Two days later, on the western horizon, they beheld the ocean. Many of the streams whose sources they had seen when they crossed the divide from the lake basin, and whose courses they had followed, were now rivers a mile wide, with the tide ebbing and rising within them many hundreds of miles from their mouths. When they reached the shore line they found the waves breaking, as on earth, upon the sands, but with this difference: they had before noted the smallness of the undulations compared with the strength of the wind, the result of the water's weight. These waves now reminded them of the behaviour of mercury, or of melted lead when stirred on earth, by the rapidity with which the crests dropped. Though the wind was blowing an on-shore gale, there was but little combing, and when there was any it lasted but a second. The one effort of the crests and waves seemed to be to remain at rest, or, if stirred in spite of themselves, to subside.
When over the surface of the ocean, the voyagers rose to a height of thirty thousand metres, and after twenty- four hours' travelling saw, at a distance of about two hundred miles, what looked like another continent, but which they knew must be an island. On finding themselves above it, they rose still higher to obtain a view of its outlines and compare its shape with that of the islands in the photographs they had had time to develop. The length ran from southeast to northwest. Though crossed by latitude forty, and notwithstanding Jupiter's distance from the sun, the southern side had a very luxuriant vegetation that was almost semi-tropical. This they accounted for by its total immunity from cold, the density of the air at sea-level, and the warm moist breezes it received from the tepid ocean. The climate was about the same as that of the Riviera or of Florida in winter, and there was, of course, no parching summer.
"This shows me," said Bearwarden, "that a country's climate depends less on the amount of heat it receives from the sun than on the amount it retains; proof of which we have in the tops of the Himalayas perpetually covered with snow, and snow-capped mountains on the very equator, where they get the most direct rays, and where those rays have but little air to penetrate. It shows that the presence of a substantial atmosphere is as necessary a part of the calculation in practice as the sun itself. I am inclined to think that, with the constant effect of the internal heat on its oceans and atmosphere, Jupiter could get along with a good deal less solar heat than it receives, in proof of which I expect to find the poles themselves quite comfortable. The reason the internal heat is so little taken into account on earth is because, from the thickness of the crust, it cannot make itself felt; for if the earth were as chilled through as ice, the people on the surface would not feel the difference."
A Jovian week's explorations disclosed the fact that though the island's general outlines were fairly regular, it had deep-water harbours, great rivers, and land-locked gulfs and bays, some of which penetrated many hundred miles into the interior. It also showed that the island's length was about six thousand miles, and its breadth about three thousand, and that it had therefore about the superficial area of Asia. They found no trace of the great monsters that had been so numerous on the mainland, though there were plenty of smaller and gentle-looking creatures, among them animals whose build was much like that of the prehistoric horse, with undeveloped toes on each side of the hoof, which in the modern terrestrial horse have disappeared, the hoof being in reality but a rounded-off middle finger.
"It is wonderful," said Bearwarden, "how comparatively narrow a body of water can keep different species entirely separate. The island of Sumatra, for instance, is inhabited by marsupials belonging to the distinct Australian type, in which the female, as in the kangaroo, carries the slightly developed young in a pouch; while the Malay peninsula, joined to the mainland, has all the highly developed animals of Asia and the connected land of the Eastern hemisphere, the narrow Malacca Strait being all that has kept marsupials and mammals apart, though the separating power has been increased by the rapid current setting through. This has decreased the chance of creatures carried to sea on drift-wood or uprooted trees getting safely over to such a degree that apparently none have survived; for, had they done so, we may be certain that the mammals, with the advantage their young have over the marsupials, would soon have run them out, the marsupials being the older and the less perfect form of life of the two."
Before leaving the beautiful sea-girt region beneath them, Cortlandt proposed that it be named after their host, which Bearwarden seconded, whereupon they entered it as Ayrault Island on the charts. After this they rose to a great height, and flew swiftly over three thousand miles of ocean till they came to another island not quite as large as the first. It was four thousand five hundred miles long by something less than three thousand wide, and was therefore about the size of Africa. It had several high ranges of mountains and a number of great rivers and fine harbours, while murmuring, bubbling brooks flowed through its forest glades. There were active volcanoes along the northern coast, and the blue, crimson, and purple lines in the luxuriant foliage were the most beautiful they had ever seen.
"I propose," said Bearwarden, "that we christen this Sylvialand." This Cortlandt immediately seconded, and it was so entered on the charts.
"These two islands," said Bearwarden, "may become the centres of civilization. With flying machines and cables to carry passengers and information, and ships of great displacement for the interchange of commodities, there is no limit to their possible development. The absence of large waves will also be very favourable to sea-spiders, which will be able to run at tremendous speeds. The constancy in the eruptions of the volcanoes will offer a great field to Jovian inventors, who will unquestionably be able to utilize their heat for the production of steam or electricity, to say nothing of an inexhaustible supply of valuable chemicals. They may contain the means of producing some force entirely different from apergy, and as superior to electricity as that is to steam. Our earthly volcanoes have been put to slight account because of the long intervals between eruptions."
After leaving Sylvialand they went westward to the eastern of the two crescent continents. It was separated from the island by about six thousand miles of ocean, and had less width than the western, having about the proportions of a three-day crescent, while the western had the shape of the moon when four or five days old. They found the height of the mountains and plateaus somewhat less than on the eastern continent, but no great difference in other respects, except that, as they went towards the pole, the vegetation became more like that of Scotland or a north temperate region than any they had seen. On reaching latitude fifty they again came out over the ocean to investigate the speckled condition they had observed there. They found a vast archipelago covering as great an area as the whole Pacific Ocean. The islands varied from the size of Borneo and Madagascar to that of Sicily and Corsica, while some contained but a few square miles. The surface of the archipelago was about equally divided between land and water.
"It would take good navigation or an elaborate system of light-houses," said Bearwarden, "for a captain to find the shortest course through these groups."
The islands were covered with shade trees much resembling those on earth, and the leaves on many were turning yellow and red, for this hemisphere's autumn had already begun.
"The Jovian trees," said Cortlandt, "can never cease to bear, though the change of seasons is evidently able to turn their colour, perhaps by merely ripening them. When a ripe leaf falls off, its place is doubtless soon taken by a bud, for germination and fructification go on side by side."
Before leaving, they decided to name this Twentieth Century Archipelago, since so much of the knowledge appertaining to it had been acquired in their own day. At latitude sixty the northern arms of the two continents came within fifteen hundred miles of each other. The eastern extension was split like the tail of a fish, the great bay formed thereby being filled with islands, which also extended about half of the distance across. The western extremity shelved very gradually, the sand-bars running out for miles just below the surface of the water.
After this the travellers flew northward at great speed in the upper regions of the air, for they were anxious to hasten their journey. They found nothing but unbroken sea, and not till they reached latitude eighty-seven was there a sign of ice. They then saw some small bergs and field ice, but in no great quantities. As their outside thermometer, when just above the placid water--for there were no waves here--registered twenty- one degrees Fahrenheit, they accounted for this scarcity of ice by the absence of land on which fresh water could freeze, and by the fact that it was not cold enough to congeal the very salt sea-water.
Finally they reached another archipelago a few hundred miles in extent, the larger islands of which were covered with a sheet of ice, at the edges of which small icebergs were being formed by breaking off and slowly floating. Finding a small island on which the coating was thin, they grounded the Callisto, and stepped out for the first time in several days. The air was so still that a small piece of paper released at a height of six feet sank slowly and went as straight as the string of a plumb-line. The sun was bisected by the line of the horizon, and appeared to be moving about them in a circle, with only its upper half visible. As Jupiter's northern hemisphere was passing through its autumnal equinox, they concluded they had landed exactly at the pole.
"Now to work on our experiment," said Cortlandt. "I wonder how we may best get below the frozen surface?"
"We can explode a small quantity of dynamite," replied Bearwarden, "after which the digging will be comparatively easy."
While Cortlandt and Bearwarden prepared the mine, Ayrault brought out a pickaxe, two shovels, and the battery and wires with which to ignite the explosive. They made their preparations within one hundred feet of the Callisto, or much nearer than an equivalent amount of gunpowder could have been discharged.
"This recalls an old laboratory experiment, or rather lecture," said Cortlandt, as they completed the arrangements, "for the illustration is not as a rule carried out. Explode two pounds of powder on an iron safe in a room with the windows closed, and the windows will be blown out, while the safe remains uninjured. Explode an equivalent amount of dynamite on top of the safe, and it will be destroyed, while the glass panes are not even cracked. This illustrates the difference in rapidity with which the explosions take place. To the intensely rapid action of dynamite the air affords as much resistance as a solid substance, while the explosion of the powder is so slow that the air has time to move away; hence the destruction of the windows in the first case, and the safe in the second."
When they had moved beyond the danger line, Bearwarden, as the party's practising engineer, pressed the button, and the explosion did the rest. They found that the ground was frozen to a depth of but little more than a foot, below which it became perceptibly warm. Plying their shovels vigorously, they had soon dug the hole so deep that its edges were above their heads. When the floor was ten feet below the surrounding level the thermometer registered sixty.
"This is scarcely a fair test," said Cortlandt, "since the heat rises and is lost as fast as given off. Let us therefore close the opening and see in what time it will melt a number of cubic feet of ice."
Accordingly they climbed out, threw in about a cart-load of ice, and covered the opening with two of the Callisto's thick rugs. In half an hour all the ice had melted, and in another half hour the water was hot.
"No arctic expedition need freeze to death here," said Bearwarden, "since all a man would have to do would be to burrow a few feet to be as warm as toast."
As the island on which they had landed was at one side of the archipelago, but was itself at the exact pole, it followed that the centre of the archipelago was not the part farthest north. This in a measure accounted for the slight thickness of ice and snow, for the isobaric lines would slope, and consequently what wind there was would flow towards the interior of the archipelago, whose surface was colder than the surrounding ocean. The moist air, however, coming almost entirely from the south, would lose most of its moisture by condensation in passing over the ice-laden land, and so, like the clouds over the region east of the Andes, would have but little left to let fall on this extreme northern part. The blanketing effect of a great thickness of snow would also cause, the lower strata of ice to melt, by keeping in the heat constantly given off by the warm planet.
"I think there can be no question," said Cortlandt, "that, as a result of Jupiter's great flattening at the poles and the drawing of the crust, which moves faster in Jupiter's rotation than any other part, towards the equator, the crust must be particularly thin here; for, were it as thin all over, there would be no space for the coal-beds, which, judging from the purity of the atmosphere, must be very extensive. Further, we can recall that the water in the hot spring near which we alighted, which evidently came from a far greater depth than we have here, was not as hot as this. The conclusion is clear that elsewhere the internal heat is not as near the surface as here."
"The more I see of Jupiter," exclaimed Bearwarden enthusiastically, "the more charmed I become. It almost exactly supplies what I have been conjuring up as my idea of a perfect planet. Its compensations of high land near the equator, and low with effective internal heat at the poles, are ideal. The gradual slope of its continental elevations, on account of their extent, will ease the work of operating railways, and the atmosphere's density will be just the thing for our flying machines, while Nature has supplied all sources of power so lavishly that no undertaking will be too great. Though land as yet, to judge by our photographs, occupies only about one eighth of the surface, we know, from the experience of the other planets, that this is bound to increase; so that, if the human race can perpetuate itself on Jupiter long enough, it will undoubtedly have one fourth or a larger proportion for occupation, though the land already upheaved comprises fully forty times the area of our entire globe, which, as we know, is still three-fourths water."
"Since we have reached what we might call the end of Jupiter, and still have time, continued Ayrault, "let us proceed to Saturn, where we may find even stranger things than here. I hoped we could investigate the great red spot, but am convinced we have seen the beginning of one in Twentieth Century Archipelago, and what, under favourable conditions, will be recognized as such on earth."
It was just six terrestrial weeks since they had set out, and therefore February 2d on earth.
"It would be best, in any case, to start from Jupiter's equator," said Cortlandt, "for the straight line we should make from the surface here would be at right angles to Saturn. We shall probably, in spite of ourselves, swing a few degrees beyond the line, and so can get a bird's-eye view of some portion of the southern hemisphere."
"All aboard for Saturn!" cried Bearwarden enthusiastically, in his jovial way. "This will be a journey."