A Journey in Other Worlds (22 page)

The next object of interest was the great red spot. It proved, as Cortlandt had predicted, to be a continent, with at that time no special colour, though they easily recognized it by comparing its outlines with those of the spot in the map. Its length, as they already knew, was twenty-seven thousand miles, and its breadth about eight thousand miles, so that it contained more square miles than the entire surface of the earth, land and water included.

"It is clear," said Cortlandt, "that at some season of Jupiter's long year a change takes place that affects the colour of the leaves--some drought or prolonged norther; for it is obvious that that is the simplest explanation. In like manner we may expect that at some times more white spots will move across the ocean than at others."

"On account of the size of these continents and oceans," said Bearwarden, "it is easy to believe that many climatic conditions may prevail here that can scarcely exist on earth. But what a magnificent world to develop, with its great rivers, lakes, and mountains showing at even this distance, and what natural resources must be lying there dormant, awaiting our call! This constantly recurs to my mind. The subjugation and thorough opening up of this red spot continent will probably supply more interesting problems than straightening the axis of the earth."

"At our next visit," replied Ayrault, "when we have established regular interplanetary lines of travel, we may have an opportunity to examine it more closely." Then they again attracted the nearest moon beyond which they had swung, increased the repulsion on Jupiter, and soared away towards Saturn.

"We have a striking illustration of Jupiter's enormous mass," said Cortlandt, as the apparent diameter of the mighty planet rapidly decreased, "in the fact that notwithstanding its numerous moons, it still rotates so rapidly. We know that the earth's days were formerly but half or a quarter as long as now, having lasted but six or eight hours. The explanation of the elongation is simple: the earth rotates in about twenty-four hours, while the moon encircles it but once in nearly twenty-eight days, so that our satellite is continually drawing the oceans backward against its motion. These tidal brakes acting through the friction of the water on the bottom, its unequal pressure, and the impact of the waves on the shore, are continually retarding its rotation, so that the day is a fraction of a second longer now than it was in the time of Caesar. This same action is of course taking place in Jupiter and the great planets, in this case there being five moons at work. Our moon, we know, rotates on its axis but once while it revolves about the earth, this being no doubt due to its own comparative smallness and the great attraction of the earth, which must have produced tremendous tides before the lunar oceans disappeared from its surface."

In crossing the orbits of the satellites, they passed near Ganymede, Jupiter's largest moon.

"This," said Cortlandt, "was discovered by Galileo in 1610. It is three thousand four hundred and eighty miles in diameter, while our moon is but two thousand one hundred and sixty, revolves at a distance of six hundred and seventy-eight thousand three hundred miles from Jupiter, completes its revolution in seven days and four hours, and has a specific gravity of 1.87."

In passing, they observed that Ganymede possessed an atmosphere, and continents and oceans of large area.

"Here," said Bearwarden, "we have a body with a diameter about five hundred miles greater than the planet Mercury. Its size, light specific gravity, atmosphere, and oceans seem to indicate that it is less advanced than that planet, yet you think Jupiter has had a longer separate existence than the planets nearer the sun?"

"Undoubtedly," said Cortlandt. "Jupiter was condensed while in the solar-system nebula, and began its individual existence and its evolutionary career long before Mercury was formed. The matter now in Ganymede, however, doubtless remained part of the Jupitersystem nebula till after Mercury's creation, and, being part of so great a mass, did not cool very rapidly. I should say that this satellite has about the same relation to Jupiter that Jupiter has to the sun, and is therefore younger in point of time as well as of development than the most distant Callisto, and older, at all events in years, than Europa and Io, both of which are nearer. This supposition is corroborated by the fact that Europa, the smallest of these four, is also the densest, having a specific gravity of 2.14, its smallness having enabled it to overtake Ganymede in development, notwithstanding the latter's start. In the face of the evidence before us we must believe this, or else that, perhaps, as in the case of the asteroid Hilda, something like a collision has rejuvenated it. This might account for its size, and for the Nautical Almanac's statement that there is a 'small and variable'

inclination to its orbit, while Io and Europa revolve exactly in the plane of Jupiter's equator."

They had about as long a journey before them as they had already made in going from the earth to Jupiter. The great planet soon appeared as a huge crescent, since it was between them and the sun; its moons became as fifth-and sixth-magnitude stars, and in the evening of the next day Jupiter's disk became invisible to the unaided eye. Since there were no way stations, in the shape of planets or asteroids, between Jupiter and Saturn, they kept the maximum repulsion on Jupiter as long as possible, and moved at tremendous speed. Saturn was somewhat in advance of Jupiter in its orbit, so that their course from the earth had been along two sides of a triangle with an obtuse angle between. During the next four terrestrial days they sighted several small comets, but spent most of their time writing out their Jovian experiences. During the sixth day Saturn's rings, although not as much tilted as they would be later in the planet's season, presented a most superb sight, while they spun in the sun's rays. Soon after this the eight moons became visible, and, while slightly reducing the Callisto's speed, they crossed the orbits of Iapetus, Hyperion, and Titan, when they knew they were but seven hundred and fifty thousand miles from Saturn.

"I am anxious to ascertain," said Cortlandt, "whether the composition of yonder rings is similar to that of the comet through which we passed. I am sure they shine with more than reflected light."

"We have been in the habit," said Ayrault, "of associating heat with light, but it is obvious there is something far more subtle about cometary light and that of Saturn's rings, both of which seem to have their birth in the intense cold of interplanetary space." Passing close to Mimas, Saturn's nearest moon, they supplemented its attraction, after swinging by, by their own strong pull, bringing their speed down to dead slow as they entered the outside ring. At distances often of half a mile they found meteoric masses, sometimes lumps the size of a house, often no larger than apples, while small particles like grains of sand moved between them. There were two motions. The ring revolved about Saturn, and the particles vibrated among themselves, evidently kept apart by a mutual repulsion, which seemed both to increase and decrease faster than gravitation; for on approaching one another they were more strongly repelled than attracted, but when they separated the repulsion decreased faster than the attraction, so that after a time divergence ceased, and they remained at fixed distances.

The Callisto soon became imbued with motion also, but nothing ever struck it. When any large mass came unusually near, both it and their car emitted light, and they rapidly separated. The sunlight was not as strong here as it had been when they entered the comet, and as they penetrated farther they were better able to observe the omnipresent luminosity. They were somewhat puzzled by the approach of certain light-centres, which seemed to contain nothing but this concentrated brightness. Occasionally one of these centres would glow very brightly near them, and simultaneously recede. At such times the Callisto also glowed, and itself recoiled slightly. At first the travellers could not account for this, but finally they concluded that the centres must be meteoric masses consisting entirely of gases, possessing weight though invisible.

"We have again to face," said Cortlandt, "that singular law that till recently we did not suppose existed on earth. All kinds of suppositions have been advanced in explanation of these rings. Some writers have their thickness, looked at from the thin edge, as four hundred miles, some one hundred, and some but forty. One astronomer of the nineteenth century, a man of considerable eminence, was convinced that they consisted of sheets of liquid. Now, it should be obvious that no liquid could maintain itself here for a minute, for it would either fall upon the planet as a crushing hail, or, if dependent for its shape on its own tenacity, it would break if formed of the toughest steel, on account of the tremendous weight. Any number of theories have been advanced by any number of men, but in weight we have the rub. No one has ever shown how these innumerable fragments maintain themselves at a height of but a few thousand miles above Saturn, withstanding the giant's gravitation-pull. Their rate of revolution, though rapid, does not seem fast enough to sustain them. Neither have I ever seen it explained why the small fragments do not fall upon the large ones, though many astronomers have pictured the composition of these rings as we find they exist. Nor do we know why the molecules of a gas are driven farther apart by heat, while their activity is also increased, though if this activity were revolution about one another to develop the centrifugal, it would not need to be as strong then as when they are cold and nearer together. There may be explanations, but I have found none in any of the literature I have read. It seems to me that all this leads to but one conclusion, viz.: apergy is the constant and visible companion of gravitation, on these great planets Jupiter and Saturn, perhaps on account of some peculiar influence they possess, and also in comets, in the case of large masses, while on earth it appears naturally only among molecules--those of gases and every other substance."

"I should go a step further," said Bearwarden, "and say our earth has the peculiarity, since it does not possess the influence necessary to generate naturally a great or even considerable development of apergy. The electricity of thunderstorms, northern lights, and other forces seems to be produced freely, but as regards apergy our planet's natural productiveness appears to be small."

The omnipresent luminosity continued, but the glow was scarcely bright enough to be perceived from the earth.

"I believe, however," said Bearwarden, referring to this, "that whenever a satellite passes near these fragments, preferably when it enters the planet's shadow, since that will remove its own light, it will create such activity among them as to make the luminosity visible to the large telescopes or gelatine plates on earth."

"Now," said Ayrault, "that we have evolved enough theories to keep astronomers busy for some time, if they attempt to discuss them, I suggest that we alight and leave the abstract for the concrete."

Whereupon they passed through the inner ring and rapidly sank to the ground. Saturn

Landing on a place about ten degrees north of the equator, so that they might obtain a good view of the great rings--since ON the line only the thin edge would be visible--they opened a port-hole with the same caution they had exercised on Jupiter. Again there was a rush of air, showing that the pressure without was greater than that within; but on this occasion the barometer stopped at thirty-eight, from which they calculated that the pressure was nineteen pounds to the square inch on their bodies, instead of fifteen as at sea-level on earth. This difference was so slight that they scarcely felt it. They also discarded the apergetic outfits that had been so useful on Jupiter, as unnecessary here. The air was an icy blast, and though they quickly closed the opening, the interior of the Callisto was considerably chilled.

"We shall want our winter clothes," said Bearwarden; "it might be more comfortable for us exactly on the equator, though the scene at night will be far finer here, if we can stand the climate. Doubtless it will also be warmer soon, for the sun has but just risen."

"I suspect this is merely one of the cold waves that rush towards the equator at this season, which corresponds to about the 10th of our September," replied Cortlandt. "The poles of Saturn must be intensely cold during its long winter of fourteen and three quarter years, for, the axis being inclined twenty-seven degrees from the perpendicular of its orbit, the pole turned from the sun is more shut off from its heat than ours, and in addition to this the mean distance--more than eight hundred and eighty million miles--is very great. Since the chemical composition of the air we have inhaled has not troubled our lungs, it is fair to suppose we shall have no difficulty in breathing." Having dressed themselves more warmly, and seen by a thermometer they had placed outside that the temperature was thirty-eight degrees Fahrenheit, which had seemed very cold compared with the warmth inside the Callisto, they again opened the port-hole, this time leaving it open longer. What they had felt before was evidently merely a sudden gust, for the air was now comparatively calm.

Finding that the doctor's prediction as to the suitability of the air to their lungs was correct, they ventured out, closing the door as they went.

Expecting, as on Jupiter, to find principally vertebrates of the reptile and bird order, they carried guns and cartridges loaded with buckshot and No. 1, trusting for solid-ball projectiles to their revolvers, which they shoved into their belts. They also took test-tubes for experiments on the Saturnian bacilli. Hanging a bucket under the pipe leading from the roof, to catch any rain that might fall--for they remembered the scarcity of drinking-water on Jupiter--they set out in a southwesterly direction.

Walking along, they noticed on all sides tall lilies immaculately pure in their whiteness, and mushrooms and toadstools nearly a foot high, the former having a delicious flavour and extreme freshness, as though only an hour old. They had seen no animal life, or even sign of it, and were wondering at its dearth, when suddenly two large white birds rose directly in front of them. Like thought, Bearwarden and Ayrault had their guns up, snapping the thumb-pieces over "safe" and pulling the triggers almost simultaneously. Bearwarden, having double buckshot, killed his bird at the first fire; but Ayrault, having only No. 1, had to give his the second barrel, almost all damage in both cases being in the head. On coming close to their victims they found them to measure twelve feet from tip to tip, and to have a tremendous thickness of feathers and down.