it as to include the zodiacal constella- tions; then, having dotted the position of the planets from day to day, as indicated in Table VII., their path is easily traced with a pen or pencil. Ex. 2. —Mars’ right ascension on the 13th of March, 1833, is 5 hours, 1 minute, and his declimation 24* north; requir- ed his situation on the map 2 Solution.—I find the fifth hour line or meridian of right ascension on Plate III. and counting upwards from the equi- noctial 24;9, I find that Mars is between the horns of Taurus, and about 5° S. W. of Beta Aurigae. Ex. 3.—Required the position of Jupiter and Saturn on the 13th of February and the 25th of May ? When the right ascension and declination of the planets are not given, they are to be sought in Table VII. PROBIEM VI. TO FIND AT WHAT MOMENT ANY STAR WILL PASS THE MERIDIAN ON A. GIVEN DAY. RULE.—Substract the right ascension of the Sun from the star’s right ascension, found in the tables; observing to add 24 hours to the star's right ascension, if less than the Sun's, and the difference will show how may hours the star culmi- mates after the Sun. ExAMPLE 1.-At what time will Procyon pass the meridi- an the 24th of February 7 Solution.—R. A. of Procyon 7h, 30m. 33s.--24h. 31 30° 33’’ R. A. of Sun, 24th of Feb. 22 29 1 Ans. 9 1 32 That is, 1 m. 32s. past 9 o'clock in the evening. PROBLEMS. 299 Ex. 2.-At what time will Demebola pass the meridian on the first of April? Solution.—R. A. of Denebola is 11h. 40' 32” R. A. of Sun, April 1, 0 41 25 -* Ans. 10 59 7 That is, at 59 minutes, 7 seconds, past 10 in the evening. Ex. 3.−At what time on the first day of each month, from January to July, will Alcyone, or the Pleiades, pass the me- ridian 2 - Ex. 4.—At what time will the Dog Star, or Sirius, culmi- nate on the first day of January, February, and March 3 Ex. 5.—How much earlier will Spica Virginis pass the meridian on the 4th of July, than on the 15th of May 2– Ans. 3 hours, 25 minutes. PROBLEM VII. TO FIND WHAT STARS WILL BE ON OR NEAREST THE MERIDIAN AT ANY GIVEN TIME. RULE.-Add the given hour to the Sun’s right ascension, found in Table III., and the sum will be the right ascension of the meridian, or mid-heaven; and then find in Table II. what star's right ascension corresponds with, or comes near- est to it, and that will be the star required. ExAMPLE 1.-What star will be nearest the meridian at 9 o'clock in the evening of the 1st of September? Solution.—Sun's right ascension 1st September, 10h 40' 30’’ Add the time from moon 9 0 0 Right ascension of the meridian 19h 40' 30’’ Now all the stars in the heavens which have this right as- cension, will be on the meridian at that time: On looking into Table II. the right ascension of Altair, in the Eagle, will be found to be 19h. 40m. ; consequently Altair is on the meridian at the time proposed ; and Delta, in the Swan, is less than two minutes past the meridian. Ex. 2.-Walking out in a bright evening on the 4th of Sep tember, I saw a very brilliant star almost directly over head; I looked on my watch, and it wanted 20 minutes of 8; required the name of the star 2 Solution.—Sun’s declination 4th of September, 10h 51' 22” Add the time from noon 7 40 . 0 * * Gives R. A. of Lyra, nearly 18 31 22 300 PROBLEMS. Ex. 3.-About 8+ minutes after 8 in the evening of the 11th of February, I observed a bright star on the meridian, a little north of the equinoctial, and 1 minute before 9 a still brighter one, further south; required the names of the stars ? PROBLEM VIII. To FIND what STARs will culminATE AT 9 o'clock IN THE EVENING OF ANY DAY IN THE YEAR. RULE.—Against the day of the month in Table IV., find the right ascension of the mid-heaven, and all those stars in Table II. which have the same, or nearly the same right as- cension, will culminate at 9 P. M. of the given day. ExAMPLE 1.-What star will culminate at 9 in the even- ing of the 26th of March 2 Solution.—I find the right ascension of the meridian, at 9 o'clock in the evening of the 26th of March, is 9h 19° 37'; and on looking into Table II., I find the right ascension of Alphard, in the heart of Hydra, is 9h 19 23”. The star is Alphard. . Ex. 2.—What star will culminate at 9 in the evening of the 28th of June 7 Ans. Aphacca. PROBLEM IX. to FIND THE SUN’s LONGITUDE OR PLACE IN THE ECLIptic, ON ANY GIVEN DAY. RULE.—On the lower scale, at the bottom of the Plan- isphere, (Plate VIII.) look for the given day of the month; then the sign and degree corresponding to it on the scale immediately above it, will show the Sun’s place in the ecliptic. - ExAMPLE 1.-Required the Sun's longitude, or place in the ecliptic, the 16th of September. Solution.—Over the given day of the month, September 16th, stands 5 signs and 23 degrees, nearly, which is the Sun's place in the ecliptic at noon on that day; that is, the Sun is about 23 degrees in the sign Virgo. N. B. If the 5 signs be multiplied by 30, and the 23 degrees be added to it, it will give the longitude in degrees, 173 º Ex. 2.-Required the Sun’s place in the ecliptic at noon, on the 10th of March. PROBLEMS, 301 PROBLEM X. GIVEN THE SUN’s LoNGITUDE, of PLACE IN THE ECLIPTIC, TO FIN D H IS RIGHT ASCENSION AND DEC LINATION. RULE.—Find the Sun’s place in the ecliptic, (the curved line which runs through the body of the planisphere,) and with a pair of compasses take the nearest distance between it and the nearest meridian, or hour circle, which being ap- plied to the graduated scales at the top or bottom of the planisphere, (measuring from the same hour circle,) will show the Sun’s right ascension. Then take the shortest distance between the Sun’s place in the ecliptic and the nearest part of the equinoctial, and apply it to either the east or west marginal scales, and it will give the Sun's de- clination. ExAMPLE 1.-The Sun's longitude, September 16th, 1833, is 5 signs, 23 degrees, nearly ; required his right ascension, and declination. Solution.—The distance between the Sun’s place in the ecliptic and the nearest hour circle being taken in the com- passes, and applied to either the top or bottom graduated scales, shows the right ascension to be about 11 hours 35 minutes; and the distance between the Sun’s place in the ecliptic, and the nearest part of the equinoctial, being applied to either the east or west marginal scales, shows the decli- nation to be about 2°45', which is to be called north, because the Sun is to the northward of the equinoctial : hence the Sun's right ascension, on the given day, at noon, is about 11 hours 35 minutes, and his declination 2° 45' N. Ex. 2.---The Sun’s longitude March 10th, 1833, is 11 signs, 19 degrees, nearly ; required his right ascension and declimation ? - Ans. R. A. 23 h. 21 min. Decl. 4°11′ nearly. PROBLEMI XI. To FIND THE RIGHT Ascension OF THE MERIDIAN AT ANY GIVEN TIME. RULE.—Find the Sun’s place in the ecliptic by Problem IX. and his right ascension by Problem X., to the eastward of which, count off the given time from noon, and it will show the right ascension of the meridian, or mid-heaven. ExAMPLE 1.-Required the right ascension of the meridi- an 9 hours 25 minutes past noon, September 16th, 1833. Solution.—By Problems IX, and X., the Sun’s right ascen- 26 302 PROBLEMS. sion at noon of the given day, is 11 hours 35 minutes; to the eastward of which, 9 hours and 25 minutes (the given time) being counted off, shows the right ascension of the meridian to be about 21 hours. Ex. 2.-Required the right ascension of the meridian at 6 hours past moon, March 10th, 1833 2 Solution.—By Problems IX. and X.. the Sun’s right ascen- sion at noon of the given day, is 23 hours and 21 minutes; to the eastward of which, the given time, 6 hours being counted off, shows the right ascension of the meridian to be about 5 hours 21 minutes. REMARK.—In this example, it may be necessary to observe, that where the eastern, or left hand extremity of the planisphere leaves off, the west- ern, or right hand extremity, begins ; therefore, in counting off the given time on the top or bottom graduated scales, the reckoning is to be trans- ſerred from the left, and completed on the right, as if the two outside edges of the planisphere were joined together. PROBLEM XII. TO FIND WHAT STARS WILL BE ON OR NEAR THE MERIDIAN AT" ANY GIVEN TIME. RULE.—Find the right ascension of the meridian by Problem XI. over which lay a ruler, and draw a pencil line along its edge from the top to the bottom of the planisphere, and it will show all the stars that are on or near the meridian. ExAMPLE 1.-Required what stars will be on or near the meridian at 9 hours 25 minutes past noon, Sept. 16th, 18332 Solution.——The right ascension of the meridian by Prob- lem XI. is 21 hours: this hour circle, or the line which passes up and down through the planisphere, shows that no star will be directly on the meridian at the given time ; but that Alderamin will be a little to the east, and Deneb Cygni, a little to the west of it; also Zeta Cygni, and Gamma and Alpha in the Little Horse, very near it on the east. PROBLEMI XIII, To FIND THE EARTH's MEAN DISTANCE FROM THE SUN. RULE.—As the Sum’s horizontal parallax is to radius, so is the semi-diameter of the Earth to its distance from the Sun. By Logarithms.-As tangent of the Sun's horizontal par- allax is to radius, so is the Earth’s semi-diameter to her mean distance from the Sun. 8”.5776: 206264”.8 :: 3962; 95,273,869 miles, PHOBLEMIS. 303 By Logarithms. As tangent of Sun’s horizontal parallax, 8’’.5776 = 5.618940? Is to radius, or 90°, = . 10.0000000 So is the Earth’s semi-diameter, 3962, = 3.5979145 To the Earth’s distance, 95.273,869 – 7.9789738 PROBLEMI XIV. TO FIND THE DISTANCE OF ANY PLANET FROM THE SUN, THAT OF THE EARTH BEING KNOWN. RULE.—Divide the square of the planet’s sidereal revolu- tion round the Sun, by the square of the Earth’s sidereal re- volution, and multiply the cube root of the quotient by the Earth’s mean distance from the Sun. - By Logarithms.--From twice the logarithm of the plan- et’s sidereal revolution, substract twice the logarithm of the Earth’s sidereal revolution, and to one third of the remain- der, add the logarithm of the Earth’s mean distance from the Sun. ExAMPLE.—Required Mercury’s mcan distance from the Sun, that of the Earth being 95,273,869 miles. - - Mercury's sidereal revolution is 87.96925S days, or 7600543’’.8912 : The Earth’s sidereal revolution is 365,256374417 days, or 55S151’’.5 7600543.9 3155S151’’.5 7600543.9 995916962096952.25 by which divide 5776S267575S27 21 and the quotient will be 0.052005106713292, the cube root of which in 0.3870977, and this multiplied by 94,8S1,891, gives 36,727,607 miles, for Mercury’s distancé from the Sun. This problem imay be performed by logarithms is as many minutes as the former method requires hours. Mercury's Sid. Rev. 7609543°.9 log. : - 6.SSUS447X2 13.7616S94 Earth's Sid. Rev. 3155S151’’. log. == 7,499.1302×2 14.99$2604 #)—2.7634290 - 1.5S7S097 Add, log. of the Earth’s mean distance, 7.97S973S Mercury’s distance, 36,880422. Ans. 7,5667S35 If the pupil have not already learned the use of logarithms, this problem- will satisfy him of their unspeakable advantage over all other modes of com- putation. By reviewing the above calculation, he will perceive that instead of multiplying 31558151’’.5 by itself, he need only multiply its logarithms by two 1 and, instead of extracting the cube root of 0.05S005106713292, he need only divide its logarithm by three 1 and, instead of multiplying 0.3870977, by 95,273, 869, he need only add their logarithms together. He need not think himself a dull scholar, if by the fortner method he come to the true result in five hours ; nor remarkably quick, iſ by the latter he come to it in five minutes, PROBLEM XV. - "TO FIND THE HOURLY MOTION OF A PLANET IN ITS ORBIT. RULE.—Multiply the planet’s mean distance from the Sun by 6,2831853, and divide the product by the time of the planet's sidereal revolution, expressed in hours, and the &lecimals of an hour. 304 PROBſ. EMS, By Logarithms.-Add 0,7981799 to the logarithm of the planet's mean distance from the Sun, and from the sum substract the logarithm of the planet's revolution expressed in hours. EXAMPLE.-Required the Earth's hourly inotion in its orbit. Log. of Earth’s distance = 7 9780738-i-0.70S1799 = 8.777) 537 Substract log, of Earth's revolution 3.94:38030 Gives Earth's horary unotion, G8,2SS miles, = 4.8343447 PROBLEMI XVI. TO FIND THE HOURLY MOTION OF A PLANET ON ITS. AXIS. RULE.—Multiply the diameter of the given planet by 3.14159, and divide the product by the period of its diurnal rotation. By Logarithms.-Add 4,0534524 to the logarithm of the planet's diameter, and from the sum substract the logarithm of its diurnal rotation, expressed in seconds. Earth’s diameter, 7924 log. = 3.S9Sſ)445 Add log. of 3000"—H·log. of 3.14159 = 4.0534524 7 gºgo Substract log. diurnal rotation, 23 h. 56’ 4”,09 = 4.9353263 Ans. 1040.00 miles = 3.0170706 PROBLEMI XVII. TO FIND THE RELATIVE MAGNITUDE OF THE PLANETS. RULE.—Divide the cube of the diameter of the larger planet, by the cube of the diameter of the less. By Logarithms.--From three times the logarithm of the larger, substract three times the logarithm of the less. ExAMPLE.—How much does the size of the Earth exceed that of the Moon 7 Earth’s diameter, 7912 log 3.8983863X3 = I 1.6948.5S0 Moon's diatricter, 2160 log, 3.3313376X3 = 10003012S The Earth exceeds the Moon, 49. 1865 times. Ans. 1.691S [61 In this example, 7912 uniles is assumed as the ºnegrº, between the Earth's equatorial and polar diameter: the former being 7924, and the latter 7808 miles. PROBLEM XVIII. TO FIND THE PROPORTION OF SOLAR LIGIIT AND HEAT AT EACH OF THE PLANETS. RULE.—Divide the square of the planet's greater distance from the Sun, by the square of the less.--Or, substract twice the logarithm of the greater distance, from twice the loga- rithm of the less. PROBLEMIS. 305 ExAMPLE.—How much greater is the Sun's light and heat at Mercury, than at the Earth 2 Log. of Earth’s distance . 7.9789738×2 = 15.9599476 — of Mercury’s - 7.5667959).<2 = 15.1335918 Ans, 6.6736 times greater = 0.82 PROBLEM XIX. "TO FIND THE CIRCUMIFERENCE OF THE PLANETS. RULE.—Multiply the diameter of the planet by 3.14159; dr, add the logarithm of the planet’s diameter to 0.4971499. PROBLEMI XX. TO FIND THE CIRCUMFERENCE OF THE PLANETARY ORBITS. RULE.—Multiply the planet’s mean distance from the Sun, by 6.2831853: or, to the logarithm of the planet’s mean distance, add 0.7981799, and the sum will be the lo- garithm of the answer. PROBLEMI XXI. TO FIND IN WIHAT TIME ANY OF THE PLANETS WOULD FALL TO THE SUN IF LEFT TO THE FORCE OF GRAVITATION ALONE. RULE.—Multiply the time of the planet’s sidereal revolu- tion, by 0.176776; the result will be the answer. By Logarithms.--From the logarithm of the planet’s si- dereal revolution, substract 0.7525750, and the remainder will be the logarithm of the answer, in the same denomina- tion as the sidereal revolution. Required the times, respectively, in which the several planets would fall to the Sun by the force of gravity. Planets would fall to Days. H. M. S. Logarithms. the Sun. Mercury, 15 13 13 16 6. 12S26S6 Venus, 39 17 19 22 6.53554.24 Earth, - 64 13 3S 55 6,7465857 Mars, 121 10 36 3 7,020SS} Jupiter, 765 21 33 35 7.820.5849 Saturn, 1901 23 24 4 8.2157186 Herschel, 5424 16 52 1 S,6708897 _Moon to the Earth, 4 19 54 57 5.6204459 26% }} , \! 4• ". †ițuiciº Ëſements of the Solar System. šidėſeaſ R ºdiu-ſ I.Ogari; huns of Pianets’ dista lices. 'True );ę;an ſ'isſanceſ; froniſ the §§ tarı ili iniles. | ·|• | Relative distances.Logarithm8. | N≡etions in Meau į Logarithins. • , !SolarĐays.| Mercury,87 939 238)||4.94 13:30,9;0&{} { Venus, ,22.4 7007 36$)|$.35 {{}{}{ 47947: Earth, 365,256374 ||2.552597,805128 Mars,ššśğ#58438|ěššēģ857$ši Vesta,1325,74×1000|8,122459,40820s Juno,1592.6608000;3ࡕ,345€6} Ceres, . .1681.39310003225869,28766$ Pallas,J686.538$600,3223996 34:23 #9 Jupiter,4332.58482{2},636747,07·1032 Saturn,1075;}.2198 17 (}} | ft:0,77967Ü Herschel,30686.8208296|4,486951,893661 -------------- → → → → →→→→ ~- - ----------~- Names of the Planets, &c. 35,880,422,34907587 7.566795,865867 68,914 654.84245489 7.83831 1,5 6319; 95,273 888.86774555 7.978973,802432 145,168,094.89281471 8.16.1871, 177398 225 016,752.147 1480) 8.332244,871143 ż54,287,00255166636 8.405324, 162513; ģ63,046 136.309 12176 7421021,444147|| 264 183,786.59075400 8,421906, 160684|| 495 5:23,836.87042950 8.696, 73,313039|| 998,747,975.06526816 8,9584,9,11875ő 1827 580,553 25499525 9.261 0.387099031323||1.587822,083445 0.723332175563|1,859337,782897 1.000000000000 1.523692662196 2.361788860064 2.(569040984584 2.76 $2.77388819$3 734.519$994 | 4 0,090000 000000 0.182897,374974 0.373241,068721 0.426350,360091 0.442047,641695 0442932,358262 5.804151614387||0.7160997512617 9.53793606 1453|0979455,336333 {\inn i eters at tlı • Relative Diał uc- {{}}°S. 1 ers in ſııiles. ComparativeVolumes. 876,529379|19.482390512469|1,282902,726957 [ſourly Motion, ſin lniłeş. Comparative Light and Heat. Sun,•�• Mercury,••! Venus, .•!}● Earth, .·• • Mars, . . . .�● Vesta, .•• ' • Juno, (, , ,•� Ceres, .�∞● Pallas, .·�• Jupiter, .∞،---- Salurn, .�● • Herschel,•�● Earth’s M. Disſ. 32 , 1.8000} 6.4${}{} 16.5(){}{} 17, 1552 8. ſ 4{}{} 1.(}{58 3,4350 4.8740 3 6 7400 2 57.4400 1 14.4000 12.02434 || SS7.681 || || 405844, 16195 37$.562,984.05339 .9618ł | 7,621.88974 1.00{}{}{}7,9241,00ſ}{0 5:}}784,223.15423 .03395|269.0{,}004 .175801,393.(){};$43 .196$41,5$2.(){}?{}{} .25 42%)2,025.{)}{3!}{) 1289.8į000 ] 106.54000 81.57020 10.88531) 10.34320 4.33688 86,255 81,954 34,363 109,757 80,293 {}S_2S8 55,322 44 435 41,799 41,05 i 41,009|| 29,943 22 ! 11 15,592 6.67363 1.9 ſ 128 100000 –2,32164 —5.57805 —7.12362 —7 65764 —7.86800 —27.05.197 —90.97260 —367.97400 TABLE I. . Containing the names of the Constellations, the number and magnitude of the Stars in each, and the days on which they come to the merid- ian at 9 o'clock in the evening. 3– .# 5 Month.|s. Constellations. C 3'; 2. 2, 1 Jan. 4. Eridanus, 2 6: Reticulus, 3 9 Taurus, 4 11, Brandenburgh Sceptre, 3 12 °raxiteles, $6 12. Caiuclopard, 7 1S. A triga, 8 18, Sword Fish, 9 19, Mons Mensae, {0 23: 1.epus, the Hare, 3, 1 23. Orion, 12 26 Painter’s Horse, 13 27, Noah’s Dove, 14|Feb. 16, Canis Major, 15 22; Monoceros, 16 23 Goinini, 17 23. The Lynx, IS . 27; Argo Navis, 19|March.| 4: Canis Minor, 20 12: Flying Fish, 21 13. Cancer, - 22 15 Mariner's Compass, 23 - à IIydra, 24|April. 1 Sextans, 25 6; Leo Minor, 26 § Leo Major, 27 6. Air Pump, 2S º Major, 29 16; Robur Carroli, 33 26}Qrater, the Cup, 34|May. || 3: Chameleon, 35 11}The Cross, 36 13; Coina Berenices, 37 13i Corvus, the Crow, 38 13 Southern Fly, 39 19 Cor Caroli, 40 23 Virgo, 41 28, Asterion et Chara, 28,93entaurus, 42|June. 9: Bootes, 43 19; Compasses, 44 2i;Mons Manalus, 45 22; Libra, 46 26; Lupus, the Wolf, 47|July. #; Borealis, 48 IRUrsa Minor, i HDocſi-śNo. of nation.éStars. 100 S.; S4 fl 1 62 S. § 10 : 0 16 N. : 141 1 15 S. 3 40 S. JG | 0 70 N.E. 5S $ 0 45 N. 66 # 1 62 S. 6 : 0 72 S. § 30 : 0 18 S. 19 & 0 0 7S $ 2 55 S. S # 0 35 S. 10 : 0 20 S. # 31 ; I 0 § 3.1 : 0 32 N.; S3 : 1 50 N.3 44 : 0 50 S. § 64 $ 2 5 N. 14 § 1 6S S. 8 || 0 20 N.; S3 # 0 30 S. 4 § {} S S. § 60 # 0 0 41 + () 35 N.; 53 # 0 15 N. 95 § 2 32 S. 3 : 0 60 N.; S7 l 50 S. 12 15 S. § 31 : 0 7S S. 10 : 0 60 S. 5 1 26 N.: 43 : () 15 S. 9 || 0 6S S. 5 || 0 39 N. 3 5 N. 110 || 1 40 N. 25 # 0 50 S. 35 2 20 N., 54 1 64 S. 4 || 0 5 N. 11 8 S. 51 || 0 45 S. 24 || 0 30 N. 21 || 0 75 N. | 24 |0 Magnitudes. *||1|| || ||27-0; 57 0 || 2 || 3 || 2 || 5 1 || 4 || Sj23 || 60 0 || 0 || 0, 4' 18 0 || 0 || 6 ||25 || 42 1 || 0 || 9 |z0| 26 0 || || 1 || 4 || 24 0 || 0 (); 0 || 30 0 3| 7 || 3 | 13 4 3| 15; 18 36 0 || 0 || 1 || 0 39 1 || 1 || 2 || 4 || 53 4 || 2 || 7 || 7 || 36 0 || 0 || 7 || 7 | 12 2 || 4 || 7 |13 27 0 0|| 3 || 5 || 25 4 || 9 || 2:37 .2S9 0 || 1 || 0 || 3 | 9 0 Új 0 || 6 || 8 0 | 0 || 3 || S 11 0 || 0 || 0 || 2; 13 1 || 0 || 13 | 16 || 45 0 || 0 || 6 || 36 0 I | 5 || 0 || 39 2 || 6 || 15 již 47 0 || 0 || 0 || 2 | IS 3 || 7 || 3 ||31 || 37 0 0|10| 9 || 14 0 || 0 || 0 || 6 || 35 2 || | | | | | | 12 0 || 0 || 13 ; 13 || 17 0 || 3| 2 || 2 || 2 0 | 0 || 4 || 0 || 17 0 || 6 || 10 16 || 71 0 || 1 || || 7 || 15 1 || 6 || 10 || 4 ||100 0 || 7 |10|18 || 30 Q Q! I I | 8 1 || 3|12| 4 || 27 0 || 3 || 3 |18 || 29 1 || 1 || 5 || 9 || 5 1|2| 4 || 6 || 4 TABLE I.—C ontinued. i § i | • #|A w º Decli. No. of Magnitudes. s Month. º Constellations. * Almation. Stars...} - -º-º-º- Z ſº 1 || 2 || 3 || 4 || 5 || 6 49|July. ºthe serpent, 235o 100 N. 64 || 0 || 1 || 9 || 5 3/40 50 4;S. Triangle, 23S 65 S. 5 - 0 || 1 || 2 || 0 || 1 || 16 51 Słºuclid's Square, 242 |45 S.; 12 || 0 || 0 || 0 || 0 || 326 52 ºpiº, 244 (26 S.; 44 || 1 || 1 || 11|10| 429 53 183Bird of Paradise, 252 75 S.* 11 : 0 || 0 || 0 || 0 || 2:16 54 2}}Ara, the Altar, 255 |55 S. 9 || 0 || 0 || 3 || 3 || 1 |30 55 21%PIercules, 255 22 N.: 113 || 0 || 1 || 8 |19|36446 56 26 Serpentarius, 260 13 N.: 74 : 0 || 1 || 5 ||10| 942 57|August. 5:Draco, 270 (66 N.S. 80 : 0 || 4 || 7 |12|25:33 5S 6#Cerberus, 271 (22 N. - 59 10:Scutum Sobieski, 275 ||10 S. - 60 }}|aurus Poniatowski, 275 || 7 N.; 16 || 0 || 0 || 0 || 3 || 1 |12 6} 13:Corona Australis, 278 |40 S. 12 || 0 || 0 || 0 || 0 || 5|10 62 13;Telescopium, | 278 |40 S.; 9 || 0 || 0 || 0 || 3| 6|30 63 19;Lyra, the Harp, 2S3 |3S N.; 21 || 1 || 0 || 2 2 6|12 64 21;Sagittarius, 285 |35 S.; 69 || 0 || 0 || 5|10|12|59 65 29;Antinous, 292 || 0 66|Sept. 1$Sagitta, 295 |18 N. 18 0 || 0 || 0 || 4 || 0|15 67 l'Aquila, 295 || 8 N.; 71 || 1 || 0 || 9 || 7 || 1438 6S 6}Pox and Goose, 300 ||25 N. 35 | 0 || 0 || 0 5||1321 69 jº. 302 |68 S.: 14 0 || 1 || 2 3 480 70 15:Delphinus, 30S 15 N. 18 0 || 0 || 5 || 2:11 71 18:2ygnus, 30S 42 N., 81 || 0 || 1 || 6||11 1649 72 18.9apricorn, 310 |20 S.; 51 : 0 || 0 || 3| 3| 7 || 4 73 18:Hadley’s Quadrary 310 S0 S. 43 || 0 || 0 || 1 || 0 6|64 74 23;Microscopium, 315 |35 S. 10 || 0 || 0 || 0 || 0 || 12 75 §he Indian, 315 |55 S. 12 || 0 || 0 || || 1 || 254 76 24;Equulus, 316 || 5 N.; 10 || 0 || 0 || 0 || 4 || 1 || 5 77|Oct. 10 The Crane, 330 |45, S.: 13 : 0 || 1 || 2 2.46|41 78 153Aquarius, 335 ||14 S., 108 || 0 || 0 || 4 || 7 |2859 79 15:Southern Fish, 335 (30 S.; 24 || 1 || 0 || 2 5 9||19 80 16:The Lizard, 336 |43 N.; 16 || 0 || 0 || 0 3| 7 || 7 81 1853epheus, 338 |65 N. 82|N 20; Pegasus, 340 ||14 N.; 89 || 0 || 3 || 3| 9|1451 $3|Nov. 9}American Goose, 359 |66 S.; ; 9 || 0 || 0 || 1 2 5|58 84 13:Officina Sculptoria. 3 ||38 S. 12 || 0 || 0 || 0 || 0 || 5:29 85 15;Pisces, 5 |10 N.; 113 || 0 || 0 |13| 52863 86 20|Phoenix, 10 |50 S. 13 | 0 || 1 || || 3 || 7 |63 87 22:Cassiopeia, 12 |60 N. 55 ; 0 || 0 || 5 || 6 || 8|38 88 23 Andromeda, 14 |34 N.: 66 - 0 || 3 || 2 |12||15|34 §g|Dec. 4|Cetus, 25 | 12 S.: 97 : 0 || 2 || 7|1311|66 90 6;Triangulum, 27 32 N.L. 16 || 0 || 0 || 0 3| 1 7 91 6}{Hydrus, 28 |68 S. 10 || 0 || 0 || 2 3 2/38 92 Aries, 30 |22 N. 66 || 0 || 1 || 1 || 2 6|22 93 10|Triangulum Min. 32 (28 N. 5 94 17|Horologium, 40 60 S. 12 || 0 || 0 || 0 Q] 239 95 17|Musc 40 |27 N. 4 -0 || 0 || 1 || 2 | 1 96 19|Chemical Furnace, 42 |30 S. 14 || 0 || 0 || 0 || 0 || 2:43 97 21|Caput Medusae, 14 |40 N. | 98. |33 Perseus, : 6 49 N. 59 10 || 2 || 4|10|14}3 TABLE II. Exhibiting the Right Ascension and Declination of the principal Fixed Stars, and the time of their coming to the Meridian. Those to which S is annexed are in South declination ; the others are ill North e declination. º i br łig woº. On the s # Names of the Stars. º Alºn. |Pamun |Meri iš | H. M. s. 9 ‘ ‘’ 1's Persei, 3| 3 47 8 39 31 37. Jan., 1 3 y Eridani, 3 3 50 15 13 59 4S. 2 §§ Eidani, 3 || 4 3 31 || 7 16 32S. 5 4's Tauri, 3| 4 is 33 |18 || 8 is 8 5|& Tauri, Aldebaran, | 1 || 4 20 21 16 10 4 10 66 º Capell ; 4 39 35 | 5 18 OS. 13 1|2 Aurigae, Capella, 5 2 |45 - §3 Orionis, j I * ; 4; § *s. ; 913 Tauri, El Nath, 2 || 3 15 11 25 37 35 22 10|n Orionis, 3 || 5 15 36 2 33 17S. 22 11|). Orionis, Bellatrix, 2 || 5 16 11 6 11 32 22 # Leporis, Nibal, | 3 || 5 21 22 20 53 46S. 23 3|d Orionis, Mintaka, 2 º 25 39S. 24 i. i.js, º' || : ; ; ; ; ; 24 |}|... Orionis, Anilam, 2 || 3 × 1 || 1 is 40s 25 16|& Tauri, 3 || 5 37 33 |2i 2 ºf 25 17|& Orionis, Alnitak, 2 | # 33 30 || 3 3 6s. 26 18|a Columbae, Phaet, 2 | f 3 $) |34 10 2S. 26 19|2: Orionis, Saiph, 3 || 5 39 20 9 4-4 2S. 27 20/3 Columbae, 3 || 5 45 6 |35 50 IQS. 29 212. Orionis, Betelguese 1 || 5 46 8 7 22 6 29 22:38Aurige,Menkalina 2 5 47 17 |44 55 24 29 £3, Geminorum, Tejatº GT5. TE : TFeb. 3 24%, Geminorum, 3 || 6 12 54 22 35 48 4 25% Canis Majoris, 3 || 6 14 4 |29 B9 36s. 5 26 (3 Ca. Maj., Mirzam, 2 | 6 15 23 |17 52 41S. 5 27|2 Navis, Canopus, 1 || 6 20 15 |52 3G 23S. 6 28.72 5.º.º. 3| 6 28 4 |16 32 18 8 20|x Canis Maj., Sirius, 1 37 / Sº, 7S 11 306 Canis Maj., Adhara, 3 § § # § ; ; 15 31|& Geminorum. 3| 53 53 |20 48 36 15 323 G. Mojº Muliphen, 3| & 55 36 |15 23 20s. 16 333 C. Majoris, Wesen, 2 || || 1 17 |26 7 53s, g 7 343 Gemino., Wasat, 3 || 7 10 § 33 1? & 19 357. Argo Navis, 3 || 7 || 7 ||36 48 S. I9 36|º C. Maj., Aludea, 2 || 7 17 16 |2S 58 50s. 21 37|2 Gemino., Castor, 2 || 7 23 56 |32 1.4 52 23 38|2 C. Minor, Procyon, 1 || 7 30 33 5 38 55 24 30ix Ar. Navis, Markab, 3 || 7 32 17 |26 26 22S. 25 40/3 Gemino., Pollux, 2 || 7 35 5 |28 25 28 26 TABLE II.-Continued. c * gºt t- 89 | Right arlin a fi . . K. 2. Names of the Stars. § Asc ension. Declination. º º & sºmº, sº --- II. M. s. 9 , a Z *-sº 41% Argo Navis, 3| 7 42 20 24 26 35S. Feb. 28 426 Argo Navis, Naos. 2 7 57 44 39 32 3S. Mar. 4 435. Argo Navis, 2| 8 4 23 46 50 43S. 5 44% Argo Navis, 2.3| 8 19 5 '58 58 33S. 9 º Argo Navis, 2.3| 8 40 7 54 5 43S. 15 464 Ursae Majoris, 3| 8 47 47 48 41 50 17 47 a Cancri, Acubéns, 3.4 8 49 45 12 30 9 18 43. Argo Navis, 2.3| 9 || 51 42 45 40S. 21 49% A. N., Maia Placid, 1| 9 12 57 '69 1 54S. 24 50% Argo Navis, 2.3| 9 16 59 .54 17 53S. 25 512 Hydrae, Alphard, 2 9 19 23 || 7 56 14S. 26 526 Ursae Majoris, 3| 9 21 47 53 26 45 27 53, Leonis, 3| 9 36 22 24 32 26 31 542 Leonis, Rasal Asad. 3| 9 42 56 26 47 32 April. | 1 55; Leonis, 3.4| 9 58 13 |17 34 34 6 562 Leonis Regulus, I | 9 59 28 12 46 52 6 57|x Ursae Majoris, 3| 10 6 58 43 44 49 8 585 Leonis, Aldhafara, 3| 10 7 23 24 14 53 8 593, Leonis, Al Gieba, 2.3| 10 10 45 20 41 16 9 G02 U. M., El Phekrah, 3| 10 11 55 42 20 15 9 61|& Leonis Minoris, 3| 10 28 47 |32 50 39 14 626 Argo Navis, 2.3| 10 37 12 63 31 I4S. 16 63|h Argo Navis, 2| 10 38 36 58 48 34S. 17 642, Crateris, Alkes, 3.4| 10 51 35 |17 24 368. 20 (35% Ursae Maj., Merak, 2 10 51 42 57 16 35 20 664 Ursae Maj., Dubhe, 2 10 53 21 |62 39 3 21 67& Leonis, Zozma, 3| 11 5 13 21 27 32 24 G88 Leonis, g 3| 11 5. 39 16 20 39 24 69|A Draconis, Giansar, 3| 11 20 17 |70 15 3 28 702 Leonis, Denebola, Tø II 40 32 15 30-22 |May. 3 713 Virginis, Zavijava, 3| 11 42 0 || 2 42 43 3 72× U. Maj., Phach'd, 2 11 45 I 54 37 35 4. 733 Centauri, 2.3| 11 59 44 49 30 15S. 8 74J Crucis, 3| 12 6 21 |57 32 4S. 10 75J Ursae M., Megrez., 3| 12 ºf 7 |57 58 46 10 767 Corvi, . 3 12 7 38 |16 36 42.S. 10 774 Crucis, 1| 12 17 23 62 10 26S. 13 783 Corvi, Algorab, 3| 12 21 38 |15 34 49S. 14 T92 Crucis, 2| 12 21 56 |56 10 22.S. 14 80% Corvi, 3| 12 25 39 |22 28 9.S. 15 TABLE II.-Continued. # Names of the Stars. # Aºn. Declination. º ã H. M. S 9 ‘’ 813: Draconis, 3|12 26 23 |70 42 38 May. 15 823 Centauri, 2.3|12 32 23 48 2 23S. 16 , 835, Virginis, 3|12 33 37 || 0 31 55S. 17 843 Crucis, 2|12 38 3 |58 46 27S. 18 85|e Ur. Majoris, Alioth, 212 46 27 |57 52 5 20 863 Virginis, 3|12 47 12 || 4 18 31 20 87|2 Cor-Caroli, 3|12 47 57 |39 13 21 20 88|e Vir., Vindemiatrix, 312 56 36 |11 51 32 22 39 y Hydrae, 3||13 9 42 22 17 9.S. 26 90% Céntauri, 3||13 10 48 |35 49 49S. 26 91%. Virginis, Spica, 1||13 16 24 10 17 10.S. 27 92% Ursae Maj. Mizar, 2|13 17 11 |55 17 59 28 93|& Virginis, 3||13 25 36 || 0 15 43 30 94's Centauri, 2.3||13 29 20 |52 32 20S. 31 95|h U. M., Benetnasch, 213 40 57 |50 8 58 June. 2 96|& Centauri, 3||13 45 II |46 27 37S 3 97% Bootis, 3||13 46 32 |19 14 39 4 983 Centauri, 1.2|13 52 8 |59 33 36S. 5 99|& Draconis, Thuban, 3||13 59 52 65 10 31 7 100|& Bootis, Arcturus, 1|14 8 3 |20 3 21 8 101|h Centauri, 2.3|14 24 54 |41 25 0S. 13 1022. Bootis, Seginus, 3|14 25 17 |39 2 32 H3 103* Centauri, 1.2|14 28 58 |60 9 28S. 14 104* Lupi, 3|14 30 46 |46 39 47S. 14 105* Bootis, Mirac, 3|14 37 41 |27 47 2 I6 1062. Librae, Zubenesch, 2.314 41 27 | 15 20 29S. 17 107|3 U. Mino., Kochah, 3|14 51 16 |74 50 17 19 I088 Bootis, Nekkar, 3|14 55 12 |41. 3 18 20 109|3 Librae, Zubenelg, 2.315 8 2 || 8 45 41S. 23 110|3 Serpentis, 3||15 26 32 || 11 6 14 28 111|& C. Bor., Alphacca, 215 27 37 |27 16 55 28 112|* Serpentis, Unuk, 2|15 36 3 || 6 57 24 30 113|3 Serpentis, 3|15 38 29 |16 57 7 || July. | 1 114|* Serpentis, 3||15 42 36 || 6 59 7 2 115ly Serpentis, 3|15 48 26 (16 12 59 3 1167, Scorpii, 3|15 48 4 125 37 11S. 3 117|3 Scorpii, 3|15 50 2.8 22 8 18S. 4 I£8|3 Scorpii, 2|15 55 44 |19 20 28S. 5 1196 Draconis, 3|15 58 37 |59 0 32 6 TABLE II.-Continued ź Names of the Stars. *- 1204 Ophiu., Yed, or Jed. 121| Ophiuchi, 122|) Hercules, 123,2. Scorpii, Antares, 124% Draconis, 125 (3 Hercules, Rutilicus, 128 & Ophiuchi, 127 2. Triang. Australis, 128 & Herculis, 129 a Scorpii, I30 a 1 Scorpii, I31 & Scorpii, 132 : Herculis, 133 n Ophiuchi, 134 & Her., Ras Algethi, 135 J Herculis, 138 & Draconis, 137 . Arae, 133 y Scorpii, Lesath, 1396 Scorpii, 1402. Qphiu, Ras Alhag. 141"g Ophiuchi, Cheleb, 142 y Ophiuchi, 143 y Draconis. Rastaben, 144 y 2 Sagittarii, 145 J Sagittarji, 146 e Sagittarii, 1472. Lyrae, Vega, 148 J Ursae Minoris, 149 (3 Lyrae, 150, a Sagittarii, 1516 Serpentis, Alga, 152 & Lyrae, 153& Sagittarii, 154). Lyrae, Jugum., 155°. Aquilae, 1566 A., Deneb el Okab, 1577 Sagittarii, 1582 Sagittarii, 1593 Draconis, bo Right - - - | tº § Asjon. Declination. Qn the Š 3. Merid.º. II. M. S. O J. a / 3|16 5 36 3 15 18S. July. 7 3| 16 9 39 || 4 16 37S. 8 3.16 14 23 |19 33 1 9. ilić iſ ió |36 3 is. 11 3, 16 21 12 ||61 53 38 11 3, 16 23 22 21 57 36 12 3. It 27 45 10 13 15S. 13 2.313 31 3 |6S 42 23S. 14 3, 16 3 || 59 |31 54 39 15 3:1; 39 4 |33 58 40S. 16 3, 16 40 8 ||37 45 14S. I6 316 42 52 |41 3 33S. 17 316 04 14 31 10 40 19. 23||7 0 50 |}5 30 35S. 21 2.317 7 2 ||14 35 17 23. 3; 17 8 20 25 2 43 23. 3. 8 23 |66 55 12 23. 3| 17 18 57 49 43 54S. 24 2.3.17 22 58 36 58 24S. 27 3.17 25 20 |42 52 55S. 27 2.17 28 11 |12 41 20 28. 3|17 35 36 || 4 38 40 30 317 39 56 2 46 42 31 2.317 52 4 51 30 42 TAug. 3 3, 17 55 5 |30 24 40S. 4 3|18 10 1 29 53 28S. 8 2.31S 12 48 |34 27 14S. S 1|18 26 11 |38 38 0 12 318 28 6 86.35 47 12 2.3, 18 43 55 33 10 33 17 2|18 44 58 |26 29 42S. 17 3|18 47 36 || 3 59 20 18 3|18 49 6 |36 41 28 18 3|18 52 1 |30 6 40S. 19 3|18 52 11 32 27 47 19. 3|18 52 26 ||14 50 4 19 3|18 57 44 |13 37 20 20 3|18 59 54 |21 16 56S. 21 3.4|19 12 19 |40 55 9S. 24 3|19 12 29 |67 21 59 24 TABLE II.-Continued. o On the # Names of the Stars. # Aºn. Declination. Merid. ă H. M. s O ( ‘’ * Aquilae, 3|19 17 5 || 2 46 57 || Aug. 26 1615 Vulpeculae, 3.4|19 21 20 24 20 5 27 162/3 Cygni, Albireo, 3|19 24 17 27 36 51 28 1630, Aquilae, Tarazed, 3}19 38 19 ió 12 48 31 164'ſ Cygni, 3|19 40 0 44 43 25 | Sept. | 1 163% Aquilae, Altair, 1.219 42 38 || 8 26 .2 1 1668 Aquilae, Alshain, 3 19 47 7 || 5 59 47 3 1670 Aquilae, 3|20 2 38 I 18 39S. 7 1682 iſdapri, Dshabeh, 320 & 23 |13 i 59s. 9 1692. 2 Capricorni, 3:20 S 47 |13 3 16S. 9 170'3 Capricorni, Dabih, 320 11 48 I5 18 15S. 10 1712. Pavonis, 1.220 12 23 |57 15 42S. 10 1722 Cygni, Sa'dr, 3|20 16 11 39 43 32 11 173's Delphini, 3|20 25 32 10 44 29 I3 174g Delphini, Rotanen, 320 29 29 |13 59 53 15 1752. Delphini, Scalovin, 320 31 53 |15 59 32 15 176'ſ Delphini, 3|20 35 29 |14 28 53 16 iii. Cygni, Beneb, 1.2|20 35 45 |44. 41 15 16 1782. Delphini, 3|20 38 29 |I5 31 47 17 1796 Cygni, Gienah, 3|20 39 16 |33 20 16 17 1803 Cygni, 3|21 5 22 |29 32 45 25 1812. Cephei, Alderamin, 321 14 35 |61 52 45 27 182% Aquarii, 3|21 22 46 || 6 1S 9S. 29 1833 Cephei, Alphirk, 3|21 26 28 |69 49 43 || Oct. 2 1845. Capricorni, 3/21 30 45 |17 24 48S. 3 183. Pegasi, Emif, 2.3|21 35 32 || 9 6 47 4 #. Capricorni, 3|2| 37 49 |16 52 33S. 9 187|2 Aquarii, 3|21 57 12 || 1 7 33S. 9 1883. Gruis, 2|21 57 40 |47 45 38S. 1 I 1893 Cephéi, 3|22 5 5 |57 22 59 13 1902. Aquarii, 3|22 12 38 || 2 13 40S. 16 1918 Piscis Australis, 3|22 21 50 |33 11 44S. 18 1924. Piscis Australis, 3|22 31 49 |27 54 48S. 19 1933 Pegasi, 3122 33 36 9 57 49 22 1944 Aquarii, Scheat, 3|22 45 43 |26 42 31S. 23 195|x Pisc. Aust., Fömalh. 122 48 24 |30 30 18S. 24 1964 Pegasi, Scheat, 222 55 32 |27 10 27 25 1972 Pegasi, Markab, T22 56 27 ||14 18 37 || Nov. 3 TABLE II.--Continued. c; bſ) Right * : * - : | Names of the Stars. : Asjon. Declination. º º H. M. S | O J / / 1987 Cephei, Er Rai, 3.23 32 16 76 41 52 | Nov. 1991. Andromedae, Alph., 223 59 46 28 10 9 2003 Cassiopeiae, Chaph, 324 0 36 58 13 47 2013. Pegasi, Algenib, 3| 0 4 39 14 15 22 2028 Hydrus, 3| 0 15 56 |78 12 7S. 203% Phoenicis, 2.3 0 18 1 |43 12 12S. 204” Andromedae, 3| 0 30 36 |29 56 0 205% Cassiop., Schedir, 3 Q 31 5 55 37 13 206.3 Ceti, Deneb Kaitos, 2 Q 33 12 18 54 17S. 207). Cassiopeia, 3| 0 46 41 |59 48 41 2084 U. M. Alruccabah, 23 1 0 19 |88 25 7 209.3 Andro., Mirach, 2 1 0 45 |34 44 10 2104 Cassio., Ruchbah, 3| 1 14 57 |59 21 54 || Dec. 211|a. Eradani, Achernar, 1] 1 31 21 |58 12 37S. 212.É. Cassiopeiae, 3| 1 42 11 |62 50 42 213|& Ceti, Baton Kaitos, 3| 1 43 35 |11 9 36S. 2143 Arietis, 3| 1 45 45 (20 59 30 215|2 Piscium, El Rischa, 3 I 53 38 || 1 57 19 216?’ Andro., Almaach, 2 l 53 54 |41 31 32 217|a. Arietis, or El Nath, 2 1 57 47 |22 40 11 2180 Ceti, Mira, 2| 2 10 36 3 43 59S. 2193 Ceti, 3| 2 30 38 || 0 23 15S. 2204 Ceti, 3| 2 31 31 | 12 34 49S. 221|y Ceti, 3| 2 34 38 || 2 31 57 222), Persei, 3 2 52 13 52 50 46 223. Ceti, Menkar, 2| 2 53 33 || 3 25 54 224|3 Persei, Algol, var. 2 56 52 |40 18 30 225. Fornax Chemica, 3| 3 5 20 |29 39 50S. 226|& Eridani, 3| 3 7 31 || 9 26 31S. 227|2 Persei, Algeneb, 2| 3 12 26 |49 15 38 228. Eridani, 3| 3 25 32 | 10 1 26S. 229|3 Persei, 3| 3 31 4 |47 14 54 230|d Eridani, 3| 3 35 31 ||10 20 16S. 231|a Pleiades, Alcyone, 3| 3 37 34 |23 35 4 232|& Persei, 3| 3 44 () |31 23 26 || Jan. TABLE III. Exhibiting the Sun's Right Ascension, in Time, for every day in the year. # January. |February. | March. April. May. June # h. m. s. 1 h. m. s.|h. m. S. h. m. s. h. m. s. hi. m. s. 1 | 18 46 21|20 58 43,2247 51| 0 41 25, 2 32 36|| 4 35 -4 | 1 2 18 50 4621 2 47.22 51 35 0.45 3 2 36 25 4 39 19| 2 3 18 55 11|21 6 5022 55 19| 0 48 42. 2 40 14|| 4 43 25 || 3 4 18 59 3521 10 5322 59 3| 0 52 20, 2 44 4|4 47 31 4 5 | 19 3 59|21 14 54.23 2 46|| 0 55 59; 2 47 55| 4 51 38 || 5 6 | 19 8 2221 18 55,23 6 28 0 59 57 2 51 46|| 4 55 45 6 7 19 12 45|21 22 55 23 10 10| 1 3 16|| 2 55 37| 4 59 52 || 7 8 || 19 17 7|21 26 54 23 13 52; 1 6 56; 2 59 30|| 5 3 59 || 8 9 || 19 21 29|21 30 53 23 17 33| 1 10 35' 3 3 22 5 8 7 || 9 10 | 19 25 50:21 34 50 23 21 14|| 1 14 15| 3 7 16|| 5 12 15 10 11 || 19 30 1121 38 47 23 24 54|| 1 17 55 3 11 10 5 16 24 || 11 12 | 19 34 3}{2} 42 43 23 28 35| 1 21 35| 3 15 4 5 20 32 12 13 |19 38 5021 46 38 23 32 14] 1 25 15| 3 19 O 5 24 41 || 13 J4 || 19 43 9:21 50 33 23 35 54|| 1 28 56|| 3 22 55| 5 28 50 | 1.4 j ñ 19 47 2721 54 27 23 39 34] 1 32 38|| 3 26 52| 5 32 59 || 15 16 || 19 51 4521 5S 20 23 43 13| I 36 19| 3 30 49| 5 37 9 || 16 17 | 19 56 122 2 12 23 46 52| 1 40 1 3 34 46|| 5 41 18 || 17 18 20 0 1822 6 4 23 50 31|| 1 43 44| 3 38 44|| 5 45 28 18 19 20 4 33:22 9 55 23 54 9| 1 47 26|| 3 42 43| 5 49 37| 19 20 |20 848/22 13 45.23 57 48] 1 51 10| 3 46 42 5 53 47| 20 21 |2013 .222 1735, 0 1 26 5453. 350 42 5 57 57| 21 22 |20 17 1522 21 24; 0 5 4 1 58 37| 3 54 42 6 2 7| 22 23 |20 21 27:22 25 13 0 8 43| 2 2 22 3 5S 44|| 6 6 16 || 23 24 |20 25 3922 29 1 0 12 21| 2 6 1 4 245 6 10 26, 24 23 |20 29 5022 32 48; Q 13 53 2 9 53| 4 6 4, 6 14 35 23 26 |20 34 Q22 36 35, Q 1937] 2 13 39|| 4 10 49| 6 18 44 || 26 27 20 38 922 40 21; 0 23 15 2 17 25 4 14 52. 6 22 54 27 28 20 42 18:22 44 6. 0 26 53] 2 21 12| 4 18 56|| 6 27 3 28 29 || 20 46 25 0 30 31|| 2 24 59' 4 23 0 6 31 11 || 29 30 |20 50 32 0 34 9| 2 28 47| 4 27 4 6 35 20 30 31 || 20 54 38 O 37 47 4 31 8 31 TABLE III.-Continued. º ſ # July. August. Sept. Oct. Nov. Dec. h. m. s. i h. m. S. h. m. s. h. m. s. h. m. s. h. m. s. 1 || 6 39 28|| 8 44 22|10 40 30|12 28 35||14 24 45|16 28 29 2 || 6 43 36|| 8 48 15|10 44 8|12 32 12; 14 28 41|16 32 48 3 || 6 47 44 8 52 7|10 47 45 12 35 50 14 32 37|16 37 8 4 || 6 51 52| 8 55 59|10 51 22|12 39 28|14 36 34; 16 41 29 5 || 6 55 59| 8 59 50|10 54 59|12 43 6, 14 40 32|16 45 50 6 || 7 0 6|| 9 3 40; 10 58 36||12 46 45|14. 44 30}16 50 12 7 || 7 4 12| 9 7 30|11 2 12 12 50 24; 14 48 30; 16 54 34 8 7 8 18; 9 11 19|II 5 48|12 54 4|14 52 30; 16 58 57 9 || 7 12 24 9 15 8||11 9 24|12 57 44|14 56 31|17 3 20 10 || 7 16 30| 9 18 56|I1 13 013 1. 24, 15 0 341.7 / 44 11 || 7 20 35 9 22 44|11 16 36||13 5 5 15 4 37.17 12 9 12 || 7 24 39| 9 26 31||11 20 1213 8 47|15 8 41.17 16 33 13 || 7 28 43| 9 30 18||11 23 4813 12 29, 15 12 45' 17 20 58 14 || 7 32 47 9 34 4|11 27 23||13 16 12:15 16 51.17 25 24 15 || 7 36 50|| 9 37 49|11 30 59||13 I9 55; 15 20 57.17 29 49 16 || 7 40 53| 9 41 34|11 34 34|13 23 3815 25 5:17 34 15 17 || 7 44 55| 9 45 19|11 38 10|13 27 23, 15 29 1317 38 41 18 7 48 57| 9 40 3; 11 41 45||13 31 8; 15 33 22, 17 43 8 19 || 7 52 58| 9 52 46||11 45 21||13 34 53; 15 37 32; 17 47 34 20 || 7 56 59, 9 56 29|11 4S 56|13 38 39:15 41 42|17 52 1 21 || 8 O 59 10 0 12||11 52 32|13 42 26;15 45 54; 17 56 27 22 || 8 4 59|10 3 5411 56 8|13 46 13:15 50 6, 18 0 54 23 || 8 8 58|10 7 35||11 59 43||13 50 ii; 54 19||18 5 21 24 || 8 12 56|10 11 16|12 3 19||13 53 5015 58 33|18 9 47 25 || 8 16 5410 14 57|12 6 55||13 57 39|16 2 47|18 14 14 26 || 8 20 52.10 1837|12 10 31|14 I 29:16 ºf 218 18 40 27 || 8 Q4 4519 22 17|12 14 7|14 5 2016 11 18, 18 23 7 2 8 28 4410 25 56|12 1744|14 9 1216 15 35.18 27 33 29 || 8 32 39.1Q 29 3512 21 2114 13 4' 16 19 52; 18 31 59 30 || 8 36 34:10 33 14|12 24 57|14 16 57, 16 24 10, 18 36 24 3i | $ 40 sió 36 53 i4 30 ài liš 40-50 # 31 TABLE IV. Showing the Right Ascension of the Mid-Heaven at 9 o'clock in the evening, for every day in the year. # *— | 27# January. |February. | March. April. May. June. h. m. s. 1 h. m. s. h, m. s. h. m. s. h. m. s. h. In. S. 3 46 21 5 58 43 ºf 47 51| 9 41 25||11 32 36||13 35 14 3 50 46|| 6 2 47 7 51 35. 9 45 3|11 36 25||13 39 19 3 55 11 6 6 50 7 55 19| 9 48 42|11 40 14|13 43 25 3 59 35| 6 10 53| 7 59 3| 9 52 2011 44 4|13 47 31 4 3 59| 6 |4 54 8. 2 46|| 9 55 59|11 47 55||13 51 38 4 8 221 6 18 55, 8 6 28; 9 59 57|11 51 46||13 55 45 4 12 45| 6 22 55| 8 10 10|10 3 16||11 55 37|13 59 52 4 17 7| 6 26 54; 8 13 52|10 6 56||11 59 30|14 3 59 4 21 29| 6 30 53| 8 || 7 33|10 10 35|I2 3 22|14 8 7 4 25 50| 6 34 50| 8 21 1410 14 15||12 7 16|14 12 15 4 30 11| 6 38 47 8 24 54|10 17 55|12 II 10|14 16 24 4 34 31|| 6 42 43| 8 28 3510 21 35||12 15 4|14 20 32 438 50 646 38 8 32 14|10 25 1512 19 014 24 41 4 43 9| 6 50 33 8 35 54|10 28 56|12 22 55|14 28 50 4 47 27 6 54 27| 8 39 3410 32 38||12 26 52|14 32 59 4 51 45| 6 58 20 8 43 I3|10 36 19| 12 30 49 14 37 9 4 56 l/ 7 2 12| 8 46 52|10 40 1/12 34 46|14. 41 18 5 0 18 7 6 4} 8 50 31}10 43 44 12 3S 4414 45 28 5 4 33| 7 9 55| 8 54 9110 47 26|12 42 43|14 49 37 5 8 48 7 13 45 8 57 48|10 51 1012 46 42|14 53 47 5 13 2. T 1.7 35| 9 || 2610 54 53|12 50 42|14 57 57 5 17 15|| 7 21 24 9 5 4:10 58 37; 12 54 42|15 2 7 5 21 27| 7 25 13. 9 8 4311 2 22 12 5S 44; 15 6 16 5 25 39|| 7 29 || 9 12 21|11 6 7, 13 2 45||15 10 26 5 29 50|| 7 32 48] 9. 15 59|11 9 53||13 6 47|15 14 35 5 34 0|| 7 36 35| 9 19 37|11 13 39||13 10 49||15 18 44 5 38 9| 7 40 21| 9 23 15||11 17 25||13 1.4 52.15 22 54 5 42 18| 7 44 6 9 26 53|11 21 I2|13 18 56|15 27 3 5 46 25 9 30 31||11 24 59||13 23 0|15 31 11 5 50 32 9 34 9|11 28 47||13 27 4|15 35 20 5 54 38 9 37 47 13 31 8 - # TABLE IV.-Continued. * gºmºsºmºe; July. August. Sept. Oct. Nov Dec. h. m. sh. m. S. 1 h. m. s. 1 h. m. sº m. S. h. m. s. 15 39 28, 17 44 22|19 40 30|21 28 35'23 24 45 1 28 29 15 43 36 17 48 15|19 44 8121 32 12 23 28 41 || 1 32 48 15 47 44 17 52 7|19 47 4521 35 50 23 32 37] 1 37 8 15 61 52 17 55 59; 19 51 22|21 39 28 23 36 34 1 41 29 15 55 59 17 59 50 19 54 59|21 43 6.23 40 32; 1 45 50 16 0 6 18 3 4019 58 36.21 46 45.23 44 30 1 50 12 16 412 18 7 3020 2 1221 50 24.23 48 30. I 54 34 16 8 18 18 11 1920 5 48|21 54 423 52 30 1 58 57 16 12 24 18 15 820 9 24.21 57 44,23 56 31, 2, 3 20 16 16 30 18 1856.20 13 0122 1 24 0 0 34| 2 || 44 16 20 35 1822 44.20 16 3622 5 5| 0 4 37|2 12 9 16 24 39 18 26 31.20 20 1222 8 47| 0 8 41| 2 16 33 16 28 4318 30 1820 23 4822 1229| 0 1245. 2 20 58 16 32 47 18 34 4'20 27 23|22 16 12| 0 16 5.1 2 25 24 I6 36 50 18 37 49 20 30 59|22 19 55 0 20 57| 2 29 49 16 40 53.1841 3420 34 3422 23 38|| 0 25 5, 2 34 15 1644 55 1845 1920 38 1022 27 23| 0 29 13| 2 38 41 16 48 57 1849 320 41 45|22 31 8 0 33 22, 2 43 8 16 52 58 1852 4620 45 21|22 34 53| 0 37 32] 2 47 34 16 56 5919 56 2920 48 5622 3839| 0 41 42 2 52 I 17 O 5919 Q 1220 523222 42 26|| 0 45 54 2 56 27 17 4 5919 3 54.20 56 822 46 13 O 50 6|| 3 O 54 17 8 58 19 7 35.20 59 4322 50 1 0 54 19 3 5 21 17 12 56 19 11 16 21 3 1922 53 50 0 58 33| 3 9 47 17 16 54, 19 14 57 21 6 55|22 57 39| 1 2 47| 3 14 14 17 20 52 19 18 37 21 10 31|23 1 29| 1 || 2 || 3 18 40 17 24 48 19 22 1721 14 7|23 5 20| 1 || 1 18| 3 23 7 17 28 44 19 25 56 21 17 44|23 9 12| 1 15 35| 3 27 33 17 32.39 19 29 35 21 21 21:23 13 4| 1 19 52| 3 31 59 17:36 34, 19 33 14-21 24 57|23 16 57| 1 24 10| 3 36 24 1740 28, 1936 52 23 20 51 3 40 50 º # TABLE V. Exhibiting the Sun's Declination for every day in the year. 3. January. February. | March. 17 April. May. June. O / / / O / / / | O / / / | O / / / O / / / | O / / / 23 1 52 17 8 57| 7 39 11 || 4 27 37; 15 0 2222 1 44 22 56 45 16 51 46|| 7 16 22 4 50 43; 15 18 26|22 9 49 22 51 10 16 34 18, 6 53 27 5 13 44; 15 36 16|22 17 30 22 45 8 16 16 32 6 30 26; 5 36 39||15 53 50|22 24 48 22 38 39 15 58 29| 6 7. 20. 5 59 28|16 11 8:22 31 43 22 31 43 15 40 11 || 5 44 9| 6 22 II | 16 28 10|22 38 14 22 24 20 15 21 36|| 5 20 53| 6 44 48; 16 44 56|22 44 21 22 16 31 15 2 46|| 4 57 34|| 7 7 17|17 1 25|22 50 4 22 8 16 14 43 40 4 34 10|| 7 29 40|17 17 37122 55 23 21 59 34 14 24 20, 4 10 43| 7 51 54; 17 33 32|23 0 19 21 50 27|14 4 45| 3 47 13| 8 14 11749 1023 4 50 21 40 55.13 44 56|| 3 23 40; 8 36 (); 18 4 30|23 8 56 21 30 37|13 24 34 3 Q 3 8 57 3018 1931|23 1239 21 20 34.13 4 39| 2 36 28, 9 19 32: 18 34 1423 15 56 21 9 47|12 44 11| 2 12 49| 9 41 4|18 48 39|23 18 50 20 58 35||12 23 30|| 1 49 9|10 2 27, 19 2 4523 21 18 20 47 ()|12 2 38; 1 25 27:10 23 40; 19 16 31|23 23 22 20 35 0|11 41 34|| 1 1 45|10 44 44|19 29 5823 25 1 20 22 37|11 20 19| 0 38 3|11 5 36||19 43 6|23 26 15 20 9 51|10 58 53|S. 14 21||11 26 18|19 55 53123 27 5 19 56 43|10 37 17||N. 9 2011 46 48120 8 2023 27 30 19 43 12|10 15 $1 0 33 1|12 7 820 20 26|23 27 29 19 29 19 9 53 36|| 0 56 41|I2 27 15|20 32 1223 27 4 19 15 4| 9 31 31|| 1 20 1812 47 10:20 43 36|23 26 15 19 0 28|| 9 9 19| 1 43 5413 6 5220 54 40.23 25 0 18 45 31|| 8 46 58] 2 7 28|13 26 21:21 5 21|23 23 21 18 30 14 § 24 56| 2 30 58|13 45 3721 1541|23 21 17 18 14 37| 8 || 53 2 54 26|14 4 40.21 25 38|23 18 48 17 58 40 3 17 5.Q14 23 232 35 1423 15 #5 17 42 24 3 41 10|14 42 221 44 27|23 12 38 |17 25 50 | 4 4 26 21 53 *º-ă “pomuſ]UOO– A GT3 WJL “y #I g; 8 |38 [& 81| Ig 88 L 86 Tº º, . . . 8I 08 ############## 03 gl §§ 16 lºg §t gº i ; ; ; log #" Gil & ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; } }} }. QI 13 $398 9, 133, 8: #. I8 8I Ig 61| 93 §§§ {: ; ; ;& Gº!:33, § º ; §§ ; 6I Q3 8 93 ; ; ; , #: ić; ; ; ; ; ; ; jö 93 83.0}, - ... .". 38 II 0& 6 0&| 8& ################# * !.3 8. : L. -/ sº 2T ſº I& ################# LW 93 834.7 63 6169 g & I li '81 gº 0& 6i T T : I |I gº &I '8T 99 * . . . ; #| || 5 || 3: 'gg g I& 8I ra: º I 83 &I gI (99 g I&| 8] 6. f6 33 of ii čilić & 6 338; gº ig gi II 91 Ial Li ; : ; ; ; ; ; ; ; ; ; ; ; # ##| # §§ 6. 391 & 8191 & 8 ft, ºw º º º #% ; I3| 9 | %; ; ; ; ; ; ; ; ; ; ; ; ; #; ; ; ; ########, ; ; ; ; ; ; ####| || * : ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ! LI y |QQ y QI.69 # , ; ; #########, ##" ºr §§ #% #######|: " : ; ; ; ; ; ; ; ##################|| 31 6ſ. 338; 8ſ. 919 § 3 ; it gigſ tº : : 3. 8ſ. 33.96 Ig 9108 Li g 81 St. st 83 & L 'o. (YC. H. 9 |8& Ig 9T SH 88 &&. ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ſº tº 33% º lºg I, , , § 3 ; ; § 0% ag| 3 ; ; ; ; #############|} ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; #####, #; ; ; ; ; ; ; ; #}} : : {#########, a #| || #; ; ; ; #########|{ a }} } º s º iſ ºf oil 7 oil 1 on 7 oil o * - t ‘92QI ‘AON ‘10O "das ‘īshānv ‘ĀInſ § TABLE VI. Exhibitin the Sun's mean place in the Ecliptic, or its Longitude, together with the Right Ascension, for every day in the year. January. February. March. April. ă Long. R. A. Long. R. A. | Long. | R. A. jLong. R. A. O 1|280 2281 3.282 4.283 5'284 6285 7,286 8,287 9:388 10:289 11290 12:291 13292 14|293 |5|294 16295 17|296 1S|297 10|299 20|300 21:301 22|302 23:303 24:304 25|305 26,306 27|307 28.30S 29.309 30|310 31|311 | | O 39|2S1 41|282 42|283 43284 44,286 45}2S7 46.288 48:2S9 49290 50|291 51292 52.293 53294. 54|295 55|296 57|297 58.299 59|300 301 302 303 304 305 306 307 308 309 310 10|311 11|312 121313 f O 35:312 41:313 4S$31.4 54315 0.316 5.317 11:318 17,319 22:320 28;321 33,322 3s;323 43;324 47;325 52:326 56 327 0.32S 4:329 8330 12:331 iš333 22:334 25:335 27:336 30:337 §33s #339 36 38 39 ſ 13 14 14 15 16 17 17 18 19 19 20 21 21 22 22 23 23 24 24 25 25 26 26 26 27 27 27 27 O 314 315 316 317 31S 319 320 321 322 323 324 325 326 327 328 329 330 331 332 334 335 336 337 33S 339 340 341 f | O 41.340 42 341 42 342 43 343 43 344 44.345 46 346 44,347 43.348 43,349 41:350 40.35i 40'352 3S353 §54 33,355 33,356 31:357 29:35S 27:359 24,000 1 f O 27 341 2S 342 2S 343 2S 344 2S 345 2S 346 2S 347 2S 348 27 349 27 350 27 351 27,352 27.353 26,353 26,354 26,355 25,356 25.357 24, 35S 24 359 24 23 22 22 21 21 20 19 1S 1S 17 0 o 5S'11 54,12 50,13 46,14 41'15 37,16 32.17 2S:18 23;19 1820 1321 gº2 423 59.24 53.25 4S25 43.26 3S27 3228 27.29 22 30 1631 10,32 5,33 0.34 54:35 49;36 42#37 3Sł3S 32.39 27 1 o 16 10 15 11 14 12 13 (3 12 - 4 11 14 10 15 9 16 S 17 6,18 519 420 3.21 122 0023 5924 57.25 56'25 5426 5327 51.28 50'29 4S:30 4731 45|32 43|3.3 42|34 40|35 38:36 36||37 ſ 21 16 29 24 19 14 5 56 51 47 43 39 cº) ºr SO 2S 25 21 18 1s 19 TABLR, WI.-Continued. 5. May. June. July. August. 3|61 Long. R. A. Long. R. A. Long. R. A. O / 40 34 41 32 42 31 43 29 44 27 45 25 46 23 47 21 48 19 49 16 50 14 51 52 53 S 54 6 56 1 56 57 58 59 60 62 45 63 43 64 40 65 38 66 35 67 33 68 30 |69 28 3S 39 40 41 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 59 60 61 62 63 64 66 67 º !: 46 4 !) 44 42 41: 41. 41. 41 41. 41; 41 41: 42. 42. 43. 44 45 46 47. O 70 71 72 73 74. 75 76 77 7S 79 79 SO S1 S2 83 S4 85 86 S7 S8 S9 90 91 92 93 94. 95 96 97 98 f 25 23 20 1S 15 12 10 f 4. 2 59 56 54 51 48 46 43 40 37 35 32 29 26 24. 21 18 15 13 10 7 O 6S 69 70 71 72 73 : 74 76 77 7S 79 S{) 81 S2 S3 S4 S5 S6 S7 88 89 90 91 92 93 94. 95 96 97 98 ſ fi o 48 50 51 53; 54:10: 56 5S 0 2 23||13 24,116 27:117 30.118 32:119 34;120 36:121 39;121 4.15122 43.123 461124 48#125 50;126 127 4| 99 1100 59,101 56;102 53, 104 50.105 44,107 42.108 109 110 111 112 113 114 115 116 117 118 119 9||120 6|121 3|122 1: 123 124 125 126 127 128 129 130 f : O 52:128 54:129 56.130 5S$131 132 133 134 135 136 137 138 139 11140 12:141 13;142 13;143 14$144 14:144 i5:145 15:146 15:147 15148 14:149 14:150 14,151 13:152 12;153 11:154 10:155 93.156 # { 9; 10 | 40 37 35 32 29 27 24 22 20 17 15 12 10 8 5 3 1 59 56 54 52 50 48 46 44 42 39 37 35 34 32 O 131 132 133 134 135 135 136 137 13S 139 140 141 142 143 144 145 146 147 148 149 150 150 151 152 153 154 155 156 157 158 159 i ºponuſuo O—'IA GHT3 VJ, £I OS3;8& 6/3 9 6/.333 8/13 0 8/.3|I& A/13 gg 9/3'6I 9/.3 Aj7 º: 9/3 07 ſ.43%I F43 i8 84.39L 843 Z3 &2&gT &46; 03 IA.&#I TA3 #I 0/.31&T 0/.3 / 69&|II 69& O S930I S9& fºg 9936 A.93 Af, g33;S 993 of #93; gº i8 8939 A3 39&# I& I93. 4. 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