A subsidiary cause of tides is found in the revolution of the earth and moon about their common centre of gravity. Revolution about an axis through the centre of a sphere enlarges the equator by centrifugal force. Revolution about an axis touching the surface of a flexible globe converts it into an egg-shaped body, with the longer axis perpendicular to the axis of revolution. In Fig. 56 the point of revolution is seen at the centre of gravity at G; hence, in the revolution of earth and moon as one, a strong centrifugal force is caused at D, and a less one at C. This gives greater height to the tides than the attraction of the moon alone could produce.

[Page 147]

If the earth had no axial revolution, the attractive point where the tide rises would be carried around the earth once in twenty-seven days by the moon's revolution about the earth. But since the earth revolves on its axis, it presents a new section to the moon's attraction every hour. If the moon were stationary, that would bring two high tides in exactly twenty-four hours; but as the moon goes forward, we need nearly twenty-five hours for two tides.

The attractive influence of the sun also gives us a tide four-tenths as great as that of the moon. When these two influences of the sun and moon combine, as they do, in conjunction—when both bodies are on one side of the earth; or in opposition, sun and moon being on opposite sides of the earth—we have spring or increased tides. When the moon is in its first or third quarter, i. e., when a line from the moon to the earth makes a right angle with one from the sun to the earth, these influences antagonize one another, and we have the neap or low tides.

It is easy to see that if, when the moon was drawing its usual tide, the sun drew four-tenths of the water in a tide at right angles with it, the moon's tide must be by so much lower. Because of the inertia of the water [Page 148] it does not yield instantly to the moon's influence, and the crest of the tide is some hours behind the advancing moon.

The amount of tide in various places is affected by almost innumerable influences, as distance of moon at its apogee or perigee; its position north, south, or at the equator; distance of earth from sun at perihelion and aphelion; the position of islands; the trend of continents, etc. All eastern shores have far greater tides than western. As the earth rolls to the east it leaves the tide-crest under the moon to impinge on eastern shores, hence the tides of from seventy-five to one hundred feet in the Bay of Fundy. Lakes and most seas are too small to have perceptible tides. The spring-tides in the Mediterranean Sea are only about three inches.

This constant ebb and flow of the great sea is a grand provision for its purification. Even the wind is sent to the sea to be cleansed. The sea washes every shore, purifies every cove, bay, and river twice every twenty-four hours. All putrescible matter liable to breed a pestilence is carried far from shore and sunk under fathoms of the never-stagnant sea. The distant moon lends its mighty power to carry the burdens of commerce. She takes all the loads that can be floated on her flowing tides, and cheerfully carries them in opposite directions in successive journeys.

It must be conceded that the profoundest study has not mastered the whole philosophy of tides. There are certain facts which are apparent, but for an explanation of their true theory such men as Laplace, Newton, and Airy have labored in vain. There are plenty of other worlds still to conquer.

[Page 150]

[Page 151] THE MOON.

New moon, [Symbol]; first quarter, [Symbol]; full moon, [Symbol]; last quarter, [Symbol].

EXTREME DISTANCE FROM THE EARTH, 259,600 MILES; LEAST, 221,000 MILES; MEAN, 240,000 MILES. DIAMETER, 2164.6 MILES [2153, LOCKYER]. REVOLUTION ABOUT THE EARTH, 29-1/2 DAYS. AXIAL REVOLUTION, SAME TIME.

When the astronomer Herschel was observing the southern sky from the Cape of Good Hope, the most clever hoax was perpetrated that ever was palmed upon a credulous public. Some new and wonderful instruments were carefully described as having been used by that astronomer, whereby he was enabled to bring the moon so close that he could see thereon trees, houses, animals, and men-like human beings. He could even discern their movements, and gestures that indicated a peaceful race. The extent of the hoax will be perceived when it is stated that no telescope that we are now able to make reveals the moon more clearly than it would appear to the naked eye if it was one hundred or one hundred and fifty miles away. The distance at which a man can be seen by the unaided eye varies according to circumstances of position, background, light, and eye, but it is much inside of five miles.

Since, however, the moon is our nearest neighbor, a member of our own family in fact, it is a most interesting object of study.

A glance at its familiar face reveals its unequal illumination. All ages and races have seen a man in the moon. All lovers have sworn by its constancy, and only part of them have kept their oaths. Every twenty-nine or thirty days we see a silver crescent in the west, and are glad if it comes over the right shoulder—so [Page 152] much tribute does habit pay to superstition. The next night it is thirteen degrees farther east from the sun. We note the stars it occults, or passes by, and leaves behind as it broadens its disk, till it rises full-orbed in the east when the sun sinks in the west. It is easy to see that the moon goes around the earth from west to east. Afterward it rises later and smaller each night, till at length, lost from sight, it rises about the same time as the sun, and soon becomes the welcome crescent new moon again.

The same peculiarities are always evident in the visible face of the moon; hence we know that it always presents the same side to the earth. Obviously it must make just one axial to one orbital revolution. Hold any body before you at arm's-length, revolve it one-quarter around you until exactly overhead. If it has not revolved on an axis between the hands, another quarter of the surface is visible; but if in going up it is turned a quarter over, by the hands holding it steady, the same side is visible. Three causes enable us to see a little more than half the moon's surface: 1. The speed with which it traverses the ellipse of its orbit is variable. It sometimes gets ahead of us, sometimes behind, and we see farther around the front or back part. 2. The axis is a little inclined to the plane of its orbit, and its orbit a little inclined to ours; hence we see a little over its north pole, and then again over the south pole. 3. The earth being larger, its inhabitants see a little more than half-way around a smaller body. These causes combined enable us to see 576/1000 of the moon's surface. Our eyes will never see the other side of the moon. If, now, being solid, her axial revolution could [Page 153] be increased enough to make one more revolution in two or three years, that difference between her axial and orbital revolution would give the future inhabitants of the earth a view of the entire circumference of the moon. Yet if the moon were once in a fluid state, or had oceans on the surface, the enormous tide caused by the earth would produce friction enough, as they moved over the surface, to gradually retard the axial revolution till the two tidal elevations remained fixed toward and opposite the earth, and then the axial and orbital revolutions would correspond, as at present. In fact, we can prove that the form of the moon is protuberant toward the earth. Its centre of gravity is thirty-three miles beyond its centre of magnitude, which is the same in effect as if a mountain of that enormous height rose on the earth side. Hence any fluid, as water or air, would flow round to the other side.

The moon's day, caused by the sun's light, is 29-1/2 times as long as ours. The sun shines unintermittingly for fifteen days, raising a temperature as fervid as boiling water. Then darkness and frightful cold for the same time succeed, except on that half where the earth acts as a moon. The earth presents the same phases—crescent, full, and gibbous—to the moon as the moon does to us, and for the same causes. Lord Rosse has been enabled, by his six-foot reflector, to measure the difference of heat on the moon under the full blaze of its noonday and midnight. He finds it to be no less than five hundred degrees. People not enjoying extremes of temperature should shun a lunar residence. The moon gives us only 1/6180000 as much light as the sun. A sky full of moons would scarcely make daylight.

[Page 154]

There are no indications of air or water on the moon. When it occults a star it instantly shuts off the light and as instantly reveals it again. An atmosphere would gradually diminish and reveal the light, and by refraction [Page 155] cause the star to be hidden in much less time than the solid body of the moon would need to pass over it. If the moon ever had air and water, as it probably did, they are now absorbed in the porous lava of its substance.

Telescopic Appearance.



Probably no one ever saw the moon by means of a good telescope without a feeling of admiration and awe. Except at full-moon, we can see where the daylight struggles with the dark along the line of the moon's sunrise or sunset. This line is called the terminator. It is broken in the extreme, because the surface is as rough as possible. In consequence of the small gravitation of the moon, utter absence of the expansive power of ice shivering the cliffs, or the levelling power of rains, precipices can stand in perpendicularity, mountains shoot up like needles, and cavities three miles deep remain unfilled. The light of the sun falling on the rough body of the moon, shown in section (Fig. 59), illuminates the whole cavity at a, part of the one at b, casts a long shadow from the mountain at c, and touches the tip of the one at d, which appears to a distant observer as a point of light beyond the terminator, As the moon revolves the conical cavity, a is illuminated on the forward side only; the light creeps down the backward side of cavity b to the bottom; mountain c. comes directly under the sun and casts no shadow, and mountain d casts its long shadow over the plain. Knowing the time of revolution, and observing the change of [Page 156] illumination, we can easily measure the height of mountain and depth of crater. An apple, with excavations and added prominences, revolved on its axis toward the light of a candle, admirably illustrates the crescent light that fills either side of the cavities and the shadows of the mountains on the plain. Notice in Fig. 58 the crescent forms to the right, showing cavities in abundance.



The selenography of one side of the moon is much better known to us than the geography of the earth. Our maps of the moon are far more perfect than those of the earth; and the photographs of lunar objects by Messrs. Draper and De la Rue are wonderfully perfect, [Page 157] and the drawings of Padre Secchi equally so (Fig. 60). The least change recognizable from the earth must be speedily detected. There are frequently reports of discoveries of volcanoes on the moon, but they prove to be illusions. The moon will probably look the same to observers a thousand years hence as it does to-day.

This little orb, that is only 1/81 of the mass of the earth, has twenty-eight mountains that are higher than Mont Blanc, that "monarch of mountains," in Europe.

Eclipses.



It is evident that if the plane of the moon's orbit were to correspond with that of the earth, as they all lie in the plane of the page (Fig. 61), the moon must pass between the centres of the earth and sun, and exactly behind the earth at every revolution. Such successive and total darkenings would greatly derange all affairs dependent on light. It is easily avoided. Venus does [Page 158] not cross the disk of the sun at every revolution, because of the inclination of the plane of its orbit to that of the earth (see Fig. 41, p. 107). So the plane of the orbit of the moon is inclined to the orbit of the earth 5 deg. 8' 39"; hence the full-moon is often above or below the earth's shadow, and the earth is below or above the moon's shadow at new moon. It is as if the moon's orbit were pulled up one-quarter of an inch from the page behind the earth, and depressed as much below it between the earth and the sun. The point where the orbit of the moon penetrates the plane of the ecliptic is called a node. If a new moon occur when the line of intersection of the planes of orbits points to the sun, the sun must be eclipsed; if the full-moon occur, the moon must be eclipsed. In any other position the sun or moon will only be partially hidden, or no eclipse will occur.

If the new moon be near the earth it will completely obscure the sun. A dime covers it if held close to the eye. It may be so far from the earth as to only partially hide the sun; and, if it cover the centre, leave a ring of sunlight on every side. This is called an annular eclipse. Two such eclipses will occur this year (1879). If the full-moon passes near the earth, or is at perigee, it finds the cone of shadow cast by the earth larger, and hence the eclipse is greater; if it is far from the earth, or near apogee, the earth's shadow is smaller, and the eclipse less, or is escaped altogether.

There is a certain periodicity in eclipses. Whenever the sun, moon, and earth are in a line, as in the total eclipse of July 29th, 1878, they will be in the same position after the earth has made about eighteen revolutions, [Page 159] and the moon two hundred and sixteen—that is, eighteen years after. This period, however, is disregarded by astronomers, and each eclipse calculated by itself to the accuracy of a second.

How terrible is the fear of ignorance and superstition when the sun or moon appear to be in the process of destruction! how delightful are the joys of knowledge when its prophesies in regard to the heavenly bodies are being fulfilled!

MARS.

The god or war; Its sign [Symbol], spear and shield.

MEAN DISTANCE FROM THE SUN, 141,000,000 MILES. DIAMETER, 4211 MILES. REVOLUTION, AXIAL, 24H. 37M. 22.7S.; ORBITAL, 686.98 DAYS. VELOCITY PER MINUTE, 899 MILES. SATELLITES, TWO.



At intervals, on an average of two years one month and nineteen days, we find rising, as the sun goes down, the reddest star in the heavens. Its brightness is exceedingly variable; sometimes it scintillates, and sometimes it shines with a steady light. Its marked peculiarities demand a close study. We find it to be Mars, the fiery god of war. Its orbit is far from circular. At perihelion it is 128,000,000 miles from the sun, and at aphelion 154,000,000; hence its mean distance is about 141,000,000. So great a change in its distance from the sun easily accounts for the change in its brilliancy. Now, if Mars and the earth revolved in circular orbits, the one 141,000,000 miles from the sun, and the other 92,000,000, they would approach at conjunction within 49,000,000 miles of each other, and at opposition be 233,000,000 miles apart. But Mars at perihelion may be only 128,000,000 miles from the sun, and earth at [Page 160] aphelion may be 94,000,000 miles from the sun. They are, then, but 34,000,000 miles apart. This favorable opportunity occurs about once in seventy-nine years. At its last occurrence, in 1877, Mars introduced to us his two satellites, that had never before been seen by man. In consequence of this greatly varying distance, the apparent size of Mars differs very much (Fig. 62). Take a favorable time when the planet is near, also as near overhead as it ever comes, so as to have as little atmosphere as possible to penetrate, and study the planet. The first thing that strikes the observer is a dazzling spot of white near the pole which happens to be toward him, or at both poles when the planet is so situated that they can be seen. When the north pole is turned toward the sun the size of the spot sensibly diminishes, and the spot at the south pole enlarges, and vice versa. Clearly they are ice-fields. Hence Mars has water, and air to carry it, and heat to melt ice. It is winter at the south pole when Mars is farthest from the sun; therefore the ice-fields are larger than at the north pole. It is summer at the south pole when Mars is nearest the sun. Hence its ice-fields grow smaller [Page 161] than those of the north pole in its summer. This carrying of water from pole to pole, and melting of ice over such large areas, might give rise to uncomfortable currents in ocean and air; but very likely an inhabitant of earth might be transported to the surface of Mars, and be no more surprised at what he observed there than if he went to some point of the earth to him unknown. Day and night would be nearly of the same length; winter would linger longer in the lap of spring; summer would be one hundred and eighty-one days long; but as the seas are more intermingled with the land, and the divisions of land have less of continental magnitude, it may be conjectured that Mars might be a comfortable place of residence to beings like men. Perhaps the greatest surprise to the earthly visitor would be to find himself weighing only four-tenths as much as usual, able to leap twice as high, and lift considerable bowlders.

Satellites of Mars.

The night of August 11th, 1877, is famous in modern astronomy. Mars has been a special object of study in all ages; but on that evening Professor Hall, of Washington, discovered a satellite of Mars. On the 16th it was seen again, and its orbital motion followed. On the following night it was hidden behind the body of the planet when the observation began, but at the calculated time—at four o'clock in the morning—it emerged, and established its character as a true moon, and not a fixed star or asteroid. Blessings, however, never come singly, for another object soon emerged which proved to be an inner satellite. This is extraordinarily near [Page 162] the planet—only four thousand miles from the surface—and its revolution is exceedingly rapid. The shortest period hitherto known is that of the inner satellite of Saturn, 22h. 37m. The inner satellite of Mars makes its revolution in 7h. 39m.—a rapidity so much surpassing the axial revolution of the planet itself, that it rises in the west and sets in the east, showing all phases of our moon in one night. The outer satellite is 12,579 miles from Mars, and makes its revolution in 30h. 18m. Its diameter is six and a quarter miles; that of the inner one is seven and a half miles. This can be estimated only by the amount of light given.

ASTEROIDS.

ALREADY DISCOVERED (1879), 192. DISTANCES FROM THE SUN, FROM 200,000,000 TO 315,000,000 MILES. DIAMETERS, FROM 20 TO 400 MILES. MASS OF ALL, LESS THAN ONE-QUARTER OF THE EARTH.

The sense of infinite variety among the countless number of celestial orbs has been growing rapidly upon us for half a century, and doubtless will grow much more in half a century to come. Just as we paused in the consideration of planets to consider meteors and comets, at first thought so different, so must we now pause to consider a ring of bodies, some of which are as small in comparison to Jupiter, the next planet, as aerolites are compared to the earth.

In 1800 an association of astronomers, suspecting that a planet might be found in the great distance between Mars and Jupiter, divided the zodiac into twenty-four parts, and assigned one part to each astronomer for a thorough search; but, before their organization could commence work, Piazzi, an Italian astronomer of Palermo, [Page 163] found in Taurus a star behaving like a planet. In six weeks it was lost in the rays of the sun. It was rediscovered on its emergence, and named Ceres. In March, 1802, a second planet was discovered by Olbers in the same gap between Mars and Jupiter, and named Pallas. Here was an embarrassment of richness. Olbers suggested that an original planet had exploded, and that more pieces could be found. More were found, but the theory is exploded into more pieces than a planet could possibly be. Up to 1879 one hundred and ninety-two have been discovered, with a prospect of more. Between 1871-75 forty-five were discovered, showing that they are sought for with great skill. In the discovery of these bodies, our American astronomers, Professors Watson and Peters, are without peers.

Between Mars and Jupiter is a distance of some 339,000,000 miles. Subtract 35,000,000 miles next to Mars and 50,000,000 miles next to Jupiter, and there is left a zone 254,000,000 miles wide outside of which the asteroids never wander. If any ever did, the attraction of Mars or Jupiter may have prevented their return.

Since the orbits of Mars and Jupiter show no sign of being affected by these bodies for a century past, it is probable that their number is limited, or at least that their combined mass does not approximate the size of a planet. Professor Newcomb estimates that if all that are now discovered were put into one planet, it would not be over four hundred miles in diameter; and if a thousand more should exist, of the average size of those discovered since 1850, their addition would not increase the diameter to more than five hundred miles.

[Page 164] That all these bodies, which differ from each other in no respect except in brilliancy, can be noted and fixed so as not to be mistaken one for another, and instantly recognized though not seen for a dozen years, is one of the highest exemplifications of the accuracy of astronomical observation.

JUPITER.

The king of the gods; sign [Symbol], the bird of Jove.

DISTANCE FROM THE SUN, PERIHELION, 457,000,000 MILES; APHELION, 503,000,000 MILES. DIAMETER, EQUATORIAL, 87,500 MILES; POLAR, 82,500 MILES. VOLUME, 1300 EARTHS. MASS, 213 EARTHS. AXIAL REVOLUTION, 9H. 55M 20S. ORBITAL REVOLUTION, 11 YEARS 317 DAYS. VELOCITY, 483.6 MILES PER MINUTE.



Jupiter rightly wears the name of the "giant planet." His orbit is more nearly circular than most smaller planets. He could not turn short corners with facility. We know little of his surface. His spots and belts are [Page 165] changeable as clouds, which they probably are. Some spots may be slightly self-luminous, but not the part of the planet we see. It is covered with an enormous depth of atmosphere. Since the markings in the belts move about one hundred miles a day, the Jovian tempests are probably not violent. It is, however, a singular and unaccountable fact, as remarked by Arago, that its trade-winds move in an opposite direction from ours. Jupiter receives only one twenty-seventh as much light and heat from the sun as the earth receives. Its lighter density, being about that of water, indicates that it still has internal heat of its own. Indeed, it is likely that this planet has not yet cooled so as to have any solid crust, and if its dense vapors could be deposited on the surface, its appearance might be more suggestive of the sun than of the earth.

Satellites of Jupiter.

In one respect Jupiter seems like a minor sun—he is royally attended by a group of planets: we call them moons. This system is a favorite object of study to everyone possessing a telescope. Indeed, I have known a man who could see these moons with the naked eye, and give their various positions without mistake. Galileo first revealed them to ordinary men. We see their orbits so nearly on the edge that the moons seem to be sliding back and forth across and behind the disk, and to varying distances on either side. Fig. 64 is the representation of their appearance at successive observations in November, 1878. Their motion is so swift, and the means of comparison by one another and the planet so excellent, that they can be seen to change their places, [Page 166] be occulted, emerge from shadow, and eclipse the planet, in an hour's watching.



ELEMENTS OF JUPITER'S SATELLITES. - Mean Distance from Jupiter. Sidereal Period. Diameter. - Miles. Days Hrs. Min. Miles. I. Io 260,000 1 18 28 2,352 II. Europa 414,000 3 13 43 2,099 III. Ganymede 661,000 7 3 59 3,436 IV. Callisto 1,162,000 16 18 5 2,929 -

It is seen by the above table that all these moons are larger than ours, one larger than Mercury, and the asteroids are hardly large enough to make respectable moons for them. They differ in color: I. and II. have a bluish tinge; III. a yellow; and IV. is red. The amount of light given by these satellites varies in the most sudden and inexplicable manner. Perhaps it may be owing to the different distributions of land and water on them. The mass of all of them is .000171 of Jupiter.

[Page 167] If the Jovian system were the only one in existence, it would be a surprising object of wonder and study. A monster planet, 85,000 miles in diameter, hung on nothing, revolving its equatorial surface forty-five miles a minute, holding four other worlds in steady orbits, some of them at a speed of seven hundred miles a minute, and the whole system carried through space at five hundred miles a minute. Yet the discovery of all this display of power, skill, and stability is only reading the easiest syllables of the vast literature of wisdom and power.

SATURN.

The god or time; sign [Symbol], his scythe.

MEAN DISTANCE FROM THE SUN, 881,000,000 MILES. DIAMETER, POLAR, 66,500 MILES; EQUATORIAL, 73,300 MILES. AXIAL REVOLUTION, 10H. 14M. PERIODIC TIME, 29T YEARS. MOONS, EIGHT.

The human mind has used Saturn and the two known planets beyond for the last 200 years as a gymnasium. It has exercised itself in comprehending their enormous distances in order to clear those greater spaces, to where the stars are set; it has exercised its ingenuity at interpreting appearances which signify something other than they seem, in order that it may no longer be deluded by any sunrises into a belief that the heavenly dome goes round the earth. That a wandering point of light should develop into such amazing grandeurs under the telescope, is as unexpected as that every tiny seed should show peculiar markings and colors under the microscope.



There are certain things that are easy to determine, such as size, density, periodic time, velocity, etc.; but other things are exceedingly difficult to determine. It requires long sight to read when the book is held [Page 168] 800,000,000 miles away. Only very few, if more than two, opportunities have been found to determine the time of Saturn's rotation. On the evening of December 7th, 1870, Professor Hall observed a brilliant white spot suddenly show itself on the body of this planet. It was as if an eruption of white hot matter burst up from the interior. It spread eastward, and remained bright till January, when it faded. No such opportunity for getting a basis on which to found a calculation of the time of the rotation of Saturn has occurred since Sir William Herschel's observations; and, very singularly, the two times deduced wonderfully coincide—that of Herschel being 10h. 16m., that of Mr. Hall being 10h. 14m.

[Page 169] The density of Saturn is less than that of water, and its velocity of rotation so great that centrifugal force antagonizes gravitation to such an extent that bodies weigh on it about the same as on the earth. All the fine fancies of the habitability of this vaporous world, all the calculations of the number of people that could live on the square miles of the planet and its enormous rings, are only fancy. Nothing could live there with more brains than a fish, at most. It is a world in formative processes. We cannot hear the voice of the Creator there, but we can see matter responsive to the voice, and moulded by his word.

Rings of Saturn.

The eye and mind of man have worked out a problem of marvellous difficulty in finding a true solution of the strange appearance of the rings. Galileo has the immortal honor of first having seen something peculiar about this planet. He wrote to the Duke of Tuscany, "When I view Saturn it seems tricorps. The central body seems the largest. The two others, situated, the one on the east, and the other on the west, seem to touch it. They are like two supporters, who help old Saturn on his way, and always remain at his side." Looking a few years later, the rings having turned from view, he said, "It is possible that some demon mocked me;" and he refused to look any more.

Huyghens, in March, 1655, solved the problem of the triform appearance of Saturn. He saw them as handles on the two sides. In a year they had disappeared, and the planet was as round as it seemed to Galileo in 1612. He did not, however, despair; and in October, [Page 170] 1656, he was rewarded by seeing them appear again. He wrote of Saturn, "It is girdled by a thin plain ring, nowhere touching, inclined to the ecliptic."

Since that time discoveries have succeeded one another rapidly. "We have seen by degrees a ring evolved out of a triform planet, and the great division of the ring and the irregularities on it brought to light. Enceladus, and coy Mimas, faintest of twinklers, are caught by Herschel's giant mirrors. And he, too, first of men, realizes the wonderful tenuity of the ring, along which he saw those satellites travelling like pearls strung on a silver thread. Then Bond comes on the field, and furnishes evidence to show that we must multiply the number of separate rings we know not how many fold. And here we reach the golden age of Saturnian discovery, when Bond, with the giant refractor of Cambridge, and Dawes, with his 6-1/3-inch Munich glass, first beheld that wonderful dark semi-transparent ring, which still remains one of the wonders of our system. But the end is not yet: on the southern surface of the ring, ere summer fades into autumn, Otto Struve in turn comes upon the field, detects, as Dawes had previously done, a division even in the dark ring, and measures it, while it is invisible to Lassell's mirror—a proof, if one were needed, of the enormous superiority possessed by refractors in such inquiries. Then we approach 1861, when the ring plane again passes through the earth, and Struve and Wray observe curious nebulous appearances."[*]

[Footnote *: Lockyer.]

Our opportunities for seeing Saturn vary greatly. As the earth at one part of its orbit presents its south pole [Page 171] to the sun, then its equator, then the north pole, so Saturn; and we, in the direction of the sun, see the south side of the rings inclined at an angle of 27 deg.; next the edge of the rings, like a fine thread of light; then the north side at a similar inclination. On February 7th, 1878, Saturn was between Aquarius and Pisces, with the edge of the ring to the sun. In 1885, the planet being in Taurus, the south side of the rings will be seen at the greatest advantage. From 1881 till 1885 all circumstances will combine to give most favorable studies of Saturn. Meanwhile study the picture of it. The outer ring is narrow, dark, showing hints of another division, sometimes more evident than at others, as if it were in a state of flux. The inner, or second, ring is much brighter, especially on the outer edge, and shading off to the dusky edge next to the planet. There is no sign of division into a third dusky innermost ring, as was plainly seen by Bond. This, too, may be in a state of flux.

The markings of the planet are delicate, difficult of detection, and are not like those stark zebra stripes that are so often represented.

The distance between the planet and the second ring seems to be diminished one-half since 1657, and this ring has doubled its breadth in the same time. Some of this difference may be owing to our greater telescopic power, enabling us to see the ring closer to the planet; but in all probability the ring is closing in upon the central body, and will touch it by A.D. 2150. Thus the whole ring must ultimately fall upon the planet, instead of making a satellite.

We are anxious to learn the nature of such a ring. [Page 172] Laplace mathematically demonstrated that it cannot be uniform and solid, and survive. Professor Peirce showed it could not be fluid, and continue. Then Professor Maxwell showed that it must be formed of clouds of satellites too small to be seen individually, and too near together for the spaces to be discerned, unless, perhaps, we may except the inner dark ring, where they are not near enough to make it positively luminous. Indeed, there is some evidence that the meteoroids are far enough apart to make the ring partially transparent.

We look forward to the opportunities for observation in 1882 with the brightest hope that these difficult questions will be solved.

Satellites of Saturn.

The first discovered satellite of Saturn seen by Huyghens was in 1655, and the last by the Bonds, father and son, of Cambridge, in 1848. These are eight in number, and are named:

Distant from Saturn's centre. I. Mimas 119,725 miles. II. Enceladus 153,630 " III. Tethys 190,225 " IV. Dione 243,670 " V. Rhea 340,320 " VI. Titan 788,915 " VII. Hyperion 954,160 " VIII. Japetus 2,292,790 "

Titan can be seen by almost any telescope; I., II., and III., only by the most powerful instrument. All except Japetus revolve nearly in the plane of the ring. Like the moons of Jupiter, they present remarkable and unaccountable variations of brilliancy. An inspection [Page 173] of the table reveals either an expectation that another moon will be discovered between V. and VI., and about three more between VII. and VIII., or that these gaps may be filled with groups of invisible asteroids, as the gap between Mars and Jupiter. This will become more evident by drawing Saturn, the rings, and orbits of the moons all as circles, on a scale of 10,000 miles to the inch. Saturn will be in the centre, 70,000 miles in diameter; then a gap, decreasing twenty-nine miles a year to the first ring, of, say, 10,000 miles; a dark ring 9000 miles wide; next the brightest ring 18,300 miles wide; then a gap of 1750 miles; then the outer ring 10,000 miles wide; then the orbits of the satellites in order.

If the scenery of Jupiter is magnificent, that of Saturn must be sublime. If one could exist there, he might wander from the illuminated side of the rings, under their magnificent arches, to the darkened side, see the swift whirling moons; one of them presenting ten times the disk of the earth's moon, and so very near as to enable him to watch the advancing line of light that marks the lunar morning journeying round that orb.

URANUS.

Sign [Symbol]; the initial of Herschel, and sign of the world.

DISTANCE FROM THE SUN, 1,771,000,000 MILES. DIAMETER, 31,700 MILES. AXIAL REVOLUTION UNKNOWN. ORBITAL, 84 YEARS. VELOCITY PER MINUTE, 252 MILES. MOONS, FOUR.

Uranus was presented to the knowledge of man as an unexpected reward for honest work. It was first mistaken by its discoverer for a comet, a mere cloud of vapor; but it proved to be a world, and extended the [Page 174] boundaries of our solar system, in the moment of its discovery, as much as all investigation had done in all previous ages.

Sir William Herschel was engaged in mapping stars in 1781, when he first observed its sea-green disk. He proposed to call it Georgium Sidus, in honor of his king; but there were too many names of the gods in the sky to allow a mortal name to be placed among them. It was therefore called Uranus, since, being the most distant body of our system, as was supposed, it might appropriately bear the name of the oldest god. Finding anything in God's realms of infinite riches ought not to lead men to regard that as final, but as a promise of more to follow.

This planet had been seen five times by Flamsteed before its character was determined—once nearly a century before—and eight times by Le Monnier. These names, which might easily have been associated with a grand discovery, are associated with careless observation. Eyes were made not only to be kept open, but to have minds behind them to interpret their visions. Herschel thought he discovered six moons belonging to Uranus, but subsequent investigation has limited the number to four. Two of these are seen with great difficulty by the most powerful telescopes.

If the plane of our moon's orbit were tipped up to a greater inclination, revolving it on the line of nodes as an axis until it was turned 85 deg., the moon, still continuing on its orbit in that plane, would go over the poles instead of about the equator, and would go back to its old path when the plane was revolved 180 deg.; but its revolution would now be from east to west, or [Page 175] retrograde. The plane of the moons of Uranus has been thus inclined till it has passed 10 deg. beyond the pole, and the moons' motions are retrograde as regards other known celestial movements. How Uranus itself revolves is not known. There are more worlds to conquer.

NEPTUNE.

God of the sea; sign [Symbol], his trident.

DISTANCE FROM THE SUN, 2,775,000,000 MILES. DIAMETER, 34,500 MILES. VELOCITY PER MINUTE, 201.6 MILES. AXIAL REVOLUTION UNKNOWN. ORBITAL, 164.78 YEARS. ONE MOON.

Men sought for Neptune as the heroes sought the golden fleece. The place of Uranus had been mapped for nearly one hundred years by these accidental observations. On applying the law of universal gravitation, a slight discrepancy was found between its computed place and its observed place. This discrepancy was exceedingly slight. In 1830 it was only 20"; in 1840,190"; in 1884, 2'. Two stars that were 2' apart would appear as one to the keenest unaided eye, but such an error must not exist in astronomy. Years of work were given to its correction. Mr. John C. Adams, of Cambridge, England, finding that the attraction of a planet exterior to Uranus would account for its irregularities, computed the place of such a hypothetical body with singular exactness in October, 1841; but neither he nor the royal astronomer Airy looked for it. Another opportunity for immortality was heedlessly neglected. Meanwhile, M. Leverrier, of Paris, was working at the same problem. In the summer of 1846 Leverrier announced the place of the exterior planet. The conclusion was in striking coincidence with that of Mr. [Page 176] Clark. Mr. Challis commenced to search for the planet near the indicated place, and actually saw and mapped the star August 4th, 1846, but did not recognize its planetary character. Dr. Galle, of Berlin, on the 23d of September, 1846, found an object with a planetary disk not plotted on the map of stars. It was the sought-for world. It would seem easy to find a world seventy-six times as large as the earth, and easy to recognize it when seen. The fact that it could be discovered only by such care conveys an overwhelming idea of the distance where it moves.



The effect of these perturbations by an exterior planet is understood from Fig. 66. Uranus and Neptune were in conjunction, as shown, in 1822. But in 1820 it had been found that Uranus was too far from the sun, and too much accelerated. Since 1800, Neptune, in his orbit from F to E, had been hastening Uranus in his orbit D from C to B, and also drawing it farther from the sun. After 1822, Neptune, in passing from E to D, had been retarding Uranus in his orbit from B to A.

We have seen it is easy to miss immortality. There is still another instance. Lalande saw Neptune on May 8th and 10th, 1795, noted that it had moved a little, and that the observations did not agree; but, supposing the first was wrong, carelessly missed the glory of once more doubling the bounds of the empire of the sun.

[Page 177] It is time to pause and review our knowledge of this system. The first view reveals a moon and earth endowed with a force of inertia going on in space in straight lines; but an invisible elastic cord of attraction holds them together, just counterbalancing this tendency to fly apart, and hence they circle round their centre of gravity. The revolving earth turns every part of its surface to the moon in each twenty-four hours. By an axial revolution in the same time that the moon goes round the earth, the moon holds the same point of its surface constantly toward the earth. If we were to add one, two, four, eight moons at appropriate distances, the result would be the same. There is, however, another attractive influence—that of the sun. The sun attracts both earth and moon, but their nearer affection for each other keeps them from going apart. They both, revolving on their axes and around their centre of gravity, sweep in a vastly wider curve around the sun. Add as many moons as has Jupiter or Saturn, the result is the same—an orderly carrying of worlds through space.

There lies the unsupported sun in the centre, nearer to infinity in all its capacities and intensities of force than our minds can measure, filling the whole dome to where the stars are set with light, heat, and power. It holds five small worlds—Vulcan, Mercury, Venus, Earth, and Mars—within a space whose radius it would require a locomotive half a thousand years to traverse. It next holds some indeterminate number of asteroids, and the great Jupiter, equal in volume to 13,000 earths. It holds Saturn, Uranus, and Neptune, and all their variously related satellites and rings. The two thoughts that overwhelm us are distance and power. The period of [Page 178] man's whole history is not sufficient for an express train to traverse half the distance to Neptune. Thought wearies and fails in seeking to grasp such distances; it can scarcely comprehend one million miles, and here are thousands of them. Even the wings of imagination grow weary and droop. When we stand on that outermost of planets, the very last sentinel of the outposts of the king, the very sun grown dim and small in the distance, we have taken only one step of the infinite distance to the stars. They have not changed their relative position—they have not grown brighter by our approach. Neptune carries us round a vast circle about the centre of the dome of stars, but we seem no nearer its sides. In visiting planets, we have been only visiting next-door neighbors in the streets of a seaport town. We know that there are similar neighbors about Sirius and Arcturus, but a vast sea rolls between. As we said, we stand with the outermost sentinel; but into the great void beyond the king of day sends his comets as scouts, and they fly thousands of years without for one instant missing the steady grasp of the power of the sun. It is nearer almightiness than we are able to think.

If we cannot solve the problems of the present existence of worlds, how little can we expect to fathom the unsoundable depths of their creation and development through ages measureless to man! Yet the very difficulty provokes the most ambitious thought. We toil at the problem because it has been hitherto unsolvable. Every error we make, and discover to be such, helps toward the final solution. Every earnest thinker who climbs the shining worlds as steps to a higher thought is trying to solve the problem God has given us to do.



[Page 179] IX.

THE NEBULAR HYPOTHESIS.

"And the earth was without form, and void; and darkness was upon the face of the deep."—Genesis i. 2.

[Page 180] "A dark Illimitable ocean, without bound, Without dimension, where length, breadth, and height, And time, and place are lost."—MILTON.

"It is certain that matter is somehow directed, controlled, and arranged; while no material forces or properties are known to be capable of discharging such functions."—LIONEL BEALE.

"The laws of nature do not account for their own origin."—JOHN STUART MILL.



[Page 181] IX.

THE NEBULAR HYPOTHESIS.

The method by which the solar system came into its present form was sketched in vast outline by Moses. He gave us the fundamental idea of what is called the nebular hypothesis. Swedenborg, that prodigal dreamer of vagaries, in 1734 threw out some conjectures of the way in which the outlines were to be filled up; Buffon followed him closely in 1749; Kant sought to give it an ideal philosophical completeness; as he said, "not as the result of observation and computation," but as evolved out of his own consciousness; and Laplace sought to settle it on a mathematical basis.

It has been modified greatly by later writers, and must receive still greater modifications before it can be accepted by the best scientists of to-day. It has been called "the grandest generalization of the human mind;" and if it shall finally be so modified as to pass from a tentative hypothesis to an accepted philosophy, declaring the modes of a divine worker rather than the necessities of blind force, it will still be worthy of that high distinction.

Let it be clearly noted that it never proposes to do more than to trace a portion of the mode of working which brought the universe from one stage to another. It only goes back to a definite point, never to absolute beginning, nor to nothingness. It takes matter from [Page 182] the hand of the unseen power behind, and merely notes the progress of its development. It finds the clay in the hands of an intelligent potter, and sees it whirl in the process of formation into a vessel. It is not in any sense necessarily atheistic, any more than it is to affirm that a tree grows by vital processes in the sun and dew, instead of being arbitrarily and instantly created. The conclusion reached depends on the spirit of the observer. Newton could say, "This most beautiful system of the sun, planets, and comets could only proceed from the counsel and dominion of an intelligent and powerful being!" Still it is well to recognize that some of its most ardent defenders have advocated it as materialistic. And Laplace said of it to Napoleon, "I have no need of the hypothesis of a god."

The materialistic statement of the theory is this: that matter is at first assumed to exist as an infinite cloud of fire-mist, dowered with power latent therein to grow of itself into every possibility of world, flower, animal, man, mind, and affection, without any interference or help from without. But it requires far more of the Divine Worker than any other theory. He must fill matter with capabilities to take care of itself, and this would tax the abilities of the Infinite One far more than a constant supervision and occasional interference. Instead of making the vase in perfect form, and coloring it with exquisite beauty by an ever-present skill, he must endow the clay with power to make itself in perfect form, adorn itself with delicate beauty, and create other vases.

The nebular hypothesis is briefly this: All the matter composing all the bodies of the sun, planets, and satellites once existed in an exceedingly diffused state; [Page 183] rarer than any gas with which we are acquainted, filling a space larger than the orbit of Neptune. Gravitation gradually contracted this matter into a condensing globe of immense extent. Some parts would naturally be denser than others, and in the course of contraction a rotary motion, it is affirmed, would be engendered. Rotation would flatten the globe somewhat in the line of its axis. Contracting still more, the rarer gases, aided by centrifugal force, would be left behind as a ring that would ultimately be separated, like Saturn's ring, from the retreating body. There would naturally be some places in this ring denser than others; these would gradually absorb all the ring into a planet, and still revolve about the central mass, and still rotate on its own axis, throwing off rings from itself. Thus the planet Neptune would be left behind in the first sun-ring, to make its one moon; the planet Uranus left in the next sun-ring, to make its four moons from four successive planet-rings; Saturn, with its eight moons and three rings not made into moons, is left in the third sun-ring; and so on down to Vulcan.

The outer planets would cool off first, become inhabitable, and, as the sun contracted and they radiated their own heat, become refrigerated and left behind by the retreating sun. Of course the outer planets would move slowly; but as that portion of the sun which gave them their motion drew in toward the centre, keeping its absolute speed, and revolving in the lessening circles of a contracting body, it would give the faster motion necessary to be imparted to Earth, Mercury, and Vulcan.

The four great classes of facts confirmatory of this hypothesis are as follows: 1st. All the planets move [Page 184] in the same direction, and nearly in the same plane, as if thrown off from one equator; 2d. The motions of the satellites about their primaries are mostly in the same direction as that of their primaries about the sun; 3d. The rotation of most of these bodies on their axes, and also of the sun, is in the same direction as the motion of the planets about the sun; 4th. The orbits of the planets, excluding asteroids, and their satellites, have but a comparatively small eccentricity; 5th. Certain nebulae are observable in the heavens which are not yet condensed into solids, but are still bright gas.

The materialistic evolutionist takes up the idea of a universe of material world-stuff without form, and void, but so endowed as to develop itself into orderly worlds, and adds to it this exceeding advance, that when soil, sun, and chemical laws found themselves properly related, a force in matter, latent for a million eons in the original cloud, comes forward, and dead matter becomes alive in the lowest order of vegetable life; there takes place, as Herbert Spencer says, "a change from an indefinite, incoherent homogeneity, into a definite, coherent heterogeneity, through continuous differentiation and integration." The dead becomes alive; matter passes from unconsciousness to consciousness; passes up from plant to animal, from animal to man; takes on power to think, reason, love, and adore. The theistic evolutionist may think that the same process is gone through, but that an ever-present and working God superintends, guides, and occasionally bestows a new endowment of power that successively gives life, consciousness, mental, affectional, and spiritual capacity.

Is this world-theory true? and if so, is either of the [Page 185] evolution theories true also? If the first evolution theory is true, the evolved man will hardly know which to adore most, the Being that could so endow matter, or the matter capable of such endowment.

There are some difficulties in the way of the acceptance of the nebular hypothesis that compel many of the most thorough scientists of the day to withhold their assent to its entirety. The latest, and one of the most competent writers on the subject, Professor Newcomb, who is a mathematical astronomer, and not an easy theorist, evolving the system of the universe from the depth of his own consciousness, says: "Should any one be sceptical as to the sufficiency of these laws to account for the present state of things, science can furnish no evidence strong enough to overthrow his doubts until the sun shall be found to be growing smaller by actual measurement, or the nebulae be actually seen to condense into stars and systems." In one of the most elaborate defences of the theory, it is argued that the hypothesis explains why only one of the four planets nearest the sun can have a moon, and why there can be no planet inside of Mercury. The discovery of the two satellites to Mars and of the planet Vulcan makes it all the worse for these facts.

Some of the objections to the theory should be known by every thinker. Laplace must have the cloud "diffused in consequence of excessive heat," etc. Helmholtz, in order to account for the heat of the contracting sun, must have the cloud relatively cold. How he and his followers diffused the cloud without heat is not stated.

The next difficulty is that of rotation. The laws [Page 186] of science compel a contraction into one non-rotating body—a central sun, indeed, but no planets about it. Laplace cleverly evades the difficulty by not taking from the hand of the Creator diffused gas, but a sun with an atmosphere filling space to the orbit of Neptune, and already in revolution. He says: "It is four millions to one that all motions of the planets, rotations and revolutions, were at once imparted by an original common cause, of which we know neither the nature nor the epoch." Helmholtz says of rotation, "the existence of which must be assumed." Professor Newcomb says that the planets would not be arranged as now, each one twice as far from the sun as the next interior one, and the outer ones made first, but that all would be made into planets at once, and the small inner ones quite likely to cool off more rapidly.

It is a very serious difficulty that at least one satellite does not revolve in the right direction. How Neptune or Uranus could throw their moons backward from its equator is not easily accounted for. It is at least one Parthian arrow at the system, not necessarily fatal, but certainly dangerous.

A greater difficulty is presented by the recently discovered satellites of Mars. The inner one goes round the planet in one-third part of the time of the latter's revolution. How Mars could impart three times the speed to a body flying off its surface that it has itself, has caused several defenders of the hypothesis to rush forward with explanations, but none with anything more than mere imaginary collisions with some comet. It is to be noticed that accounting for three times the speed is not enough; for as Mars shrunk away from the [Page 187] ring that formed that satellite, it ought itself to attain more speed, as the sun revolves faster than its planets, and the earth faster than its moon. In defending the hypothesis, Mitchel said: "Suppose we had discovered that it required more time for Saturn or Jupiter to rotate on their axes than for their nearest moon to revolve round them in its orbit; this would have falsified the theory." It is also asserted that the newly discovered planet Vulcan makes an orbital in less time than the sun makes an axial revolution.

In regard to one Martial moon, Professor Kirkwood, on whom Proctor conferred the highest title that could be conferred, "the modern Kepler," says: "Unless some explanation can be given, the short period of the inner satellite will be doubtless regarded as a conclusive argument against the nebular hypothesis." If gravitation be sufficient to account for the various motions of the heavenly bodies, we have a perplexing problem in the star known as 1830 Groombridge, now in the Hunting Dogs of Bootes. It is thought to have a speed of two hundred miles per second—a velocity that all the known matter in the universe could not give to the star by all its combined attraction. Neither could all that attraction stop the motion of the star, or bend it into an orbit. Its motion must be accounted for on some hypothesis other than the nebular.

The nebulae which we are able to observe are not altogether confirmatory of the hypothesis under consideration. They have the most fantastic shapes, as if they had no relation to rotating suns in the formative stages. There are vast gaps in the middle, where they ought to be densest. Mr. Plumer, in the Natural Science Review, [Page 188] says, in regard to the results of the spectroscopic revelations: "We are furnished with distinct proof that the gases so examined are not only of nearly equal density, but that they exist in a low state of tension. This fact is fatal to the nebular theory."

In the autumn of 1876 a star blazed out in Cygnus, which promised to throw a flood of light on the question of world-making. Its spectrum was like some of the fixed stars. It probably blazed ont by condensation from some previously invisible nebula. But its brilliancy diminished swiftly, when it ought to have taken millions of years to cool. If the theory was true, it ought to have behaved very differently. It should have regularly condensed from gas to a solid sun by slow process. But, worst of all, after being a star awhile, it showed unmistakable proofs of turning into a cloud-mist—a star into a nebula, instead of vice versa. A possible explanation will be considered under variable stars.

Such are a few of the many difficulties in the way of accepting the nebular hypothesis, as at present explained, as being the true mode of development of the solar system. Doubtless it has come from a hot and diffused condition into its present state; but when such men as Proctor, Newcomb, and Kirkwood see difficulties that cannot be explained, contradictions that cannot be reconciled by the principles of this theory, surely lesser men are obliged to suspend judgment, and render the Scotch verdict of "not proven." Whatever truth there may be in the theory will survive, and be incorporated into the final solution of the problem; which solution will be a much grander generalization of the human mind than the nebular hypothesis.

[Page 189] Of some things we feel very sure: that matter was once without form and void, and darkness rested on the face of the mighty deeps; that, instead of chaos, we have now cosmos and beauty; and that there is some process by which matter has been brought from one state to the other. Whether, however, the nebular hypothesis lays down the road travelled to this transfiguration, we are not sure. Some of it seems like solid rock, and some like shifting quicksand. Doubtless there is a road from that chaos to this fair cosmos. The nebular hypothesis has surveyed, worked, and perfected many long reaches of this road, but the rivers are not bridged, the chasms not filled, nor the mountains tunnelled.

When men attempt to roll the hypothesis of evolution along the road of the nebular hypothesis of worlds, and even beyond to the production of vegetable and animal life, mind and affection, the gaps in the road become evident, and disastrous.

A soul that has reached an adoration for the Supreme Father cares not how he has made him. Doubtless the way God chose was the best. It is as agreeable to have been thought of and provided for in the beginning, to have had a myriad ages of care, and to have come from the highest existent life at last, as to have been made at once, by a single act, out of dust. The one who is made is not to say to the Maker, "Why hast thou formed me in this or that manner?" We only wish the question answered in what manner we were really made.

Evolution, without constant superintendence and occasional new inspiration of power, finds some tremendous chasms in the road it travels. These must be spanned by the power of a present God or the airy imagination [Page 190] of man. Dr. McCosh has happily enumerated some of these tremendous gaps over which mere force cannot go. Given, then, matter with mechanical power only, what are the gaps between it and spirituality?

"1. Chemical action cannot be produced by mechanical power.

"2. Life, even in the lowest forms, cannot be produced from unorganized matter.

"3. Protoplasm can be produced only by living matter.

"4. Organized matter is made up of cells, and can be produced only by cells. Whence the first cell?

"5. A living being can be produced only from a seed or germ. Whence the first vegetable seed?

"6. An animal cannot be produced from a plant. Whence the first animal?

"7. Sensation cannot be produced in insentient matter.

"8. The genesis of a new species of plant or animal has never come under the cognizance of man, either in pre-human or post-human ages, either in pre-scientific or scientific times. Darwin acknowledges this, and says that, should a new species suddenly arise, we have no means of knowing that it is such.

"9. Consciousness—that is, a knowledge of self and its operations—cannot be produced out of mere matter or sensation.

"10. We have no knowledge of man being generated out of the lower animals.

"11. All human beings, even savages, are capable of forming certain high ideas, such as those of God and duty. The brute creatures cannot be made to entertain these by any training.

[Page 191] "With such tremendous gaps in the process, the theory which would derive all things out of matter by development is seen to be a very precarious one.

The truth, according to the best judgment to be formed in the present state of knowledge, would seem to be about this: The nebular hypothesis is correct in all the main facts on which it is based; but that neither the present forces of matter, nor any other forces conceivable to the mind of man, with which it can possibly be endowed, can account for all the facts already observed. There is a demand for a personal volition, for an exercise of intelligence, for the following of a divine plan that embraces a final perfection through various and changeful processes. The five great classes of facts that sustain the nebular hypothesis seem set before us to show the regular order of working. The several facts that will not, so far as at present known, accord with that plan, seem to be set before us to declare the presence of a divine will and power working his good pleasure according to the exigencies of time and place.



[Page 193] X.

THE STELLAR SYSTEM.

"The heavens number out the glory of the strong God."—DAVID.

[Page 194] Richter says that "an angel once took a man and stripped him of his flesh, and lifted him up into space to show him the glory of the universe. When the flesh was taken away the man ceased to be cowardly, and was ready to fly with the angel past galaxy after galaxy, and infinity after infinity, and so man and angel passed on, viewing the universe, until the sun was out of sight—until our solar system appeared as a speck of light against the black empyrean, and there was only darkness. And they looked onward, and in the infinities of light before, a speck of light appeared, and suddenly they were in the midst of rushing worlds. But they passed beyond that system, and beyond system after system, and infinity after infinity, until the human heart sank, and the man cried out: 'End is there none of the universe of God?' The angel strengthened the man by words of counsel and courage, and they flew on again until worlds left behind them were out of sight, and specks of light in advance were transformed, as they approached them, into rushing systems; they moved over architraves of eternities, over pillars of immensities, over architecture of galaxies, unspeakable in dimensions and duration, and the human heart sank again and called ont: 'End is there none of the universe of God?' And all the stars echoed the question with amazement: 'End is there none of the universe of God?' And this echo found no answer. They moved on again past immensities of immensities, and eternities of eternities, until in the dizziness of uncounted galaxies the human heart sank for the last time, and called out: 'End is there none of the universe of God?' And again all the stars repeated the question, and the angel answered: 'End is there none of the universe of God. Lo, also, there is no beginning.'"



[Page 195] X.

THE OPEN PAGE OF THE HEAVENS.

The Greeks set their mythological deities in the skies, and read the revolving pictures as a starry poem. Not that they were the first to set the blazonry of the stars as monuments of their thought; we read certain allusions to stars and asterisms as far back as the time of Job. And the Pleiades, Arcturus, and Orion are some of the names used by Him who "calleth all the stars by their names, in the greatness of his power." Homer and Hesiod, 750 B.C., allude to a few stars and groups. The Arabians very early speak of the Great Bear; but the Greeks completely nationalized the heavens. They colonized the earth widely, but the heavens completely; and nightly over them marched the grand procession of their apotheosized divinities. There Hercules perpetually wrought his mighty labors for the good of man; there flashed and faded the changeful star Algol, as an eye in the head of the snaky-haired Medusa; over them flew Pegasus, the winged horse of the poet, careering among the stars; there the ship Argo, which had explored all strange seas of earth, nightly sailed in the infinite realms of heaven; there Perseus perpetually killed the sea-monster by celestial aid, and perpetually won the chained Andromeda for his bride. Very evident was their recognition of divine help: equally evident was [Page 196] their assertion of human ability and dominion. They gathered the illimitable stars, and put uncountable suns into the shape of the Great Bear—the most colossal form of animal ferocity and strength—across whose broad forehead imagination grows weary in flying; but they did not fail to put behind him a representative of themselves, who forever drives him around a sky that never sets—a perpetual type that man's ambition and expectation correspond to that which has always been revealed as the divine.

The heavens signify much higher power and wisdom to us; we retain the old pictures and groupings for the convenience of finding individual stars. It is enough for the astronomer that we speak of a star as situated right ascension 13' 45", declination 88 deg. 40'. But for most people, if not all, it is better to call it Polaris. So we might speak of a lake in latitude 42 deg. 40', longitude 79 deg. 22', but it would be clearer to most persons to say Chatauqua. For exact location of a star, right ascension and declination must be given; but for general indication its name or place in a constellation is sufficiently exact. The heaven is rather indeterminably laid out in irregular tracts, and the mythological names are preserved. The brightest stars are then indicated in order by the letters of the Greek alphabet—Alpha (a), Beta (b), Gamma (g), etc. After these are exhausted, the Roman alphabet is used in the same manner, and then numbers are resorted to; so that the famous star 61 Cygni is the 111th star in brightness in that one constellation. An acquaintance with the names, peculiarities, and movements of the stars visible at different seasons of the year is an unceasing source of pleasure. It [Page 197] is not vision alone that is gratified, for one fine enough may hear the morning stars sing together, and understand the speech that day uttereth unto day, and the knowledge that night showeth unto night. One never can be alone if he is familiarly acquainted with the stars. He rises early in the summer morning, that he may see his winter friends; in winter, that he may gladden himself with a sight of the summer stars. He hails their successive rising as he does the coming of his personal friends from beyond the sea. On the wide ocean he is commercing with the skies, his rapt soul sitting in his eyes. Under the clear skies of the East he hears God's voice speaking to him, as to Abraham, and saying, "Look now toward the heavens, and tell the number of the stars, if thou be able to number them."

A general acquaintance with the stars will be first attempted; a more particular knowledge afterward. Fig. 67 (page 201) is a map of the circumpolar region, which is in full view every clear night. It revolves daily round Polaris, its central point. Toward this star, the two end stars of the Great Dipper ever point, and are in consequence called "the Pointers." The map may be held toward the northern sky in such a position as the stars may happen to be. The Great Bear, or Dipper, will be seen at nine o'clock in the evening above the pole in April and May; west of the pole, the Pointers downward, in July and August; close to the north horizon in October and November; and east of the pole the Pointers highest, in January and February. The names of such constantly visible stars should be familiar. In order, from the end of the tail of the Great Bear, we have Benetnasch ae, Mizar z, Little Alcor close to it, [Page 198] Alioth, e Megrez, d at the junction, has been growing dimmer for a century, Phad, g Dubhe and Merak. It is best to get some facility at estimating distances in degrees. Dubhe and Merak, "the Pointers," are five degrees apart. Eighteen degrees forward of Dubhe is the Bear's nose; and three pairs of stars, fifteen degrees apart, show the position of the Bear's three feet. Follow "the Pointers" twenty-nine degrees from Dubhe, and we come to the pole-star. This star is double, made of two suns, both appearing as one to the naked eye. It is a test of an excellent three-inch telescope to resolve it into two. Three stars beside it make the curved-up handle of the Little Dipper of Ursa Minor. Between the two Bears, thirteen degrees from Megrez, and eleven degrees from Mizar, are two stars in the tail of the Dragon, which curves about to appropriate all the stars not otherwise assigned. Follow a curve of fifteen stars, doubling back to a quadrangle from five to three degrees on a side, and thirty-five degrees from the pole, for his head. His tongue runs out to a star four degrees in front. We shall find, hereafter, that the foot of Hercules stands on this head. This is the Dragon slain by Cadmus, and whose teeth produced such a crop of sanguinary men.

The star Thuban was once the pole-star. In the year B.C. 2300 it was ten times nearer the pole than Polaris is now. In the year A.D. 2100 the pole will be within 30' of Polaris; in A.D. 7500, it will be at a of Cepheus; in A.D. 13,500, within 7 deg. of Vega; in A.D. 15,700, at the star in the tongue of Draco; in A.D. 23,000, at Thuban; in A.D. 28,000, back to Polaris. This indicates no change in the position of the dome [Page 199] of stars, but a change in the direction of the axis of the earth pointing to these various places as the cycles pass. As the earth goes round its orbit, the axis, maintaining nearly the same direction, really points to every part of a circle near the north star as large as the earth's orbit, that is, 185,000,000 miles in diameter. But, as already shown, that circle is too small to be discernible at our distance. The wide circle of the pole through the ages is really made up of the interlaced curves of the annual curves continued through 25,870 years. The stem of the spinning top wavers, describes a circle, and finally falls; the axis of the spinning earth wavers, describes a circle of nearly 28,000 years, and never falls.

The star g Draconis, also called Etanin, is famous in modern astronomy, because observations on this star led to the discovery of the aberration of light. If we held a glass tube perpendicularly out of the window of a car at rest, when the rain was falling straight down, we could see the drops pass directly through. Put the car in motion, and the drops would seem to start toward us, and the top of the tube must be bent forward, or the drops entering would strike on the backside of the tube carried toward them. So our telescopes are bent forward on the moving earth, to enable the entered light to reach the eye-piece. Hence the star does not appear just where it is. As the earth moves faster in some parts of its orbit than others, this aberration is sometimes greater than at others. It is fortunate that light moves with a uniform velocity, or this difficult, problem would be still further complicated. The displacement of a star from this course is about 20".43.

[Page 200] On the side of Polaris, opposite to Ursa Major, is King Cepheus, made of a few dim stars in the form of the letter K. Near by is his brilliant wife Cassiopeia, sitting on her throne of state. They were the graceless parents who chained their daughter to a rock for the sea-monster to devour; but Perseus, swift with the winged sandals of Mercury, terrible with his avenging sword, and invincible with the severed head of Medusa, whose horrid aspect of snaky hair and scaly body turned to stone every beholder, rescues the maiden from chains, and leads her away by the bands of love. Nothing could be more poetical than the life of Perseus. When he went to destroy the dreadful Gorgon, Medusa, Pluto lent him his helmet, which would make him invisible at will; Minerva loaned her buckler, impenetrable, and polished like a mirror; Mercury gave him a dagger of diamonds, and his winged sandals, which would carry him through the air. Coming to the loathsome thing, he would not look upon her, lest he, too, be turned to stone; but, guided by the reflection in the buckler, smote off her head, carried it high over Libya, the dropping blood turning to serpents, which have infested those deserts ever since.



The human mind has always been ready to deify and throne in the skies the heroes that labor for others. Both Perseus and Hercules are divine by one parent, and human by the other. They go up and down the earth, giving deliverance to captives, and breaking every yoke. They also seek to purge away all evil; they slay dragons, gorgons, devouring monsters, cleanse the foul places of earth, and one of them so wrestles with death as to win a victim from his grasp. Finally, by [Page 201] an ascension in light, they go up to be in light forever. They are not ideally perfect. They right wrong by slaying wrong-doers, rather than by being crucified themselves; they are just murderers; but that only plucks the fruit from the tree of evil. They never attempted to infuse a holy life. They punished rather than regenerated. It must be confessed, also, that they were not sinless. But they were the best saviors the race could imagine, and are examples of that perpetual effort of the human mind to incarnate a Divine Helper who shall labor and die for the good of men.

[Page 202]

Equatorial Constellations.

If we turn our backs on Polaris on the 10th of November, at 10 o'clock in the evening, and look directly overhead, we shall see the beautiful constellation of Andromeda. Together with the square of Pegasus, it makes another enormous dipper. The star a Alpheratz is in her face, the three at the left cross her breast. b and the two above mark the girdle of her loins, and g is in the foot. Perseus is near enough for help; and Cetus, the sea-monster, is far enough away to do no harm. Below, and east of Andromeda, is the Ram of the golden fleece, recognizable by the three stars in an acute triangle. The brightest is called Arietis, or Hamel. East of this are the Pleiades, and the V-shaped Hyades in Taurus, or the Bull. The Pleiades rise about 9 o'clock on the evening of the 10th of September, and at 3 o'clock A.M. on June 10th.

[Page 203]

Fig. 69 extends east and south of our last map. It is the most gorgeous section of our heavens. (See the Notes to the Frontispiece.) Note the triangle, 26 deg. on a side, made by Betelguese, Sirius, and Procyon. A line from Procyon to Pollux leads quite near to Polaris. Orion is the mighty hunter. Under his feet is a hare, behind him are two dogs, and before him is the rushing bull. The curve of stars to the right of Bellatrix, g, represents his shield of the Nemean lion's hide. The three stars of his belt make a measure 3 deg. long; the upper one, Mintaker, is less than 30' south of the equinoctial. The ecliptic passes between Aldebaran and the Pleiades. Sirius rises about 9 o'clock P.M. on the 1st of December, and about 4 o'clock A.M. on the 16th of August. Procyon rises about half an hour earlier.

[Page 204]

Fig. 70 continues eastward. Note the sickle in the head and neck of the Lion. The star b is Denebola, in his tail. Arcturus appears by the word Bootes, at the edge of the map. These two stars make a triangle with Spica, about 35 deg. on a side. The geometric head of Hydra is easily discernible east of Procyon: The star g in the Virgin is double, with a period of 145 years. z is just above the equinoctial. There is a fine nebula two-thirds of the way from d to ae, and a little above the line connecting the two. Coma Berenices is a beautiful cluster of faint stars. Spica rises at 9 o'clock on the 10th of February, at 5 o'clock A.M. on the 6th of November.

[Page 205]

Fig. 71 represents the sky to the eastward and northward of the last. A line drawn from Polaris and Benetnasch comes east of Arcturus to the little triangle called his sons. Bootes drives the Great Bear round the pole. Arcturus and Denebola make a triangle with a, also called Cor Coroli, in the Hunting Dogs. This triangle, and the one having the same base, with Spica for its apex, is called the "Diamond of the Virgin." Hercules appears head down—a in the face, b, g, d; in his shoulders, p; and ae; in the loins, t in the knee, the foot being bent to the stars at the right. The Serpent's head, making an X, is just at the right of the g of Hercules, and the partial circle of the Northern Crown above. The head of Draco is seen at b on the left of the map. Arcturus rises at 9 o'clock about the 20th of February, and at 5 A.M. on the 22d of October; Regulus 3h. 35m. Earlier.

[Page 206]

Fig. 72 portrays the stars eastward and southward. Scorpio is one of the most brilliant and easily traced constellations. Antares, a, in the heart, is double. In Sagittarius is the Little Milk-dipper, and west of it the bended bow. Vega is at the top of the map. Near it observe z, a double, and e, a quadruple star. The point to which the solar system is tending is marked by the sign of the earth below p; Herculis. The Serpent, west of Hercules, and coiled round nearly to Aquila, is very traceable. In the right-hand lower corner is the Centaur. Below, and always out of our sight, is the famous a Centauri. The diamond form of the Dolphin is sometimes called "Job's Coffin." The ecliptic passes close [Page 207] to b of Scorpio, which star is in the head. Antares, in Scorpio, rises at 9 o'clock P.M. on May 9th, and at 5 o'clock A.M. on January 5th.



In Fig. 73 we recognize the familiar stars of Pegasus, which tell us we have gone quite round the heavens. Note the beautiful cross in the Swan. b in the bill is named Albireo, and is a beautiful double to almost any glass. Its yellow and blue colors are very distinct. The place of the famous double star 61 Cygni is seen. The first magnitude star in the lower left-hand corner is Fomalhaut, in the Southern Fish. a Pegasi is in the diagonal corner from Alpharetz, in Andromeda. The star below Altair is b Aquilae, and is called Alschain; the one above is g Aquilae, named Tarazed. This is not a brilliant section of the sky. Altair rises at 9 o'clock on the 29th of May, and at 6 o'clock A.M. on the 11th of January.

[Page 208]

Fig. 74 gives the stars that are never seen by persons north of the earth's equator. In the Ship is brilliant Canopus, and the remarkable variable ae. Below it is the beautiful Southern Cross, near the pole of the southern heavens. Just below are the two first magnitude stars Bungala, a, and Achernar, b, of the Centaur. Such a number of unusually brilliant stars give the southern sky an unequalled splendor. In the midst of them, as if for contrast, is the dark hole, called by the sailors the "Coal-sack," where even the telescope reveals no sign of light. Here, also, are the two Magellanic clouds, both easily discernible by the naked eye; the larger two hundred times the apparent size of the moon, lying between the pole and Canopus, and the other between Achernar and the pole. The smaller cloud is only one-fourth the size of the other. Both are mostly resolvable into groups of stars from the fifth to the fifteenth magnitude.

[Page 209] For easy out-door finding of the stars above the horizon at any time, see star-maps at end of the book.

Characteristics of the Stars.

Such a superficial examination of stars as we have made scarcely touches the subject. It is as the study of the baptismal register, where the names were anciently recorded, without any knowledge of individuals. The heavens signify much more to us than to the Greeks. We revolve under a dome that investigation has infinitely enlarged from their estimate. Their little lights were turned by clumsy machinery, held together by material connections. Our vast worlds are connected by a force so fine that it seems to pass out of the realm of the material into that of the spiritual. Animal ferocity or a human Hercules could image their idea of power. Ours finds no symbol, but rises to the Almighty. Their heavens were full of fighting Orions, wild bulls, chained Andromedas, and devouring monsters. Our heavens are significant of harmony and unity; all worlds carried by one force, and all harmonized into perfect music. All their voices blend their various significations into a personal speaking, which says, "Hast thou not heard that the everlasting God, the Lord, the creator of the ends of the earth, fainteth not, neither is weary?" There is no searching of his understanding. Lift up your eyes on high, and behold who hath created all these things, that brought out their host by number, that calleth them all by their names in the greatness of his power; for that he is strong in power not one faileth.

[Page 210] Number.

We find about five thousand stars visible to the naked eye in the whole heavens, both north and south. Of these twenty are of the first magnitude, sixty-five of the second, two hundred of the third, four hundred of the fourth, eleven hundred of the fifth, and three thousand two hundred of the sixth. We think we can easily number the stars; but train a six-inch telescope on a little section of the Twins, where six faint stars are visible, and over three thousand luminous points appear. The seventh magnitude has 13,000 stars; the eighth, 40,000; the ninth, 142,000. There are 18,000,000 stars in the zone called the Milky Way. When our eyes are not sensitive enough to be affected by the light of far-off stars the tastimetre feels their heat, and tells us the word of their Maker is true—"they are innumerable."[*]

[Footnote *: Telescopic Work.—Look at the Hyades and Pleiades in Taurus. Notice the different colors of stars in them both. Find the cluster Praesepe in Fig. 70, just a trifle above a point midway between Procyon and Regulus. It is equally distant from Procyon and a point a little below Pollux. Sweep along the Milky Way almost anywhere, and observe the distribution of stars; in some places perfect crowds, in others more sparsely scattered. Find with the naked eye the rich cluster in Perseus. Draw a line from Algol to a of Perseus (Fig. 67); turn at right angles to the right, at a distance of once and four-tenths the first line a brightness will be seen. The telescope reveals a gorgeous cluster.]

Double and Multiple Stars.

If we look up during the summer months nearly overhead at the star e Lyra, east of Vega (Fig. 72), we shall see with the naked eye that the star appears a little [Page 211] elongated. Turn your opera-glass upon it, and two stars appear. Turn a larger telescope on this double star, and each of the components separate into two. It is a double double star. We know that if two stars are near in reality, and not simply apparently so by being in the same line of sight, they must revolve around a common centre of gravity, or rush to a common ruin. Eagerly we watch to see if they revolve. A few years suffice to show them in actual revolution. Nay, the movement of revolution has been decided before the companion star was discovered. Sirius has long been known to have a proper motion, such as it would have if another sun were revolving about it. Even the direction of the unseen body could always be indicated. In February, 1862, Alvan Clark, artist, poet, and maker of telescopes (which requires even greater genius than to be both poet and artist), discovered the companion of Sirius just in its predicted place. As a matter of fact, one of Mr. Clark's sons saw it first; but their fame is one. The time of revolution of this pair is fifty years. But one companion does not meet the conditions of the movements. Here must also be one or more planets too small or dark to be seen. The double star x in the Great Bear (see Fig. 70) makes a revolution in fifty-eight years.