\' v/ I. Platt (f' thze -rc/q)t plonte.,f the Ed.iptic TH1E SOLAR SYSTEM. I. Birdspeve viewofthle Orbits. 1I. leclimmntils of I he Orbits. ELECTRO DESIGNED FOR SCHOOLS, ACADEMIES AND LADIES' SEMINARIES, WITH EXPLANATORY NOTES, QUESTIONS AND ANSWERS. BY REV. J. W. SPOOR, A. M. ROCHESTER, N. Y. F ULLY I LLU ST RAt E ]D. "THE HEAVENS DECLARE THE GLORY OF GOD, AND THE FIRMAMENT SHOWETH HIS HANDIWORK, DAY UNTO DAY TJTTERETIIH SPEECH, AND NIGIIT UNTO NIGHT SHOWETH IKNOWLEDGE."-PSA. XIX: 1. ALBANY, N. Y. cd>- WEED, PARSONS AND COMPANY, PUBLISHERS, C.1874. Entered, according to act of Congress, in the year eighteen hundred and seventy-three, BY THE AUTHOR, JOSEPH W. SPOOR, A. M., in the office of the Librarian of Congress, at Washington. THE design of the author in presenting this work to the public is: To meet a great wMant in giving instruction in the interesting science of ELECTRICAL AS WELL AS PHYSICAL ASTRONOMY. Hitherto, the knowledge of Astronomy has only been taught in our Universities, Colleges and High Schools, and in them in a very limited manner, hence, those in our public schools have been entirely deprived of all knowledge of this useful branch of education. Teachers of public schools have heretofore felt great embarrassment on introducing this branch of instruction in such schools, because of their incompetency to impart instruction to their pupils in the science, hence their objection to its introduction. This objection is entirely removed in presenting this work. It not only presents to the teachers an easy method of gaining instruction in the science, but an easy and pleasing way of imparting the same to their pupils. / It is the purpose of the author to present to the public an elementary work, and to bring this instruction within the reach of children from twelve to sixteen years of age, and so simplify and arrange it, that they can learn it as easily as they canl learn Geography. He has also adopted the calechetical form of instruction as a more popular method than the topical, because better adapted to their youthful comprehension, and they can the more easily retain the knowledge sought. Some years since, he constructed and designed to publish a Diagram of the Solar System, to aid in the instruction of this science, for which the highest commendations were given by some of the most Scientific and Learned in the Universities and Colleges in this country. 4 ~PREFACE. This Diagram is pronounced the best of any yet exhibited to the public, from the fact that it is the only one that presents the whole SOLAR SYSTEM to the eye at one view, and represents the orbits according to the true scientific angles by which they cross the plane of the Ecliptic. The author is happy to announce that this Diagram is published and may be found in the front portion of the Atlas, and a description of it and its uses accompanies its introduction. The author, having for many years investigated the laws of Electricity, and fnding them intimately connected with Astronomy, in the evolutions of the Planets, hopes to be able to throw attractions around the study of Astronomy which will not fail to interest the lovers of science as much in this as in any branch of education ever presented to the scientific world. He claims for this work a set of Diagrams and Illustrations exhibiting the most recent discoveries and observations mnade in this science down to the present time. The progress of Astronomy is so rapid that almost all Text-Books are behind in this particular. With these intentions and observations the work is published and presented to the public. In preparing this work the Author has also freely consulted the following works among others: "Mitchell," "Guillemin," "Schellen," "Brewster," "Burritt." AUTHOR. |CyE~ I>7Z~tS7-g' 1. 9 va~r.'J - - l 9 1,9./1 6 I b/M 2oo,9E;eil:'r20E'9 916'8, W40 0 1l0 0 I47I - c 9i7; 9 V /t Z7G 6' A olk A7WtyL WE.-r 91~i'Wl 6 -o.9S t6Zol 09 O Z / W -- 09 I0G7/?1- / lo70 "0!8 0 Zao,6V0000aOagj a7,zy oo~z1 _lfffay [66R E y/C| sy~ 0,o~ I-U~Zz752r3z6, 6oZo |e~ U|A.S' a tS eOD/iB~ri8> >>a/OOi3to7EZw ZCI vloo'o~ il ~ F.5171 nTPil /Op 1000'8 5;r l~t~;2.(6'6 - f;, e0. 661o S. C W Z r oYG 0 r/JY; i 6 ~. I /6d'ri-;I I e/LgE 100i#93 GRMMS8 oo+! 2 h li t r Y\ I I~~~~~~~~~~~~~~~~~~' IL -1r l r f Pio 69s,'P 1 ~ r 096b L L_ [~~) l e91 43 EN, 9 \ 1A ob,;.* f 1o91o/ 0oaz'i 0649Z........99X,~,' 61- S. oosfzd zz \ 4~c;r rl'I iy-l q9 0~2! v Y I M'P oe~p. C Sff F71-f-,7~~ Irlw-l't 9 L-/E IZ/ 6WO Y' 7009P76g0000OW1000006 i~~8 g Y~7! 6C1 P N 0 Z;e-A9,'.z^Z ~^ f 49 000'0W'-6opoooWPP9 00Mao1-06 rfz olX6,- e * 7>^ff; z"^6 t0 e 1qt/>>yw/ge,~7 7 |0;6 +8 laAOO/525IOO2^SI DOOODJO',e1 6g7 O 491I9 b SL iU %l bC.9/6 10 el c' oO xV96 |oj ||] l7 TV l t\ ~~P~~i~~~L L~~I I loo~~~~~~,~~~i~~ufi~~~-~~~~l~~illN~~~~906s fo j —s1os 1 XDrra,6 u7,>,,, ~g' t ob aG JX14 81 aalurls-u | aDMR W g9'-|.~ 1 0t ts \I JI a-Llutj, JOU\ JW a. |W 3 IWS XS' a1~90S 3H1.40 M31A mVinsLj\ A i':1 1 4c I / /I/\ \ I \ @~ ~ {~t / //1/l\ \~\1 \ l l / + S Se - I I /' / | - C t7/ tX FX / \ \ \~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ I~ I s. \\\,,\J 1~/ C z / / 1:RE / Xl q-w / l l I~~~~~~~~~~~~~~~~~~~~~~~~~~I l~~~~~~= INTROD UCTION. Accompanying this work is a Diagram, which, at the time of recitation, when necessary, can be spread open before the pupils that they may the more clearly apprehend the instruction imparted by it. A description of its design and use will now be given: The object of this is to aid the teacher the more clearly to illustrate, and the scholar the more easily to apprehend the instruction to be received of this interesting science. The Planetary System embraces the Sun, the Planets which move around him in their respective orbits, the Satellites or Moons connected with their respective primaries, together with the Asteroids and Comets. The Diagram exhibits at one view and in an oblique form this entire structure of the Solar System. Other Solar charts now in use present only parts of this System to the eye at the same time, and represent the orbits as lying on the sanie plane and in true circles, and give a very imperfect view of the manner in which the Planets are enlightened by the Sun during the different months of the year. The design of this Diagram more particularly is to exhibit and explain the true cause and philosophy of equal Day and Night; of the changes of the Seasons; why we have a difference in the length of Day and Night; the evident cause of the Eclipses, both Solar and Lunar; what produces the changes of the Moon, or, in other words, why we behold the Moon assuming so many different phases; and gives a comprehensive view of the movements of the heavenly bodies. The Diagram also represents the Sun as the grand common center around which all the Planets move in their respective orbits, at different distances from the Sun, and the inclination of their axes. It also represents the Moon and Secondaries in their orbits, as they are moving around their respective primaries; and represents all as having their enlightened sides turned toward the Sun, their great central luminary. It represents, also, the relative magnitude of the planets, and their comparative distances from the Sun. It shows the elongated orbits of the Comets -their respective nodes and longitudes. There is also a tabular view showing the distance of each planet from the Sun; the diameter of each planet and its time around the Sun representing the length of its year; the time required to revolve around its axis, showing the length of its day; the inclination their orbits make to the Ecliptic; the inclination of their axes to their own orbits; their density and the eccentricity of their orbits, and the difference in their Polar and Equatorial diameters. Having given the design of the accompanying Diagram, I will proceed to give a description of the several parts explanatory of the principles it is designed to teach, with suitable questions and answers. TESTIMONIALS. UNIVERSITY OF ROCHESTER, N. Y. Ladies' Seminaries. We have been much interested in the examination of the Diagram, and cannot Jani t, 1861. hesitate in expressing our judgment that its plan I have examined with much interest and pleasure and execution are, in several important respects, a Diagram of the Solar System, exhibited by Dr. greatly superior to those of any Diagrams of the J. W. SPOOR, of this city. It is one of the best I kind to which our attention has been called. It have ever seen, and when the modifications which cannot fail to facilitate, in a high degree, the study he proposes to make are perfected it will be the of the very interesting branch of knowledge for very best. It will greatly aid the young student of whose illustration it is designed, materially aiding, Astronomy in forming a just conception of the as it must, the teacher in communicating correct order and arrangement of the bodies of our system, notions, and the pupil in apprehending them, in and will give him a tolerably good idea of the respect to the characteristic and leading facts physical peculiarities of each body. appertaining to our Solar System. J. F. QUINBY, GEO. W. EATON. Prof. of Math. andc Nat. Phil. Pr'es. of'Madison University. [Signed by every member of the Faculty.] UNIVERSITY OF ROCHESTER, Janutary 7th, 1862. HAMILTON COLLEGE, As an improved means of communicating im- Novemzber 18th, 1861. portant knowledge and of diffusing it among the people, the Diagram of the Solar System, by Dr. SPOOR, deserves high commendation. I gladly DEAR SIR: I was pleased with your idea of unite in the judicious statement of Prof. Quinby, preparing a Diagram of our Solar System for the and cordially commend it to the schools and their use of schools. There can be no doubt but a good teachers and to the people in general. Diagram may be used with great advantage iln C. DEWEY, acquiring elementary notions of Astronomy; it,7of -emistry. fwill assist both the teacher and the pupils. It is Proqft. oyf (,/l~e}}?y. also obvious that a very great amount of valuable information can be brought within a very small MADISON UNIVERSITY, compass; nearly the entire statistics of the Solar November 15th, 1861. System may be presented on such a Diagram as you propose to publish. * * * Dr. J. W. SPOOR has exhibited to us, to-day, a propose to publish Diagram of the Solar System, which he is about to Yours, respectfully, publish for the use of institutions of learning, O. ROOT, especially of Common Schools, Academies and Prof. of Jlfath. and Nat. Phil. LE 1 N. B. - Instruction to Teachers in the use of Diagram, pages 91-92. CONTENTS. PAGE. LESSON I.-Circle Defined - Circumference - Diameter - Arc - Radius - Degrees.............1............... 18 LESSON II. - Semi-Circles - Quadrant - Circles - Equator - Ecliptic - Tropics................................. 13 LESSON III. - Lines; Curved, Straight, Parallel - Point - Surface - Ellipse - Its Diameter..................... 14 LESSON IV. - Angles: Right, Acute, Obtuse - Triangle....................................................... 14 LESSON V. - Astronomy - Heavenly Bodies - Solar System - Sun - Size Compared with the Earth - Distance from the Earth - Terms Aphelion and Perihelion - Its Weight - How Known - Physical Nature - Appearance, 15 LESSON VI. - Hypothesis - Element - Electricity - Its Discovery - By Whom - Diversity of its Operation...... 16 LESSON VII. - Sun - Relation to the Solar System - Its Electrical Power - Developed in Attraction and Repulsion - Position Confirmed by R. A. Proctor and Other Eminent Astronomers - Pervading of all things by Electricity, 16 LESSON VIII. - Sun's Motion - Time Revolution - How now it Revolves -Its Axis - Spots on its Disc - Accounted For- Drummond Light Compared with the Sun........................... 1'7-20 LESSON IX. - Solar Promlinences - Time of Appearance - Production - Duration - Height - Appearance of Jets - Scenes from Harvard College - Spots - Passage over Disc - Appearance - Uniform Time.................. 21 LESSON X. - Dimensions - Compared to the Globe - Measurements of Schroeter - Of Sir W. Herschel - Of Captain Davis - Remark - Physical Organization of the Sun - Views of Sir W. Herschel - Of Kerchoff- Of Sir John Herschel - Why Vary in Appearance - Way the Sun Turns on its Axis - Do all the Planets and Constellations Turn the Same Way? - Evidence of their Revolution from West to East - Time of Revolution of Sun - Inclination to Ecliptic.................................................................................... 22-23 LESSON XI.- Planets - Why thus called - Division - Primary - Secondary - Equilibrium of Motion - Law of Attraction and Repulsion - Law explained........................................................ 23 LESSON XII.- Distribution of Secondary Planets - Interior Planets - Exterior -Their Conjunctions -How shine - Distinguished From Stars............................................................... 24 LESSON XIII.-Apparent Motions of the Sun, What -Called -How Caused-The Daily Phenomenon Connected with the Apparent Motions of the Sun - Changes in the Points of Rising and Setting - Point of Culmination - Solstices and Equinoxes - Note - Ecliptic - Coincidence with the Plane of the Earth's Orbit - Intersection of the Circle of the Celestial Sphere and the Orbit of the Earth - Obliquity of the Ecliptic.....2.................... 24-26 LESSON XIV.- Mercury - Situation - Rate of Motion - Time of Revolution - Indications - Diameter - Inclination of Orbit to Plane of Ecliptic - Inclination of Axis -Time of Revolution on its Axis - Uniformity of Appearance.................................26-27 LESSON XV. -- Transit - Primaries Making Transits - When Occur - Condition of Earth and Planets when it Occurs- Ecliptic - Nodes - Months in which Transits of Mercury Occur - Whly? - Called What? - First Transit - Time of Others........................................................................... 27-28 LESSON XVI. - Mercury — Density-Heat - Solar Light - Velocity - Why so Great - Conjunctions - NamesDistances from Earth in Different Conjunctions - In what Months Most Favorably Seen.................... 28-29 8 @CONTENTS. PAGE. LESSON XVII. - Venuts -Situation - Distance from Sun - Time of Revolution - Indication- Inclination of Orbit witlh Ecliptic - Time of Revolution on Axis - Indication - Rate of Motion -- Inclination of BAxis with Plane of Orbit - How Distinguished.30.......................................................... 30 LESSON XVIII. - Satellites - Venus and Mercury Satellites of the Sun — Evidence — How Discovered - What Names -- Diameter- Appearance - Similarity to Moon - Conj unctions - Appearance in Each............. 30-31 LESSON XIX. - Venus - Different Changes - Diameter - Difference in Size - Transit - Time When - Benefit Derived - Appearance in Transit - Time of Transit - Time of Last One - Occur When -Tilme of Last - When Next -Peculiarity of Twentieth Century-How far Recede from Sun-.............-.-.... 31-32 LESSON XX. - Mountains of Venus - Height - Schroeter's Statement - Volume - Light Compared to that of the Earth - Distance from the Earth - In Different Conjunctions - Circumnference of Orbit - Phases - Evidence of What - How Change Her Appearance............................................. 32-33 LESSON XXI. - The Earth - Situation - Form - Spherical - Evidence - Not Perfect - Proved - Difference of Diameter - Position Im t................................... 33-35 LESSON XXII. - Revolution of the Earth - Time - Indication - Changes of Seasons - Axis - Position - Time of Revolution on Axis -- Production- Cause of its Revolution on its Axis —Explanation - Illustration - Law Equally Essential in all Planets -Problem Solved -Distance from Sun-Circumference of Orbit-Rate of Motion - Inclination of Axis................................................................... 5LESSON XXIII. - Time - How Reckoned- Uniformity — Advantage Derived - Remarks - Plane of Ecliptic Illustrated - Kepler's Law -- Location of Sun in Eartlh's Orbit - Shape of Orbit................... 36........... -37 LESSON XXIV. -- Causes of their Change - How far is the Axis of Rotation Inclined to Plane of Ecliptic - Time of Year - Equal Day and Night - Why Then — Why Day — Why Night - The Result of the Revolution of the Eartl on its Axis - Points Called - Way of the Revoltion.................................................. 37 LESSON XXV. - Difference of Tile in the Days and fNights Explained - Summer Solstice - Why So Called - Dis tance the Sun Shines Beyond the North Pole -Situation of South Pole-Movements of the Sun Further Explained....................................................................................... 38 LESSON XXVI. - Length of the Days and Nights ConsidereC — Number of Seasons - What Called - ZODIACAL LIGHT - Time of Appearance - In what Part of the Heavens - Form of the Light - Compared with Milky Way - Not Seen at all Seasons -- When Only - In what Months -- Favorable Night, - Zodiac - What is it -- Description of Belt - How Occupied - Location of Ecliptic - Termn "Constellation "- By Whom Used - Why Called Zodiac - What Use is made of the Signs of the Zodiac — Names - Correspondents of these - The Earth in Capricorn -Where then is the Sul Vertical?......................39-40............... 39-4 LESSON XXVII. T-What Does This Show - Why Warmer on the 21st of June — Sun Further Away - Difference in Diameter - Difference of Time in Equinoctial Points — Nearest the Sun Perihelion - Farthest Aphelion - Motion Faster at Which -- Density - Variation of Equinoctial Points -- Difference of Diameter -- DiscoveryWeight at the Poles and the Equator - Cause of This.................................................... 41 LESSON XXVIII. - The Moon - Form of Orbit - Perigee - Apogee -Mean Distance -- Inclination of its Orbit to Plane of Ecliptic - Lulnar Days in a Year - How much of Moon Seen - Illustrated - Evidence of any Life on the Moon - Result if there Were -- Any Seas, Lakes, Rivers — Any Winds or Tornadoes.......... 42 LESSON XXIX. — Phases of the Mloon - Explanation of them - First appearance where - At what time - Way of Revolution - Deog-rees in twenty-four hours -- Her changes Explained - Time of Full Moon - Position now in Respect to Sun - Why in Opposition............4344....I....................... 4344 LESSON XXX. - Appearance in the First Half of her Orbit - Appearance in the Last Half - What Remarkable in her History - When called New Moon - When Full Moon - Relation to the Earth - Satellite - Time of Revolutions - What Called - How Near the Earth - Revolutions in a year - Synodic and Siereal Revolution.. 45-46 LESSON XXXI.- Physical aspect of the Moon - Appearance Variable - Cause of this - Appearance Through Telescope - Rough - Mountains - Compared to those of the Earth - Peculiar Formations - Ring Mountains - Description - Eclipses - Cause of Eclipse - Philosophical Cause Given..........................I... 46-48 CONTENTS. 9 PAGE. LESSON XXXII. - Eclipse - When occur - Explained - When they cannot occur - Result, if the Orbits of the Earth and Moon were on the same Plane - Cause of an Eclipse of Sun - When only occur - Tides - How produced - Time of Spring Tides - Why? - Effect of Sun - That of Sun less than Moon - Why?.............. 48-50 LESSON XXXIII. -Planet Mars - Location - Appearance; To the Naked Eye - Distance from Sun - Tilne around it - Indication - Time of Revolution on Axis - Indication? - Diameter - Inclination - Exterior - Why? - Resemblance to Earth - Changes of Climate - Divisions of Land and Water - Geography Similar - Mars Probably Uninhabited - Circumference of Orbit - Distance from Earth - Opposition - Where looked for - Position of the Earth -Appearance of Mars.......................................................................... 51-52 LESSON XXXIV.- Wlhen take place - Cause of brilliancy — Distance one side of Orbit - Inclination - Rate of Motion - Light, compared with that of Earth - Difference of Diameters - Density, compared with the Earth - Difference of Weight - Ratio from Sun of the Orbits of Planets described- Rapid Changes - White Spots - Snow Zones.......52-5..................... 8................ 0*v*.. 2-3 LESSON XXXV.- The Minor Planets - What are they? - Number - Space occupied - Kepler's impression - Not witnessed in his Day -Two Hundred Years after - Discovery Made - Four Found - CERES, PALLAS, JUNO and from Sun - Time around it - Inclination - Appearance in Size and Color - Pallas - Time and by whom Discovered - By whom Measured - Distance from Sun - Time around it - Inclination - Appearance as to Size and Color-Juno - Time and by whom Discovered-By whom Estimated - Appearance as to Size and Color- Distance from Sun - Time around it - Inclination of Orbit -Vesta - Time when and by whom discovered - Comparison with the other Minor Planets - Diameter - Distance from Sun - Time of Revolution - Inclination of Orbit- Description of all nearly the same..54.56.................................................. 56 LESSON XXXVII. - Planet Jupiter - Situation - Why Distinguished - Distance from the Sun - Time around it - Indication - Diameter - Time of Revolution on its Axis - Indication - Circumference of Orbit - Rate of Motion - Effect of Motion on the Weight of Bodies on his Surface -Weigllt of Bodies on his Surface compared with their Weight on the Earth - Cause of Difference - Satellites - Variable Appearance - Observations of Mr. Dawes.............................................................................. 57 LESSON XXXVIII. - Satellites of Jupiter - Number - Names - iiameters - Distances - and Revolutions - Eclipses - Number per Month - Eclipse of Sun effected by them - Inclination of the Axis of Jupiter to Plane of his Orbit- Plane of Orbit to Plane of Ecliptic - Eccentricity of Orbit- Solar heat compared with Earth.... 58-59 LESSON XXXIX.- Observations of Astronomers - Appearance of Belts - What known - Situation - How esteemed by Astronomers - Uniformity considered - Other peculiarity of appearance - Accounted for - Difference of Jupiter's Diameters...........,.......................,................................................. 59-60 LESSON XL. - Saturn - Situation - Distance from Sun - Time round it - Indication- Diameter - Revolution on Axis - Indication - Inclination of Axis to its Orbit - Inclination of Orbit to the Ecliptic - Eccentricity of its Orbit - Difference of Diameters - Solar Light compared with that of Earth - Rate of Motion - Density - Difference of Weight - Why one of the most magnificent Planets - Rings and Moons......................... 60 LESSON XLI. - Rings of Saturn - Situation of them - Revolution - Detached -How known to be Separate - Distance from Planet to Interior Ring - Breadth of it - Width between Rings - Thickness of Rings - Consists of what - How determined - Importance of them to the planet..66............2.............................. 61-62 LESSON XLII. - Circles not True - Centers coincide with the Center of Planet - Giravity of These Rings - Importance to the Stability of the System of Rings - Moons of Saturn - Number - Seldom Seen -Revolve with the Rings - Respective Distances from Saturn - Inclination of their respective Orbits to the Plane of SaturnEclipses of these satellites - Seldom Suffer - Respective Sizes.................................... 62 LESSON XLIII. - Uranus - Situation - Distance from Sun -Time of Revolution round the Sun - DiameterTime of Revolution on Axis not known - Inclination of Orbit - Rate of Motion - Light compared with that of the Earth - Density - Eccentricity of Orbit - Difference of the VWeight of Bodies on the Earth and the Surface of Uranus - Satellites of Uranus - Number - Respective Distances and Periodic Times - Their Variation in Revolution - Size of them - Seldom suffer Eclipse............................. 62-63 10 CONTENTS. PAGE. LESSON XLIV. - Neptune - Situation — Orbit - Distance from Sun - Revolution round it - Diameter - Rate of Motion - Inclination of Orbit to the Ecliptic - Time on Axis unknown. - One Satellite --- Situation - Time around the Primary - Indication................................................................................. 63-65 LESSON XLV. - Comets - Where found - Appearance - Why called Comets - Appearance Varied - Distinguished from Planets — Form of Orbits- How are they distinguished...................... 65-67 LESSON XLVI. - Elements of Comets - Orbits - Number computed -- Classes Elliptic - Long Periods - Shorter Periods - Number Reappeared - They are generally named after their discoverers - Size of Orbits - Comparative inclination of them - Way of Revolution................................................ 67-68 LESSON XLVII. - Comparative Periods of Comets - Course of Revolution of Comets whose Orbits have been ascertained - One-half of them in opposite directions - Inclinations very diverse - Velocity compared with Planets in general - Far Greater - Number Discovered.............................................................. 68 LESSON XLVIII. -- Celebrated Comets - Comet of 1811 - Dimensions - Aphelion distance - Halley's Comet - How distinguished - Appeared in many previous years - Comet of 1843 - How distinguished - Encke's Comet - Period of Return - What peculiar in its return - Donati's Comet appeared in 1858 - Effect producedWonder of Many- For what distinguished - Law by which they are Governed - Description of its Operation -- Longitude of the Parhelion of the Comet 1858 - Longitude of its Node - Longitude of the Parhelion of the Comet 1862 -- Longitude of its Node - Rapidity of Comets - Cause for it................................. 69-71 LESSON XLIX. - What supposed to be - How produced - What called - Why so called- How many seen in an Hour - Showers of Stars - When exhibited - At what Intervals - Hombold and Bompland's Observations - Arago's Observations - Regular Periods of Showers - Intersection of the Earth and the Orbit of the Comet - Brilliant display accounted for - Light produced by their rapid flight through the Atmosphere - Annual Exhibition of Meteors in August -Regularity accounted for — Schiaparrelli's discovery............. 72-74 LESSON L. - Remarks - Constellations - Design in presenting all Elementary Work - Not Extensive or Critical - In considering the Stellar Universe - The Object in Presenting Constellations - How differ from Planets - In Twinkling and Scintillating — Description of a few - Exhibited in the Northern Sky - The best time of observing them - What Called - Why Called Northern Circumpolar - North Pole point of Revolution -- Consideration of Maps - MAP I. - Constellation Great Bear, oUrsa Manor - Time of appearancce- Number of Stars contained in the Group - Figure formed Large Dipper - Two Northern Stars Pointers -Why called thus - Polaris the object to which they point - Revolution - 2d Constellation - Little Bear - How Distinguished - Contains Polaris- North Pole Star - A Fixed Stal - Why called Fixed Stars - They revolve in the Universe - Great Velocity - Time its Light travels down to us - 3d Constellation - assiopia - Location - Form of Figure - Sprawling " W "- Ceplleus and Draco - Where Located - Nothing Striking - Perceus elsewhere.......... 74-76 LESSON LI.- Constellation Orion -Time of favorable appearance - Names of the Constellations - Distinguished - The most beautiful Constellation in the Sky - WVhale better seen elsewhere - Stars of Belt of Orion -The Bull or Taurus - Situation - How Marked - Cluster called Hyades -Another cluster called Pleiades - Another Constellation called Gemini, or the Twins - Where Situated - Names of the most important Stars - Castor and Pollux - Little Dog - Location - How Distinguished - Procyon and Gomelza - Great Dog - Situation - Name of the largest - Sirius Brightest Star - Rate of Motion - Time it takes to reach the Earth - Distance estimated -Diameter - Constellation The Whale - Situation............................................................ 76-77 LESSON LII. - MAP III —Constellation Virgo - Favorable time for Inspection -When seen in the Heavens - How known -Large Constellation - One Star of first Magnitude - Spica its name - Leo, or the Lion -Where situated -How easily known - Shaped like a Sickle- An inverted figure 5- Regulusthe largest - On the Ecliptic - Gamma -Where situated - 3d Constellation - Hydra - Situation -Form of Serpent Swimming from East to West - Stars small..................................................................... 77-78 LESSON LIII. - MAP IV - Constellation Bootes -- Time of Appearance - In June - Situation in the Heavens - The Brightest Star Arcturus -- Where found - On Meridian - Shape Parallelogram - Four bright Stars - Form -- Coffin - Another group East - Like a boy's cap - Northern Crown - Large Constellation furthei East - Hercules - Size - What figure - Two Quadrilaterals -Opinion respecting the course of the Solar System - Drifting toward Hercules............................................ 8 CONTENTS. 11 PAGE. LESSON LIV. -- MAP V- Constellation The Swan -- Time favorable -Where found — Overhead — Figure formed - Large Cross - Principal Star at foot - Albireo - Multiple Star - The Eagle - Where situated - South of Swan- How distinguished — A Large Star - Atair- Pegasus — Where located- North-east of Eagle- Figure of these Stars - Perfect Square - The most Western found — Heacl of Andromedia -The Lyra - Where situated — West of Swan and North-west of Eagle — What Star Prominent - Vega —What completes the groupFour faint Stars................................................................................ 79 LESSON LV.- MAP VI - Constellation Perseus - Whllen favorably seen — December - Where found - Meridian Well North in Milky Way -Figure of chief Star - Tnrkish Sword —Bent at the point — What near the point -- Mass of Telescopic Stars, very beautiful - One marked -- Called Algol -- Constellatio, Aries or Pam -- Where seen - South of Perseus — Figure formed of Principal Star- Right Angled Triangle - Point in the Seasons marked - Vernal Equinox - What Constellation South of the Ral - Whale - Figure easily traced Pentigon of Stars........................................................80 LESSON LVI. - Contrast of the Distance of the Sun and that of the Fi.xed Stacrs from the Earth - Remarks. - Rate of motion of ball from an Armstrong gun - Time taken to reach the Sun -- Time for the sound of the Explosion to reach the Sun - Prof. Mendenhall on nervous sensation - The infant burns its finger by touching the Sun - Time necessary to realizing the sensation - Earth on disc of Sun - Require a large telescope to discover itDistance of Sun from Earth compared to that of the Fixed Stacrs - The Fixed Stars, Suns — Do not remain unmoved - Revolve in the Universe like other Planets - Principal Suns named - Why appear small - Distance cannot be computed by miles - Velocity of light considered - Miles per second - Number in 24 hours At this rate how long to reach the nearest _Fixed Stcar - 61 cygni - Vega - Sirius - Ursce Majoris - Arcturus - Polaris and (Cappella -- These do not shine by reflection - Suns in other Systems.......................... 81-82 LESSON LVII. - Light - What is it - Views of Sir Isaac Newton - Flowing out from the " Orb of Dcay " -- Recuperation, or Waste Away - Space embraced in Solar System - Rapidity of light -- At this rate how long will it take to fill the Space - Does not remain Stationary - Moves on in Circle -- Light changes its Polarity -- Is received back to the Sun- How does the Sun remain undiminished and brilliant as ever - By recuperation in the return of it to the Sun - No indication of a continued work of creation - Principle illustrated by... 82-84 LESSON LVIII.- Attraction of Gravitation - Attraction of Gravitation defined - Seen in the power the Sun exerts over the Planets - All under the magnetic influence of the Sun - Planets rendered Magnets by the electrical power of the Sun - This inherent magnetism controls the Satellites —This magnetism called Terrestrial Magnetism- Subject Terrestrial Magnetism or the Magnetism of the Earth - This magnetism accounted for - Sun a great Galvanic Reservoir - Heat of Torrid Zone - Compared with Temperate and Frigid Zone — Intensity of the heat of the Sun - Three hundred times greater than any point on the Earth's surface - Sir John Herschel's estimate - Note...................................84............................................. 84 LESSON LIX. -- Terrestrial Magnetism - Continued - Torrid regions - More deeply electrified -- Result - They are positive - Polar negative - Reasons for this - Effect produced upon the Earth -- Earth filled with electricity becomes a magnet — This Terrestrial Magnetism seeks and flows out of the Magnetic Poles -- Points of the greatest cold - Both North and South - Result - Consequence of the combined action of these forces - Explanation -- Effect of these currents on the Needle -- Magnetic Poles and Geographic not the same - At the Geographic no effect on the needle - Reasons why - Note.................................................. 85-86 LESSON LX. -Aurora Borealis - How produced - Caloric and Electricity the same - Currents within the Earth naturally seek the point of the greatest cold, flow out and form a lambent waving light - Called Aurora - This illustrated - Historic evidence -- Captains Parry and Ross - Their testimony - The ultimate conclusion -- This clearly explained - Power of Terrestrial Magnetism controls the Moon —On the principle of Attraction and Repulsion — The same law by which the Sun governs the Planets and they their Secondaries in the Solar System, 86-87 LESSON LXI.- Attraction and Repulsion - Subject defined - Law governing - Ultimate particles have opposite polarities - Law manifest -- Laws of the whole are the laws of its parts - By this rule only can Attraction and Repulsion be accounted for - Magnetism and Electricity considered the same agent -- Galvanism differs only in the mode of exhibition - Experiment - Result from passing a current of Galvanism through Soft Iron; change the poles of Battery - Change the polarity of the Iron - This explained - Distinction of polarity manifest in the direction of the current -This explained - Positive and negative end to every thing - Running electricity - The inward current always negative - The outward current positive - Remtark.............. 87-88 12 CONTENTS. PAGE. LESSON LXII. - Attraction and Repulsion - Continued - Another mode of illustration - Current of Galvanism passed around Steel - Result -- A magnet - Cut the Steel in pieces - Each arranged with the same polarity of the whole - Logical inference - Conclusively evident - How illustrated - By the atmosphere and ocean.. 88-89 LESSON LXIII. — Attraction and Repulsion - Continued - This theory explained -- Two magnets - Effect when Positive and Negative are presented to each other - They attract - Result when like polarities are presented - Entirely opposite; they now Repel each other - Two Positives repel - A Positive and Negative attract each other - Scientific World challenged to give a clear explanation on any other principle -A body charged with electricity has an outward current, and will attract a negative with an inward current - Clearly shown by the magnets - These laws applied in the Attraction and Repulsion - How accomplished.................................... 89-90 Elements of the Solar System...................9.................................................................. 94 Elements of the Minor Planets..................................................................................... 94-96 ELECTRO-ASTRONOMICAL ATLAS. DEFINITIONS. LESSON I. ANALYSIS. - Circle Defined - Circumference - Diameter - Are - Radius - Degrees. A. A line passing through the center of a circle, and terminated by the circumference. Q. What is any part of the circumference g ~ ~ Rdu +) called? A. An Are. ~~C&Q \ /~~~ Q. What is the Radius a A. A straight line drawn from the center to the circumference. Fig. 1. Q. How is the circumference of a circle diQ. What is a Circle? [See Fig. 1.| vided? A. A figure bounded by a curved line, every A. Into 360 degrees. point of which is equally distant from the center. Q. Into how many equal parts is a degree Q. What is the circumference of a circle? divided? A. The curved line that bounds it. A. Sixty equal parts, called minutes. Q. What is the diameter? LESSON II. ANALYSIS. - Semi-Circles - Quadrant - Circles - Equator - Ecleptic - Tropics. Q. What is a Semi-circle?. Q. What is a small Circle? A. One-half of a circle, or 180 degrees. A. A circle whose plane divides the sphere into Q. What is a Quadrant? two unequal parts. A. A quarter of a circle, or 90 degrees. Q. Mention the principal great Circles? Q. How many kinds of circles are there? A. Equator and Ecliptic. A. Two: great and small. Q. Mention the principal small Circles? Q. What is a great Circle? A. The Tropic of Cancer, the Tropic of CapriA. A circle whose plane divides the sphere into corn, and the two Polar Circles. two equal parts. 14 ELECTRO-ASTRONOMICAL ATLAS. LESSON III. ANALYSIS.- Lines: Curved, Straight, Parallel - Point - Surface - Ellipse - Its Diameter. Q. What is a Line? Q. What is a Surface? A. It is that which has length without breadth A. It is that which has two dimensions - length or thickness. and breadth. Q. What is a Curved Line? Q. What is an Ellipse? A. One that continually changes its direction. A. It is a figure bounded by a curve, from any Q. What is a Straight Line? point of which, if straight lines be drawn to two A. A line which has the same direction at fixed points within, called the Foci, the sum of every point. these lines will be the same. Q. What are Parallel Lines? Q. What is the longest diameter of an Ellipse A. Lines that extend in the same direction, and called? are at the same distance from each other at all A. Major Axis. points. Q. What is the shortest diameter called? Q. What is a Point? A. Minor Axis. A. It is that which is conceived to have neither length, breadth or thickness, but position only. LESSON IV. ANALYSIS. - Angles: Right, Acute, Obtuse - Triangle. A. An angle tormed by a straight line meeting tue. a perpendicular line. Q. What is an Acute Angle? A. An angle less than a right angle. Q. What is an Obtuse Angle. A. One greater than a right angle. Q. What is a Triangle? Fig. 2. A. A figure bounded by three sides. Q. What is an Angle? [see Fig. 2.] Q. What is a Sphere or Globe? A. The opening of two lines that meet in a A. A round body, every part of the surface point. being equally distant from a point within, called Q. Name the different kinds of Angles? the center. A. Right, Acute, and Obtuse. Q. What is a Hemisphere? Q. What is a Right Angle. A. Hlalf a sphere,- hemi meaning half. .......~~~~~~~~~~~~~~^-.;-.;i:f:: ~ ~~~:::i:8;:_::::;:::::.:; ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~~~......... Mon.'X~a:~ w~f~\ K. Hilv \ 4\l 1"EMEN::::::::,g:::~:::.: -~:j i...................................................... i~i~ l':.:,::.;-~.........::l........:i m................::0 ~,a-~ ~ ~ ~ ~ ~ ~~ ~~.................w ~~~,~-: ~-~:~:-~:~:-:. -:~:~ r-:;:;~:~ -:;:-:~:i::~is~:~::;-_:-:::::I::............:i~i::~:;:'::~::::::i:~i:~ 1-: j::~~~~.~- ~~n~::i ~ ~ Flo~ —........... i:j:~ ia~::d l::-iI:::ii::~:::'i::a: ~~C:':-::::::':':':~~''':H IC,"::'' ~ ~:':::~:::I:j~ ELECTRO-ASTRONOMICAL ATLAS. 15 LESSON V. ANALYSIS. - Astronomy - Heavenly Bodies - Solar System - Sun - Size Compared with the Earth - Distance flrom the Earth - Terms Aphelion and Perihelion - Its Weight - How Known - Physical Nature - Appearance. ASTRONOWYW. A. It is impossible for the human mind to Q. What is Astronomy. form an idea of its vastness. A. It is that branch of science which treats of Q. What is the diameter of the Sun? the heavenly bodies. A. Its real diameter is 852,900 miles. Q. What are the names of the heavenly Q. What is the distance of the Sun from the bodies Earth? A. The Sun, Planets, Satellites, Comets and A. Recent investigations show the distance, Stars. when the Earth is in Aphelion, to be 93,000,000 SOLAR SYSTEM. miles; but when it is in Perihelion, it is 90,000,000 Q. What is the Solar System? miles, the mean distance being 91,500,000 miles. A. The Solar System is composed of these Q. What is meant by the term Aphelion? heavenly bodies, moving in harmony round the A. That point of the orbit which is farthest Sun, as their common center. from the Sun. Q. How many bodies are embraced in the Q. What is meant by the term Perihelion: Solar System? A. That point which is nearest the Sun. A. There are one hundred and sixty-four. Q. How does the weight of the Sun compare Q. How are they divided? with all the planets, satellites and comets of the A. There are the Sun, eight primary planets, Solar System twenty-one secondaries, and one hundred and A. About seven hundred and fifty times as thirty-four Asteroids, or Minor planets. heavy as all of them taken together. Q. How do we ascertain its weight? TEZI SIUN. |A. From the power of its attraction. Q. What is the Sun? Q. What is known of the physical nature and A. A vast, brilliant globe, around which the constitution of the Sun? planets, their satellites, and comets revolve. A. Various are the theories of astronomers Q. What is the size of the Sun compared with | respecting its physical nature and constitution. the planets surrounding it? The recent and most reliable hypothesis is, that A. The Sun is by far the largest of the heavenly the nucleus of the Sun is an incandescent solid bodies, being more than five hundred times as or liquid mass. large as all the planets taken together. Q. How does it appear to us when seen Q. WMhat is its magnitude when compared with through a telescope? that of the Earth? Z A. It presents the appearance of an enormous A. The Sun is equal to 1,400,000 globes the | globe of fire, frequently in a state of violent agisize of the Earth. tation or ebullition. Q. Can we form an adequate conception of its vast dimensions l 1.6 -ELECTRO-ASTRONOMICAL ATLAS. LESSON VI. ANALYSIS.- Hypothesis - Element - Electricity - Its Discovery - By Whom - Diversity of its Operation. A. Electricity is also derived from another Greek word, Electore, which signifies "beaming sun." ________ — - Rs~~~k.emark-This seems to' indicate that the ancients supposed the Sun to be the fountain of this subtle fluid. _ Q. WThat led him to make the discovery _ A. He ascertained that the amber, when rubbed, acquired the power of attracting to itself certain Fig. 3. light bodies surrounding it. E LECTBICITY. From the fact that the Sun is the source of all light, heat, and How can this interesting phenomenon be life in the realm of nature, and that light and heat are component illustrated by the student without this amber? parts of Electricity, therefore, the Hypothesis is entertained that A. By taking a stick of sealing wax and the Sun is constituted with the all-pervading element Electricity. brushing it briskly with a piece of silk, or Q. What element naturally flows out of the woolen cloth, and passing it over small pieces of Sun? rsee Fig. 3.] paper. A. Electricity. Q. Is Electricity uniform in its manifestation? Q. What is Electricity'? A. Infinite wisdom has constituted Electricity A. Electricity is an imponderable fluid, eman- a mighty agent, in various ways, his "wonders ating from the Sun. to perform." Q. When and by whom was Electricity discov- Q. In what manner more particularly is it ered? revealed? A. It was discovered 600 years before the A. It is not simply manifest in the thunderbolt, Christian era, by Thales, a celebrated Grecian but in the agitative power of galvanism; in the sage of the city of Miletus in Ionia. permeating influence of magnetism; in a univerQ. How did he make the discovery? sal flood of light, and in the all-pervading maniA. He detected it in a substance called amber, festations of heat. which, in the original Greek, is called Electron, Q. What are other modified representations of from which is derived the term Electricity. this same imponderable principle a Q. Is it derived from any other word? A.o The attraction of gravitation and cohesion. LESSON VII. ANALYsIs. - Sun - Relation to the Solar System - Its Electrical Power - Developed in Attraction and Repulsion - Position Confirmed by R. A. Proctor and Other Eminent Astronomers - Pervading of all Things by Electricity. RELATION OF THE SUN TO THE SOLAR SYSTEM. I A. The Sun is the great fountain of electricity, Q. What relation does the Sun hold to the from which emanates, as from a galvanic battery, entire Solar System all the power necessary, under the, established ELECTRO-ASTRONOMICAL ATLAS. 17 electrical laws of attraction and repulsion* to Q. Is this element all-pervading in its influence govern the motion of the planets in their diurnal A. It permeates every thing -from the largest and annual revolution around the Sun. planet, Jupiter, to the smallest particle of sand Q. What other principle does it produce? upon the sea shore. A. It produces the vivifying principle of both animal and vegetable life, all chemical changes in the realm of nature, and is the active and effi- | Remarz. - What Pope said of the Divine escient agent, both in decomposition and recompo- sence is as truly said of this all-pervading prinsition of the organic structure of men and ciple: animals. a It warms in the sun, Q. Is there any part of the Solar System in Refreshes in the breeze, which this principle is not manifest? Glows in the stars, A. There is 1no department of the entire Solar And blossoms in the trees; Lives through all life, System in which this imponderable principle does Lives through all life, Extends through all extent, not exert a quickening and controlling influence Spreads undivided, or power. And operates unspent." * In a letter written the N. Y. fHerald, from Cleveland, O., Jan. NOTE. - We should never lose sight for a moment of the 28,1874, Richard A. Proctor holds this language on the evolution great self-existent principle we call Deity, whose Attributes are of the earth: "During all these years, she has been gathering up Omniscience, Omnipresence, Omnipotence and Eternity; who crea few.... chips scattered about the mighty workshop in ated all things, and established the universe, composed probably which the giant workmen Attraction and Repulsion had fash- of hundreds of solar systems like our own, and sent them spinioned the Solar System." Other eminent astronomers have re- ning through infinite space, balanced and controlled in perfect cently confirmed me in my position as to the law of Attraction harmony, under those electrical laws by which He governs all and Repulsion governing the planetary world. things in His vast and infinite domain. LESSON VIII. ANALYSIS. - Sun's Motion - Time Revolution — How know it Revolves - Its Axis - Spots on its Disc - Accounted For - Drummond Light Compared with the Sun. MOTION OF THE SUN. A. By the motion of certain dark spots on its Q. In what time does the Sun revolve on its disc. axis? Q. What is the axis of the Sun a A. Twenty-five days, eight hours and nine A. An imaginary line on which it revolves. minutes. Q. What is meant by the disc of a body? Q. What proof have we that the Sun turns on A. The circular illuminated surface. its axis? 4 18 ELECTRO-ASTRONOMICAL ATLAS. DARK SPOTS ON THI-IE SUN. Q. Since that time has the Sun always preQ. When and by whom were the dark spots on sented a spotted disc.? the disc of the Sun discovered? A. From the year 1676 to the year 1684 the A. By Galileo in the beginning of the year 1611. Sun presented an unspotted disc. >< < e;*;i\T-;\ 1 \ ~;E= 2 ~e X; -a * 5' —----------- = — Fig. 4 Q. Do they always take the same direction over A. They are owing to the fact that the axis of the San's disc? the Sun is inclined to the Ecliptic; so that as we A. They do not. Sometimes they seem to move view the Sun from different points in the earth's across it in straight lines; at others, in curved orbit, the direction of the spots must necessarily lines. Sometimes upward, as they cross from vary. east to west; at others, they incline downward. The following diagram will serve to illustrate Q. What causes these changes? this: A C — I /X Fig. E. /-_-;~=~=~====-===" Of w A/ —-= —~r-~~~~;-~~~' id I'':\V 43r5t,QiI~.:-'r~-j —-'-~~ Y —— I —=~~ —~-:i:'`: "'`l::fijS~~~~L=;;ii B r Z~~~~~~~~~~~~~~~:~5 W~~ ~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~ v~ll 7S=I-:~s wS -~' — L e v # e X~~~~~\- ~ /-v'~i!;ri,;..-~; _C==:=:=. -_~-~_-,= — \-=.-.1=~ —a g u e;; hi my; ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~:~_-_=== {,7e,7a~j7->< X, n"F I —~- -of-.... -.-,-.t,....-;; i Ss;2;e \......... IAi d i_< IS i==r3 - Fig. 4.~~~~~~~~~~~~~~~~~~-= — |~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~~~~P Q. Dote lay aete aedrcto vr A.Te r oigt hefc ht h xso Z~~~~~~~~~~~~~~~~~4 heSl'sd~. h u sicie oteElptc ohaasw |. hedont.Soetms hesemo ov |vewth Sn rm ifern pins nth ert' ~~ —-~==i~~Fi A. d-' —~= ELEC TRO-ASTRONOMICAL _t ATLAS. 19 The annexed diagram will still further illus- | Fig. 7 affords a striking example of this aspect trate the cause of the change of direction of the of the penumbra. solar spots: This spot presents the peculiarity, not at all S< /- g Gw t unfrequent, that the dark umbra is divided into several fragments by luminous bridges, spanning < it, as it were, from one side of the penumbra to the other. \/ X ark/<,/ | The umbra itself is far from offering an uniform N \ s / N black tint. In reality it always presents the appearance of varied shades, as if the penumbra <> ),- 1 - | and umbra were mrlingled, and mixed up their tints in varied proportions. [We owe to the Rev. WT. R. Dawes the discovery that the umbra is but a darker kind of penumbra; for under the best conditions of air and / N FiN. 6. N | instrument, he has found within some umbrae a Fig. 6. much darker portion- which he calls the n7uQ. How are the spots on the disc accounted cleus. This he finds to be of the most intense for? | blackness; but in saying this we must warn our A. The atmospheres surrounding the Sun, being readers that such a word as applied to the Sun made up of the bright scintillations of electricity{ is comparative only. Sir J. Herschel has shown which radiate from within, become so ex- ~i.i'. ceedingly brilliant and luminous, that when at any time an opening appears in them.,... and the main body is seen, though incans gel FiT. descent, yet in contrast with the dazzling w corruscations surrounding it, the nucleus, or ba | Bds amh mass, appears in spots, dark and opaqueiiji~8:lll li1~ F~:l9ii~iii The forms ot the spots, as shown by the pn Cidrawings placed before the reader, are most ot a varied. The penumbra most freqyuently reproduces the principal contours of the ii.............ii ~~~~i. umbra, and often presents a great va~riety of shades, w'hen exramined with considlerablle.~....~.i< —maniyigpoer.On the exterior edges ~ of the penumbra, the: grey tint seems generally Fig. 7. -WILLOW LEAF. the deepest, either b3y the effect of contrast with Sun-spots, sliowing Umbra, Penumlbra, and Luminous the brilliant portions that surrounda it, or because Bigs Nsyh) in reality it possesses at these points a more that a ball of ignited quicklime, in a Drummond's decided tint. oxyhydrogen lamp, which itself gives out an 20 ELECTRO-ASTRONOMICAL ATLAS. apparently near approach to sunlight, when pro- bright scintillations of electricity have upon the jected on the Sun appears as a black spot. So appearance of the nucleus of the Sun that the Sun-spots, properly so called, may not A. When these openings are made, the mass or be so black after all!] body of the Sun, although under the most vivid The transits of Mercury, moreover, over the incandescence, appears dark in comparison to Sun's disc have taught us that the umbra is less the luminous envelope which surrounds it. dark than the unilluminated face of a planet. Q. How does the most brilliant light of which We shall now speak of the real dimensions of we have any knowledge compare with the light the spots, the successive changes which they of the Sun undergo, and what astronomers call their " proper A. The Drummond light, the most powerful, motion,'" that is, their actual movement on the between our vision and the Sun prewhen held between our vision and the Sun, loreSun's surface in any direction. sents a dark spot. Q. What effect do you say these exceedingly If we imagine that on the surface of the dark on its axis brings a spot nearer to the center, nucleus there are formed from time to time gaseous hence gives us a more direct view of the opening, masses, incandescent by reason of their high tem- and we discover more of the dark body. Again, perature; or again, if there exist on the samle sur- the nucleus will disappear as it passes by the center, face centers of volcanic disturbance, the eruptions until we only can see the side of the opening, proceeding from these and in a short time craters, piercing and the penumbra will tearing away success- also pass from our ively the two interior i? view. atmospheres of the _ a But it may happen Sun, would produce that the opening thus holes of the greater or made in the photoless extent, openings.. sphere will be smaller through which t h e than that in the central nucleus or the cloudy stratum. In overlying umbra this case the black could be seen. These ~ nucleus will be alone openings, therefore, visible, and it is thus should present gen- that a spot without erally the form of an penumbra is exirregular cone, plained. If, on the widened at the upper contrary, the rupture part, exposing at its in the first envelope center the solid and closes up before the obscure part of the photosphere, then the Sun, and all around obscure body will be this the cloudy atmos- invisible, a circumphere. of a greyish: piHere of a greyisha stance which easily tint. Hence, black explains penumbra s p o t s, surrounded without a nucleus. with penumbra. The Sun revolving Fig. 8. Explanation of sun-spots on Wilson's hypothesis: a a, photosphere; b b, cloudy stratum; A, spot with nucleus (umbra) and penumbra; B, nucleus (umbra without penumbra); C, penumbra without nucleus (umbra). ooneaS se lg X;-a~.~ 8~ — b & oh Jr g asSw Y~2ZEII' S.*A3N IMWOld ~VqOS zrg P., >aso>.AHPBy.yaswoov~a ry..^A~YM i i :~::::: ~:i ~ i~i;;:::::"::::::':~:-::v iilii a::': i:: ~~~~~~~~~~:, :iiiiiiri:l~'7'::::i~ijEi I';:1(:~,~-B:i;~ii'::i:i'i:iiiii':~$:i::1: 1:1:1 ~~~:::::~: ~:':~~ ~::-::,~,,,ici:11::::::i::4';:'~1~:~::ii:~ ~.~.~.~i~'ii'~:::'~-'1 5::::::'r: liH::~::::::::; i:j:::::j:~:::::::::i X~;:l:l -::::::::::: I::::~::::::: irX-:j: B ir::: c::::: T.: I.i::i:I::::::~::l:i:;::~,i 1::: i% LB i.:iii:iiiii:i.iii:ii:u,:,::liiili.ii liiiiiiiiiiiili:iliii.i::i iil:liijiliiiiii':ei:iiC:i:i ~ :l~iiiiii:ii:::: i:I':i::: j::::: 1::, lli F:::::: N~ tg i-d 3es -a aa r =ri9 o iiii t'J (u Z:~: $S:::'Z Q ::: i0::..:::::,:i h:: B 31 in n gi::i:::::s s::~I1 I::: gl wi; ~~~: iB ~::::::::i::::::'.:.::::::::::I:::i:i i:i::::::'::::~::: 1:::I-::::I i: r.::::::::-:::'i.::I:;::i:,::~::::::::; i~:~:r -I j:::::::::.: i::::::::: O:-i C,:::'::: i:::::::.:::::i;z:l:~;:::: it::::,::::-:i;i::i-:_iiiiiiiis"i: it;i:iiiiili:i::i:::::;::;:Jr::::: i:iii:: liiij::::;: iiii:: it ii: I:r::: iii :::::.:;:::::I'L:i::::::::::::B I:I )iil iS tB! I:I:i::i :: ic:i-:i~a ~x~~;; E,~IIBBpji;i~::::::::::~ : p m I. a h Ir:ibj B i3 s,:iijiirii::: ili~!j ~S XI P. :si::~ i'i 4 u r, C ELECTRO-ASTRONOMICAL ATLAS. 21 LESSON IX. AN.ALYSIS.- Solar Prominences - Time of Appearance - Production - Duration - Height - Appearance of Jets - Scenes from Harvard College - Spots - Passage over Disc - Appearance - Uniform Time. Q. How long do they remain? SOLAR PROMINENCES. A. There is a great difference in their duration; Q. What phenomenon is often revealed when a sometimes they remain only a few moments; at total eclipse of the Sun occurs? others, they continue for several days. A. There are manifest certain solar proini- Q. To how great an elevation do these often nences. arise2 Q. What is the general appearance of the solar A. Sometimes to the height of eighty thousand prominences? miles. A. They originate in brilliant jets, either verti- Q. What is there peculiarly interesting in these cal or oblique. illustrations. Q. How are these solar prominences produced. A. The varied appearance of these brilliant A. They are produced by incandescent mole- jets, some straight, some oblique, and others cules, or emanations of the electrical element from rising and then falling again on the Sun, like jets the Sun. of our fountains. - See plates II and III. Fig. 9. Q. Which way do these spots pass over the sun, it assumes the same forms, only reverse in disc of the sun? the order. Ai. They pass fr~om east to west. 2Q. How long do these spots remain visible? Q. In illustration (Fig. No. 9), describe the A. About forteen days. form of the spot just entering upon the sun's Q. Is this length of time ascribed to all of theni? disc. A. Their time is usually uniform. A. It appears oval in form, the greatest length being at right angles to its motion across the sun. Remacrc. —So uniform is their time, that just Q. Does its form continue the same. fourteen days from the time the spot disappears A. In proportion as the spot approaches the on the western border, it again reappears on the centre, it widens, so that it becomes nearly circu- eastern, often changed in form, it is true, but lar, and as it passes off the western portion of the generally recognizable. 5 22 ELECTRO-ASTRONOMICAL ATLAS. LESSON X. ANALYSIS. - Dimensions - Compared to the Globe - Measurements of Schroeter - Of Sir W. Herschel - Of Captain Davis - Re mark - Physical Organization of the Sun - Views of Sir W. Herschel - Of Kerchoff- Of Sir John Herschel - Why Vary in Appearance - Way the Sun Turns on its Axis - Do all the Planets and Constellations Turn the Same Way? - Evidence of their Revolution from West to East - Time of Revolution of Sun - Inclination to Ecliptic. Q. Are the dimensions of the spots uniform. A. He supposed the Sun to be a solid, dark A. They are extremely varied as to size. body, surrounded by a vast atmosphere, almost Q. How will they compare to our globe? always filled with luminous clouds, occasionally A. It is not uncommon to see them with their opening, and disclosing the dark mass within. surface larger than the earth. Q. What are the views expressed by Kerchoff Q. How extensive was one measured by A. The idea entertained by him was, "that the Schroeter? Sun is an incandescent solid, or liquid mass," by A. He measured one which was equivalent to which he means that its nucleus has the appearsixteen times the surface embraced by a great ance of being white heated, the vapors of which circle of our Earth, or four times the entire super- form the atmospheres; the denser and lower one ficies of our globe. being luminous, from the incandescent particles Q. How great was its diameter? that float into it. A. Nearly four times the diameter of the Earth, Q. What were the views expressed by Sir John that is, more than twenty-nine thousand miles. Herschel respecting the brilliant atmosphere Q. What was the size of a spot measured by enveloping the Sun? Sir W. Herschel? A. He contended that the gaseous, brilliant, A. It consisted of two parts, the diameter of atmospheric representations arose from the elecwhich was not less than fifty thousand miles. trical magnetism of the Sun. Q. How large were some observed by Captain Q. Why do the spots vary in their appearDavis in 1839? ance. A. The most extensive was not less than one A. The varied appearance of these spots dehundred and eighty-six thousand miles in its pends upon the changes of temperature in these greatest length, and the surface embraced about atmospheres, giving rise to tornadoes and other 25,000,000,000 miles. violent agitations. The descending currents proRecnar7c.-The question as to what is the phys- duce the various openings which are dark, beical organization of the Sun is one on which as- cause filled with clouds of various condensation. tronomers have entertained various opinions, and Q. In what direction does the Sun turn on its to which they have failed, thus far, to give a satis- axis? factory answer. The Sun appears to some to be A. From west to east. surrounded by an ocean of inexhaustible flame, Q. Do all the planets and satellites revolve in with dark spots of enormous size now and then the same direction? floating on its surface. A. All of them except the satellites of Uranus Q. What views were entertained by Sir W. and Neptune; they revolve in the opposite direcHerschel i tion. PLATE: IV. WUED.PARSONS & CO.,ALBANY, N.Y. A. TO LL Es PV'torL1T. o. COMPARATIVE DiMENSiONS OF THE SUNTHE PLANETS AND THEIIR SATE LLTES. ELECTRO-ASTRONOMICAL ATLAS. 23 Q. How is it evident that planets, etc., revolve A. At the rate of 14,400 miles in an hour. from west to east 2 Q. What is the inclination of the axis of the A. By the order of the signs of the zodiac. Sun to the Ecliptic? Q. How fast does the Sun revolve in its orbit 3 A.. Seven degrees and twenty minutes. LESSON XI. ANALYSIS. - Planets - Why thus Called - Division - Primary — Secondary- Equilibrium of Motion - Law of Attraction and Repulsion -- Law Explained. THE PLANETS. EQUILIBRIUM OF THE MOTION OF THE PLANETS. Q. What are planets 3 All acknowledge that God created the planets and set them A. Dark bodies revolving around the Sun. rolling in their respective orbits, and that he constituted certain Q. From whence do they derive their name 3 laws, by which they are continued in their revolutions; hence we lay down the hypothesis, that they are continued in their A. From the Greek word Planatis, meaning revolutions by the electrical law of attraction and repulsion. wanderer. Q. How are these planets balanced and kept Q. Why was this term applied to these dark in their respective orbits 3 bodies?. ~~~~~bodies 32~ |A. By the immutable law of attraction and A. Becaus he they change their positions in the repulsion; in other words, by centripetal and cenheavens, while tile fixed stars maintain the same trifugal force. trifugal force. relative position. Q. What is the origin or foundation of the law Q. How are the planets divided? of attraction and repulsion 3 A. Into primary and secondary planets. | A. This law has its origin in the electrical Q. Mention the primary planets Q.'~ M t tpower the Sun exerts over the planets. A. Mercury, Venus, the Earth, Mars, Jupiter, Explanation.-I. Two positives repel each other. II. A posiSaturn, Uranus and Neptune. tive and a negative attract each other. Q. Why are they called primary planets? The Sun is the fountain of all electricity to the A. Because they revolve around the Sun. planetary system, therefore always positive in his Q. Why are the others called secondary plan- nature. ets. The planet drawing near the Sun becomes posiA. Because they revolve around their prima- tive, and is repulsed; receding from the Sun beries, al with them around the Sun. comes negative, and is drawn again toward the Q. How many secondary planets are there Sun. A. Twenty-two. | 24 ELECTRO-ASTRONOMICAL ATLAS. LESSON XII. ANALYSIS. - Distribution of Secondary Planets - Interior Planets -Exterior - Their Conjunctions -HowV Shine -Distinguished From Stars. DISTRIBUTION OF SECONDARY PLANETS. called exterior because they are seen at all disQ. How are the secondary planets distributed tances from the Sun. among the primaries? Q. What are the planets lying without or beA. The Earth has one; Jupiter four; Saturn yond the orbit of the Earth called? eight; Uranus eight, and Neptune one. A. Exterior planets. Q. What planets revolve within the orbit of the Q. How many conjunctions have they? earth? A. They have one conjunction and one oppoA. Mercury-and Venus. sition each. Q. What are they called? Q. When are they in conjunction? A. Interior planets. A. When they are beyond the Sun and in range Q. What planets revolve without the orbit of with it and the Earth. the Earth? Q. When are they in opposition? A. Mars, Jupiter, Saturn, Uranus and Nep- A. When in range with the Earth and Sun, and tune. the Earth is between them and the Sun. Q. What are these planets called? Q. What causes the planets to shine? A. Exterior planets. A. The reflection of light received from the Q. Why is this distinction of qualification Sun. made? Q. How may they be distinguished from the A. Mercury and Venus are called interior be- stars? cause they are but a short distance from the Sun, A. Their light is steady, while the light of the and are seldom seen; and the other planets are stars appears to twinkle. LESSON XIII. ANALYSIS. - Apparent Motions of the Sun, What Called -How Caused - The Daily Phenomenon Connected with the Apparent Motions of the Sun - Changes in the Points of Rising and Setting - Point of Culmination - Solstices and Equinoxes - - Note - Ecliptic - Coincidence with the Plane of the Earth's Orbit- Intersection of the Circle of the Celestial Sphere and the Orbit of the Earth - Obliquity of the Ecliptic. APPARENT MOTIONS OF THE SUN. Q. Which way does he appear to revolve in his Q. How many apparent motions around the diurnal motion. Earth has the Sun? A. From west to east. A. He has two. Q. Which way in his annual motion? Q. What are they called? A. From east to west. A. They are diurnal and annual. Q. How are these changes produced? ELECTRO-ASTRONOMICAL ATLAS. 25 A. The diurnal motion is caused by the rota- Q. Why called equinoxes? tion of the earth on its axis, and the annual by A. Because the days and nights are equal. the revolution of the earth around the Sun. NOTE.- From this it is seen there is a constant movement of Q. How often, and at what seasons of the year | the points of rising and setting alternately from north to south, and a constant variation, up and down, of the point of culminadoes the Sun appear to rise exactly at the east tion, except that the Sun culminates at the same altitude for point of the horizon and set at the west point? several days, about the 21st of June and the 22d of December. A. Twice each year; about the 20th of March These two stationary points of culmination are called the so01and the 23d of September. stices. Q. What is the meridian altitude of the Sun? Q. What is the Ecliptic? A. The highest point to which the Sun appar- A. It is the great circle of the celestial sphere ently rises above the horizon. in which the Sun appears to revolve around the Q. During what time does the Sun's meridian Earth every year. altitude increase? Q. How does the plane of the Ecliptic coincide A. From March 20th till June 21st, and the with the plane of the Earth's orbit points at which the Sun rises and sets move from A. The great circle of the celestial sphere is inthe east and west toward the north. tersected by the Earth's orbit. Q. At what time of year does the meridian alti- Q. What is the inclination of the axis of the tude of the Sun diminish? Earth to the plane of its orbit? A. From June 21st till September 23d, and A. It is sixty-six and one-half degrees. meanwhile the points of rising and setting move Q. Then at what point do the Ecliptic and back toward the east and west. equinoctial cross each other? Q. Does the meridian altitude vary at other A. At an angle of twenty-three and one-half times in the year? degrees. A. The points of the rising and setting of the OBLIQUITY OF THE ECLIPTIC. Sun, from September 23d till December 22d, move The inclination of the Earth's axis to the plane toward the south, and the altitude decreases of the Ecliptic causes the equinoctial to depart also from December 22d till the 20th of March, 230 28' from the Ecliptic. This angle made by the points of rising and setting move backward the equinoctial and the Ecliptic is called the toward the east and west, and the meridian alti- Obliqubity of the Ecliptic. tude increases. Let the line A A A represent the axis of 2-38 Q. At what points of time does the Sun seem poles or axis of the Ecliptic. Now, if the to reach his culmination?,cline A A Ncline toward the plane of the 22' / A. On the 21st of June and the 22d of Decem- Ecliptic, or, in other PZAM / O /F H /C words, departs from _ Z TO the line B B to the x<0 23".:280 amount of 230 28', it is obvious that the plane Q. What are these points called? of the equator, or A. They are called solstices. art from the same amouptic This departure, shown Q. What are the points at which the culmi- by the angles C C, con- A stitute the Obliquity of nation of the Sun coincides with the celestial the Ecliptic. FIG. 10. -OBLIQUITY OF THE ECLIPTIC, equator called? Hitherto, we have considered these great priA. They are called equinoxes. mary circles in the heavens as never varying their 7 26 ELECTRO-ASTRONOMICAL ATLAS. position in space, nor with respect to each other. Q. How are they distinguished? But it is a remarkable and well-ascertained fact A. The one which the Sun passes in March is that both are in a state of constant change. We called the VERNAL EQUINOX; that which it have seen that the plane of the Earth's equator is passes in September is called the AUTUMNAL constantly drawn out of place by the unequal EQUINOX. attraction of the Sun and Moon acting in different Q. What are the two points opposite the Eclipdirections upon the unequal masses of matter at tic, at which the Sun is farthest from the equinocthe equator and the poles; whereby the intersec- tial, called? tion of the equator with the ecliptic is constantly A. They are called SOLSTITIAL POINTS, or SOLretrograding- thus producing the precession of STICES. the equinoxes. Q. How are they distinguished? Q. What are the points opposite the Ecliptic A. The one north of the equinoctial is called where it crosses the equinoctial called? the Summer Solstice; the one south of it the A. They are called EQUINOCTIAL POINTS, or Winter Solstice. EQUINOXES. LESSON XIV. ANALIYSIS. -Mercury — Situation - Rate of Motion - Time of Revolution - Indications - Diameter - Inclination of Orbit to Plane of Ecliptic — Inclination of Axis - Time of Revolution on its Axis - Uniformity of Appearance. MERCURY. Q. What is the inclination of the plane of his Q. Which is the nearest planet to the Sun? orbit to the plane of the Ecliptic? A. Mercury.' A. Seven degrees. Q. How far is it from the Sun? Q. What is the inclination of its axis to the A. Thirty-seven million miles. plane of its orbit a Q. WMhat is its rate of motion around the Sun? A. Seven and one-third degrees. A. One hundred and ten thousand miles an Q. How long does it take Mercury to turn on hour. its axis? Q. How long does it take Mercury to make his A. Twenty-four hours and six minutes. flight around the sun? Q. What does this indicate? A. Eighty-eight days. A. The length of his day. Q. What does this indicate? Q. Is he always uniform in his appearance? A. The length of his year. A. He is not; he presents different phases like Q. What is the real diameter of Mercury?. the moon; sometimes a crescent form, then gibA. Two thousand nine hundred and fifty miles. bons; at other times a full face. See Fgs. 11 and 12. 7~~fL~V -~~ - mu K - ~~~~~~~~~~~~~~~~~~~~~~~~V' NMII - ~~~~~~~ ~~~~~~~~~~~ ELECTRO-ASTRONOMICAL ATLAS. 27 Let us speak first of f r o m henceforward its form. Mercury, in characterizes it more the course of one of and more, until it is its oscillations, pre- only visible as a fine sents phases entirely luminous t h r e a d. analogous to those ol We give some of these our Moon. It is at phases. The progressfirst a luminous disc, Fig. 11. ive increase of its PHASES OF MERCURY WHEN SEEN AFTER SUNSET. nearly circular, which apparent dimensions is also shown in exact by degrees is reduced proportion. The on the side toward same appearances are the east, until not more observed, but in inthan a half-circle is verse order, when visible at the period Mercury is observed of its greatest appar- during the period in ent distance from the which he is a morning ~~~~~Sun ~; the crescent PHA OF Fig. 12. S u n; t h e crescent PHASEIS Or MERCURY, WHEN SEEN BEFORE SUNRISE. star. LESSON XV. ANALYSIS.- Transit — Primaries Making Transits - When Occur — Condition of Earth and Planet when it Occurs — Ecliptic — Nodes - Months in which Trausits of Mercury Occur - Why? - Called What? - First Transit - Time of Others. TRANSITS. A. They must be on the same side of the EclipQ. What is a transit? tic and the Earth, on the same line of its nodes. A. The passage of a planet between the Earth Q. What is the Ecliptic? and the Sun and apparently over his disc. A. The Ecliptic is the plane of the Earth's Q. Which of the primary planets have been orbit; or the great circle the Sun appears to deknown to pass over the Sun's disc. scribe annually among the stars. A. Mercury and Venus. Q. What are nodes? Q. When can a transit never occur? A. The points at which a planet's orbit crosses A. When the interior planet is in or very near the plane of the Ecliptic. the Ecliptic. Q. When do all transits of Mercury take Q. When a transit takes place, what must be place? the condition of the Earth and the planet? A. In the months of May and November. 28 ELECTRO-ASTRONOMICAL ATLAS. Q. Why?. Q. What are these months called? A. Because the nodes of Mercury are on each A. They are called node months. side of the Ecliptic, and passed by the Earth in these months. NOTE. —The Earth passes the ascending node of Mercury in November, and the descending node in May. The former of WAD ~~ ~~~~~which is in the 16th degree of Taurus, and the latter in the 16th degree of Scorpio. 2 CCk4w44.CCC'C' CCCCCCCCCCCCCC.CCC'CC'C,.C.4 4...,.. C A". "' "" C'''..4'.Z444?4.W'4. C CCC. C' CC.CC.' CC CCC.C.CC4CC.CCCCCC.CCC'.C)C4?CPCC'. ,,C,. 4,fC44C ky"'?4)C4. 44. 4 4?4CCC)C)....4g444.C.44CC'C C .4444444. "CCC'. CACC'CC'C 4.C444 4?..4..,'CCC., C.C..CC..44.'CC '4.' 44"' 444C43CC4CC 4.C' CC')'. 4.CCC4'44f'.4'' C.4 C4CCJC'CC.C1 C'44.4C.) 4$' A44,C. CC.CCCCCCCCC . ) C.43CCCCC.4.CC,CC.C449C.C4C4CCCC4.,'C.' 4C CC CC....44? CCC C.'44C'.CC.C' 4"'C ,C C -CCC CC44.C'CCYC'C C CC,"'.'C4,4CC'CC CC4.CC44C,'C'CC C".""''444"''C... C,..'? C:CCCC...$. /CC.4CCC..,. C4w * *CCCCCCCCC 44444-2. C. CCC~4.C'C 4,4,4CC ('.CC4C )4?CC',.4CCCCCCCC\ 44,44.;.4C'.)4.,44 '4, C.444,.'. CCCC CCCCC" 'CC' 44?. 44CC.')..''\4,"4C. CCCCC'' 4""C'44CC'.C.C' C)' WEED PARSONS CO ALSANY N'r A COLL C'HC'TO UI'H ELECTRO-ASTRONOMICAL ATLAS. 49 Q. Why do we have an Eclipse of the Sun only a total Eclipse of the Sun. Here the dark shadow at New Moon? of the Moon falls on the Earth and obscures the A. At any other point in the orbit the shadow entire body of the Earth. of the Moon would fall away from the Earth, Again, if the Cone of the Moon's shadow does hence, it would be impossible at any other time not reach the earth, there will be annular eclipses to have an Eclipse of the Sun. visible in those parts comprised in the prolongation of the Cone; a partial eclipse to those which ECLIPSES OF THE SUN. are only found in the penumbra. This case is Solar Eclipses are of three kinds. Some are represented by the next figure. (Fig. 32.) total; the dark disc It will be seen, of the Moon then therefore, that t h e entirely covers th e ii;i!" conditions of the posSun. Others are _ _, sibility of a total partial; t h a t is, a ~:j ~ [:'gi?-,-ii': eclipse of the Sun portion only, large or are the following: small, of the Solar -- The Moon must be disc is eclipsed. Last- l_ in conjunction, that ly, there are annular, Fig. 31. is, she must be new; which take place TOTAL ECLIPSE OF THE SUN. She must at t h e when the disc of the Moon is not large enough to same time be near a node; entirely cover that of the Sun, and leaves a lumi- Lastly, her distance from the Earth must bea no-Ls ring visible __ less than the length round its own body. = =_ of the cone of shadow As the M o on is projected by her into much smaller than 1 1 _ S. space. the Sun, it will be __i; __.:::_.The same coudiunderstood that it is.:_;__:_:;:__'~ tions, except the last, its small relative.'"' —'~~,~~:,~ are necessary for an distance which causes - annular eclipse. its disc to appear of Fig. 32. equal and even great- ANNULAR ECLIPSE OF THE SUN; THEORY. er dimensions than that of the Sun. This distance Q. How many solar eclipses do we generally varies by reason of the elliptical form of its orbit, have each yeara and hence the dimensions Goingoff. Annular. Comiloll. A. Two. of the lunar disc are some-:_' Q What is the greatest times larger, sometimes number possible? smaller than, and some- b / X _A. It is seven. times equal to those of the - Sun. If you turn to Il I' Fig. 31, you will witness Fig. 33. PRlOGRESBS OF A CENTRAL CELIPSE. 13" 50 ELECTRO-ASTRONOMICAL ATLAS. THE TIDES. and still greater It is well known height,and after six that twice a day at I_ _ hours gains its maxian interval of 12 mum. hours and 25 min- BgBBScarcely is the inutes the shores of stant of high water the ocean present us orflood tide attained with the spectacle of then the flow or rise the flow of the tide. of the water ceases; The tide by degrees the descent comrises, gaining on the mences, and the ebb beach, which it succeeds to the covers to a greater flow. Fig. 34. Q. What phenomenon results mainly from the it to rise another the influence of the Moon f A. The Tides. foot, making it six ~~~~~A.~~feet. ItThe Tides.is then high Q. What causes the Tides? feet. It is then high A. The Earth attracts the Moon, and the Moon tide on tai side of the Earth toward in turn attracts the Earth. The solid particles of the Moon and on matter composing the surface of the Earth not the exact opposite being free to move, the attraction of those parti- the of the Earth, while cles is not perceptible by us, but the particles of at the two sides of matter composing the surface of the ocean being the Earth it is low free to move, the attraction is perceivable, which tide. causes the water to rise and form a wave. (See Q. Why does not fig. 4.) | ~~~~~~~~~~fig. 34.) ~the Sun exert a Q. At what time do we have spring tides m more powerful atA. At New Moon. traction upon the Q. Why? Earth, it being so A. The Moon is then between the Earth and ar g t much larger than Sun, and in range with them. th e MMoon? Q. How does that effect the Tides to make A. The Moon is ab o u t 91,260,000 A. The Sun and Moon, being on the same side of the Earth, and in range with it, the attraction E ta the Earth than the Sun of both acts together on the Earth. (See fig. 35.) is at New Moon. Q. What proportion do they attract? A. The Moon causes the water to rise five feet Fig. 35. PLATE XIII. ~i~~2 I 3 EERIE~~~~~~~~~~~~OS WIEED PRSNSe-ALAN. A T LL. I 70 MARS AND THE EARTH.~ a CO MPARAIVE imirtj-qnm ELECTRO-ASTRONOMICAL ATLAS. 51 LESSON XXXIII. ANALYSIS.- Planet Mars - Location - Appearance; To the Naked Eye - Distance from Sun - Time around it - Indication - Time of Revolution on Axis - Indication? - Diameter - Inclination - Exterior - Why? - Resemblance to Earth - Changes of Climate -Divisions of Land and WVater - Geography Similar — Mars Probably Uninhabited - Circumference of Orbit - Distance fromn Earth - Opposition - Where looked for -Position of the Earth - Appearance of Mars. THE PLANET MARS. Q. Are there similar changes of cold and heat Q. Where is Mars located in the order of the in Mars as in the Earth? Planets? A. At certain seasons Winter scenes are preA. He is the fourth planet in the order of dis- sented, and at others, rain is apparent and the tance from the Sun, between the Earth and the snow-caps disappear. Asteroids. Q. Are there other analogies? Q. WThat is its appearance? A. In divisions of seas and land. A. To the naked eye it is distinguished for its Q. Any thing known of its geography? brilliant red light. A. It is nearly as well known and as well deQ. How far is this planet from the Sun? fined as that of the Earth. See Fig. 36. A. The average distance is 145,205,000 nliles Q. Is there evidence that Mars is inhabited? from the Sun. A. The conditions of life on these planets are Q. How long does it take Mars to revolve so unequal, it seems hardly possible or even proaround the Sun? bable, for Mars to be inhabited. A. It takes 687 days. Q. What seems to confirm this position? Q. What does this indicate? A. Mars receives but one half the amount of A. The length of his year. heat or light enjoyed on the Earth, hence, the Q. How long does it take to turn on its axis? apparent impossibility of human existence. A. Twenty-four hours and forty minutes. s._ s.p. Q. What does this show? |; U S1 A. The length of his day.' a:J', c Q. What is his diameter?, /': J1 / A. It is 4,200 miles. Oeane Q. Wthat is the inclination of the plane of e D- - - o'iizhis orbit to that of the Ecliptic?..' --- <, A. One degree and fifty-three minutes. roi Q. Is Mars an interior or exterior planet? l l A. He is an exterior planet. N.P. Q. Why. A. Because he lies wholly beyond the orbit of the Earth. Q. To what globe has Mars a near resenmblance'?. Fig. 36. A. The Earth. CHART OF MARS, FROM DRAVWINGS BY MIR. DANES. Q. In what respects is this manifest? Q. What is the circumference of its orbit? A. in climates. A. It is 901,064,000 miles..I' 52 ELECTRO-ASTRONOMICAL ATLAS. Q. What is the mean distance of Mars from the Q. Then where would be the position of the Earth? Earth? A. Hle is 50,000,000 miles. A. Between the Sun and Mars. Q. Is he then in conjunction or opposition? Q. At this time what is the appearance of Mars? A. In opposition. A. It appears with a surface twenty-five times Q. Which way do we look to see him? larger than when in his conjunction? A. In the direction opposite to the Sun? LESSON XXXIV. ANALYSIS.- When take place - Caulse of brilliacy - Distanc oe side of Orbit - Intlination - Rate of Motio - Light, compared with that of Earth - Difference of Diameters - Density, compared with the Earth - Difference of Weight - Ratio from Sun of the Orbits of Planets described - Rapid Changes - White Spots - Snow Zones. Q. W;hen does this take place? l |______1 A. When he is in that part of his orbit i.... A. He is 240 000000 miles. Q. Does this account for the changes in the size and brilliancy of the planet? Fig. 37. A. It does. DIAIETER OF MARS AT EXTREME LEAST AND MEAN DISTANCES. Q. How far is the Sun one side of the orbit of Mars? Q. What is the density of Mars compared with A. He is 13,463,000 miles. the Earth? Q. What is the inclination of his axis to the A. It is much less. plane of his orbits Q. How much would a, body weigh on the A. It is thirty degrees and eighteen minutes. planet Mars that weighs one pound on the Earth? Q. What is Mars' rate of motion in his revolu- A. It would weigh 5 ounces and 6 drachms. tion around the Sun? Q. What is the ratio of the distance from the A. It is 54,640 miles an hour. Sun, of the orbits in which the planets already Q. What proportion of light falls upon Mars described move? compared to that on the Earth?| A. Venus' mean distance is about twice as far A. About one-half as much. as Mercury; that of the Earth twice as far as Q. What is the difference between the polar Venus, and the mean distance of Mars twice as and the equatorial diameter of Mars? far as tll Earth. A. It is two hundred and sixty-three miles. :~iE~:~~~~~~~~~~~~~:). i~ Zt I K ~; ~:-,,, o ~:..~:~Iiii: *i',;.I..' )!I;) P LATE __. /3' 4 \o 6\OV 7\' /\O __. /. ~ OFr THE _ -E/7l 7iiq t7e relaf;' Poisozbu of/ /he L T O / / E --'iz,~_ anJad1ewi, k-hcdvaf lo thfle re," -"' -ITI~,/ / rnr aP of the ECXIIP-TITC. -, I ~ /- / / -__ ~~e Zt 3;/3o1 — the Zod~at " -.,..i InJ tXB of ie E 4r -— t- 13tia,,n,~.; _. —. - 3 <4 I. I - / // 10,-_ 20_en S cl / o./..... 0d f I ~, \ ~t ~ o -...._ o I.,, o. \\ 3,@ - Wo 5/0 20 / 7?I,~amrs~ir7~juzt- / / / / /. —— t - —. Im,.............. I21'g1 2"___"........... I',,,' —:'".: —— t- 7" 1 \6E /n'-'u'"' lo\. 2 I 20 ~,~~~~~~~~~~~ ON,~_1FgDST C ~ xlv.,, /...70 6 50 0. ~," C'- _ 4'.,. %Q/ /.. _ tirat t i 0 0 F~~~y ff~Cof ePlwnet' - - o -ifereUr 2Ceres.' f 9 fion2'lze ztraenus iPalasl Earth: 8 fpi 847,~~" h e, re sPla, VferscceaZ~v- UTzrzt.-4 of of Tsi.'w \e ~,,./oSs/S 2WE PLANI-f"iS -1?OM TflE OrUiW --- ---- -c 7 e o So l f Se idi' ee f 100 20t 30z 41 5t0 ee / 7r Am, ho& -i:ipAh; S.,_ I... _ -..... 5%,.. —-—.,- - /......... and/,"~q - S e —— v'-_oc_ ~~ 180 ELECTRO-ASTRONOMICAL ATLAS. 53 There are constant and rapid changes going on, as in Fig. 38. You perceive the change manifest in an interval of two hours. These changes in the brightness of the disc are owing, it is supposed, to the variations of the clouds of vapor in its atmosphere. No mountains have yet been discovered. In the region of the poles are brilliant white spots, which are supposed, by some, to be masses of Fig. 38 Snow. These Snow Zones recede in VIEWS OF AIlS AT TWO HOURS' INTERVAL. (WARREN DE LA RI.) summer and increase on the approach of winter. Q. What small planets lie between Mars and Hence, we can observe in fact most, if not all, Jupiter the changes of the seasons which take place on A. They are the Minor Planets. the surface of our neighboring planet. LESSON XXXV. ANALYSIS.- The Minor Planets - What are they? - Number - Space occupied - Kepler's impression - Not witnessed in his Day - Two Hundred Years after - Discovery Made - Four Found - CERES, PALLAS, JUNO and VESTA. THE MINOR PLANETS. Q. Who commenced it? Q. Where are the Minor Planets? A. Twenty-four Scientific Explorers, in 1800, A. There are a large number of Minor Planets commenced a search for the hidden planet. lying between Mars and Jupiter. Q. Who was the first to detect the new planet? Q. How many do they number A. It was an Italian astronomer by the name A. There are now known to be one hundred of Piazzi, in 1801, and called it Ceres. and thirty-four Minor Planets. Q. What effect did this discovery produce on Q. How large a space do they occupy? the Scientists of that day? A. Not less than 35,000,000 miles. A. It gave a new impulse to astronomical Q. What impression was made on the mind of investigations. Kepler in view of this unoccupied space? Q. What was the result? A. He was of opinion that within that space A. Not simply one but four were discovered. there must lie an undiscovered planet. Q. What were they named? Q. How long after his day before a thorough A. They were called Ceres, Pallas, Juno and research was made? Vesta. A. Some two hundred years. 5;4 ELECTRO-ASTRONOMICAL ATLAS. LESSON XXXVI. ANALYSIS.- Ceres — Time and by whom discovered — Estimate by Sir W. Herschell — Diameter — Distance from Sun — Time around it - Inclination - Appearance in Size and Color - Pallas - Time and by whom Discovered - By whom Measured - Distalnce from Sun - Time around it - Inclination -Appearance as to Size and Kolor -Juno - Time and by whom Discovered - By whom Estimated - Appearance as to Size and Color - Distance from Sun - Time around it - Inclination of Orbit - Vesta - Time when and by whom discovered — Comparison with the other Minor Planets - Diameter - Distance from Sun - Time of Revolution - Inclination of Orbit - Description of all nearly the same. CERES. Q. What is the time of its revolution. Q. In Tw~hat year and by whom was Ceres dis- A. It is one thousand six hundred and eighty. covered Z four days. A. In the year 1801, by Professor Piazzi, an Q. What is the inclination of the plane of its Italian astronomer of Palermo. orbit with the plane of the Ecliptic. Q. Who has given the most accurate estimate A. It is thirty-four degrees thirty-seven minutes and twenty seconds. of this planet?' A. Sir Wmn. Herschell. lQ. What is its appearance as to size and Q. What is its diameter color?. A. It is 1 63, miles. t A. It shines like a star of the seventh mnagnitude and is of a yellowish light. Q. What is her mean distance from the Sun? A. It is 262,764,110 miles. Q. How long does it take to revolve around the Sun? Q. Who discovered Juno, and in what year? A. It takes about 1680 days. | A. It was discovered by Professor Harding, of Q. What is the inclination of her orbit to the Lilienthal, on the 1st of September, 1804. Q. What is its appearance as to size and color? A. It is ten degrees and thirty-seven minutes. A. This planet shines as a star of the eighth Q. What is its general appearance as to color magnitude and is of a reddish color. and size? I Q. What is its mean distance from the Sun? A. This planet shines with a pale, reddish A. It is 253,524,410 miles. Q. What is the time of its revolution around lustre, and like a star of the eighth magnitude. the Sun? A. It is one thousand five hundred and thirtyPALLAS. two davs. Q. At what time and by whom was this dis- Q. What is the inclination of the plane of its covered? orbit to the plane of the Ecliptic? A. On the 28th of March, 1802, by Dr. Olbris. A. Thirteen degrees three minutes and seventeen seconds. Q. Of whom has been received the most reliable measurement of this planet? A. It has been given by Dr. Lamont of Munich. VESTA. Q. What is its mean distance from the Sun? Q. At what time and by whom was Vesta disA. It is 263,186,670 miles. covered? ELECTRO-ASTRONOMICAL ATLAS. 55 A. She was discovered by Dr. Olbris, on the of fresh bodies in this zone between Mars and 29th of March, 1807. Jupiter? A. How does she compare with the minor A. This is a difficult question to solve, but planets it is probable that we are now acquainted, if not A. She is a small planet of the sixth or seventh with the largest of the Minor Planets, at all events magnitude, yet, when she appears in opposition with all those most easily visible from the Earth. to the Sun, she appears the brightest of all the The discovery of others will, therefore, become Minor Planets. more and more difficult, and the extension of Q. What is her diameter 2. their number is partly subordinate to the use of A. She is only 295 miles in diameter. larger instruments in the research, and more Q. How far is she from the Sun? detailed celestial maps. At all events, M. LeverA. She is 224,327,905 miles. rier, from. mathematical considerations, has asQ. What is the period of her revolution? signed to the total mass of the bodies which comA. It is one thousand three hundred and pose the ring, such a limit, that if we suppose twenty-five days. them to possess a density equal to that of our Q What is the inclination of the plane of her own globe, those already discovered form only orbit to that of the Ecliptic? the mT0th part of it. This would make the numA. It is seven degrees eight minutes and ber of the Minor Planets about 150,000. But, twenty-five seconds. admitting that this number may be excessive, and NOTE.-The Minor Planets are so nearly similar, that.it is in reducing it to the tenth of its value, this swarm unnecessary to speak further of them separately. of celestial bodies will still be counted by thousands. The four planets of JUPITER. which we have From that region of space where we have just just given some seen the smallest members of our system circulad e t ails, are ting in their orbits, we pass without transition to am ong the the largest planet —the colossal Jupiter. most important To the naked eye, Jupiter appears as a star of of the group. Fig. 39. the first magnitude, the brightness of which, variCOMPAATIVE] DDIMENSIONS OF THE EARTH AND JUNO, The smallness CERES PALLAS AND VESTA. able with its distance from the Earth, is someof nearly all the others is such that it is not possi- times, when the Moon is absent, sufficient to throw ble to measure their diameters, as they appear a shadow. Its light is constant, and scintillates in a telescope merely as luminous points. It is but rarely. But if, to examine it, a rather powerprobable that the least of these microscopic bodies ful telescope is used, the point expands into a have diameters which do not reach many score well-defined disc, and is generally seen to be miles, and that a good walker could easily in a accompanied by three or four little points of light day make a tour of many of these miniature which oscillate in short periods of time round the worlds. central planet: These are the Satellites of Jupiter. Q. How long shall we go on making discoveries Venus, Mercury and Mars, as we have seen, 56 ELECTRO-ASTRONOMICAL ATLAS. are without satellites; the Earth has only one. The reason of this difference between the appaJupiter with its four moons, which the powerful rent diameters of the disc is easily explained. attraction of its bulk compels to revolve round The orbit of Jupiter, like that of Mars, encircles him, exhibits to us, therefore, a small system the terrestrial one, and the motions of the two analogous to the solar one of which it forms part bodies in their respective orbits bring them, once and which it reproduces on a smaller scale. in every thirteen months, in the same straight To arrive in our journey from the Sun as far as line with the Sun, and on the same side of it; the Jovian system, we must pass over a distance Jupiter is then in opposition, and its distance which exceeds five times the mean distance of the. from the Earth is measured by the difference of Sun from the Earth, or, in the mean, 500,000,000 the distances of the two bodies from the Sun. miles. But the orbit described by Jupiter round In a similar period the two planets are still in a the Sun differs from the circular form more than straight line with regard to the Sun, but on oppodoes the Earth's. Its distance, therefore, is more site sides of it. This is the conjunction of Jupivariable, and while at Perihelion it reaches 472,- ter, and the distance of the two planets is found 000,000 miles, at its greatest distance it is not less by adding their respective distances from the Sun. than 520,000,000 miles from the Sun, hence the These distances themselves are sometimes smaller difference being 48,000,000 miles. and sometimes greater than at others, and thereJupiter, therefore, as seen from the Sun, pre- fore the same thing happens with regard to those sents an apparent diameter sometimes greater, which separate the Earth from Jupiter at the sometimes less than its mean one; and, of course, time of opposition and conjunction. the same phenomenon is seen by observers situa- At its greatest distance from the Earth, Jupiter ted on the Earth, but in a much greater propor- is 617,000,000 miles from us; at opposition it tion. Fig. 40 will give an idea of the variations may be within 375,000,000 miles; but in the mean, the distance of Jupiter at conjunction with the Sun is 591,000,000 miles, and at opposition 400,000,000 miles, the difference being the diameter of the Earth's orbit. From the preceding numbers we may perceive the immense development of the orbit described by this member of our planetary system. Thus, to traverse this path, it requires twelve years. This gives a mean rate of upwards of 700,000 miles a day, or nearly 30,000 miles an hour. The movements with which we are acquainted on the Earth can give us no idea of such a mass Fig. 40. | traveling eternally through the depths of space PITS EAND EXE DISTANES FRO TE ERTwith a velocity eighty times greater than that of a of size which the disc of Jupiter, at the time of cannon ball. its mean and extreme distances from the Earth, presents to us. ,,;~~: I 3~~1:;sa:r:~ I Ls ~~::- ~::~ ~;:: ~-r~ i:-~'-)'''''I:'-~::':I"':~';':':: ::':"::l:~:~t-::-.ii~;:~,~~::a:~~:?,_~i'?l:~!.:;i::: .Z~2.~'i :'V ~i::~::'i~'Llr 1~~~: i":;:j'~~~_ ~: ~::~~~: ~~~li:i::::~~: ~-~::~ic i~I.. ~~.~-~=..:,I: Ihi s:i:I; ~~.::~:::~:-' ~:r 8 I pi:~ I~riir:r:~~~~::::::,~:::~::: z:r21ry,.2. ~:;"::i~i:~ x:S/':I~S~:::~':~:::~~~( B. ~.:~ ~1- i:~-:..13,Ds~j:s~:"::~:'i ~:~:,:c~:a,:,- -i;I"2''~ _~..sniii~~;-~~~~:~:-. dtk Be ":a i~Yi"'~:':'"'i" ~":~:~i~.:I:i_i:::::::'~'::'''' i I I I::::::i'd::"r' iiii;::.i~d;8'z::Y~~1'9:~":::~~:::::: i i"'~S.~:~1.::is;:;-~i~t~::::::''.'~''~;: b.:: iiFr~~:,:::: .:.~::i:::i':i';.:'::i:::::::.:l:~iirt:::::::;'15::1~.::~::i::::':,:,:dR:2:i:::?2~:: 3 il~;:::::':~,,.:g:l~':-' r-iji::::::~_:-~f ei.iu-:~a~ si ol:,:,~'~~'i~a::r:~: IG lfa'~:Btii 1 *z:~d: ~si 4,~j ~::?..~x."u.T:~:I-~)": ~Fi xc i.":~ "li7:::1';e 8::~t:";~:'~UaI i r~:i~~j~~~:, i:~::: ~::-dai:i I:p:::~-:::::~:j.::;::: "'9iB:::;.~..:::. -:.: ~~~-~..:::;,,t~ib.-~ iii:,:'..:~i'':::::::~~:::~,'~~ i::::~.-"i~l i j ZcSii: i:-::: i:"_::i;~~~.;,~jii::::~;:: i: X 9ij i~:::::l:~:i.:l:j:: Il:j: i*c.:6:;m*''l~7::-'"li:i:i~.~i'~ "C*: i~lii i .r_,i:-i:::.:i::-:::-: I:::::l:i sr rri~r~::~~i I-~'~:. 9 ~ai i: *s cl~:~:; iI:- :.::: 4~' i 1 i4:PB3,i i:U F 1 I'~i""'- O:C:i-4:"iT: Ia Ygt jp:i'" *r'~~`::iii I: ELECTRO-ASTRONOMICAL ATLAS. 57 LESSON XXXVII. ANALYSIS.- Planet Jupiter - Situation - Why Distinguished - Distance from the Sun - Time around it - Indication - Diammeter - Time of Revolution on its Axis - Indication - Circumference of Orbit - Rate of Motion - Effect of Motion on the Weight of Bodies on his Surface - Weight of Bodies on his Surface compared with their Weight on the Earth -Cause of Difference- Satellites - Variable Appearance- Observations of Mr. Dawes. JUPITER. Q. What effect does this rapid motion on his Q.. What. paelenaxis have upon the weight of bodies on his surface? Q. What planet lies next to the Minor Planets in. theregla orer rothSuA. It makes them lighter than they would be in the regular order from the Sun? A. It is Jupiter. were its motion no greater than that of the Earth. QFor what is Jupiter distinguished..Q. What is the weight of bodies on the surface of Q. For what is Jupiter distinguished ~. mgi-Jupiter compared with their weight upon our A. He is regarded the largest and most magnifi- th cent planet of the Solar System. Q. How far is Jupiter Sfrom the Sun? A. A body that weighs one pound upon the A. Hoae is 49 Ju817,000 miles.f Earth at the Equator, would weigh two pounds A. He is 495,817,000 miles. four ounces and a half on the Equator of Jupiter. Q. How long does it take this planet to make a What causes the difference?. ~~~~~~~~~~~Q. What causes the difference ~. revolution around the Sun? revolution around the Sun? A. The immense size of Jupiter. A. It takes him 4,332 days 14 hours and 2 minutes, or nearly 12 years. SATELLITES. Q. What does this indicate Four luminous points- four small stars- unA. The length of his year. ceasingly accompany Jupiter in its twelve-yearly Q. What is the mean diameter? revolution. They are easily observed with small A. It is eighty-nine thousand miles. telescopes. Q. How long does it take Jupiter to turn on From hour to hour their positions vary, and his axis? they seem to oscillate from one side to the other of A. It takes 9 hours and 56 minutes. the disc, in paths nearly parallel to the direction of Q. What does this show? the belts, that is to say, to the equator of Jupiter. Q. The length of his day. These are its moons or satellites. They are beQ. What is the circumference of this orbit? sides frequently seen to disappear, one, two, and A. It is 3,110,000,000 miles. even three at a time. It sometimes, indeed, even Q. What is his rate of motion? happens that not one of the four is visible. JupiA. It is estimated at 30,000 miles an hour. ter then appears alone, deprived of its companions. Q. WVhat is said of his motion on his axis? This state of things was observed by Mr. Dawes, A. It is said to be greater than that of any on the 27th of September, 1843. But it only hapother planet in the Solar System. pens very rarely. I 15______ __ _ ELECTRO-ASTRONOMICAL ATLAS. LESSON XXXVIII. ANALYSS.- Satellites of Jupiter - Number - Names - Diameters - Distances - and Revolutions - Eclipses - Number per Month - Eclipse of Sun effected by them - Inclination of the Axis of Jupiter to Plane of his Orbit - Plane of Orbit to Plane of Ecliptic - Eccentricity of Orbit- Solar heat compared with Earth. Lastly, as mentioned, above, it may happen that during the disappearance of the three -_ ~ _ satellites, the fourth is between the Earth and the planet. Then the planet eually appears solitary and deprived of its comanions. JIER Fig. 41. ruSAELT.Fig. 42 will render clear the various posiJUPITER AND ITS FOUR SATELLITES. tions which the satellite may occupy with referQ w satellites has Jupiter a. ence to the Earth. One of them in this figure is Q Wha ethey called? represented Eclipsed, the other is seen projected Q. Wht arethey called?~ on the disc, on which also its shadow is thrown a, Ganymede and Callisto. a third is hidden by the planet, and Taking these satellites in the order of their entirely visible. distances, the times of their revolutions are as follows: First satellite (lo)... 1 day, 15 hours, 28 minutes. _____ Second (Europa). 3 13" 43 Third (Ganymede) 7 " 3 " 43 Fourth" (Callisto). 16" 16" 32____ __ In comparing these times with that of the revolution of the Moon, it is seen that the movements of the satellites of Jupiter are _ much more rapid than that of our Moon. This rapidity is the more marked, as their distances Fi g. 42. DIM ESIONS OF THE SATELLITES OF JUPITER COMIPARED WITH THOSE OF from the planet, and, therefore,. the lengths of THE EARTH AND MOON. their orbits are more considerable than in the case We have. seen what are the apparent dimenof our satellite. Measured from the center of the sions of the four satellites as seen from Jupiter, planet, the mean distances of these satellites are as compared to the apparent size of our Moon. But follows: we must -not confound the apparent with the real Q. What are their respective diameters, distan- diameters. (See the above table of diameters.) ces and periods of revolution around their So, the third and fourth in the order of distance primary? are the first and second in order of magnitude; A. DIAMETER. DrSTANCE. DasREVOLUTION. S one only is less than our Moon; taken together, Io... 2,440 278,500 1 15 27 34 they would form a body 91, times larger than it, Europa. 2,190 443,000 3 13 14 36 o bu n-it ftevlm fteErh Ganymede 3,580 707,000 7 3 42 33 o bu n-it ftevlm fteErh Callisto. 3,060 1,243,500 16P 16 312 50 Lastly, the volume of the largesqt exceeds~ by ELECTRO-ASTRONOMICAL ATLAS. 59 two-thirds the volume of the planet Mercury. Q. How many can cause an eclipse at a time? Here, then, we have a secondary body larger than A. All of them can never be eclipsed or cause a primary one of the first order, and far surpass- an eclipse at the same time; seldom ever but two ing in size those which circulate between Mars of them. and Jupiter. Q. What is the inclination of Jupiter's axis to the plane of his orbit? ECLIPSES OF THESE SATELLITES... A. Eighty-six degrees and fifty-four and a half Q. How many Eclipses do they suffer every Qmont~how mnEis th sfevr minutes, or three degrees and five and a half I ~~~~~month?~ 2 1minutes from the perpendicular. A. The first suffers eighteen; the second, eight Q. What is the inclination of the plane of his or nine; the third, about four. The fourth does orbit to the plane of the ecliptic orbit to the plane of the ecliptic 2. not suffer as much as either of the other three, as A. One degree and nineteen minutes.,A. One degree and nineteen minutes. it frequently passes its opposition without being Q What is the eccentricity of the orbit of Q. What is the eccentricity of the orbit of involved in the shadow of Jupiter. Jupiter? Q. When either or all of them are between A. It is 23 810 000 miles. Jupiter and the Sun, what takes place Q. W i,A. Terfalpotepae y Q. What is the intensity of its solar heat when A. Their shadows fall upon the planet as they. ~~~~~~~~~~~compared with the heat of the Earth ~. come between it and the Sun causing an eclipse A. itwtee te Es A. It is twenty-seven times less. of the Sun. LESSON XXXIX. ANALYSIS.- Observations of Astronomers - Appearance of Belts - What known - Situation - How esteemed by Astronomers - Uniformity considered - Other peculiarity of appearance - Accounted for - Difference of Jupiter's Diameters. -2 A|11~'1:1 ~1:' [ Q. What is the appearance of these belts? ----- __:__-. __ - A. They appear like dark stripes across the..... disc of this planet.. —: =Q. What is known of these belts? I~~~~_._l~~~ |A. They are known to vary as to their number,.| —_._- ____ —__ _... | —_-_ — distance from each other and their positions. _ - Q. How do they appear to be situated? = —-:- "A. Parallel to one another and to the equator of Jupiter.. ~ ~~~~~~............ Fig. 43. —' —-Q. How are these regarded by astronomers? Fig. 43. TELESCOPIC VIEW OF JUPITER. A. They are esteemed by some to be openings in the luminous atmospheric envelope of Jupiter, Q. What has been particularly observed b|by others that openings betray the dark surface| astronomers relative to the planet Jupiter? of the planet, and that glimpses thus caught of A. On certain occasions as many as eight belts the solid body constitute the narrow, dusky belts have been seen, at others only one. or bands. t 1~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~I 60 ELECTRO-ASTRONOMICAL ATLAS. Q. Are they at all times the same in length and the belts, sometimes they continue. Cassini obwidth? served one in the same position for forty years. A. They continue for months without variation, Q. How are these belts and spots accounted and a new belt is seen to form in a few hours; for? sometimes they decrease in length and then in- A. They are regarded as nothing more than crease ill width until they run into each other to atmospheric phenomena resulting from the rapid the extent of five thousand miles in breadth. motion of the planet on its axis. Q. What other peculiarity is manifest in their Q. What is the difference between the Equatoappearance rial and the Polar diameters of Jupiter? A. There are at times seen bright and dark A. The Equatorial is sixty-three hundred miles spots in these belts, which usually disappear with the longer. LESSON XL. ANALYSIS.- Saturn - Situation - Distance from Sun - Time round it -Indication - Diameter - Revolution on Axis - Indication - Inclination of Axis to its Orbit - Inclination of Orbit to the Ecliptic- Eccentricity of its Orbit - Difference of Diameters- Solar Light compared with that of Earth - Rate of Motion- Density - Difference of Weight- Why one of the most magnificent Planets - Rings and Moons. SATURN. Q. What is the inclination of its axis to the Q. Where is the planet Saturn situated? plane of its orbit? A. Next to Jupiter, in the order of distance A. It is perpendicular. from the Sun, and between the orbits of Jupiter Q. What is the inclination of its orbit to the and Uranus. plane of the Ecliptic? Q. What is the distance of Saturn from the A. Two degrees and twenty-nine and a half Sun? seconds. A. It is nine hundred and seven million miles. Q. What is the eccentricity of its orbit? Q, What is the diameter of this planet? A. It is forty-nine million miles. A. It is seventy-nine thousand miles. Q. What is the difference between its EquatoQ. How long does it take to make a revolution rial and Polar diameters? around the Sun? A. The Equatorial is six thousand and seven A. It takes twenty-nine and a half years. hundred miles longer than its Polar. Q. What does this show? Q. What proportion of solar light does this A. It indicates the length of its year. planet receive compared with that of the Earth? Q. How long does it take Saturn to turn on its A. It is about one-nineteenth part of the ~~axis?~~~~~~ ~amount of light. axis ~ Q. What is its rate of motion? A. Ten hours and sixteen minutes. Q hti t aeo oin A. Ten hours and sixteen minutes. A. It is twenty-two thousand miles an hour. Q. What does this indicate? Q. What is the density of this planet? A. The length of her day. A. It is about as great as cork. N // *. N N 7 N N N4 N4 k N N t N ELECTRO-ASTRONOMICAL ATLAS. 61 LESSON XLI. ANALYSIS.- Rings of Saturn - Situation of them - Revolution - Detached - How k1nown to be Separate - Distance from Planet to Interior Ring - Breadth of it - Width between Rings - Thickness of Rings - Consists of what - How determined - Importance of them to the planet. Q. A body that weighs one pound on the sur- A. It would weigh about twenty-seven and a face of the Earth would weigh how much on the half pounds. surface of Saturn? Q. Why is the planet Saturn considered one A. One pound and four drachms. of the most magnificent and interesting objects in Q. How much would a body that weighs one the planetary system? pound on the surface of the Earth, at the equator, A. It is attended with eight moons and a suite weigh if transported to the Sun? I of gorgeous rings. RINGS OF SATURN. Q. How are the Q. What is the rings of Saturn situ- breadth of the interior ated in regard to each ring. other and to the A. It is nineteen planet. thousand and fifty A. They are con- miles. centric, or one lies Q. What is the between the other and width of the opening the planet, and they between t h e t wo are over the equator rings of the planet. A. It is two thouQ. How do the y sand and nine hunknow they are sepa- SATUR AD THE EARTH CPAAT DIENSIOS. A. I t i s s e v e n rate or wholly detached from each other? thousand and three hundred miles. A. The fixed stars have been seen in the dis- Q. What is the thickness of the rings. taut heavens through the openings between them A. They are not more than one hundred miles and between the planet and the first ring. in thickness. Q. What is the distance from the planet to the Q. Of what do they consist? interior ring? A. Various opinions are entertained as to their A. It is thirty-three thousand and six hundred composition; some that they are a solid comand fifty miles. pact substance, and others that they are fluid. 16 62 ELECTRO-ASTRONOMICAL ATLAS. Q. What reason have they for the latter con- Q. What importance are they to the planet clusion? A. They serve to reflect light upon its surface. A. It is the fact they are almost infinitely divided. LESSON 0XLII. ANALYSIS.- Circles not True - Centers coincide with the Center of Planet - Gravity of These Rings - Imnportance to the Stability of the System of Rings - Moons of Saturn - Number - Seldom Seen -Revolve with the Rings - Respective Distances from Saturn - Inclination of their respective Orbits to the Plane of Saturn - Eclipses of these satellites - Seldom Suffer - Respective Sizes. Q. Are they in true circles edge of the ring being but about 31,000 miles. A. They are not exactly. On the other hand, Japetus is nearly ten times Q. Does the center of their rings coincide with more distant from Saturn than we are from our the center of the planet. satellite, so that the diameter of the Saturnian A. It does not exactly. system measures nearly 4,500,000 miles. Q. What is known of their centers of gravity? A. The center of gravity of these rings oscil- THE MOONS OF SATURN. lates around that of the planet, describing a small orbit. Q. How many Q. What importance is this to the stability of moons o r satelthe system of rings? lites has Saturn? A. It prevents the rings from being shifted from A. Eight. their equilibrium by any external force or attrac- Q. Are they tion of other heavenly bodies. easily discovered? We give below the names of the eight moons Fig. 45. A. They are of Saturn, with their distances from the center of SATURN AND ITS SATELLITES. (sIRJOIINIESCIEL.) only seen w i t h the planet, and the time of their revolution in good instruments and under favorable circumterrestrial mean solar days: — stances. Q. When is the best time to take a view of Distance from Saturn's Time of Siderial Revolution. Center in Miles. Days I.'rs. Mii. Sec. them 2 Mimas... 119,725.... 0 22 27 23 A. When the planet is at its Equinox, then the Enceladus 153,630.... 1 8 53 7 Tethys. 190,225.... 1 21 18 26 rings are nearly invisible. Dione.. 43,670.... 2 17 41 9 Q. How do these satellites revolve? Rhea..... 340,320.... 4 12 25 11 Titan. 788,915.... 15 22 41 25 A. They revolve eastward with the rings of the Hyperion,....954,160.... 21 7 7 41 I planets; in orbits nearly circular, and, with the Japetus.... 2,292,790.... 79 7 54 40 exception of the eighth, in the plane of the rings. The first four satellites are all nearer to Saturn Q. What are their respective distances from the than the Moon is to the Earth. Mimas is, more- planet? over, but 82,000 miles from Saturn's surface, and A. 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A.A'..AA...AAAAA AA',AA, AAAA.AA i~~~~~~~~~~~~~~~~~~~~il~~AAAAA A'A4A7AAAA::'::~~ ~~~ ~~ AAA/AAAAAAA'/AAA'AA'A' AAAAA'y4A' A' AAAAAAAAAA AAA:AAAAAAAAA44/A A A,,AAAAAA A.AA.A.A.AAAA ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~A...AAAA A A AA~/'A A,,::i~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~/://'AA4A''.A'.'.."A'.'.'..'.""...."./A.A.~ ~ ~ ~ ~~ ~~~~~~~~~~~~~~~~~~~~~i~~. AA4./.'A".A.AAA...AAAAAAA".A.A.A AAAAAAAAAAAAAAAAAA/A.AAAAAAAAAAAAAA/AAAAAAAAAAAAAA,,,, AA/AAAAAAAAAAAAAAA AAAAAAAAAA AA ELECTRO-ASTRONOMICAL ATLAS. 63 Distances in Mile Periodic t'mes. Q. What is known in regard to these satellites Mimas.. 123,000. 00 days, 22 hours. Enceladus. 128,000. 1 " 8 " Tethys.. 196,000. 1" 21 A. They seldom suffer an eclipse, and they Dione.. 251,000. 2 " 17" happen only when the rings are seen edgewise. Rhea.. 351,000. 4 " 12 " 55 seconds. Q. What is the respective sizes of these satelTitan.. 811,000. 15" 22 " 51 " lites? Hyperion. 2,766,000. 79 " 7 " 54 " ilyperion.2,706,000.79 7 54A, The two nearest to Saturn are the smallest, Japetus.. 2,336,000. 46 " 12 " 00 the third and fourth the next in size, the fifth and Q. What is the inclination of their respective sixth are somewhat larger, the seventh and eighth orbits to the plane of Saturn's orbit? are the largest. The eighth is about four thouA. The orbits of the six inner satellites are in- sand two hundred miles in diameter and turns on clined about thirty degrees; the other two about its axis, and it is probable all the others do the twenty-four degrees and forty-five minutes. same. LESSON XLIII. ANALYSIS.- Uranus - Situation - Distance from Sun - Time of Revolution round the Sun - Diameter - Time of Revolution on Axis not known - Inclination of Orbit - Rate of Motion - Light compared with that of the earth - Density - Eccentricity of Orbit - Difference of the Weight of Bodies on the Earth and the Surface of Uranus - Satellites of Uranus - Number - Respective Distances and Periodic Times - Their Variation in Revolution - Size of them - Seldom suffer Eclipse. URANus. A.. It is but very little inclined; forty-six minQ. Where is the planet Uranus situated? utes and twenty-six seconds. A. Uranus is the eighth planet in the order of Q. What is its rate of motion? distance from the Sun, its orbit lying between the A. It is fifteen thousand miles an hour. orbits of Saturn and Neptune. Q. What is the proportion of light of this Q. How far is Uranus from the Sun? planet compared with that on the Earth? A. It is 1,824,000,000 miles. A. It is three hundred and sixty times less. Q. How long does it take this planet to revolve Q. What is the density of this planet?. around the Sun? A. About that of water. A. It takes eighty-four years. Q. What is the eccentricity of its orbit?. Q. What is the diameter of Uranus? A. It is eighty-five million miles. A. It is thirty-five thousand miles. Q. What would a body weighing one pound on Q. How long does it take to turn on its axis? the Earth's surface weigh if removed to the planet A. Owing to its immense distance from the Sun Uranus? its diurnal motion has not as yet been ascertained. A. It would weigh fourteen ounces and fourQ. What is the inclination of its orbit to the teen drachms. plane of the ecliptic 64 ELECTRO-ASTRONOMICAL ATLAS. SATELLITES OF URANUS... Uranus, like Saturn, is the center of a little system, comprising, besides the principal planet, |. \ eight moons or satellites, revolving in planes..."..' i... DIFFETtENCE BETWEEN THE APPARENT FORMS OF A FLATTENED GLOBE, SEEN IN TWO DIFFERENT POSITIONS. nearly perpendicular to the plane of the planet's X:.. orbit. These bodies, whose revolutions are acco m-.. plished, the nearest in two days, and the most: --. - distant in about 108 days, possibly compensate, Fig. 47. in some degree, by their reflected light, during The first satellite is but 128,000 miles, or about the nights of the planet, the feeble intensitycof half the distance of our Moon, from the planet. the daylight. The Sun is visible at Uranus as a The most distant of the four of which we have a cersmall disc, whose superficial extent is but one tainknowledgeis392,000miles. Ofthesefour,the 370th of the extent o the solar disc as seen from two nearest, Ariel and Uimbriel, were discovered our globe. The heat received from it, too, is but by Lassell and Otto Struve respectively; the six one 370th of that we receive from the Sun. refmaining ones (two of which have received the We have shown in fig. 47, the relative dimen- names Tilania and Oberon), by Sir W. Herschel. sions of the orbits of the satellites, as they would be seen if we could obtain a bird' s-eye view of Q. How many satellites has Uranus? the plane in which they revolve. We have A. It has eight? already mentioned the fact that their movements Q. What is their respective distances and are performed in a direction nearly perpendicular period of times? to the plane in which the planet revolves around A. Dist. PERIOD TMES. Dist. in PERIODIC the Sun. Another peculiarity, and this is found Miles. d. h. m. s. Miles. d.., First Satellite 224,000 5 21 25 26 Fourth Satellite 390,000 11 10 56 29 Second " 296 000 8 16 57 47 Fifth " 777,000 38 48 84 00 nowhere else throughout the solar system, further Third 340,000 10 23 2 47 Sixth 1,53600, 107 16 39 56 nowhe elseo thr ouge rein ou the slrsysen distinguishes Uranus - the direction of these NOTE-Ofte emainintobut littleis knowand hence.W... but little can be said. movements is retrograde; that is to say, it is con-ec e. trary to that of all th e other known movements Q. In what respect do the satellites of Uranus of satellites and planets. But this anomaly prob- vary from the analogy of the motion of all the ably results from the very great inclination of other satellites in our planetary system? their orbits, shown in fig. 47. A. Their motions in their orbits are known to Seeend "~~~ 29:0 51 7Ffh 7,0 84 40 nowher els thoghu th oa ytmutr ( Thr,00 1234Sit1, 5600176396 ditngihs rns-h dircinoths ~oT.-o~thereaiintwbt little is knw~ he ELECTRO-ASTRONOMICAL ATLAS. 65 be retrograde, so that instead of advancing for- owing to their vast distance from the Earth, but ward in their orbits from west to east around their were they not about three thousand miles in diamprimary, as other satellites do, they move in the eter they could not be seen. opposite direction. Q. What is known of these satellites suffering Q. What is known of the size of these satel- an eclipse? lites? A. They seldom suffer eclipses, but may suffer A. They have never been accurately measured, two a year. LESSON XLIV. ANALYSIS.- Neptune - Situation - Orbit - Distance from Sun - Revolution round it - Diameter - Rate of Motion - Inclination of Orbit to the Ecliptic - Time on Axis unknown. One Satellite --- Situation - Time around the Prinary -Indication. NEPTUNE. At a distance nearly equal to that of the Moon Neptune is invisible to the naked eye. In tele- from the Earth, that is to say, about 225,000 scopes, it has the aspect of a star of the eighth miles, a satellite revolves round Neptune in a magnitude. Its apparent movement is extremely very circular orbit, in 5 days, 21 hours, 8 minslow; but, as the orbit which it describes round utes:* this has enabled astronomers to calculate the Sun is so immense, its real velocity is, nevertheless, considerable; it is about 12,400 miles an hour. Like all other planets, it is sometimes nearer and sometimes further from the Earth. At the | - Neptiel time of conjunction it is distant from us, on the average, 2,958,000,000 miles, whilst its minimum distance at opposition is less by 218,000, 000 miles. The real dimensions are somewhat considerableo,' and in virtue of them Neptune is the third planet of the system. Its diameter is 37,000 miles greater Satellite than the diameter of the Earth. The surface of Fig. 48. the globe of Neptune is more than twenty-two SATELLITE OF NEPTUNE. times that of the Earth, and its volume is | the mass of the primary. It is equal to about the nearly 105 times. 1-17000th part of the mass of the Sun, or to 21 The intensity of the heat and light received by times tat of the Earth. Hence, the density of that planet is but little more, at that enormous the matter of which Neptune consists is less distance, than the thousandth part of that received than the fourth of that of the Earth, or nearly by us. But, as nothing is known of its physical equal to the density of nitric acid, and a little less and atmospheric conditions or of its rotation, than that of sea-water. From this point of view, nothing can be determined on the climnatic con- * This disc has not yet presented any perceptible trace of flattening neither can any spot be distinguished on it, so that the time of its rotation ditions of the planet. remains unknown ~~~~~~~~~.... 66 ELECTRO-ASTRONOMICAL ATLAS. Jupiter is the planet most analogous with this A. It is one degree forty-six minutes and fifty body, whilst the force of gravity at its surface is seconds. about the same as on Saturn and Uranus. Q. What is its time on its axis? Q. Where is the planet Neptune situated? A. Owing to its vast distance, its diurnal A. His orbit encircles the entire solar system, motion has not been ascertained. being the ninth planet in the order of distance Q. How many satellites revolve around this from the Sun. planet? Q. What is the distance from the Sun? A. Only one has as yet been discovered. A. It is 2,850,000,000 miles from the Sun? Q. How far from its primary is this satellite Q. What is its diameter? situated? A. It is thirty-five thousand miles. A. It is two hundred and twenty-three thouQ. How long does it take this planet to per- sand miles. form a revolution around the Sun? Q. In what time does this satellite revolve A. It takes one hundred and sixty-six years. around its primary? Q. What is its rate of motion? A. In five days and twenty-one hours. A. It is eleven thousand miles an hour? Q. What does this indicate? Q. What is the inclination of its orbit to the A. The time of a lunar month on the planet. Ecliptic? LESSON XLV. ANALYSIS.- Comet - Where found -- Appearance - hy called Comets - Appearance Varied - Distinguished from Planets - Form of Orbits - How are they distinguished. COMETS. Q. What other planets are found circulating among the planets of the Solar System A. They are Comets. Q. What is their appearance? |. A. They are bodies of the nebulous form, composed of a nucleus of a bright center or head.; the coma, a kind of envelope of a nebulous substance, and a tail moving in an opposite direction from the Sun. g Q. WVhy called Comets? 1. TAILLESS COMET. 2. READ WITHOUT TAIL O.R NUOLEUS. A. They derive their name from the Greek some have no tails, others have several tails, some word "Come," which means "hair," they resem- appear without any nucleus. bling it in appearance, hence called Comets. Q. When these bodies are far away from the Q. Is their appearance uniform? Earth and Sun how are they distinguished from A. They are extremely varied in appearance, the planets? ;i~i " ~"~'~'~~'~i~'.......... i,,.~'.l.... ~ ~4~.,.,.~ ~..~ ~ ~.~,..~ ~ i'~ " ~"7 " "'........'"~' ~ "~'~~~~'~~~~~~.............. "''~'~~.~...,~. ~....~..~.~..~,~;,~~~~...~.... w""~'~"~" "~~~~'i!~....'~it I''""~''~'~'~~ i~i'i~ll'~."'~i' ~ii~ ~ ~ ~ l~i'""'~',,, —~ ~'.~ ~ ~ ~i..,,,..,,,,..,.,,,,..~...,. ~..~.,..,~!~ i~.~'~.~.~'".~.~,'1 ~ ELECTRO-ASTRONOMICAL ATLAS. 67 A. By the size and position of their orbits and A. Those moving in elliptical orbits belong to the direction of their motions. the Solar System. The others are occasional visiQ. What is the form of their orbits? tors, coming from far distant regions of space, A. They move around the Sun either in ellipti- moving around one side of the Sun, then fly away cal orbits or curved lines called parabolus or in paths which continue to diverge, and never hyperbolus. return again. Q. How are they to be distinguished? LESSON XLVI. ANALYSIS.- Elements of Comets - Orbits - Number computed - Classes Elliptic - Long Periods - Shorter Periods - Number Re appeared - They are generally named after their discoverers - Size of Orbits - Comparative inclination of them - Way of Revolution. ELEMENTS OF A COMET'S ORBIT. Q. Of these how many have re-appeared? Q. What are the elements of a Comet's orbit? A. Of the shorter class seven have re-appeared A. 1st. The longitude of the Perihelion. 2d. and been identified and established by an entire The longitude of the correspondence of their Ascending Nodes. 3d. elements. The inclination of the.Q. Which of these is plane of the Ecliptic.. most distinguished 4th. The eccentricity. A. The CometEncke; 5th. The direction of its period has been the motion. 6th. The ~ /'"\"", about three and a-half Perihelion distance years, a n d eighteen from the Sun. A/' returns have been reQ. The elements of. corded. how many Cometary l Q. What of the others? orbits have been com- others ptd Dedico's is five and A. More than two a-half years; W i nhundred and forty, necke' 5 (f ieand a-af and of that number \X At / )8X Brorsen's five and aonly nineteen are \ half years; Bielas six known to be Elliptic \ and three-fifth years; and five hyperbolic. I)onati's six and fiveQ. Into how many eighth years; Tarje's seven and a-half years. classes are E llip tic Fig. 50. Q. After whom were Comets divided? ORBITS OF COMETS. these Comets named? A. In two; those of short periods and those of A. After the distinguished Astronomers who long periods. discovered them. 68 ELECTRO-ASTRONOMICAL ATLAS. Q. What is the comparative size of their orbits? A. They are small, the average being twelve A. They are small, all revolving within the and a-half degrees; the greatest thirty-one, and orbit of Saturn. the least three degrees. Q. What is the comparative inclination of Q. Which way do they revolve? their orbits. i A. They revolve from west to east. LESSON XLVII. ANAILYSIS.- Comparative Periods of Comets - Course of Revolution of Comets whose Orbits have been ascertained- One-half of them in opposite directions - Inclinations very diverse — Velocity compared with Planets in general - Far Greater — Number Discovered. COMPARATIVE PER.IODS OF COMETS. A. The number is larger, from the earliest Q. What are the comparative periods of these period up to the present time more than eight Comets? hundred have been recorded, of which three hunA. With the exception of a few Comets whose dred have their orbits computed, and of the latter periods have been computed to be about seventy- fifty-four have been identified as returns of prefive years, they are considered of very long vious Comets. Since optical aid has been used in periods, some more than one hundred thousand searching for Comets, it is estimated that the years. actual number of Comets brought to view, includQ. Of all the Comets whose orbits have been ing both Hemispheres, is not less than 4,000 to ascertained, what is the course of the revolution? 5,000. A. About one-half are direct, that is, they re- Q. How far from the Sun are they generally volve from west to east, and the remainder are discovered.? retrograde. A. About 1,824,000,000 rniles. Q. What is said of their inclinations a Q. Among those Comets which have been noA. They are very diverse, some revolve within ticed, how many passed between the Sun and the zodiac and others at right angles with the Mercury? Ecliptic. A. There were thirty. Q. What is their velocity in comparison to the Q. How many between the other respective planets in general? orbits 2 A. Very much greater. The Comet of 1680 was A. Between Mercury and Venus, forty-four; be880,000 miles an hour, and that of 1843, was 1,260,- tween Venus and the Earth, thirty-four; between 000 miles an hour, or 350 miles per second. the Earth and Mars, twenty-three; between Mars Q. How many Comets have been discovered and Jupiter, six. ELECTRO-ASTRONOMICAL ATLAS. 69 LESSON XLVIII. ANALYSIS.- Celebrated Comets - Comet of 1811 - Dimensions - Aphelion distance - Halley's Comet - How distinguished - Appeared in many previous years - Comet of 1843 - How distinguished - Encke's Comet - Period of Return - What peculiar in its return - Donati's Comet appeared in 1858 - Effect produced - Wonder of Many - For what distinguished - Law by which they are G(overned - Description of its Operation - Longitude of the Parhelion of the Comet 1858- Longitude of its Node - Longitude of the parhelion of the Comet 1862 - Longitude of its Node -- Rapidity of Comets - Cause for it. CELEBRATED COMETS OF THE PRESENT CENTURY. Q. Among the Comets which have made their A. He on examining the great Comets of 1531, appearance during the present century, which are 1607, and 1682, believed they were only the reapthe most distinguished? | pearance of the same Comet. A. The one of 1811 is esteemed by Astronomers Q. What period did he fix as the time in which as a most magnificent Comet. it uniformly returned? Q. What were its dimensions? A. He established the time of the interval at A. The head was 112,000 miles in diameter; its seventy-five years. nucleus was 400 miles. Q. Howhashecon Q. What was the vinced the world that shape and the length he was correct in his of its tail? conclusions? A. Its tail was a A. He declared that beautiful fan - shape, the Comet wouldagain extending not less than make its appearance 112,000,000 miles. in the last of 1758, or Q. What is the pQ. What dis tha e of in the beginning of aphelion distance of 1759. this Comet? Q. What was the A. It is fourteen ^ result of his prophecy? times that of Nep- A. G reat interest tune, or 40,000,000,000 was felt, and though he died before the miles, reaching far be- he died before the time, yet on Christyond the Solar System time, yet on Christmas night, 1758, a or the stretch of the Fg. m i 1 Gr theT COMET OF 1811, FROM A DRAWING BY ADMIRAL.SMYT, IN THE peasant near Dresden largest telescope. "~SPECULUM ARTWELLIAIUM." discovered the Comet. Q. What is said of the Comet of 1835, commonly Q. In looking back upon past history, have we known as Halley's Comet? reason to believe that this Comet had made its A. This is remarkable as being the first Comet appearance at similar intervals before the days of whose period of revolution was satisfactorily Halley? established. A. It was seen in England in 1066, when it was Q. What led Dr. Halley to suspect that this regarded as the forerunner of the victory of was the reappearing of a former Comet? William of Normandy. 18 70 ELECTRO-ASTRONOMICAL ATLAS. Q. What then was its appearance 2 A. It has never been excelled for the brilliancy A. It was then in size equal to the full Moon, of its nucleus and the graceful curvature of the and in 1456 its tail reached from the Horizon to tail. the Zenith. Pope Calixtus indited a prayer for Q. When will it return? the people as follows: "Lord save us from the A. In about 2,000 years. Devil, the Turk, and the Comet." Q. What great law controls the motion of the Q. What is regarded the earliest record given Comets of this Comet? A. They are controlled by the same specific A. In the 130th year before Christ. law which governs Planets of the Solar System. Q. What was said of its light? When in their orbits thousands of millions miles A. That its light surpassed the brilliancy of the from the Sun, they move very slow in the arc of Sun. an ellipse, almost immeasurable, having lost their Q. For what was the Comet of 1843 distin- charge of Coloric, they become minus. The Sun guished? being positive and they deeply negative, it begins A. It was so intensely brilliant as to be visible to exert a controlling influence over them, as that in full daylight; and it was so near the Sun as attraction increases continually in proportion as almost to graze his surface. the squares of the distance decrease, they move Q. What period is designated as the time of the swifter and swifter until, as they approach the return of Encke' s Comet? I Sun, they sometimes fly more than eight hundred A. Its period is only three and a half years. thousand miles an hour. At their Perihelion Q. What interesting discovery has been made they are very near the Sun and become very from observations upon its motion? highly positive, and hence are propelled back A. It returns invariably to its perihelion, two again into fields of space with the same lightning and a half hours earlier than the most perfect speed that they were attracted toward the great calculations indicate. Fount of all motion. Q. What- is the longitude of the Perihelion of the Comet of 1858? DONATI'S CoMET. A. It is thirty-six degrees and thirteen minutes. Q. WThat is said of Donati's Comet which ap- Q. What is the longitude of its Node? peared in 1858? A. It is one hundred and sixty-five degrees and It produced great excitement and was the cause nineteen minutes. of universal wonder. Q. What is the inclination of its Angle? Q. What was its distance from the Earth when A. Sixty-three degrees and two minutes. first discovered? Q. What is the longitude of the Perihelion of A. In June of that year it was 240,000, 000 miles the Comet of 1862? and in August traces of its tail were observed A. It is forty-nine degrees and seven minutes. which extended to about 50,000,000 miles in Q. What is the longitude of its Node? length. A. It is two hundred and seventy-eight degrees Q. For what other manifestations has this Comet and fifty-eight minutes. been distinguished? ELECTRO-ASTRONOMICAL ATLAS. 71 Q. What is the inclination of its orbit with the nomena which these bodies present, which is still plane of the Ecliptic? so obscure. A. It is fifty-eight degrees and twenty-nine Comets, as we have said, form part of our Solar minutes. System. Like the planets, they revolve round the Sun, traversing with very variable velocities extremely elongated orbits; the form of the cometary orbits furnishes us with the first of their specific characters. * Q. Why do Comets pass out of sight so rapidly after passing their Perihelion? A. They move around the Sun in orbits much more elongated than that of the Earth and when they cross the plane of the orbit of the Earth on their flight to regions of space, they are then moving in one direction and the Earth in another, and as the Earth moves at the rate of sixty-eight thousand miles an hour and the Comets at the rate of a million miles an hour, they seem to move much faster as they soon disappear, while their Fig. 52. motion is slower and slower till they arrive at COMET OF 1744 (CESEAUX'S COMET), WITH MULTIPLE TAILS. their Aphelion point. their Aphelion point. It is right to say that among the numerous Q. What may be considered a remarkable fact comets observed up to the present time, either in respect to Comets? with the naked eye, or by means of telescopes, A. That the real diameter of their nebulosity the majority are distinguished by a nebulosity increases proportionally as they become more dissurrounding the nucleus, and a great number, tant fromn the Sun, and the nearer they come, the especially of the most brilliant ones, possess a smaller the nucleus but the more brilliant. luminous train or tail. With others, the tail, Q. What forms the ground work of all our caldisplayed fan-like, is divided into many branches, culations respecting the distances of all celestial as if the body had in reality several distinct tails. orbs? Fig. 52 gives an idea of the varied forms of these A. The semi-diameter of the Earth. I cometary appendages. Q. What is necessary or sufficient to enable a This diversity of aspect will, perhaps, some person to understand the mode by which the disday, enable astronomers to class comets into gen- tances of the heavenly bodies are determined? era, species and varieties, and will doubtless A. A slight knowledge of Geometry and Trigofacilitate the perfection of the theory of the phe- nometry. * NOTE. As we go to press, a new Comet is announced, discovered first at Marseilles, France, April 17, by Mons. Coggia, and recently detected by Prof. Swift of Rochester, N. Y. Although its direction is represented as earth-ward, yet no fears are entertained of a collision, for the electrical law of radiation is sufficient to prevent it. Reference as to location, may be had to Map 1 of the Star Sketches in this Atlas, page 75. 72 ELECTRO-ASTRONOMICAL ATLAS. LESSON XLIX. ANALYSIS. - What supposed to be - How produced - hat called - Why so called - How many seen in an Hour- Showers of Stars - When exhibited - At what Intervals - Hombold and Bompland's Observations - Arago's Observations — Regular Periods of Showers - Intersection of the Earth and the Orbit of the Comet - Brilliant display accounted for - Light produced by their rapid flight through the Atmosphere —Annual Exhibition of Meteors in August —Regularity accounted forSchiaparrelli's discovery. METEORS, SHOOTING STARS oR AEROLITES. A curious circumstance, and one which helps In the immense number of meteors which invade to prove the relationship between the shooting the regions of the air in a year, there are some per- stars and meteors, is the fact that the appearances haps that only pass through its domain and of meteors are more frequent in August and continue their path in space, after having presented November than at other epochs of the year; and us with the spectacle of a transient illumination. the total number from July to December exceeds A great number, on the other hand, not only do also that observed from December to July. not again leave our atmosphere, being vaporised therein, but, when of large size, attain the very surface of the Earth. Falls of stones, ferruginous masses, and dust, from the upper regions of the air, are proofs of this assertion. From shooting stars to meteors, or bolides, the transition in our narrative is easy: the difference between these two orders of phenomena is not Fig. 3. Fig. 53. very strongly marked. APPEARANCE OF A METEOR IN A TELESCOPE. (SCxoMDT.) Bolides are luminous bodies of circular, or [One of the most curious observations of a rather of spherical, form, and of sensible apparent meteor which have been recorded, leaving that of diameter. Like shooting stars, they appear sud- 1783 out of the question, was recently made by denly, but generally they move more slowly, and Dr. Schmidt, who was fortunate enough to observe disappear after some seconds. Their light is a large meteor in a telescope, under a magnifving ordinarily less vivid, but their much more con- power of eight times. The fire-ball was twin, and siderable apparent dimensions are sufficient to was followed by several smaller ones, following compensate this difference of intensity. The side by side with parallel motions of translation illumination of the landscape by the presence of until all were extinguished (fig. 53). This obsera meteor somnetimes approaches that of moonlight. vation lends'force to the supposition that meteors Most of them leave behind a luminous train; exist in space as a crowd of bodies, revolving others explode with violence, and sometimes the round each other, before they enter our atmosexplosion is accompanied with reports like dis- phere.] charges of artillery. Q. What are they supposed to be, and how are they produced? The appearance of meteors is more rare than A. Of metallic substances similar in composition that of shooting stars, the total number of obser- to the Comets themselves accompanying them in to the Comets themselves accompanying them in vations recorded amounting at most to a thousand, their revolutions around the Sun, as cosmical reckoning those recorded by the ancients. clouds, or meteoric swarms. ELECTRO-ASTRONOMICAL ATLAS. 73 Q. Why called Shooting or Falling Stars? | Q. How can you account for the brilliant disA. Because of their rapid motion in darting play of light exhibited in their passing through through the heavens. the heavens? Q. How many may be observed in ordinary A. Their light seems to be produced by their times in the interval of an hour. rapid flight through the atmosphere, causing A. From ten to twenty may be seen. their ignition by the compression of the air and Q. At what periods of their consumption in time does the shower of - their passage. Stars exhibited on the _ _______Q. What are we to 12th and 13th of Novem- _ understand respecting ber occur __. the meteors annually A. At intervals of =_= exhibited on the 10th of thirty-three years. _= August. Q. What evidence _ A. The August Metehave we of this pheno- _X__ ors annually revealed to menon? _. us are produced by their A. H o m b o l d t and ______I_ annual revolution interBompland observed on __ secting the Earth's orbit the 12th and 13th of _____ Eon the 10th of August. November,. 1799, a ~ —— f — - - -p-c -— Q. What reason have shower of Stars, as a real __-__ _ l - we to conclude that this rain of fire. I ring of meteoric stones Q. In what following ____ _ _ represents the orbit of a year did it recur in great }_______ previous Comet? force?. ____ A. Schiaparelli has in A. In the year 1833, _ - fact discovered so close Novemnber 12th, Arago _ = — -~ —5 -- a resemblance between compared the shower to --- = 1 - ----- — the path of the August a fall of snow. Fig.. meteors and that of the Q. XThen did the last ORBITS O THE AUGUST AnD NOVEMBER METEOR-SHOWERS. (ORBITS OF Comet 1862, No. 3, that..... COMETS III., 1862, and I., 1866.) periodic shower occur O there cannot be any A. It was again observed on the 14th of No- doubtas to their complete identity. vember, 1867. Q. How is the regularity of these seasons ac- The calculations of Schiaparelli, Oppolzer, counted for or determined Peters, and Le Verrier, have also discovered the A. On the principle of the regularity of the co'met producing the meteors of the November revolution of the Earth, and the intersection of its shower, and have found it in the small comet of orbit by the passage of the meteoric shower when 1866, No. I., first observed by Tempel, of Marthe Earth is passing through the cloud or very seilles. Its transformation into a ring of meteors near it at the time of the periods above mentioned. has not proceeded nearly so far as that of the 19 74 ELECTRO-ASTRONOMICAL ATLAS. comet of 1862, No. III. Its existence is of a much part of our solar system, was first seen as a comet. more recent date; and, therefore, the dispersion of The orbit of this comet is much smaller than the meteoric particles along the orbit, and the that of the August meteors, extending at the consequent formation of the ring, is but slightly aphelion as far as the orbit of Uranus, while the developed. perihelion is nearly as far from the Sun as our According to Le Verrier, a cosmical nebulous Earth. The comet completes its revolution in cloud entered our system in January, A. D. 126, about 33 years and 3 nionths, and encounters and passed so near the planet Uranus as to be the Earth's orbit as it is approaching the Sun brought by its attraction into an elliptic orbit toward the end of September. It is followed by round the Sun. This orbit is the same as that of a large group of small meteoric bodies, which the comet discovered by Tempel, and calculated form a very broad and long tail, through which by Oppolzer, and is identical with that in which the Earth passes on the 13th of November. Those the November group of meteors make their revo- particles which come in contact with the Earth, or lution. approach so near as to be attracted into its atmosSince that time, this cosmical cloud, in the form phere, become ignited, and appear as falling stars. of a comet, has completed fifty-two revolutions As the Earth encounters the comet's tail, or round the sun, without its existence being other- meteoric shower, for three successive years at the wise made known than by the loss of an immense same place, we must conclude the comet's track number of its components, in the form of shooting- to have the enormous length of 1,772,000,000 stars, as it crossed the Earth's path in each revolu- miles. In Fig. 54, C ID represents a portion of the tion, or in the month of November, in every 33 orbit of this comet which is identical with the years. It was only in its last revolution, in the orbit of the November meteors. - Spectrum year 1866, that this meteoric cloud, now forming Analysis. LESSON L. ANALYSrS. - Remarks - Constellations - Design in presenting an Elementary Work — Not Extensive or Critical - In considering the Stellar Universe —The Object in Presenting ConsteIlations - How differ from Planets - In Twinkling and Scintillating — Description of a few - Exhibited in the Northern Sky - The best time of observing them - What Called - Why Called Northern Circumpolar - North Pole point of Revolution -- Consideration of Maps -MAP I. - Constellation Great Bear, Ursa Major - Time of appearance - Number of Stars contained in the Group -Figure formed Large Dipper -Two Northern Stars Pointers -Why called thus - Polaris the object to which they point — Revolution - 2d Constellation - Little Bear - How Distinguished - Contains Polaris- North Pole Star -A Fixed Star - Why called Fixed Stars - They revolve in the Universe - Great Velocity — Time its Light travels down to us - 3d Constellation - Cassiopia -Location -Form of Figure -Sprawling " W" -Cepheus and Draco - Where Located - Nothing Striking -Perceus elsewhere. CONSTELLATIONS. they have been arranged in groups, called ConstelRemarks. - It is not my design in this Element- lations. ary Work to be very extensive or critical in what We will now present some of these Constellamay be presented of the Stellar Universe. tions, and describe a few of the principal stars In studying the stars, that we may the more contained in them, as exhibited in our northern easily comprehend their location in the heavens, sky, with the best time for looking at them. ELECTRO-ASTRONOMICAL ATLAS. 75 Q. How do they differ in appearance from the A. Because they point out and are always in planets? range with a bright star called Polaris. A. They twinkle or scintillate, and no telescope Q. How often does the dipper revolve around has been able to enlarge them into a disc. this star a Q. What are these constellations called? A. Once in twenty-four hours, never sinking A. They are called Northern Circumpolar and below the horizon. Southern Constellations. Q. What other constellations are revealed on Q. Why called Northern Circumpolar? this map? A. Because they revolve around the north polar A. Little Bear and Cassiopia. star, recognized on map I, as Polaris. Q. In considering the following Star Maps, how LITTLE BEAR, on URSA MINOR. are their points of the compass arranged. Q. For what is this constellation distinguished? A. The right hand west, the left hand east, the A. Its form is that of a little dipper, containing top of map north and the bottom south. seven stars, one of them distinguished as the Pole Star, called Polaris. MAP I. Q. WThy called the Pole Star? CONSTELLATION THE GREAT BEAR, - URSA A. It is esteemed the point of the northern pole MAJOR. of the Earth. Q. What time of the MAP I. Q. To what importyear are the constel- ant class of stars does lations on this map Polaris belong? most clearly revealed? A. To those called A. About the first Fixed Stars or Suns. of November, at nine Q. Why are they o'clock in the even- called Fixed Stars or ing, in our latitude, Suns? they are visible every A. Because t h e y night. Ih a v e appeared for Q. How many stars ages to occupy the in this constellation same place. are visible to the l Q. Dotheynot renaked eye? volve in their orbits A. There a r e one Fig. 55. like the planets? hundred and thirty-eight. A. Their rate of motion is far greater than that Q. How are the seven principal stars arranged? of many of the planets. A. They appear in the form of a Large Dipper. Q. What is the rate of motion of Polaris? Q. What are the two extreme northern stars in A. It is ninety miles per minute. the cup called?| Q. How long does it take its light to reach the A. They are called pointers. Earth? Q. Why are they so called? A. It takes fifty years. 76 ELECTRO-ASTRONOMICAL ATLAS. Q. Ilow many stars are visible in this constella- A. They are arranged somewhat like a brokention a backed chair, or a sprawling capital W. A. There are twenty-seven. Q. What other constellations are found on this map? CONSTELLATION - CASSIOPIA. A. Cepheus and Draco are located nearly south Q. Where is this constellation located on the of Polaris. map Q. is there any thing striking in their features? A. Nearly east of Polaris. A. There is nothing, and Perseus is better Q. What is the form in which the principal represented on another map. stars are grouped. LESSON LI. CONSTELLATION ORION. AN;ALYSIs. - MAP II —Time of favorable appearance —Names of the Constellations — Distinguished - The most beautiful Constellation in the Sky - Whale better seen elsewhere —Stars of Belt of Orion —The Bull or Taurus - Situation —How Marked - Cluster called Hyades - Another cluster called Pleiades - Another Constellation called Gemini, or tile Twins - Where Situated —Names of the most important Stars - Castor and Pollux - Little Dog - Location — How distinguished - Procyon and Goomelza - Great Dog - Situation -Name of the largest - Sirius Brightest Star - Rate of Motion - Time it takes to reach the Earth -Distance estimated - Diameter- Constellation The Whale- Situation. MAP II. A. There are three stars in a line, near the cenQ. What time of year may the constellations on ter of the parallelogram, called the belt of Orion. this map be most easily pointed out? A. About the first MAP II. BULL, oi TAURUS. of February, at nine Q. Wihere is the o'clockin the evening. group called the Bull, Q. Wlat are the situated? names of the constel- A. It is in the northlations on this map? west, and marked by A. Orion, Bull, a V shaped cluster, Twins, Great Dog, called Hyades. Little Dog, and the Q. What cluster or Whale. stars is found near it? Q. For what is A. A group of seven Orion distinguished? stars may be found A. It is the most Y Xsr ljnorth-west of Bull, beautiful constella- called Pleiades. tion in the sky. Fig. 56. Q. Where can the Q. How many stars form the belt of Orion and constellation Geminii or the Twins be found? where are they located?, A. North-east of Orion, at this time. ELECTRO-ASTRONOMICAL ATLAS. 77 Q. How is it marked, or what is its shiape? what is it distinguished? A. It is marked by a large quadrilateral of A. It is called Sirius, and is the largest star in stars. the whole heavens. Q. What are the names of the most important stars in this group? SIRIUS. A. They are Castor and Pollux, the most north- Q. What is the rate of motion of Sirius ern and brightest stars of the group. A. It is eight hundred and forty miles perg minute. LITTLE DOGS. I Q. How long does it take the light to reach the Q. Where is the location of the Little Dog Earth? A. It is situated east of Orion. It takes twenty-two years. A. It takes twenty-two years. Q. How is it distinguished Q. What is its estimated distance from the A. It is marked by two solitary stars, Procyon Earth and Gomelza. | A. It is said to be 3,375,000 times that of the Sun from us. THE GREAT DoG. Q. What is its diameter? Q. HIow is this constellation marked and where Q. Twelve millions miles in diameter. located a A. It is a group of several stars, located south- THE WHALE. east of Orion. Q. Where is he situated? Q. What is the name of the largest star and for A. He is located north-west of Orion. LESSO N LII. CONSTELLATION VIRGO. ANALYSIS. -MAP III- Favorable time for Inspection-When seen in the Heavens -How known-Large Constellation -One Star of first Magnitude -- Spica its name -- Leo, or the Lion — Where situated -I-lHow easily known - Shaped like a Sickle — An inverted figure 5j - Regulus the largest — On the Ecliptic —Gamma -Where situated - 3d Constellation —Hydra — Situation - Form of Serpent Swimming from East to West - Stars small. MAP III. A. It is a large VIRGO. constellation, w i t h Q. At what time is one star of the jfrst this constellation magnitude, called more clearly seen? Spica; the others are A. On the first of not easily traced withApril, at nine o'clock out a Plenisphere. in the evening. Q. Where in the LEO, OR THE LION. heavens-may it be seen Q. Where situated'1 at this time? A. Just west of A. Near the Mer- Virgo. idian. Q. How is it easily Q. How may it be recognized? known? Fig. 57. A. By six stars, 78 ELECTRO-ASTRONOMICAL ATLAS. shaped like a sickle or an inverted fig- the radient point of the November meteoric ure 5. shower. Q. Which of these stars is the brightest, and where situated? (CONSTELLATION HYDRA. A. It is a star called Regulus, and is on the Q. Where situated? Ecliptic. A. It is located south of Leo and Virgo. Q. What is the next important star in this group Q. What is its form, course and size of the stars? and where located? A. It is the form of a serpent, swimming from A. It is Gamma, and is generally situated near east to west, and its stars are small. LESSON LIII. CONSTELLATION BOOTES. ANALYSIS. - MAP IV -Time of Appearance - In June - Situation in the Heavens - The Brightest Star Arcturus — Where found - On Meridian - Shape Parallelogram - Four bright Stars - Form — Coffin -- Another group East - Like a boy's cap - Northern Crown -Large Constellation further East- Hercules - Size- What figure Two Quadrilaterals -Opinion respecting the course of the Solar System -Drifting toward Hercules. MAP IV. Q.- What form does this group of stars representS CONSTELLATION BOOTES. A. They form a figure somewhat similar to a Q. What is the time of its appearance? coffin. A. In the month of June, nine o'clock, P. M. Q. What group of stars is found east of Bootes? Q. Where in the A. A semi-circle of'MAP IV. heavens may this con- stars, like a boy's cap, stellation be found at called the Northern this time? Crown. A. It may be seen Q. What large conon the meridian, stellation may be south-east of the found further east? Great Bear. A. It is called HerQ. What is the cules. name of its largest Q. What is the size star a of the stars and what A. It is called Arc- figure do they form. turus. A. They are small Q. Where in the and present the figure heavens may it be of two quadrilaterals. found at this time 2. Fig. 58. Q. W h a t is the A. Facing the south, you will see it on the present opinion entertained as to the course the meridian, and in shape like a parallelogram, of Solar System is now taking? four bright stars. A A. It is supposed to be drifting toward Hercules. ELECTRO-ASTRONOMICAL ATLAS.' 79 LESSON LIV. CONSTELLATION THE SWAN. ANALYSIS. - MAP V — Time favorable — Where found- Overhead —Figure formed - Large Cross-Principal Star at foot Albireo — Multiple Star —The Eagle —Where situated —South of Swan — How distinguished —A Large Star —Atair — Pegasus —Where located- North-east of Eagle -Figure of these Stars —Perfect Square - The most Western found —Head of Andromedia —The Lyra —Where situated —West of Swan and North-west of Eagle-What Star Prominent —Vega — What completes the group - Four faint Stars. MAP V. PEGASUS. CONSTELLATION THE SWAN. Q. Which way from the Swan is this group Q. What time in the year does this constellation located? make its appearance? A. It is situated directly east of the Swan, and A. On the first of September, 9 o'clock in the north-east of the Eagle. evening. Q. What is the figure represented by these stars Q. Where can the Swan be found at this time?. A. A perfect square is formed by four of the A. Overhead, in the MAP V. principal stars. Milky Way. Q. Where is the Q. What is the fig- most western one ure formed by the found? stars of this constella- A. It is located in tion. the head of AndroA. They are so ar- media. ranged as to form a LY large cross. I Q. Where is this Q. What is the -h~, - - I,constellation situname of the principal -ated star at the foot?' C -- I A. It is found loA. It is called Al- cated west of the bireo, a multiple star. Swan, andnorth-west Fig. 59. of the Eagle. THE EAGLE. Q. What distinguished star is found in this Q. Where is it situated? constellation? A. Nearly south from the Swan. A. There is a very bright star called Vega. Q. How is this constellation distinguished? Q. What other stars complete the group? A. It is marked by a very large star called A. Just below Vega are four faint stars, formAtair, and several small ones. ing an oblique parallelogram.. - ~ 80 ELECTRO-ASTRONOMICAL ATLAS. LESSON LV. CONSTELLATION PERSEUS. ANALYSIS.- MAP VI - When favorably seen - December — Where found - Meridian - Well North in Milky Way -Figure of chief Star - Turkish Sword — Bent at the point -- What near the point -- Mass of Telescopic Stars, very beautiful - One marked - Called Algol - Constellation Aries or Ram — Where seen - South of Perseus -- Figure formed of Principal Star - Right Angled Triangle - Point in the Seasons marked - Vernal Equinox - What Constellation South of the Ram - Whale - Figure easily traced - Pentigon of Stars. MHAP VI. A. It is called Algol, distinguished as a strange, CONSTELLATION PERSEUS. variable star. Q. What time is most favorable for its exhibition? CONSTELLATION ARIES, OR THE RAM. A. In the month of December, 9 o'clock P. M. Q. Where is this seen? Q. Where then can MAP VI A. It is discovered it be found? - south of Perseus. A. On the meridian, Q. WYhat kind of a well to the north, in figure is formed by the Milky Way. the principal stars? Q. What is said of | A. It forms a rightthe chief stars in this angled triangle. constellation? Q. What point in A. They are not the Seasons is marked very bright, but they by this constellation? form the figure of a A. Long ago it has Turkish sword, much been known to mark bent at the point. the place of the VerQ. What is dis- nal Equinox. covered near the point Fig. 60 Q. What very large of the sword? yet indistinct constelA. There is a mass of telescopic stars, the most lation is found south of the Ram? beautiful, perhaps, in the sky. A. It is the Whale. Q. What one is found near this group which is Q. What figure is easily traced in it? rather a marked star. A. There is clearly seen one pentigon of stars. ELECTRO-ASTRONOMICAL ATLAS. 81 LESSON LVI. CONTRAST OF THE DISTANCE OF THE SUN AND THAT OF THE Fixed Stars FROM THE EARTH. ANALYSIS.- Remarks.- Rate of motion of ball from an Armstrong gun - Time taken to reach the Sun - Time for the sound of the Explosion to reach the Sun - Prof. Mendenhall on nervous sensation -The infant burns its finger by touching the Sun - Tilme necessary to realizing the sensation - Earth on disc of Sun - Require a large telescope to discover it - Distance of Sun from Earth compared to that of the Fixed Stars - The Fixed Stars, Suns -Do not remain unmoved - Revolve in the Urnziverse like other Planets - Principal. Suns named - Why appear small - Distance cannot be computed by miles - Velocity of light considered -- Miles per second - Number in 24 hours - At this rate how long to reach the nearest Eixed Star - 61 C/ygni - Vega - Sirius - Urscae Ifajoris - Arcturus - Polaris and Ctappella - These do not shine by reflection - Suns in other Systems. ON THE DISTANCE OF THE SUN. Q. With all this disparity of the size and. disenemark. -- Reflection only can bring to our tance of the Sun from the Earth, how much greater minds an adequate idea of the immense distance the size and distance from the Earth is one, even which exists between us and the Sun. the nearest of what are termed Fixed Stars? Q. What is the rate of motion of a ball fired A. We can only answer this question by comfrom an Armstrong gun. | parison - hence, call your attention to the followA. It is four hundred yards per second. ing in respect to what is said of the Fixed Stars. Q. At this rate, how long will it take for it to reach the Sun FIXED STARS. A. It will take thirteen years. Q. What are they? Q. How much longer before the sound of the A. They are called Suns. explosion would reach the Sun? Q. Why Fixed Stars? A. Six months later. A. They appear always to occupy the same Q. Which travels the faster, sound or nervous place in the heavens. sensation? - Q. Do they remain unmoved as Fixed Stars? A. Prof. Mendenhall says, sensation upon the A. They revolve in their respective orbits in the nerves travels ten times slower than sound. Universe, like other planets. Q. If, therefore, an infant were born, with an Q. Can you name the principal Fixed Stars? arm of the somewhat inconvenient length of 91,- A. Alpha Centauri, 61 Cygni, Vega, Sirius, 500,000 miles, so as to reach the Sun, and should Ursae Majoris, Arcturus, Polaris, Capella. he stretch out his arm, touch the Sun, and burn Q. Why are they so small? his finger, how long before he would feel the A. They are so far from us. sensation? Q. How far off is the nearest? A. That child must live till it has grown to man- A. So far it is impossible to compute its distance hood, and reaches the age of 135 years, before he by miles. will be conscious of the fact that the tip of his Q. How can we obtain an adequate idea of its finger was burned. distance from the Earth? Q. Suppose the Earth be placed on the disc of A. Something of an idea may be gained of the the Sun, could it be seen with the naked eye? distance if we consider the rapidity with which A. It would require the aid of a large telescope light travels. to make it visible. Q. What then is the velocity of light? 82 ELECTRO-ASTRONOMICAL ATLAS. A. It is one hundred and ninety-two thousand 2. 61 Cygni, nine years and four months. miles per second. 3. Vega, twenty-one years. Q. How many seconds are contained in twenty- 4. Sirius, twenty-two years. four hours? 5. UrsTe Majoris, twenty-two years. A. Eighty-six thousand and four hundred. 6. Arcturus, twenty-six years. Q. According to this basis of reckoning, how far 7. Capella, seventy-two years, or 390,541,824,will light travel in twenty-four hours? 000,000 miles. A. It will traverse sixteen billions five hundred and eighty-eight millions eight hundred thousand POLARIS. miles. Q. At this rate, how many days will it take the 8. Polaris, fifty years, or 271,209,600,000,000 light of the nearest fixed star to reach us? miles. A. It must continue its course at this tremendous Q. What is the rate of motion of Polaris? velocity thirteen hundred days, or over three and A. It is ninety miles per minute. a-half years, before a glimpse of it can be obtained Q. How long does it take its light to reach the by any of the inhabitants of the Earth. earth? Q. If this incomprehensible distance lies between A. It takes fifty years to travel down to us. us and the nearest Fixed Star, what must be that Q. Do you perceive the utter impossibility that lying between the Earth and the most distant? these stars shine by reflected light? A. In answer, we will give the number of years A. It is evident that they are Suns -each of required by light to travel the different distances them is a focus of light and heat, and probably of other fixed stars: the center of a system comprising, like ours, 1. Alpha Centauri, three years and six months. planets, satellites and comets. LESSON LVII. LIGHT. ANALYSIS.-What is it -Views of Sir Isaac Newton - Flowing out from the " Orb of Day " —Recuperation, or Waste Away - Space embraced in Solar System - Rapidity of light - At this rate how long will it take to fill the Space - Does not remain Stationary - Moves on in Circle - Light changes its Polarity - Is received back to the Sun - How does the Sun remain undiminished and brilliant as ever - By recuperation in the return of it to the Sun - No indication of a continued workl of creation - Principle illustrated by. Q. What is light? Sun through that space which is occupied by A. It is an electrical effusion of brilliant parti- those opaque bodies which are governed by its cles or bright scintillations emanating from the Sun. influence. Q. WVhat was the theory of Sir Isaac Newton Q. If light be an emanation of infinitesimal respecting the origin of light? atoms, or particles of matter flowing out from the A. That light is an emanation of inconceivably "Orb of day," why is it not diminished and minute particles flying off from the body of the wasted away? ELECTRO-ASTRONOMICAL ATLAS. 83 A. This could not fail to be manifest if there Q. Are we then to understand that the great was not a constant recuperation or increase of the ocean of light, filling the entire Solar System, original fountain. passes on and gives place to another a Q. To what extent does light emanate from the A. On this principle the vast ocean of light Sun? must give place and the space be filled by another, A. It is an acknowledged and well-authenticated every four hours, then displaced and filled again fact in science, that light radiates in every direc- in the same short space of time, and so on, in tion from this central luminary, filling the entire endless succession. space occupied by the Solar System. Q. What must have been the inevitable result, Q. How many miles of space are embraced in if light be the emanation of infinitesimal effusions the Solar System?. from the Sun, unsupplied from some source? A. Not less than seventeen billions one.hundred A. The Sun long since would have frittered million miles. away and been utterly annihilated by waste. Q. What is the velocity of light? Q. How then has it remained undiminished and A. Light travels at the rate of one hundred and as brilliant as ever? ninety-two thousand miles in a second. A. Evidently this waste must be supplied either Q. At this rate, how long will it take to fill the by the return, in some imperceptible manner, of vast and almost infinite space described above, these particles to their original source, or that the with light? Sun, the great fountain of light, be constantly fed A. It will take about four hours. by creative agency exerted upon it. Q. When this vast expanse is once filled with Q. If the latter conclusion be entertained, what this ocean of light, does it continue to occupy this principle in the order of creation would be vioimmense space? lated A. Overflowing light is one of the forms in A. From the order of creation we learn that all which the element of the Sun, electricity, is mani- things were created in a limited time, hence, no fested throughout the Solar System. indication is given of a continued work of creation. Q. What peculiar course does electricity pursue Q. What may be regarded the most reliable and when it flows out from the Sun? correct position to be occupied in this matter? A. Electricity always runs in a circle, hence A. We are, from full evidence, inclined to the returns to its original fountain. former position, and in sustaining it, present the Q. What conclusion must necessarily be drawn fact that light is only the ever-flowing scintillations in respect to the course taken by light? of electricity, and, like it, necessarily runs in a A. That light being an exhibition of one of the circle; hence, having accomplished its mission, forms of electricity, it must in like manner flow in returns, like all electrical currents, to its original a circle, and again return to the place whence it fountain, the Sun. emanated. Q. What beautifully illustrates this principle Q. Do you ask how light can return to the Sun? of action a? A. It was thrown out by the positive force of A. The ocean, by evaporation, supplies the the Sun, and having changed its polarity it is at- clouds with water, this is borne over the globe, tracted and received back to the Sun. and discharged among the mountainous regions to 84 ELECTRO-ASTRONOMICAL ATLAS. supply the high lakes and fountains, these, in re- into the ocean again, and keep that immense turn, send forth the little rills and streams, which, reservoir from becoming exhausted. meeting in their course, form rivers, which empty LESSON LVIII. ATTRACTION OF GRAVITATION. ANALYSIS.- Attraction of Gravitation defined - Seen in the power the Sun exerts over the Planets - All under the magnetic influence of the Sun - Planets rendered Magnets by the electrical power of the Sun - This inherent magnetism controls the Satellites - This magnetism called Terrestrial Magnetism - Subject Telrrestrial yfagnetism or the Mcagnetism of thbe Earth - This magnetism accounted for - Sun a great Galvanic Reservoir - Heat of Torrid Zone - Compared with Temperate and Frigid Zone - Intensity of the heat of the Sun - Three hundred times greater than any point on the Earth's surface - Sir John Herschell's estimate - Note. Q. What is the attraction of gravitation.? TERRESTRIAL MAGNETISM, OR THE MAGNETISM A. It is the magnetic influence which one body OF THEI EARTH. has over another in attracting it to itself. Q. How is terrestrial magnetism accounted for. Q, How is this manifest in the planetary system r A. Upon the theory that the Sun, being the A. It is seen in the power exerted by the Sun great Galvanic reservoir, pours its streams of light over the planets, and in the controlling power of and heat vertically upon the space embracing these over their satellites. forty-seven degrees of the Earth's middle regions, Q. How do the planets receive their magnetic or twentv-three and a-half degrees each side of the influence. equator, constituting the torrid zone. A. They receive it from the Sun. Q. What is the heat of the torrid zone when Q. Are all bodies, more or less, under the influ- compared with the temperate or frigid zones ence of magnetism? A. Far greater, and always uniform and exA. All the heavenly bodies in the Solar System cessive. are more or less under the influence' of this magic Q. What is supposed to be the intensity of the power. heat at the surface of the Sun? Q. How do they receive their magnetic influence A. It has been estimated to be three hundred from the Sun? times that received at any point of the Earth's surA. The Sun is a great Galvanic Battery, and, by face. its electrical power, renders the Earth and every Q. WVhat estimate did Sir John Herschell place planet a magnet. upon the heat of the Sun? Q. What is th'e influence these planets exert A. He supposed that it would be sufficient to upon their satellites and other bodies surround- melt a cylinder of ice forty-five miles in diameter, ing them? plunged into the Sun, at the rate of two hundred A. This inherent magnetism of the planet con- thousand miles a second. trols its satellites and every thing else within the NOTE.- This estimate being correct, we are not scope of its influence. surprised that the entire planetary system is under Q. What is this magnetism called which is the electrical control of this great Galvanic Battery, manifest in the Earth? and, as a consequence, revolve in their respective A. It is called terrestrial magnetism. spheres, accomplishing the will of their Creator. ELECTRO-ASTRONOMICAL ATLAS. 85 LESSON LIX. TERRESTRIAL MAGNETISM CONTINUED. ANALYSIS.- Torrid regions - More deeply electrified - Result - They are positive - Polar negative - Reasons for this - Effect produced upon the Earth - Earth filled with electricity becomes a mnaygnet - This Terrestrial Magnetism seeks and flows out of the Magnetic Poles - Points of the greatest cold - Both North and South - Result - Consequence of the colnbined action of these forces - Explanation - Effect of these currents on the Needle - Magnetic Poles and Geographic not the same - At the Geographic no effect on the needle - Reasons why - Note. Q. What is the consequence of those torrid polar being negative, there is a mutual attraction regions being more directly under the influence of of the positive, or the superabundant fluid of the the Sun's rays? one and the negative of the other. A. Those regions become more deeply electrified Q. Upon what principle is this clearly understood? than either the temperate or frigid zone. A. On the immutable and universal chemical Q. What other results necessarily follow? principle, viz.: that opposite properties, or a posiA. The equatorial regions are positive, while tive and a negative, always attract, or that coloric the polar regions are comparatively negative. always seeks to keep up an equilibrium, or to Q. What reasons can be given for this? restore it when disturbed. A. The first reason is, that the forty-seven Q. What is the result? degrees, or the 3,2661 statute miles of the Earth's A. That there are actually two forces operating surface, embraced between the 23] degrees of upon the superabundant electricity or caloric of north and 231 degrees of south latitude, constitute the equator. the bulkiest part of the globe, under the powerful Q. What is then the consequence of the cormrays of the Sun. bined action of the two forces? Q. This being the case, what effect is produced A. Why, there will be two strong currents of upon the Earth? electricity rushing continually with lightning A. The torrid regions receive the greatest speed form the points of the greatest cold, or the amount of electricity, and, through them, the magnetic poles, instead of the geographic poles, Earth is filled with it, and becomes a mlagnet. to the equator. Q. At what points of the Earth's surface does Q. Now, will you give us an explanation of its internal magnetism naturally radiate and flow -magnetic attraction? out? A. It is evident that currents of electricity A. From the negative portions of the Earth, influence the needle, and the reason why the especially through the magnetic poles-the points North Pole guides the needle north of the equaof the greatest cold, both North and South. tor and the South Pole, when south of the equator, Q. What other reason is given why the one is is, that these currents of electricity, rushing from positive and the other negative. the poles upward, constitute what is called terresA. Because the torrid regions receive the rays trial magnetisml. of the Sun more vertically than the other. Q. What effect do these currents have upon the Q. What application can be made of this infal- needle? lible rule A. They give direction to the needle of the comA. The equatorial regions being positive and the pass, and, as the point of the greatest cold varies, 22 86 ELECTRO-ASTRONOMICAL ATLAS. so these currents vary, and as they vary, so the at the North Pole to change the point of the needle varies. greatest cold, particularly in the summer season, Q. Were the geographic pole of the Earth the when the floating icebergs or ice islands of the point of attraction, what effect would it have on Arctic are continually changing their position. the needle? NOTE. — There are other hitherto mysterious A. It would never vary at all, but as it is, it phenomena which can be rationally and philovaries both diurnally and annually. sophically accounted for only on the supposition Q. Why is this so? that such currents of electricity exist, as we have A. Because there are causes always operating described. LESSON LX. AuRORA BOREALIS. ANALYSIS.- HOW produced - Caloric and Electricity the same - Currents within the Earth naturally seek the point of the greatest cold, flow out and form a lamllbent waving light - Called Aurora - This illustrated - Historic evidence - Captains Parry and Ross - Their testimony - The ultimate conclusion - This clearly explained - Power of Terrestrial Mlagnetism controls the Moon - On the principle of Attraction and Repulsion -The same law by which the Sun governs the Planets and they their Secondaries in the Solar System. Q. How are the phenomena of the Aurora Q. What historic evidence have we that these Borealis and Aurora Australis, the Northern and positions are tenable Southern Lights, produced? A. Captains Parry and Ross, in their expedition A. Now, if caloric and electricity be the same, to discover the North-west passage, ascertained that of which there is no doubt, then these currents, the focal point from which streams upward the issuing from within the Earth, naturally seek the Aurora Borealis, was exactly the point of magpoint of the greatest cold, in the frigid zone. netic attraction. Q. When it arrives at that point, what becomes Q. What conclusive evidence did they obtain. of this electric fluid? A. That when drawing near that point, the dipA. It streams up into the rarer regions of the ping needle stood exactly perpendicular, while atmosphere, and, in its return to its original the horizontal needle would not traverse at all, but source, it spreads out into the lambent, waving would remain in any position in which it was light, exhibited by Aurora. placed. Q. How is this illustrated?. Q. What other important fact did they disA. The appearance being precisely the same as cover a electricity exhibits in passing through an ex- A. They ascertained also, what we have heretohausted tube - the same cause - the rarity of the fore maintained, that this point of attraction was atmosphere, operating in both cases, to produce a comparatively that of the greatest cold. luminous, waving cloud, which proves that they Q. From this investigation and this course of must be identical. reasoning, what is the ultimate conclusion a ELECTRO-ASTRONOMICAL ATLAS. 87 A. That caloric streams down from the Sun, Q. How is it that the Earth holds the moon deeply electrifies the equatorial regions, penetrates steady in its orbit, while revolving around it? the Earth, rendering it entirely magnetic, and that A. The Earth, having been made a magnet by its internal magnetism seeks an egress through the electrical power of the great galvanic battery, the points of the greatest cold, streams upwards the Sun, now by its terrestrial magnetism, controls as it passes out from the magnetic poles, rises into the moon in its revolution, on the principle of the rarer or thinner regions of the atmosphere, attraction and repulsion, the same law by which and, like electricity in its passage through the the Sun governs all the planets and they their exhausted tube, spreads out into a waving, lulmi- secondaries in the Solar System. nous cloud, and forms the Aurora Borealis at the north, and the Aurora Australis at the south. LESSON LXI. ATTRACTION AND REPULSION. ANALYSIS.- Subject defined - Law governing - Ultimate particles have opposite polarities - Law manifest - Laws of the whole are the laws of its parts -- By this rule only can Attraction and Repulsion be accounted for - Magnetism and Electricity considered the same agent - Galvanism differs only in the mode of exhibition - Experiment -- Result from passing a current of Galvanism through Soft Iron; change the poles of Battery - Change the polarity of the Iron - This explained - Distinction of polarity manifest in the direction of the current - This explained - Positive and negative end to every thing - Running electricity - The inward current always negative - The outward current positive - Remark. Q. Now, what is the solution of the apparent agent- galvanism differs only in the mode of its difficulty? exhibition. A. It is this, every ultimate particle of electricity Q. What is the result if you pass a current of has opposite polarities, that is, each end of each galvanism around soft iron, bent in the shape of a individual particle has a different property; like horse shoe, wound with insulated copper wire? ends, or polarities, repel, and unlike ends or A. You make the iron magnetic, and the two polarities attract. ends have different polarities. Q. W~hat immutable truth is clearly evident Q. What is meant by different polarities. from this position? A. That one is negative and the other positive, A. That the laws of the whole are the laws of or, what one end attracts, the other will repel. its parts. Q. Suppose we change the poles of the battery, Q. By the operation of this rule,what phenom- and pass the current of electricity in the opposite enon can be rationally accounted for? direction around the spiral wire, what will be the A. The phenomenon of Attraction and Repul- result? sion among both atoms and planets. A. There will be a change in the polarity of the Q. What is the difference between electricity iron, and make the end that was positive, negative, and galvanism? and the end that was negative, positive. A. They are generally conceded to be the same Q. How can this be clearly shown? 88 ELECTRO-ASTRONOMICAL ATLAS. A. It can be shown by experiments in electro- certain direction, we make one end of a bar of iron magnetism. positive and the other negative, what must be the Q. Upon what, then, does a positive and nega- polarity of each individual particle? tive state evidently depend?2 A. Each particle must have a positive and a A. They entirely depend upon the direction in negative end. which the current runs. Q. In the passing of the current, how are we to Q. What distinction of polarity is manifest in distinguish the polarity? the direction of the current? A. The positive end is always leading, and the A. The end, where the current passes inward, negative, of course, always following. is always negative, and the end where it passes Q. Why should we naturally infer this? outward, is always positive. A. From the fact that the laws of the whole are Q. What reason have we for this phenomena a the laws of its parts, and the laws of its parts are A. It is readily found in the admirable rule the laws of the whole. "that the laws of the whole are the laws of its Remzark. - It would be utterly impossible that parts." the whole of a thing should have a quality the Q. If by running a current of electricity in a opposite of the parts of which it is composed. LESSON LXII. ATTRACTION AND REPULSION - CONTINUED. ANALYSIS. —Another mode of illustration - Current of Galvanism passed around Steel - Result - A magnet - Cut the Steel in pieces - Each arranged with the same polarity of the whole - Logical inference - Conclusively evident - How illustrated - By the atmosphere and ocean. TAKE ANOTHER ILL-USTRATION. of the pieces will be arranged in the same direction Q. Suppose we pass a current of galvanism as in' the whole. around a bar of steel, spirally, in the same man- Q. What then is the unavoidable and logical ner it is passed around soft iron, what will be the inference? consequence? A. That each ultimate particle of electricity A. We make it permanently magnetic, the end which made it magnetic and kept it magnetic has where the current enters is negative, and the end opposite polarities, as well as the whole current. that is outward is positive, and so it will remain Q. Why is this conclusively evident? for years. A. Because the polarities of the whole are most Q. Now should we cut that bar of steel in ten assuredly made up of the properties of its parts. thousand pieces, what would be the polarity of Q. How may this be clearly illustrated? each piece? A. A mere thimble-full of atmosphere contains A. Each piece would have a positive and a nega- its proportion of oxygen and nitrogen, as well as tive end, and the positive and negative polarities the whole mass. A drop of water contains its ELECTRO-ASTRONOMICAL ATLAS. 89 relative proportion of oxygen and hydrogen as a hesitancy to investigate its laws, or, if such well as the ocean — and so with every thing else. investigation has been made, there has been a ]Remarkc. -The question as to what is the real reluctance to express the opinions entertained cause of attraction and repulsion is one that has respecting them, for fear those opinions would not been clearly understood, and hence has not become a subject of ridicule to the Scientific World' heretofore been satisfactorily explained. These laws, when fully understood, clear up the Electricity has been esteemed so mysterious and mystery. complicated in its operations that there has been LESSON LXIII. ATTRACTION AND REPULSION -CONTINUED. ANALYSIS.- This theory explained - Two magnets - Effect when Positive and Negative are presented to each other - They attract - Result when like polarities are presented - Entirely opposite; they now Repel each other - Two Positives repel - A Positive and Negactive attract each other - Scientific World challenged to give a clear explanation on any other principle - A body charged with electricity has an outward current, and will attract a negative with an inward current - Clearly shown by the magnets - These laws applied in the Attraction and Repulsion - How accomplished. Q. Our first inquiry is, will not the above theory A. It shows that there is attraction in the former explain the phenomena of attraction and repul- case and repulsion in the latter. sion. Q. Does not the admission of this principle and. A. We think the facts above stated are true, its explanation show conclusively that electricity and can be fully and satisfactorily illustrated. must be the controlling power in attraction and Q. How can this principle be easily and scien- repulsion a tifically explained A. We cannot see how "two positives repel, A. Take two steel magnets, with equal power, and a positive and a negative attract," can be let them be dipped in iron filings until they have explained on any other principle, and challenge accumulated as large an amount as they can the Scientific World to give another. retain upon their poles, and the opposite poles of Q. Why is it that a body charged highly with each be presented within a short distance of each electricity, has an outward current, and will attract other, the filings will spin out and fill up the one that is negative, with an inward current? space between them, and present an oily, ropy A. Because it has been shown by the magnets appearance. that the body thus charged always presents its Q. What will be the consequence if we change positive end, and the body, negative, with an inand let like poles be presented? ward current, is attracted, and presents its negative A. Then the filings will be blown back, as it end to the positive. were and stand out like hair around the points of Q. What is clearly indicated by this representathe magnets. tion? Q. Now what does this indicate? A. That these two bodies, one having an out23 90 ELECTRO-ASTRONOMICAL ATLAS. ward and the other an inward current, present Q. How is this accomplished? opposite polarities to each other, and are attracted A. The Sun, being positive, pouring a flood of from the immutable law, that opposite polarities light upon one portion of a planet, soon renders attract. that portion positive, hence, is repulsed by the Q. Now suppose we apply these laws of attrac- Sun, while the other portion, being negative, is tion and repulsion, as exhibited by the magnets, I attracted by the Sun, thus clearly illustrating the to the planets. principle of repulsion and attraction, by the unA. We have a correct solution of the apparent changeable law that two positives repel, and a difficulty. positive and negative attract each other. INSTRUCTION TO TEACHERS. 91 INSTRUCTION TO THE TEACHER IN THE USE OF THE DIAGRAM AND IN POINTING OUT AND EXPLAINING THOSE PRINCIPLES THAT PERTAIN TO THE MOTION OF THE PLANETS. In teaching, the teacher should have the pupils recite in concert the Tabular view. When they become familiar with that, then point to any planet in the Solar System, and ask how far that planet is from the Sun. Soon as they observe where the teacher points, and sees the name of the planet, they will know how far it is from the Sun; having learned it in the Tabular Table, at the same time they can see the Sun, as the grand center, around which the planets moved. This enables the pupil to associate the idea with the form, and conceive in his mind distance. II. The teacher, as he asks the questions laid down in the lesson, will point to the planet about which he is asking questions. III. When he speaks of the distance the planet is from the Sun, he will convey to the mind of young scholars a more clear idea of distance by moving his pointer from the Sun to the planet of which he speaks. IV. When he asks how long it takes a planet to make a revolution around the Sun, he should hold his pointer even with the axis of the planet, inclined in the same way with it; and as he moves it around the Sun from west to east, he gives an idea of yearly motion. V. In showing the cause of equal day and night, the teacher will show the pupil how the Earth is represented in the Diagram on the 21st of March and the 23d of September. Show him that the Sun then strikes vertical at the equator, and shines from pole to pole, illuminating the whole side of the Earth, while the side from the Sun is dark, as represented in the Diagram. VI. Then to show why tile days grow longer and the nights shorter, he can illustrate it from the Diagram, that as the Earth moves from her place in March to the one she occupies in June, the north polar circle is advancing further into the light, and the south polar circle is receding into the dark, to a corresponding extent, at the same time. Then, by holding the pointer parallel with the equator, the part of the Earth above the pointer will show how 92 INSTRUCTION TO TEACHERS. much of the Northern Hemisphere is enlightened, and the part below the pointer will show how much of the Southern Hemisphere is enlightenled, so that when the days are growing longer north of the equator, h-ey are growing shorter south of the equator; and while the days are growing shorter in the Northern Hemisphere, they are growing longer in the Southern Hemisphere; the same may be shown of the nights. VII. The teacher will give a correct idea to the pupils why it is winter in the Southern Hemnisphere while it is summer in the Northern, by placing his pointer parallel to the equator, so as to show that a great part of the Northern Hemisphere is continually in the light of the Sun, while at the same time so little of the Southern Hemisphere is enlightened. VIII. Again, he can show by placing his pointer on the equator in the same way as before, that the inhabitants south of the equator have the same season of the year that we have north, when the Earth arrives in the exact opposite point of the orbit. For instance, on the 21st of.December they have the same season that we do when the Earth reaches that point, of her orbit designated as on the 21st June, for in every opposite point of the Earth's orbit, the same is represented in the Diagram, showing as much enlightened north of the equator as is enlightened in the opposite point of the equator. ECLIPSE. In explaining the causes of an eclipse, the teacher can show by his book or his pointer, its shadow. The pupil will perceive that a body always casts its shadow in the opposite direction from the light. Then as the Sun is the great source of light, the Earth is represented as casting her shadow in the opposite direction from the Sun. IX. The Diagram represents the moon in the Earth's shadow, which causes it to be eclipsed. The teacher will be particular to show the pupils the manner in which the M/loon is enlightened by the Sun, and that the rays of incidence and reflection are in equal angles; so that rays of light from the Sun that strike upon the moon are reflected to the Earth in like angles, causing the side of the moon toward the Earth to show a constantly expanding crescent from new till full moon, then a continuous wane, till no rays from the Sun can be reflected to the Earth from the moon, as she is at new moon, between the Earth and the Sun. X. The teacher will point out the path or orbit in which the Earth moves around the Sun, and show theml that its circumference is 600,000,000 miles, and as the Earth flies through this space once every year, in the period of one month she will move one-twelfth of 600,000,000 miles, which is NO,OOO,000, andl the north polar circle has advanced a little further into the light, from the 21st of March, as represented ill April on the Diagram; and by holding his pointer just as the axis of the Earth is inclined, and passing it along round toward June, can show how many million miles the Earth moves from her place in March, before the north polar circle is wholly in the light and the south polar circle is entirely in the dark, which is INSTRUCTION TO TEACHERS. 93 150,000,000 miles, and as the axis points always in the same direction in the heavens, of course the south pole will remain in the dark while the Earth moves 150,000,000 miles still further, showing why we have six months day at the north y le, and night during the, same time at the south pole. Then the south pole begins to come into the light, and remains in it from the 23d of September until the 21st of Mtarch, and the north pole is in the dark during the same time, showing why we have in turn six months day at the south pole, and night during the same time at the north pole. XI. Reference to the diagram should be made whenever the teacher can associate an idea with the form, especially with the beginner in the study of Astronomy, for nothing is better calculated to call forth and develop the reasoning faculties of the young scholar than to associate ideas with forms. XII. Again, these principles that pertain to the motions of the Earth are principles that prompt the first inquiry of the pupil, and are most difficult of explanation by the teacher. XIII. It is not only important that the education the youth receives should be virtuous and purely moral, flowing from well cultivated minds, but it is equally important that it should be correct, and an occular demonstration will render those principles clearer to young scholars, without which their imagination cannot be stretched to make them understand without going beyond their capacity. APPENDIX. TABLE I. -ELEMENTS OF THE SOLAR SYSTEM- (SUN'S PARALLAX, 8.94"). o | Mean E art.Distance Sidereal Period. Inclination Mean 9 Mass, Earth O m Meanf Distance Tmoo ~NAiumE.~ in Time_ _P of Diameter. 4 being one. * Millions., Rotation. Axis. O0 u q 3 Years. Days. Days. SUN...... 852,900 315,000 1.42 2...................5 d. 8 h. 70 20' MERCURY, 2,962..063 6.86 35.4.205 70~.. 88 116 23 h. 56 m.I. VENUS... 7,510 |.885 5.84 66'.15.0069 3~. 224 | 584 23 h. 21m. 750 EARTI-I.... 7,912 9 1. 5.67 91.5.017......... 3651 24 h. 230 28' MARS.... 4,300.118 3.97 139.3.093 1~051' 1 322 780 24 h. 37 m. 280 42' JUPITER.. 85,000 | 301. 1.37 475.75.048 1019' 11 315 399 9 h. 55m. | 30 6' SATURN... 70,100 1 90..74 872..056 2030' 29 167 378 10 h. 29 m. |260 49/ URANUS.. 33,247 -, 12.65.97 1,754..047 461' 84 6 369. NEPTUNE. 36,806? 16.8.91 2,746..0087 1047' 164 226 3671.................... MooN. 1 2,162 1 0 1 3.4.2388.055 5{.. 27.. 297 2 27 d. 60 39/ TABLE II. -ELEMENTS OF THE MINOR PLANETS.;4. 4 NAhME., o k | Discoverer. a O, Earth's-1l. Yrs. Dys. FLORA..............22.......... 8 2.2014.157 5 53 3 97 Hind......................... 1847 ARIADNE.................... 43 2.2034.168 3 28 3 99 Pogson...................... 1857 FERONIA...................... 71 2.2661.12 5 24 3 150 C. H. F. Peters............... 1861'HARMONIA....................... 40 2.2677.046 4 16 3' 151 Goldschmidt.................. 1.856 MELPOiMENE.................... 18 2.2956.217 10 9 3 174 Hind... 1852 SAPPHO......................... 80 2.2963.2 8 37 3 175 Pogson....................... 1864 VICTORIA.. 12 2.3344.219 8 23 3 207 Hind... 1850 EUTERPE........................ 27 2.3467.173 1 35 3 217 Hind...................... 1853 VESTA............................ 4 2.3733.09 7 8 3 229 Olbers................... 1807 URANIA....................... 30 2.3655.126 2 6 3 223 Hind......................... 1854 NE IAUSA....................... 52 2.3657.066 9 57 3 223 Laurent...................... 1858 CLIO............................ 84 2.3675.238 9 22 3 225 Luther......... 1865 IRTs............................ 7 2.3862.231 5 28 3 240 Hind.... 1847 METIS.................... 9 2.3866.123 5 36 3 251 Graham...................... 1848 ECHO........................... 62 2.393 185 3 34 3 256 Ferguson..................... 1860 APPENDIX. 95 TABLE II. -ELEMENTS OF THE MINOR PLANETS -CONTINUED. S NaarE~~~~~~~~~~~~~~~~~~~-. 8Ao ~~~~~~~0~~~~~~ NAME. so Discoverer. z (5 Earth's= 1 o Yrs. Dys, AsoNIA..................... 63 2.395.126 5 47 3 258 De Gasparis.................. 1861 PHOCEA......................... 25 2.4008.254 21 35 3 263 Chacornac.................. 1853 MASSILIA - 20 2.4097.144 41 3 270 De Gasparis................. 1852 ASIA............................. 67 2.4217.185 5 59 3 280 Pogson..................... 1861 NYSA........................... 44 2.422.151 3 42 3 281 Goldschmidt................. 1857 HEBE............................ 6 2.4259.203 14 47 3 284 Hencke................. 1847 BEATRIX...................... 83 2.4287.084 5 2 3 287 De Gasparis................... 1865 LUTETIA..2................... 21 2.4354.162 3 5 3 292 Goldschinidt................ 1852 Isis............................. 42 2.44.225 8 34 3 296 Pogson....................... 1856 FORTUNA...................... 19 2.4411.158 1 33 3 297 Hind......................... 1852 EURYNOME..................... 79 2.4431.195 4 37 3 299 Watson..................... 1863 PARTHENOPE.................... 11 2.4519.099 4 37 3 306 De Gasparis.................. 1850 THETIS.......................... 17 2.4735.128 5 36 3 325 Luther........................ 1852 HESTIA.......................... 46 2.5265.164 2 18 4 6 Pogson........................ 1857 89 2.5498.18 16 11 4 26 Stephan...................... 1866 AMIfPHITRITE............2....... 29 2.554.074 6 8 4 30 Marth....................... 1854 EGERIA.......................... 13 2.5766.087 16 31 4 50 De Gasparis................ 1850 ASTREA........................ 5 2.5771.187 5 19 4 51 H-encke...................... 1845 IRENE........................... 14 2.586.166 9 8 4 58 Hind.......................... 1851 POMONA......................... 32 2.58738.083 5 29 4 59 Goldschmidt.................. 1854 91 2.5958................ Stephan..................... 1866 MELETE.47 2.5959.237. 8 1 4 67 Goldschrnidt...................1857 PANOPEA........................ 70 2.6133.183 11 38 4 82 ~................. 1861 CALYPSO....................... 54 2.6197.204 5 7 4 88 Luther........................ 1858 DIANA......................... 78 2.6228.205 8 38 4 90 ",.............. 1863 THALIA......................... 23 2.6271.232 10 13 4 94 Hind......................... 1852 FIDES.......................... 37 2.6414.177 3 7 4 107 Luther....................... 1855 EUNOMIA...................... 15 2.6437.187 11 44 4 109 De Gasparis.................. 1851 VIRGINIA........................ 51 2.6491.287 2 48 4 114 Ferguson..................... 1857 MAIA........................... 66 2.6512.158 3 4 4 116 H. P. Tuttle.................. 1861 Io............................... 85 2.6536.191 11 53 4 118 Peters....................... 1865 PROSERPINE..................... 26 2.6561.087 3 36 4 120 Luther...................1853 CLYTIE.......................... 73 2.6666.043 2 25 4 129 Tuttle............ 1862 JUNO............................. 3 2.6684.257 13 1 4 131 Harding. 1804 EURYDICE..................... 75 2.6698.307 5 0 4 133 Peters................... 1862 FRIGGA.......................... 77 2.6719.136 2 28 4 134.... ANGELINA.................... 64 2.6809.128 1 20 4 142 Tempel............... 1861 CIRCE......................... 34 2.6863.107 5 26 4 147 Chacornac.................... 1855 CONCORDIA...................... 58 2.7003.042 5 2 4 160 Luther............... 1800 ALEXANDRA,........ 55 2.7123.197 11 47 4 171 Goldschmidt.................. 1858 OLYMPIA........................ 60 2.7131.117 8 37 4 172 Chacornac............... 1860 EUGENIA....................... 45 2.7212.08 6 35 4 179 Goldschniidt.................. 1857 LEDA........................... 38 2.7401.155 6 58 4 196 Chacornac................... 1856 ATALANTA....................... 36 2.7461.301 18 42 4 201 Goldschmidt.................. 1855 NIOBE....................... 72 2.7554.174 23 19 4 209 Luther............... 1861 PANDORA........................ 56 2.7591.145 7 14 4 213 Searle......................1858 ALCMENE........................ 82 2.7603 226 2 51 4 214 Luther....................... 1864 CERES........................... 1 2.7667.08 10 36 4 220 Piazzi.........1801 LzETITIA........................ 39 2.7671.115 10 22 4 221 Chacornac.................. 1856 DAPHNE.......................... 41 2.7691.266 15 59 4 223 Goldschrnidt............... cc PALLAS.......................... 2 2.7696.24 34 43 4 223 Olbers.................... 1802 THISBE......................... 88 2.7702.165 5 15 4 224 Peters...............1866 GALATEA........................ 74 2.7777.238 3 59 4 231 Tempel..............1862 BELLONA........................ 28 2.7785.15 9 21 4 232 Luther..................... 1854 LETO............................ 69 2.7804.188 7 57 4 2331861 TERPISCHORE.................... 81 2.8563.212 7 55 4 302 Tempel................... 1864 POLYHYMNIA.................... 33 2.8641.339 1 56 4 309 Chacornac...................1854 AGLAIA......................... 48 2.8812.132 5 0 4 325 Luther..................... 1857 CALLIOPE....................... 22 2.9107.098 13 44 4 353 Hind......................... 1852 PSYCHE......................... 16 2.9237.135 3 4 5 De Gasparis................. HESPERIA.................... 68 2.9717.174 8 28 5 45 Schiaparelli.. 1861 DANAE...-..-.-............. 59 2.9848.162 18 15 5 57 Goldschmidt.........1860 96 APPENDIX. TABLE II. -- ELEMENTS OF THE MINOR PLANETS - CoNTINUED. 0 rd o4~~~~~T NAME. 0 P' Disooverer. Oq; 00 Earth's1 o' Yrs. Dys. LEUCOTIHEA..................... 35 3.0066.217 8 12 5 78 Luther....................... 1855 PALES.......................... 50 3.0825.237 3 9 5 150 Goldschmidt..1857 SEMELE.........................86 3.0908.205 4 48 5 158 Tietj en............... 1866 EuRoPA......................... 53 3.0999.004 7 25 5 168 Goldschmidt.................. 1858 DORIspE....................... 49 3.1094.077 6 29 5 176 " ~................. 1857 ANTIC.......................... 90 3.1188.148 2 16 5 186 Luther............... 1866 ERATO.. 61 3.1297.169 2 12 5 196 Forster............... 1860 THEMIm......................... 24 3.1431.117 49 5 209 De Gasparis............ 1853 HYGEIA......................... 10 3.1511.1 3 49 5 217 C.................. 1849 EUPHROSYNE............. 31 3.1527.22 26 27 5 218 Ferguson..1854 MNEMOSYNE....................5 57 3 1565.104 15 8 5 222 Luther..1859 FREIA.......................... 6 3.3877.188 2 2 6 86 D'Arrest..1862 CYBELE.........................65 3.4905.12 3 28 6 119 Tempel....................... 1861 SYLVIA..........................87 3.4927............... 6. 193 Pogson............... 1866 MINEEA..92.......Watson..1807 U~~~~~m~ A.. 93....... Peters.. MINEI~VA iii P MIJEVA....................92............ Watson U NDINA......................... 9)3...................................... Peters........................ A URORA........................ 9)4....................................... W atson...................... c ARETHUSA................. 95................................. Luther....................... c ZEGINA................B........ 6............ orelly...........86..... 868 CLOTHO.................... 97............................. Tempel................ IANTHE................. 8.. 98............................... Peters........................ HTECATE..............99.......Tepel............... HELENA..100....... Watson................1.......0... "1........................0...........102P e..r............ 1......... P s........................103..Watson.................................................. 104 ".................................105................... 0................. c..............1 "..................... 106...........................:ND I::: ililil r~~~ 3 ~..........~..... I~..., ees,..,...... PLATE XX,. Al~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~l S: ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~-~ ~ ~ ~ ~ ~ ~~~: 1tVI~~~~~~~~~~~~~~~~~~~~~~ MI, "W~;~Av i~~~~~~~~~~~~~~~~i WEED, PARSONS & (~?,ALBANY. A.TOLLE, PHOTO. LITH.'[HE GREAT EQ"UATORIAL. (P ARIS OBSE-RV^TOR~t.)