MITH’S' ILLUSTRATED ASTRONOMY rwr, sd I'FXEScopii: in size in thf united states, at the Cincinnati observai ouv N t ro - ^ d r k : DANIEL BUKGESS'& CO., 60 JOHN.STREET (LATE CADy >iR Wm. Hkrsciiki/s do. at Greenwich, London, -It) do. inleiu'th (not muse ) J lie Dorpat 1 cleseope, at Dorpnt (K.u.ssia,') Prof. Strovb, 16 “ Sir .mhrs Soi.'Tii's 'J’eh'scope at Imndon, 1 !) “ Cirieirinali 'I’clescope, (Ohio,) PitoF. MirciiRi,, 17 “ 'I’elescopc at O.mihridgc, Ma.ss 2B “ t'-imher cTll'yh-Tr^nrlicih^ wtierjevi-r a leaeon i» /(iven to a class, that the orted it upon his shoulders : hut, what kept the waters in their plare, or upon what the Elephant, Turtle, or Atlas stood— this was a mystery they coui o nevkr solve ] Q. Did they believe the earth extended the same distance in all directions ? A. They believed it to extend much farther from east to west than from nortli to south. [They observed that in going east or west, on the same parallel of latitude, no change took place in tlie appearance of the heavens ; hut in going north or south, on the same meridian, every sixty miles caused a dift'erence of one degree in the elevation of the pole and in the position of the circles of daily motion of the sun and other heavenly bodies ; therefore they concluded that the earth was very long fromrf^ast to west, hut comparatively narrow from north to south From this originated the' use of the terms longitude and latitude ; longitude meaning length, and latitude, breadth ] Q. What ideas had they respecting the motions of the sun, moon, and Stai's ? A. They supposed that they revolved around the earth, from east to west, every day. Q. What was this system called, that supposed the earth to be at rest in the centre, and all the heavenly bodies to revolve around it? A. The Ptolemaic system. [Ptolemy asserted, that the sun, moon, planet.^ and stars revolved around the earth, from east to west, every ’^4 hours ; and to account for their not falling upon the earth, tvhen they passed over it. he supposed that they were each fixed in a separate hollow crystalline globe, one within the other. Thus the moon was in tlie first ; Merctjry in the second ; Venus in the thisd ; the sun in the fourth ; .Mars in the fifth ; Jtipiter in tlie sixth ; Saturn in the seventh ; — (the planet Herschel was not known at this time) — the fixed .stars in the eighth. He supposed the stars to be in one sphere as they are kept in the same positions with respect to each other. To permit the light of the stars to pass down to the earth, he supposed these s])heres or globes were perfectly clear or transparent like gla.ss The power which moved these spheres, he supposed, was communicated from above the sphere which contained the stars ] LESSON II. Question. Every one is conscious that the sun, which rises daily in the east and sets in the west, is the same body ; where does it go during the night ? Answer. It appears to pass round under the earth. Q. When we look out upon the stars, on successive evenings, they appear to have a definite position with respect to each other, and a westward movement like the sun ; what motion do they appear to have from their setting to their rising ? A. They appear to pass under the earth. Q. From the north to the south point of the heavens, there is a con- tinuous arc of stars, and in their passage under the earth they are not at all disarranged, what can you infer from this fact? A. That they pass completely around the earth, and ! every thing attached to it. Q. We see no body at rest that does not touch some permanent sup- port, hut we see bodies in motion supported for different lengths of time, without resting upon any other surface ; if the earth is hung upon nothing, is it probably at rest? A. It is more probable that it is in motion. Q. If we throw a ball, does the same side always remain forward? A. It does not; it turns over continuously. Q. What do we call the line round which it turns ? A. Its axis. Q. If a fly were on the ball, would distant objects appear to him to be stationary? A. They would appear to revolve around the ball, as often as it turned over. Q. If the earth is moving in space, is it in accordance with the known motion of ordinary bodies, to suppose that the same side remains forward ? A. It is not. It is more reasonable to suppose that it turns on its axis. Q. If the earth turns, and we are carried round on its surface, xvhat appearance must the sun and distant stars necessarily present ? A. They must appear to move around the earth in the opposite direction. LESSON III. Question. What other reason can 3'ou give for the earth’s turning? Answer. The stars are so distant, that their motion would be immensely swift, in compari.son with the mo- tion of the earth, to produce the same effect. Q. But have we not positive proof, and that too of different kinds, that the earth turns on its axis ? yl. We have. — 1. The shape of tlie earth, elevated at the equator and depressed at the poles, can be ac- counted for on no otlier supposition. 2. A body at the equator, dropped from a great height, falls eastward of the perpendicular. 3. The trade winds and ocean currents in the tropi- cal regions are clearly traceable to the same cause. Q. If the earth is moving in space, does it proceed in a straight line ? A. It does not ; but it would do so, Avere it not attracted by other bodies. Q. What is the attraction, by which all particles of matter tend towards each other, called ? A. The attraction of gravitation. Q. What large body, by its attraction, causes the earth to revolve around it in a curve line ? A. The sun. Q. What other similar bodies revolve around the sun ? A. The planets. Q. What may we call the earth, when considered with regard to its size, shape, motions, &c. ? A. One of the planets. Q. What science describes these characteristics of the earth, and other heavenly bodies ? A. Astronomy. 8 iHERSCMtL • ASTP«A COMET MERCURY# VENUS EARTH MARS STEROIDS^!:! - COMPARATIVE MAGNITUDES 3U PIT£ j;^ ' . ' I I L L U S '1' 11 A 1' E D LESSON IV. ASTRONOMY. Question. What is astronomy? Answer. Astronomy is tlie science wliicli treats of the heavenly bodies. Q. What arc the heavenly bodies ? A. The sun, moon, planets, comets, and stars, Q. What are some of their characteristics, of wiiich astronomy treats ? A. Their appearance, size, shape, arrangement, dis- tance, motions, physical constitution, mutual influence on each other, &c. Q. Are they all of the same magnitude, or size ? A. The sun and stars are much larger than the other bodies. Q. Are they all at the same distance from the earth ? A. They are not ; the moon is the nearest, and the stars the most distant. Q. Do they all emit light of themselves? A. They do not. Q. How are they divided in this respect? A. They are divided into two classes, luminous and opake. Q. What is a luminous body? A. It is a body which shines by its own light. Q. What is an opake body ? A. It is a .body which shines only by reflecting the light of a luminous body. Q, Which are the luminous bodies in the heavens? A. The sun and fixed stars are luminous bodies. Q. Which are the opake bodies in the heavens ? A. The moon, planets, and comets. Q. Why do the moon, planets, and comets appear luminous? A. Because they reflect to us the light of the sun. Q. What is the shape of the heavenly bodies ? A. They are round like a globe or ball. Q. What do the sun, moon, planets, and comets constitute ? A. They constitute the solar system. LESSON V. THE SOLAR SYSTEM. Question. How are the bodies constituting the solar system arranged ? Answer. The sun is placed in the centre of the sys- tem, with the planets and comets revolving around it at unequal distances. Q. How many planets are there in the solar system ? A. Fifty-two is the number known at present. Q. How are they divided with respect to their motion ? A. They are divided into two cloisses, primary and secondary. Q. VV'^hat is a [)rimary planet ? A. It is a planet which revolves around the sun only. Q. What is a sticondary planet ? A. It is a planet which revolves around its primary, 1 and with it around the sun. Q. What are the secondary jdanets usually called ? A. They are called satellites or moons. Q. How many primary planets are there ? A. 8 large planets and 23 asteroids or small planets. A S '1' il () N O MY. 9 Q. Wliat are their names, beginning at the suti ? A. Mercury, Venus, the Etirth, Mars, (Twenty-three Asteroids or small Planets,) .Jupiter, Saturn, Herschel, or Uranus, and Leverrier, or Neptune. Q. How many secondary j)lanets or moons are there? A. Twenty-one. Q. \Vhich planets have moons ? A. The Earth has 1, Jupiter 4, Saturn 8, Herschel 6, and Leverrier 2. LESSON VI. Question. How many revolutions has a primary planet? Answer. Two; one on its axis, and another around the sun. Q. What is the axis of a planet ? A. It is a straight line, round which it turns. Q. What is the path called, in which a planet revolves avound ihe^pn ? A. It is called its orltit. Q. What is the earth’s orbit ctilled ? A. It is called the ecliptic. Q. Why is it so called ? A. Because eclipses take place, only when the moon is in its plane. • Q. How many revolutions has a secondary planet? A. T4ree. 1st, the revolution upon its axis ; 2d, the revolution around its primary ; 3d, the revolution with its primary around the sun. Q. How are the planets divided, with respect to their distance from the sun ? A. Into inferior and superior, according as their dis- tance from the sun is inferior or superior to that of the earth. qt Which arc the inferior planets? A. Mercury and Venus. Q. Which are the superior ? A. Mars, the Asteroids, Jupiter, Saturn, Herschel, and Leverrier. LESSON VII. DIAMETERS. Magnitudfs ; THE Earth BEING 1. Distances from THE Sun. Revolution O.N THEBR AXIS. Revolution AROUND THE Sun. Miles. Miles. Days. Hours. Years. Days. Sun, 886,952 1,384,472 25 10 Mercury, .3,200 1 37,000,000 24 88 Venus, 7,700 9 68,000,000 23J 224 Earth, 7,912 1 95,000,000 24 1 0 Mars, 4,189 1 142,000,000 24i 1 321 Vesta, 270 I • • • 'c'STtrh 22.5,000,000 Unknown. 3 230 Astriea, unknown. Unknown. 253,000,000 (6 4 105 Juno, 1,400 254,000,000 (( 4 131 Ceres, 1.600 1 263,000,000 44 4 222 Pallas,* 2,100 1 263,000,000 44 Hebe, unknown. Unknown. Unknown. 44 Iris, a a U 44 Flora, a (( u (4 Jupiter, 87,000 1,280 485,000,000 10 11 314 Saturn, 79,000 1,000 890,000,000 10^ 29 167 Herschel, 35.000 80 1,800,000,000 84 5 Leverrier 35,000 80 2,850,000,000 166 * Herschel estimated the diameter of each of the asteroids to he under 000 miles. Their groat dis tance, extreme smallnoss, and ucbulous appearance, render it extremely difiicult to ascertain their size with accuracy. CIRCLES NOT INTHES^PLANE AN OBLIUHEVIEW OFTKEOUTER CIRCLE APHELION MfAN PLACE MEAN PLACE -jjSrmfuc**- roptf CIRCLE op > KEPLERS LAWS THE MEAN PLACE OFA PLANET IS BEFOflETHE / TRUE PLACE WHILE ins/ M.0VIN& FROM THE / APHELIONTOTHE /ycl? PERIHELION / . d SZ?;f<" juNEi” ® thetrue placeofa planet &' \ IS BEfOAETHE MEANWHILE \it 1SMOVINC fROMTHE \periheliontothe . \ APHELION / ^ JUNE I” \ J I ILLUSTRATED LESSON VIII. CENTRIPETAL AND CENTRIFUGAL FORCE. (^tr.slion. What is tliat force called with which all bodies attract each other io proportion to their mass ? Answer. The attraction of gravitation. Q. What is centripetal force ? A. It is the force vt hich draws a body towards the centre round which it is revolving. Q. What large body by its attraction exerts a centripetal force upon all the primary planets and comets? A. The sun. Q, What body exerts a centripetal force upon the moon ? A. The earth. Q, What bodies exert a centripetal force upon the other moons ? A. The primary planets around which they revolve. Q. What is the centrifugal force of a heavenly body 1 A. It is that force which moves it forward in its orbit, Q. How do these two forces cause the planets to move ? A. They cause them to move in circular or elliptical orbits. Q. What is a circle ? A. It is a plane figure bounded by a curve line, all parts of which are equally distant from the centre. — (Fig. 4.) Q. What is an ellipse ? A. It is an oblique view of a circle. (Fig. 4.) [Note. — Teachers should be sure that the pupils understand the definition of an ellipse, because in viewing some of the diagrams they may receive a wrong impression. In the diagram repre* seating the seasons, the earln’s orbit appears very elliptical : this would be well understood by the pupil, should the teacher call his particular attention to it. Also, a plane of a circle should bo well understood.] Q. What are the foci of an ellipse? A. They are the two points around which the ellipse is drawn. (Fig. 7.) Q,. Where are these points situated ? A. In the greater axis, at equal distances from the centre. Q. What is the eccentricity of an ellipse? A. It is the distance from the centre to either of the foci. (Fig. 7.) Q, Where is the sun situated within the orbit of each planet? A. It is situated in one of the foci. (Fig. 8.) Q. When are circles in the same plane? (Fig. b.) A. When their planes lie in the same straight line, Q. When are circles not in the same or parallel planes ? A. When their planes intersect each other. (Fig. 6.) LESSON IX. Question. How many laws did Kepler discover, which bear his name ? Answer. Three. Q. To what do they relate ? A. They relate to the motions of the planets. Q. What is the first law of Kepler ? A. That all the planets revolve in elliptical orbits, having the sun in one of their foci. (Fig. 7.) Q. What is the second law ? A. That the radius vector passes over equal spaces in equal portions of time. Q. What is the radius vector ? A. It is a line drawn from the sun to a planet, in any part of its orbit. (Fig. 7.) Q. M'hat is the third law ? A. It is that the squares of the times of the revolu- tions of the planets around the sun, are proportional to the cubes of their mean distances from the sun. ASTRONOMY. ii THE MEAN AND TRUE PLACE OP A PLANET. Q. What is the mean place of the earth, or a planet in its orbit ? A. It is that point in its orbit where it would be if it moved in a circle, and with the same velocity at all times. (Fig. 8.) Q. What is the true place of the earth or a planet ? A. It is that point in its orbit where it really is at any given time. (Fig. 8.) Q. What is the aphelion ? A. It is that point in the orbit of the earth or planet farthest from the sun. (Fig. 8.) Q. When is the earth in the aphelion, or farthest from the sun ? A. July 1st. (Fig. 8.) Q. What is the perihelion ? A. It is that point in the orbit of the earth or planet nearest to the sun. (Fig. 8.) Q. When isrthe earth in the perihelion, or nearest to the sun ? A. January 1st. (Fig. 8.) LESSON X. Question. In what points of a planet’s orbit do its mean and true places coincide ? Answer. At the aphelion and perihelion. (See Fig. 8.) Q. What straight line connects these points, and passes through the sun ? A. The apsis line. Q. When is the true place of the earth or planet behind its mean place ? A. While it is moving from the aphelion to the peri- helion. (See Fig. 8.) Q. When is the true place of the earth or planet before its mean place ? A. While it is moving from the perihelion to the aphelion ? (See Fig. 8.) Q. When does it move with the least velocity ? A. When it is at its greatest distance from the sun. Q. When is the motion of the earth or planet in its orbit increasing? A. When it is moving from the aphelion to the peri- helion. Q. Why does the motion increase from the aphelion to the perihelion ? A. Because it is approaching nearer to the sun. Q. What causes it to approach the sun ? A. The centrifugal force at the aphelion is not sufii- ciently great to prevent its falling towards the sun. Q. When does the earth or planet move with the greatest velocity? A. When it is the nearest to the sun. Q. When is the motion of the earth or planet decreasing ? A. While it is moving from the perihelion to the aphelion. Q. Why does the motion decrease from the perihelion to the aphelion ? A. Because the planet is receding from the sun. Q. What causes it to recede from the sun ? A. The centrifugal force at the perihelion is so great as to carry it farther from the sun. CENTRIPETAL AND CENTRIFUGAL FORCES. A body projected by any force would always move forward in a straight line, and with the same velocity, unless acted upon by some other force. A ball discharged from a gun or thrown from the hand soon looses its projectile force by the resistance of the atmosphere, and is brought to the ground by the attraction of the earth, or centripetal force. (Fig. 3 ) These Iw’O forces can be well Ulustrated, (Skk Fig. I, 2,) by tying a string to a ball and swinging it round j the centrifugal force imparted to the ball by the hand and by means of the string, causes the ball to move in a circle j but if the string should break, the centrifugal force would carry it ofl‘ in a straight line, if the ball were not attracted by the earth. The string corresponds to the attraction of the sun in our solar syg- tem, which causes the planets to move in regular curves around the sun, instead of straight lino. If the attraction of the sun or centripetal force should cease, the planets would fiy ofi' into space in straight lines ; but if the centrifugal force should cease and the centripetal force continue, the planets would immediately fail into the sun. 1 I II REMARKABLE SPOTS THAT HAVE ^ / TM£ tPOrs KmSTAPP / or THf suN.PAst evtn CAP on rue tAtr HDr\ MO Bictrrejii on m itfh THCte SPOTS eXHItlT THt CM At \ uNoeneo DUA! ne T/t£//i pas NOES WHICH THErrpeaucHTL r MB 0 VSR THE SUM'S DISK , SOUTH TRANSITS OF MERCURY 8c VENUS UNTIL THE BEEN DISCOVERED UPON THE SUN YEAR 19 00 :/!*'•** NORTH LS'JTA I L L U S 'I' 11 A 'r E DAS T R O X O M Y 13 LESSON XI. THE SUN. (^iirs/hn. What body is in tlic centro of the solar system? i AiLswcr. The sun. (1. Describe the sun ? A. The suii is a larp^o luminous body, wliich gives ' light and heat to the whole solar system. ' Q. What is (he diameter of the sun ? A, 886,952 miles. Q. How much larger is the sun than the eartli? A. It is 1,384,472 times greater. j What is the specific gravity oftlie sun? A. It is Is the weight oi' water. (1.38.) Q, What is the size of the sun compared wil'i the planets? A. It is 5U0 tiuies as gretil as the bulk of all the planets. Q. What can you say of its mass or weight ? A. It is about 750 times the mass of all the planets. (}. \\'hat is the distance of the smi from the eartli ? A. It is about 95,000,000 of miles. Q. What did the ancient astronomers consider the sun to bo ? yl. A large globe of fire. Q, What do astronomers at the present day consider it to be ? A. An opake body like the earth, surrounded by a luminous atmosphere. Q. What motions has the sun ? A. It has three motions — 1st, on its axis; 2d, around i the centre of gravity of the solar system; 3d, around j the centre of the universe. [The term universe is used by astronomers, though perhaps improperly, to designate the great cluster or firmament of stars in wliich our sun is situated.— (S kf, pao^-s 45 and 46) This cluster i tic In lies all ilie single stars th^t can be seen with the naked eye. and all those comy>osing the galaxy or milky way 'I'ho number of stars or suns in the cluster is e.stimatcd at many millions ; all which, like our sun. are supposed to revolve around the common centre of gravity of the whole cluster. Several thousand other distinct clusters or nebul®, situated without our firmament, can be seen by the best teiescot>es, nearly all of wliich are invisible to the unassisted eye.] LESSON XII. Qupstion. What is the inclination of the sun’s axis to that of the ecliptic ? Ansioer. About 7? degrees. Q. In what time does it revolve on its axis? yl. Ill about 25 days and a half. Q. How is the revolution of the sun on its axis determined ? yl. By spots on its surface, which first appear on the east side, pass over, and disappear on the west side. Q. What is the nature of these spots ? A. They are supposed to be openings in the luminous atmosphere, which enable us to see the dark body of the sun. Q. tVhat occasions these openings in the luminous atmosphere? A. They have been attributed to storms and various other causes. Q. Do these spots undergo any changes ? yl. They are constantly changing, and sometimes very rapidly. Some have appeared, others disappeared sud- denly. Q. On what part of the sun do they appear? A. Within about thirty degrees of the equator. Q. Is the surface of the sun, in the region of the spots, tranquil or I agitated ? I yl. It is in a state of continual and violent agitation. Q, W’hat reasons have we to suppose that the luminous part of the sun is intensely hot? A. 1st, the heat of its rays, when collected info a focus, is very great. 2d, its rays pass through glass with the greatest fiicility, (a property belonging to arti- ficial heat in direct proportion (o its intensity.) 3d, the brightness of the siin is grtmter than the most vivid flames, or the most infensely ignited solids, LESSON XIII. TRANSIT OF MERCURY AND VENUS. Qitpslion, WYiat is the transit of a heavenly body ? Ansive?'. It is its passage across the meridian. Q. What is generally meant by the transit of Mercury and Venus? A. It is (heir ptissage across the sun’s disc. What is the disc of the sun or a planet ? yi. It is the circular illuminated surface visible to us. Q. How do Mercury and Venus appear, when passing across the sun’s disc ? A. They appear like black spots moving across the sun. Q. What proof have we that Mercury and Venus are not luminous bodies ? A. When viewed with the telescope they appear horned like the moon, Q. On wliich side of the sun does a transit begin ? A. On the east side, and terminates on the west side. THB SPOTS ON THE SUN. • Astronomers do not agree, in all respects, as to the cause of the spots on the sun From the facts already known, the follow’ing appears to be the most rational view' ol the subject The body of the sun, wliich is opake. is surrounded by a transparent atmosphere, in which float two strata of lumi- nous clouds ; the lower stratum being more dense and opake. and les.s luminous than the upper; wliile the latter, by its brilliancy, furnishes the greater poKion of tlie intense light of the sun. Above the upper stratum, the transparent atmosphere extends to a great height. ‘'J'lie agency by which the light and heat of the sun are generated, is not known. 'l‘he only agent of which we know, that presents analogous phenomena, is electricity. The northern lights are supposed to exhibit, in a feeble manner, an action similar to the luminous strata of the sun. The polar regions of the sun are tranquil, and the equatorial comparatively so ; but the surface on each side of the equator, from 16 to ‘25 degrees therefrom, is in a state of constant and violent agitation It is in this di'^turbed region that the spots are seen ; no spot ever occurring farther tlian about 30 degrees from the equator. The spots, besides revolving w'ith the sun. are found to have a motion from the equa- tor low'ards the poles, and when they arrive at the comparatively calm region, they gradually dis- appear. Sometimes they close up with great rapidity, at others they appear to be suddenly broken into fragments and dispersed Bright spots and streaks, called faculte. apparently caused by weaves in the luminous portion of the atmosphere, also appear on various parts of the disc, but are seen most di.stinctly near the margin. In the places where spots appear, faculte are usually seen on the day previous to their breaking out But w'hat causes the agitation of the sun's atmosphere, which is so great as frequently to burst open the luminous strata ? Astronomers, at difl’erent limes, have suggested various causes for the sun’s spots, such as jets of gas issuing from the sun and decomposing the luminous clouds ; high mountains, extending through the luminous strata; volcanoes, sending forth ashes, smoke, &c ; to say nothing ol exploded theories of an older date, such as ashes, scoris, &c., on the surface of tlie melted, burning mass ; or bodies very near tlie sun, revolving round it. But if we are permit- ted to reason from what takes place on the earth, we would say, that a close analogy e.xists betw'een the phenomena observed in our owm atmosphere and in that of the sun. On the earth the heat of the torrid zone causes the air to expand and rise, causing currents in the lower part of the atmosphere towards the equator, and in the upper part of the atmosphere currents tow'ards the poles. The turning of the earth on its axis causes the under currents to take a westerly direction, while the tipper currents sweep in a curve, westerly first, then towards the poles, and finally east- ward. The principal disturbance of the atmosphere caused by the trade wind is in the vicinity of the tropics. Storms commencing in the torrid zone, are carried in the direction of the upper cur- rents of air. Forinstance, a storm started in the West Indies, by the heating of the air over one of its islands, thus causing an upward and circular movement of the air. u.suafly sweeps to the west and north over Florida, or the Gulf of Me.xico, and then northeast, over the United States. Similar causes acting upon the atmo-sphere of tlie sun.'would exhibit phenomena similar to those which fli*e see. This explanation supposes the atmosphere of tiie sun to he warmer at the equator than at the poles ; but as the sun does not, like the earth, receive its heat from any extraneous body, its difler- ence of temperature must be sought for in the escape of its heat. It could attain this condition either by a more fiee radiation of heat at the poles than at the equator, or by its absorption as latent heal, in the evaporation from large bodies of water in the polar regions. As the sun turns on its axis, its equatorial diameter must be greater than its polar, and the stratum of atmosphere above the luminous clouds must be thicker over the equatorial region than over the polar. This must render the radiation less free at the equator than at the poles, and cause that part of tlie sun to be of a higher temperature An excess of heat at tlie sun’s equator, with its rotation on its axis, is sufti- cient to cause currents in its atmosphere similar to our trade winds, and thus disturb its equatorial regions ; and if the spots are caused by storms bursting open the luminous strata, their receding from the equator towards the jioles is undoubtedly the effect of the same physical causes that gi\e a similar motion to storms upon the earth. Some have supposed the body of the sun to be protected by the lower opake portion of the inner stratum of clouds, from the intense heat of the luminous strata, and thus rendered inhabitable ; but several objections will at once arise to this theory. First, the body of the sun being surrounded by dense and opake clouds, could not send off' Us heat into space by radiation, and therefore the beat received from tlie clouds would accumulate and cause a high temperature. Second, the force of gravity being about thirty times as great as that of the earth, a common sized man would weigh some two or three tons ; rendering it necessary to have an entirely different muscular organization. Third, it is improbable that living beings would be shut up within an impenetrable veil, and cut off' fiom a knowledge of the planets, the stars, and the countless w'onders existing in the boundless realms of space These and other considerations render it probable that the sun is not inhabited. | tin:: ILLUSTRATED ASTRONOMY 15 Q. Wliich sign does the earth enter at tliis tiiric ? A. Caj)ricort)iis. Q. Which signs does the sun enter, when the north pole leans side- ways to the sun '! LESSON XIV. ZODIAC. Question. What is the Zodiac? Answer. It is a circular belt in the lieavens 16 degrees wide; 8 degrees on each side of the ecliptic. Q. How is the zodiac divided ? A. It is divided into 12 equal parts, called signs or constellations of the zodiac. Q. How is each sign divided ? A. Each sign is divided into 30 degrees; each degree into 60 minutes; each minute into 60 seconds, ,&c. Q. What great circle is in the middle of the zodiac? A. The ecliptic, or orbit of the earth. Q. What are the names of the constellations of the zodiac and the signs of the ecli[)tic ? A. Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpio, Sagittarius, Capricornus, Aquarius, and Pisces. Q. Do the constellations of the zodiac and the signs of the ecliptic occupy the same places in the heavens ? A. They do not: the signs in -the ecliptic have fallen back of the constellations about 31 degrees. Q. Did the constellations of the zodiac and signs of the ecliptic ever correspond ? A. They corresponded to each other about 22 centu- ries ago. Q. What is the cause of the falling back of the signs of the ecliptic among the constellations? A. It is caused by the retrograde motion of the equi- noxes. (Note.) Q. Upon what does the length of the seasons depend ? A. They depend upon the revolution of the earth from one equinox to the same, again. Q. Does the earth revolve around the sun in exactly the same time that it moves from one equinox to the same equinox again ? A. It moves from either equinox to the same again, seventeen minutes sooner, than around the sun. LESSON XV. Question. Dons the sun appear to move in the heavens among the sta I's ? Answer. It has an apparent motion in the ecliptic, east- ward around the heavens, during the year. Q. How is this appearance caused, as the sun is in the centre, and ioes not move? A. It is caused by the earth’s moving around the sun. Q. If the earth is in the sign Aries, where does the sun appear to be? A. It appears to be in the opposite sign, Lihra. Q. As the earth moves around in the ecliptic, where does the sun appear to move ? * A. It appears to move in the opposite part of the hea- vens, and in the opposite direction from the motion of the earth. Q. Which sign does the sun enter, when the north pole leans exactly towards the sun ? A. Cancer. (21st June.) A. Aries and Libra. Q. Which sign does the sun enter, when the north pole leans exactly from the sun ? A. Capricornus. (22d December.) Q. Which are the equinoctial signs? A. Aries, 21st of March — Libra, 23d of September. Q. Which are the solstitial signs? A. Cancer, 21st of June — Capricornus, 22d of De- cember. LESSON XVI . Question. How are the signs of the ecliptic divided ? Answer. They are divided into four divisions, corres- ponding to the seasons. Q. Which are the spring signs? A. Aries, Taurus, Gemini. Q. Which are the summer signs ? A. Cancer, Leo, Virgo. Q. Which are the autumnal signs ? A. Libra, Scorpio, Sagittarius. Q. Which are the winter signs? A. Capricornus, Aquarius, Pisces. Q. In what time do the equinoxes fall back through the whole circle of the Zodiac ? A. 25,800 years. Q. What is this time called? A. The Platonic, or great year. Q. How is this motion caused ? A. It is caused by a slow annual motion of the earth’s axis. (Note.) Q. What is longitude in the heavens ? A. It is the distance from the first degree of the sign Aries, reckoned eastward on the ecliptic, the whole circumference of the heavens. Q. When the sun enters Aries, what is its longitude ? A. It has no longitude. Q. What is the longitude of the earth at that time? A. 180 degrees. Q. When the sun enters Cancer, what is its longitude ? A. 90 degrees — the earth’s longitude at the same time 270 degrees. Q. When the sun enters Libra, what is its longitude ? A. 180 degrees — the earth’s longitude 0 degrees. Q. When the sun enters Capricornus, what is the longitude ? A. 270 degrees — the earth’s longitude at the same time 90 degrees. [Note. — T his variation is caused by the pole of the earth varying a little every year Tins mo- tion of the pole of the earth is similar to that sometimes shown by a top. as it spins around on the point — The stem of the top will have a circular motion, describing a cone with the ape.x or top down. This circular motion of the pole of the earth is very slow, varying only 50" every year, and requires 25,863 years to complete a revolution — which is called the Platonic or great year. The pole of the earth is increasing its distance from the north star and in 12,900 years it will be about 47® from it : and when the north star is on the meridian, it will be in the zenith of the noi-thern part of the United States : but in 25.800 years the pole will have made a complete revolution -so that it will point again to the north star.] I L I. U S 'r II A 1’ K D LESSON XVII. MERCURY. Queslion. Which planet is the smallest and nearest the sun? Answer. Mercury. Q. What is the diameter of Mercury? A. 3,200 miles. Q. What is its distance from the sun ? A. 37 millions of miles. Q. What is its magnitude, compared with the earth ? A. It is -n of tlie earth’s magnitude. Q. What is the specific gravity of the planet Mercury? A. It is about 15 times the weight ol water. (15.111.) Q. In what time does it revolve on its axis, or perform its daily revo- lution ? A. In about 24 hours. (24 hours 5 minutes.) Q. In what time does it revolve around the sun ? A. In about 88 days. (87d. 23h. 14m. 33s.) Q. How fast does it move in its orbit around the sun? A. It moves 112,000 miles an hour. Q. What is the light or heat at Meicury, compared with that of the earth ? A. It is about seven times as great. Q. What is elongation ? A. It is the apparent distance of any planet from the sun. Q. What is the greatest elongation of Mercury? A. 30 degrees; which may be eitlier east or west of the sun. Q. Why is Mercury never seen in superior conjunction ? A. Because it is so much involved in the light of the sun. Q. Does Mercury experience any change of seasons ? A. It does not, because its axis is perpendicular to its orbit. This causes the sun to be continually vertical at the equator. LESSON XVIII. VENUS. Question. What planet is next to Mercury? Ansiver. Venus. Q. What is the diameter of Venus ? A. 7,100 miles. Q. What is its distance from the sun A. 68 millions of miles. Q. What is its magnitude com.pared with the earth ? A. It is about to of the earth’s magnitude. Q. What is the specific gravity of Venus ? A. It is 5 times the weight of water. (5.058.) Q. In what time does it revolve on its axis ? A. In about 23^ hours. (23h. 21m.) Q. In what time does it revolve around the sun ? A. In 224 days. (224d. 16h. 41m. 27s.) Q. How fast does it move in its orbit around the sun ? A. It moves 75,000 miles an hour. Q. What is the comparative light or heat at Venus ? A. It is about double that of the earth. Q. What is the greatest elongation of Venus ? A. About 47 degrees. Q. When is Venus a morning star? A. When it is west of the sun, and rises before it. Q. When is it an evening star ? A. When it is east of the sun, and sets after it. A S T R () X O M Y . 17 Q. How long is \'emis a morning or an eiening star, alternately? A. About 200 diiys. Q. Why is t’eniis a morning or an evening star GO days longer than the time of its revolution around the snn ? A. Because the earth is tnoving around the sun the same way. [Sec diagram. If we sn[)poso Venus to be in conjunction, or between the earth and sun, as they move the same way, Venus will move half around the sun, or 180 degrees, while the earth moves only 110 degrees. Venus will during this time be a morning star, and when Venus has completed its revolution around tin* sun, the earth will have passed through •220 degrees of its Orbit, and \Y*iins will still continue a morning star, although it has made a complete revolution around the sun. It will therefore hiive to ntidxe one complete revolution and lOG degrees over, before it can be seen oti the other side of the sun ; it will then be an evening star for the same length of time.] LESSON XIX. Question. How much is the axis of Venus inclined to that of its orbit ? Answer. 75 degrees. Q. When the north pole of Venus inclines directly towards the sun, how many degrees will the axis point above the sun ? A. Only 15 degrees. Q. How wide a torrid zone does this make ? A. 150 degree.s — 75 degrees on each side of tlie equator. Q. 'I'he tropics are within how many degrees of the poles ? A. M^ithin 15 degrees. t,'. The |)olar circles are within how many degrees of the equator ? A. 15 degrees. Q. What is the diameter of the polar circles ? A. 150 degrees. Q. Has Venus any variation of seasons ? A. She has two summers and two winters at the equator, and a summer and winter at each of the poles, during the year. Q. liow does Venus appear when viewed xvith a telescope ? A. She exhibits phases similar to those of the moon. Q. How are conjunctions divided ? A. Into inferior and superior. Q. When is a planet in inferior conjunction ? A. When it is between the earth and sun. Q. What planets have inferior conjunction ? A. Mercury and Venus; also the moon. Q. When is a planet in superior conjunction ? A. When it is beyond the .sun. Q. What planets hav*e superior conjunction ? A. All, except the eartli. Q. When is a planet in opposition to the sun? A. When it is on the opposite side of tlie earth. Q. What planets have opposition ? A. The superior planets. Q. What apparent motions have the planets ? A. Three ; direct, stationary, and retrograde. Q. When does a planet’s motion appear to be direct ? A. When it appears to move from west to east among the stars. Q. When is a planet’s motion said to be stationary ? A. When it is moving directly towards or from the earth. Q. When is a planet’s motion said to be retrograde ? A. When it appears to move backwards, or from east to west among the stars. 18 j'€^NO RTn ^\M n n ir a IBIC;© PEHKECI ClBClX or THE HEAVEjyj • w ♦ ♦ » It. * * * ♦ /C !!- « - * AF< DISTANCE 90* ILLUSTRATED LESSON XX. EARTH, DEFINITIONS, &c. Question. Wiiat is the shape ofthe eai'th? Answer. It is round like a globe or ball, a little flat- tened at the poles. Q. How do we know the earth to be round ? A. 1st. Navigators have sailed round it, by a con- tinued westerly or easterly course. — 2d. The top-rnast of a ship coming in from the sea, always appears first. — 3d. The earth’s shadow upon the moon, in a lunar eclipse, is circular. Q. In what manner do the inhabitants stand upon the earth ? A. They .stand with their feet directed towards the centre ofthe earth. (See Diagram.) Q. What do you understand by the terms upward and downward ? A. Upward is from the centre ofthe earth, downward is towards the centre of the earth. Q. What keeps the inhabitants, (fee., upon the surface of the earth ? A. The attraction of tlie earth. Q. What is the axis of the earth ? A. It is the .straight line round which it performs its daily revolution. Q. What are the poles of the earth ? A. They are the extremities of its axis. Q. What is the equator? A. It is a great circle, whose plane divides the eartli into northern and southern hemispheres. O. To what is the plane ofthe equator perpendicular? A. It is perpendicular to the earth’s axis, and equi- distant from the poles. Q. What is the meridian of a place on the earth? A. It is a great circle passing through the place, and the poles of the earth. Into what does the plane of the meridian divide the earth ? A. Into eastern and western hemispheres. Q. What is the latitude of a place on the earth ? A. It is its distance from the equator, north or south. Q. On what is it measured ? A. On a meridian ? Q. How far is latitude reckoned ? T.. Ninety degrees ? Q. What places have 90 degrees of latitude 7 A. The poles. LESSON XXI. Q. Which is the first meridian ? A. It is the meridian from which longitude is reck- oned, Q. Which meridian is generally used in this country as the first mej idian ? A. The meridian of London, Q. WTat is the longitude of a place on the earth ? A. It is its distance east or west of the first meridian. Q. What angle expresses the longitude of a place? A. The angle between the meridian of the place, and the first meridian. Q. Where is this angle f<)rmed ? A. At the poles, where the meridians intersect each other. Q. On what circle is this angle measured ? A. On the equator. A S T R O N O MY. 19 j j Q. How far is terrestrial longitude reckoned ? A. It is reckoned 180 degrees, or half round the earth. Q. What is the horizon ? A. It is a great circle which separates the visible heavens from the invisible, Q. How many horizons are there ? A. Two; the visible and the rational. Q. MTat is the visible or sensible horizon ? A. It is that circle where the earth and sky appear to meet. Q. What is the rational horizon ? A. It is a great circle, parallel to the visible horizon, w hose plane passes through the centre of the earth. Q. Into what does it divide the earth ? A. Into upper and lower hemispheres. Q. Is the rational horizon above or below the visible horizon ? A. It is below the visible horizon. LESSON XXII. Q. Do all places on the earth have the same horizon ? A. They do not; if w^e change our place on the earth, the horizon changes. Q. What are the poles of the horizon ? A. The zenith and nadir. Q. What is the zenith ? A. It is that point in the heavens directly over oui heads, Q. Do all places have the same zenith ? A. They do not ; every place has a different zenith. Q, What is the nadir ? A. It is that point in the heavens which is opposite to the zenith, or directly under our feet. Q. Are the zenith and nadir fixed points in the heavens ? .A. They are not; they make a complete revolution in the heavens every 24 hours. Q. What is the altitude of a heavenly botly ? A. It is its height or distance from the horizon. Q. What is the altitude of the star at A ? (See Diagram.) A. It has no altitude, being in the liorizon, Q. What is the altitude of the star at B ? also at C ? (See Diagram.) Q. What is the polar distance of a heavenly body? A. It is its distance from the pole. Q. What is the polar distance of the star at D ? also at E. and F ? (See Diagram.) Q. Who are the antipodes? A. Those wdio live on directly opposite sides of the earth. Q. Who are the antceci ? A. Those w'ho live in equal latitude, on directly oppo- site sides of the equator. Q. Who are the perioeci ? A. Those who live in equal latitude on opposite sides of the pole. Q. What ppc\iliarity of circumstances have the antipodes? A. They have opposite latitude, seasons, longitude, and day and night. Q. What have the antceci ? A. They have opposite latitude and seasons, but the same longitude, and day and night. Q. What have the perioeci ? A. They have the same latitude and seasons, but opposite longitude, and day and night. 90 WINTER IN THC NORTHTRN HCMItPhCRC SMORTIST C/VVS t LONCLST N &HTS mni mnv 'rrS' i - •• .• 1 /., ; I',.' ■■ N ' -i-v ••.•..... _.i. ■ - ■1 m i I L L U S T R A TED A S 'I' R () N O ]\I Y . 21 LESSON XXIII. EARTH AND SEASONS. Question. What is the shape of the earth? Answer. It is round like a globe or ball, a little Ibit- tened at the poles Q, What is its position in the solar system ? A. It is the third planet from the sun. Q. What is the mean diameter of the earth ? ^.7,912 miles. [Equatorial diameter 7,926 miles; polar diameter 7,899 miles.) Q. How much greater is the equatorial than the polar diameter ? A. About 27 miles. Q. What causes the equatorial diameter to he greater than the polar? A. It is caused by the revolution of the earth on its axis. [As the greater portion of the surface of Uie earth is covered with water ; and as the earth revolves on its axi^he water recedes from the poles towards the equator, until its tendency to run back towards the poles, just balances the effects of the centrifugal force. This causes the equatorial diameter to be greater than the polar. If the earth should stop revolving on its axis, the water at the equator would settle away towards the poles, until the earth had assumed the form of a globe as near as possible. Thus large portions of land in the torrid zone, which are now covered by the ocean, would be left dry, and new continents and islands would be formed.] Q. What is the mean distance of the earth from the sun ? 2. About 95,000,000 of miles. [The mean distance of a j)lanet, is the distance it would always bo from the sun, if its orbit should be reduced to a true circle.] Q. What is the specific gravity of the earth? A. It is 52 times the weight of water. (5.48.) Q. In what time does the earth revolve on its axis, or perform its diurnal revolution ? A. In 24 hours. (In 23 hours 56 minutes ; as seen from the stars.) Q. Which way does it revolve ? A. From west to east. Q. What causes day and night ? A. The light of the sun causes day, and the shade of the earth causes night. Q. How great a portion of the earth is continually in the light of the sun ? A. One half; the other half being in the shade of the earth. Q. What does the revolution of the earth upon its axis, cause ? A. The succession of day and night. LESSON XXIV. Question. As the earth turns upon its axis, what effect is produced ? Answer. The sun is continually rising to places in the west, -and continually setting to places in the east. Q. In what time does the earth revolve around the sun, or perform its annual revolution ? A. In 365 days 6 hours. Q. How fast does it move in its orbit around the sun? A. 68,000 miles an hour. Q. How are the changes of the seasons caused ? A. They are caused by the earth’s axis being inclined to that of its orbit, and its revolution around the sun. Q. How many degrees is the earth’s axis inclined towards its orbit ? A. Twenty-three degrees atid a half (23" 28'.) Q. Is the direction of the earth’s axis changed during the year ? A. Its chatige is so slight that it may be considered as pointing to the same place in the heavens. Q. When does the north pole lean directly towards the sun? A. On the 21st of June, called the summer solstice. (See Diagram.) Q. How many degrees does it lean towards the sun ? A. 23i degrees ; and the sun is vertical 23.2 degrees north of the equator. Q. What seasons docs this produce ? A. Summer in the northern hemisphere, and winter in the southern. Q. When does the north pole lean directly fi-om the sun ? A. On the 22d of December, called the winter sol- stice. (See Diagram.) Q. When the north pole leans from the sun, what are the sea- sons ? A. Winter in the northern hemisphere, and summer in the southern. LESSON XXV. Question. At what points of the ecliptic is the earth at the time of the solstices ? A. At the solstitial points. Q. Through how much of its orbit does the earth pass, in moving from one solstitial point to the other? A. One half of its orbit, or from one side of the sun to the other. Q. What are those two points called half way between the solstitial points ? A. The equinoctial points. (See Diagram.) Q. Why are they so called ? A. Because, when the earth is in these points, the sun is vertical at the equator, and the days and nights are every where equal. Q. When is the sun at the vernal equinox ? A. On the 21st of March. Q. When is it at the autumnal equinox ? A. On the 23d of September. Q. Which way does the pole lean when the earth is at the eqinoc- tial points ? A. It leans sideways to the sun, the sun being verti- cal at the equator. Q. When the north pole leans towards the sun, why is summer pro- duced in the northern hemisphere ? A. Because the rays of the sun strike it so directly as to cause many rays to fall on a given surface. Q. When the north pole leans from the spn, why is winter produced in the northern hemisphere ? A. Because the rays of the sun strike it so obliquely, that they spread over a greater surface. Q. At what points do the ecliptic and equinoctial intersect each other ? A. At the equinoctial points. (See Diagram.) Q. How far are the solstitial points from the equinoctial points ? A. Ninety degrees. tt I T. L U S T R A T E D A S T R () N O M Y . /wO AEROLITES, METEORS, &c. 1 Question. What are meteors ? Answer. They are luminous bodies seen in the ni^lit shooting through the heavens. Q. What are they usually called? A. Shooting stars, and sometimes fire-balls. Q. What is an aerolite ? A. It is a stone falling from the air. Q. Have stones ever been known to fall from the air? A. They have, and in great numbers. (See Table.) Q. How did Laplace, Olbers, and other astronomers account for the falling of these stones? A. They believed that they were ejected from vol- canos in the moon, beyond the moon’s attraction, and therefore attracted to the earth. Q. How did they account for the meteors ? A. They believed them to be gaseous matter col- lected in the upper regions, and ignited by some un- known cause. Q. What is the present tlieory in regard to aerolites and meteors ? A. Astronomers believe that they have the same origin. Q. Do all meteors produce stones which fall to the earth ? A. They do not; very few of them are of suffi- cient density to reach the earth before they are consumed. Q. Do tliese meteors originate in our atmosphere ? A. The most of them have their origin far beyond our atmosphere. Q. What is the present theory of meteors? A. Astronomers maintain that the planetary regions contain detached portions of chaotic and uncon- densed matter, and that the earth in its orbit fre- quently meets with such masses. Q. What effect would be produced by such contact? A. The matter in its passage through the atmos- phere would suddenly be ignited and the gaseous portion consumed, and the mineral portion, if any, would be condensed and precipitated to the earth in the form of a stone. Q. What is a peculiar characteristic of meteoric stonSs? A. They are composed of the same materials an;! nearly in the same proportions, and are unlike any combination of minerals found on the earth. Q. What does this fact prove ? A. It conclusively proves that they have a common origin. Q. When was the greatest meteoric dfsplay ever known ? (See Note 2.) A. On the night of the 12th and 13th of No^a^iiber, 1833. Q. What was the altitude of the meleors on this occasi? A. Prt/essor Olmstead says they were not less than 2238 miles above the earth. Suh.^tance. Place. Period. Shower of stones .At Korno Under Tullus Hostiliu.s. Shower of stones At Homo Consuls C. iMarlius and Tor- quatiis. Shower of iron In Lucania Year before the defeat of Crassus. Shower of mercury [n Italy Large stone Near the river Negos, Thrace Second year of the 70lt» Olym- Year before J. C. 45‘i. Three large stoites In Thrace Shower of fire .At Qnesnoy January 4^1717. Stone ol 7i2 ihs. Near Larissa, Macedonia January, 1706. About l iOO Slones — one of 1-20 } lbs , another of 60 lbs. ^ Near Padua. Italy Ill UlO. Another of 51) lbs. On Mount Vasier, Province November 27, 1037. Sliower of Sand for 15 hours In the Atlantic April 6, 1719. Shower of sul[)hur Sodom ami (lomorra Sulphurous luin In the Duchy of Mansfield In 1658. The same Copenhagen Ill tots. Shower of sulphur Brunswick October, 1721. Shower of unknown matter Ireland In 1695. Two large stones, weighing ? SiO lbs. $ Liponas, in Bresse September, 1753. stony mass .Niort, Normandy In 1760. A stone of 7 1*2 lbs. At Luce, in Le Maine September 13, 17GS .A stone .\t Aire, in Artois In 176.S. A stone In Le Cotenlin In 1768. Extensive .shower of stones Environs of Agen Inly ’j;, 1790. About iZ stones Sienna, Tnscanv July, 1791. A l^rge stone of 56 lbs. Wold Cottage, Yorkshire December 13, 1795. A stone of about 20 lbs. Sale, Department of the Rhone .March 17, 1768. A stone of 10 lbs. in Portugal February 19. 1796. Show'er of stones Benares, East Indies December 19, 1793 Shower of stones At Plana, near Tabor, Bohemia Jnlv 3, 170.'}. Mass of iron, 70 cubic feet America -April 6. ISOO Mass of iron, 14 quintals .•\bakauk, Siberia Very old. Shower of stones Rarboiitan, near Roquefort .Inly, 1789. Large stone of 260 lbs. Ensisheim, Upper Rhine November 7, 1492. Two stones, 200 and 300 lbs. Near Verona In 1767. March 12, 1793 A stone of 20 lbs. Sales, near Ville'Franclie Several stones from 10 to 17 } lbs. ^ .Near LhAigle, Normandy 1 April 26, 1803, NOTE. One of the instances in the table is of sufficient interest to deserve a notice. A singular relation respecting the stone of Knsisheini on the Rhine, (at which philosophy once smiled incredulously, regarding it as one of the romances of the tiiiddle ages,) may now be admitted to sober attention as a piece of authentic history. A homely narrative of its fall was drawn up at the time by order of the emperor Max- imilian, and depo.sited with the stone in the church. It may thus be rendered ; — “In the year of the Lord 14.‘)2, on Wednesday, which was Martinmas eve, the 7th of November, a singular miracle occurred ; for, between eleven o’clock and noon, there was a loud clap of thunder, and a prolonged confused noise, which was heard at n great distance ; and a stone fell from the air, in the jurisdiction of Ensisheim, which weighed two hundred and sixtv pounds, and the confused noise was. besides, much louder than here. Then a child saw it strike on a field in the upper jurisdiction, towards the Rhine and Inn, near the district of Giscano, which was sown with wheat, and it did it no harm, except that it made a hole there ; and then they conveyed it from that spot ; and many pieces were broken from it, whicb the landvogt forbade. They, therefore, caused it to be placed in the church, with the intention of suspending it as a miracle : and there came here many people to see this stone. So there were remarka- able conversations about this stone : but the learned said that they knew not what it was ^or it was beyond the ordinary course of nature that such a large stone should smite the earth from the height of the air ; but that it was really a miracle of God ; for, | before that time, never anything was heard like it, nor seen, nor described. When they found that stone, it had entered into the earth to the depth of a man’s stature, which every body explained to be the will of God that it .should be found; and the noise of it was heard at Lucerne, at Viiting, and in many other places, so loud that it was believed that houses had been overturned: and as the King .Maximilian was here the Monday after St. Catharine’s day of the same year, his royal Excellency ordered the stone which had fallen to be brought to the Castle, and, after having conversed a long time about it with the noblemen, he said that the people of Ensisheim should take it, and order it to be hung up in the church, and not to allow any body to take anything from it. His Excellency, however, took two pieces of it ; of which he kept one, and sent the other to the Duke .■'igi.-mund of Austria : anil they spoke a great deal about thi.s stone, which they suspended in the choir, where it still is ; and a great many peo- ple came to see it.” Contemporary writers confirm the substance of this narration, and the evidence of the fict exists ; this aerolite is precisely identical in its chemical composition with that of other meteoric stones. It remained for three centuries sus- pended in the church, was carried off to Colmar during the French revolution ; but has since been restored to its former site, and Ensisbeim rejoices in the possession of the relic. NOTES. We now come to by far the most splendid display on record ; and as it was the third in successive years, and on the same day of the month, it S'^eiped to invest the meteoric showers with a periodical character; and hence originated the title of November meleors. An incessent play of dazzlingly brilliant meleors was kept up in the heavens for several hours Some of these were of considerable magnilnde and peculiar form. One of large size remained for some time almo.ct stationary in ibe zenith, over the Falls of Niagara, emitting streams of light. The wild dash of the waters, as contrasted with the fiery uproar above ibem, formed a scene of unequalled sublimity. In many districts, tbe mass of the population were terror-struck, and tbe more enlight- ened were awed at conterniilaling so vivid a picture of the Apocalyptic image — that of the stars of heaven f.dling to the earth, even as a fig-tree casting her untimely figs, when she is shaken of a mighty wind. A planter of South Carolina thus describes the efl'ect of the scene upon the ignorant blacks; — I was suddenly awakened by the most dis- tres.sing cries that ever fell on my ears. Shrieks of horror and cries for mercy I could hear from most of the negroes of three qilantations, amounting in all to about six or eight hundred. While earnestly listening for the cause, 1 heard a faint voice near the door calling my name. I arose, and taking my sword, stood at the door. .At this moment. T heard the same voice still beseeching me to ri.«e, and saying ‘ O mj' Cod. the world is on fire.’ 1 then opened the door, and it is difficult to say which excited me rno.-^t — tbe avvfiilness of the scene, or the distressed cries of the negroes. Upwards | of one hundred lay prostrate on the ground — some speechless, and some with the bit- j terest cries, but with their hands ri'.rsed, imploring God to save the world and them. The scene was truly awful ; for never did rain fill much thicker than the meteors fell 1 towards the earth; east, west, north and south, it vvas the same.” I Wl I L L U S T II A T i: D AS T R O N 0 M Y . 25 LESSON XXVI. MARS. Question. What is Mars ? Answer. Mars is the fourth planet from the sun. Q. What can you say of its size ? A. It is the smallest except Mercury and the asteroids. Q. What is its diameter ? A. 4,189 miles. Q. What is its distance from the sun ? A. 142 millions of miles. .Q. What is its magnitude ? A. It is about one seventh of the size of the earth. Q. What is the specific gravity of Mars ? A. It is about five times the weight of water. (5.19.) Q. In what time does it revolve on its axis ? A. In about 242 hours. (24h. 39m. 22s.) Q. In what time does it revolve around the sun ? A. In one year, 321 days. Q. H o\v fast does it move in its orbit ? A. 55,000 miles an hour. Q. How many degrees does the axis of Mars lean towards its orbit? A. About 30 degrees, (30® 18'.) (See Diagram.) Q. Does Mars have any change of seasons ? A. The seasons are similar to those of the earth, but nearly twice as long. Q. Why are they longer ? A. Because Mars is nearly two of our years in revolv- ing around the sun. Q. What is the appearance of Mars when seen with the naked eye? A. It appears of a red, fiery color. LESSON XXVII. Q. H ow does Mars ajipear when viewed with a telescope ? A. Outlines of apparent continents and seas, are dis- tinctly seen. Q. What appearance have the continents ? A. They have a ruddy color, arising probably from the nature of the soil. Q. Of what color are the seas ? A.. They appear of a greenish color, caused no doubt by contrast with the red color of the continents. Q. Does Mars present different phases ? A. It sometimes appears gibbous. Q. When does a planet appear gibbous ? A. When we can see more than half, but not the whole, of the illuminated surface. Q. Does Mars ever appear horned like the moon ? A. It does not, because it does not pass between us and the sun. Q. What other appearances does Mars exhibit -when viewed with a telescope ? A. Bright spots are seen alternately at the poles. Q. When do these spots appear ? A. When it is winter, or continual night at the poles. Q. What is supposed to be the cause of these spots ? A. Snow and ice, which has accumulated at the poles during u inter. Q. Do these spots continue through the year ? A, They entirely disappear as the summer advances upon the poles. Q. What amount of light and heat has Mars ? A. It has about half as much as the earth. ASTEROIDS. Question. What are the asteroids ? Answer. They are small bodies between the orbits of Mars and Jupiter. Q. How many are there'? A. Twenty three is the number known at present. Q. What is their magnitude ? A. They are very small with the exception of Pallas. Q. What have some astronomers supposed in regai d to them ? A. That they were once united in one planet ; but blown to pieces by some internal explosion. Q. What facts do they advance to prove this theory ? A. They are rough with sharp angular points. NOTE. Astronomers in comparing the distances of the planets, found that there was a great distance between Mars and Jupiter which did not coincide with the unifor- mity exhibited by the other planets. This led them to suspect that there was an undiscovered planet circulating in that region, and Baron de Zach went so far as to calculate in 1784-5, the orbit of this ideal planet. So confident were astrono- mers of the existence of a planet, that in 1800, six astronomers, of whom Baron de Zach was one, assembled at Lilienthal, and formed an association of twenty- four observers, the principal object of which was to use their own language “ to force this planet from the regions of analogy into the realms of sense ; ” but before they had got fully organized. Piazza discovered Ceres ; after another year Olbers discovered Pallas, and Juno and Vesta were brought in at intervals of a few years. The search continued fruitless for ten years, it was fairly concluded that this region was exhausted. In consequence of the discovery of four small planets instead of one large planet, the new and somewhat novel idea was advanced by Dr. Olbers, that these bodies were originally united in one planet; but by some internal ex- plosion had been blown in pieces. This theory has been fully discussed by astronomers from that time to the pres- ent day. Several support the theory of Olbers, while others discard it entirely as untenable. In 1845, astronomers turned their telescopes again to this field for exploration, and they have succeeded in discovering Jimeteen new asteroids which makes the whole number twenty-three. The first tour, Ceres, Pallas, Juno and Vesta are from the sixth to the eighth magnitude ; while the nineteen new o.nes are less than the ninth in magnitude ; all of these bodies are very small and are rough with sharp angular points ; these facts would seem to indicate that they had formerly been united in one body. The following is a list of the names, date of discovery, and by whom discovered. Name and Number. Date of Discovery. Name of Discoverer. 1. Ceres 1800, Jan. 1. Piazza, of Sicily. 2. Pallas 1802, Mar. 28. Olbers, of Bremen. 3. Juno 1804, Sept. 1. Harding. 4. Vesta 1807, Mar. 29. Olbers. 5. Astrea 1845, Dec. 8. , Hencke, of Germany. 6. Hebe 1847, July 1. Hencke. 7. Iris 1847, Aug. 13. Hind, of London. 8. Flora 1847, Oct. 18. Hind. 9. Metis 1848, April 26. Graham, of Ireland. 10. Hygeia 1849, April 12. De Gasparis, of Naples. 11. Parthenope 1850, May 11. De Gasparis. 12. Victoria 1850, Sep. 13. Hind. 13. Egeria 18.50, Nov. 2. De Gasparis. 14. Irene 1851, May 19. Hind. 15. Eunomia 1851, July 29. De Gasparis. 16. Psyche 1852, Mar. 17. De Gasparis. 17. TheMs 18.52, April 17. Luther, of Germany. IS. Melpomene 1852, June 24. Hind. 19. Fortuna 18.52, Aug. 22. Hind. 20. Massilia 18.52, Sept. 19, De Gasparis. 21. Lutetia 18.52, Nov. 15. Goldschmidt, of Germany. 22. Calliope 1852, Nov. 16. Hind. 23. Thalia. 18.52, Dec. 1.5. Hind. 1 26 //////>>; 1280 HI TELESCpPICr VIEWS OF MARS si: ^ K\ I \^ y A ' ' * ’. '< ’ '' L %i W i - ■ y £ m ' ""f ' w 1 fk ' / . 1 ■ ■ ' "1 0iB'^ .'A 'V_ ' ' 1 ' . J ILLUSTRATED A S T R O N O M Y . 27 LESSON XXVIII. JUPITER. Question: What is Jupiter ? Answer. Jupiter is the largest planet in the solar system. Q. How many times larger is Jupiter than the earth? A. It is 1,280 times greater. Q. What is the specific gravity of Jupiter? A. It is about H times the weight of water. (1.30.) Q. How far is Jupiter from the sun? A. 485 millious of miles. Q. What is its diameter ? A. 87,000 miles. Q. Which diameter is the greater, the polar or equatorial ? A. The equatorial diameter is 6,000 miles greater than the polar. Q. What causes the equatorial diameter, so much to exceed the polar ? A. The quick rotation of the planet upon its axis. Q. In what time does it revolve upon its axis ? A. In about 10 hours. (9h. 55m. 50s.) Q. In what time does it revolve around the sun ? A. In eleven years, 314 days. Q. How fast does it move in its orbit around the sun ? A. 30,000 miles an hour. Q. How many moons has Jupiter ? A. Four. Q. What is their magnitude ? A. They are about the size of our Moon. Q. Who first discovered them ? A. Galileo, the inventor of the telescope in 1610. Q. How are the orbits of these Moons situated ? A. They are directly over his equator. Q. Do these moons frequently eclipse the Sun ? A. They do at each revolution around the Sun. Q, What great discovery was made by observing these eclipses ? A. The velocity of Light. (Note.) Q- Has .Jupiter any change of seasons? A. It has no change of seasons. Q. Why do its seasons not change ? A. Because its axis is nearly perpendicular to the plane of its orbit, Avhich causes the sun to be always vertical at the equator. (See Diagram.) Q. H ow does Jupiter a|)pear, when viewed with a telescope ? A. Light and dark belts appear to surround it. (See Fig. 1 and 2.) Q. What are the light belts ? I A. They are supposed to be clouds, which are thrown ' into parallel lines by the quick rotation of the planet upon its axis. Q. What are the dark belts ? A. They are probably the body of the planet, seen between the clouds. Q. Do these belts always appear the same ? A. They change frequently, and sometimes the clouds break to pieces. (See Fig. 3.) Q. What is the velocity of its equatorial parts, in turning on its axis ? A. 25,000 miles an hour. Q. What amount of light and heat has Jupiter ? A. It has 27 times less than the earth. SATURN’S RINGS. {From the JJmerican Jllmanac and liepository of useful Knowledge, 1852). Wn M T a few months the inquiry has been started with fresh interest, By how many rings is Saturn siinoundcd, and in what way are these rings sustained ? Short saw two or three divisions outside ol the centre of breadth. Herschcl the lirst, in 1780, saw a new division near the innet , edge. As tliis appearance was temporary, he thought that observation would not justify the sup- po.sition of multiple rings. Lines of demarcation were seen on both rings in 1813 and 1814. Que> telet saw the outer ring divided m 18*23 In 1825 and 18*26 three divisions were seen on the outer ring by Kater. In 1H37 Encke noticed that the outer ring was divi led, and that there were se- veral marks near the inner edge of the inner ring. De Vico has given an account of several divi- sions seen by him on both rings. In 1838 several divisions were seen at Home, which arc described by Decuppis. In 1643, Lassell and Dawes saw a division of tlie outer ring. Smyth gives an ac- count of the last case, and adds : “After such unquestionable evidence, there can be no reason- able doubt of the outer ring’s being multiple ” On the 1 1th of November, IS. 7 O, G. P. Bond saw what he thouglit at the time a second division of the ring, near tlic inner edge of the inner ring. On the 15th, his father thought the new. ring was wholly disconnected with the old, though the edge next to the planet w'as Ijetter defined than the outer edge. Micrometric observations gave for the inner diameter of the inner division 26“. 3, whereas, according to Kncke, the inner diameter of the old inner ring should be at that time 29“ 8. From this it was inferred that the large re- fractor at Cambridge had revealed an entirely unknow'n and darker ring of Saturn, which was not to be confounded with the division of the old inner ring which had frequently been noticed. The outer edge of the new ring Is l“.d within the inner edge of any ring hitherto visible. This con- clusion was confirmed by observations continued for several w’eeks. Similar appearances were noticed on the ‘25th and 26th ol November, by Mr. Dawes, and afterwards by Lassell of Liverpool, and Schmidt of Bonn. On the 16th of April, 1861, G P. Bond communicated to the American Academy of Arts and Sciences at Boston, a memoir on the rings of Saturn. Alter rehearsing the facts already detailed in regard to extraordinary divisions of the rings, he draws attention to the circumstance that other observers, as Struve, Bessel, J, F. W. Ilerschel, and, we may add, Smyth, have seen only the usual division, even with the best instruments, and under the most favorable circumstance.?. More- over, the divisions on both rings are not always seen simultaneously ; and the Cambridge teles- cope w'hich has brought to view a ring always before invisible, does not indicate any of the un- usual divisions in the two ol