When near the great lake's upper end,they passed the mouth of a river on their left side,which,from its volume,they concluded must be the principal source,and therefore they determined to trace it.They found it to be a most beautiful stream,averaging two and a half miles in width,evidently very deep,and with a full,steady current.After proceeding for several hours,they found that the general placidity grew less,the smooth surface occasionally became ruffled by projecting rocks and rapids,and the banks rose till the voyagers again found themselves in a ravine or canon.
During their sojourn on Jupiter they had had but little experience with the tremendous winds that they knew,from reason and observation,must rage in its atmosphere.They now heard them whistling over their heads,and,notwithstanding the protection afforded by the sides of the canon,occasionally received a gust that made the Callisto swerve.They kept on steadily,however,till sunset,at which time it became very dark on account of the high banks,which rose as steeply as the Palisades on the Hudson to a height of nearly a thousand feet.
Finding a small island near the eastern bank,they were glad to secure the Callisto there for the night,below the reach of the winds,which they,still heard singing loudly but with a musical note in what seemed to them like the sky.
"It is incomprehensible to me."said Ayrault,as they sat at dinner,"how the sun,at a distance of four hundred and eighty-three million miles,can raise the amount of water we have here passing us,and compared with which the discharge of the greatest river on earth would be insignificant,to say nothing of the stream we ascended before reaching this.""We must remember,"replied Cortlandt,"that many of the conditions are different here from those that exist on earth.We know that some of the streams are warm,and even hot,and that the temperature of Deepwaters Bay,and doubtless that of the ocean also,is considerably higher than ours.This would facilitate evaporation.The density of the atmosphere and the tremendous winds,of which I suspect we may see more later,must also help the sun very much in its work of raising vapour.But the most potent factor is undoubtedly the vast size of the basin that these rivers drain.""The great speed at which the atmospheric currents move,"said Bearwarden,"coupled with the comparative lowness of the mountain chains and the slight obstruction they offer to their passage,must distribute the rain very thoroughly,notwithstanding the great unbroken area of the continents.There can be no such state of things here as exists in the western part of South America,where the Andes are so high that any east-bound clouds,in crossing them,are shoved up so far into a cold region that all moisture they may have brought from the Pacific is condensed into rain,with which parts of the western slope are deluged,while clouds from the Atlantic have come so far they have already dispersed their moisture,in consequence of which the region just east of the Andes gets little if any rain.It is bad for a continent to have its high mountains near the ocean from which it should get its rain,and good for it to have them set well back.""I should not be surprised,"said Cortlandt,"if we saw another waterfall to-morrow,though not in the shape of rain.In the hour before we stopped we began to see rapids and protruding rocks.That means that we are coming to a part of the channel that is comparatively new,since the older parts have had time to wear smooth.I take it,then,that we are near the foot of a retreating cascade,which we may hope soon to see.That is exactly the order in which we found smooth water and rapids in river No.1,which we have named the Harlem."After this,not being tired,they used the remaining dark hours for recording their recent adventures.
CHAPTER XII.
HILLS AND VALLEYS.
With the first light they resumed their journey,and an hour after setting out they sighted,as Cortlandt had predicted,another cloud of vapour.The fall--for such it proved to be--was more beautiful than the other,for,though the volume of water was not so great,it fell at one leap,without a break,and at the same tremendous speed,a distance of more than a thousand feet.The canon rang with the echoes,while the spray flew in sheets against the smooth,glistening,sandstone walls.Instead of coming from a river,as the first fall had,this poured at once from the rocky lip,about two miles across,of a lake that was eleven hundred feet above the surging mass in the vale below.
"It is a thousand pities,"said Bearwarden,"that this cataract has got so near its source;for,at the rate these streams must cut,this one in a few hundred years,unless something is done to prevent it,will have worn back to the lake,and then good-bye to the falls,which will become a series of rapids.Perhaps the first effect will be merely to reduce by a few feet the height of the falls,in which case they will remain in practically the same place."About the shores of this lake they saw rhinoceroses with long thick wool,and herds of creatures that much resembled buffaloes.
