It was a considerable time before the two men, clinging to the supports of the bridge, were able to maintain their equilibrium sufficiently to render it possible to utter a few connected words. As soon as he could speak with reasonable comfort Cosmo exclaimed:
"Now I see what it is that causes the billows, but it is a phenomenon that I should never have anticipated. It is all due to the nebula. Evidently there are irregularities of some kind in its constitution which cause the formation of almost solid masses of water in the atmosphere—suspended lakes, as it were—which then plunge down in a body as if a hundred thousand Niagaras were pouring together from the sky.
"These sudden accessions of water raise stupendous waves which sweep off in every direction, and that explains the billows that we have encountered."
"Well, this nebular navigation beats all my experience," said Captain Arms, wiping the water out of his eyes. "I was struck by a waterspout once in the Indian Ocean, and I thought that that capped the climax, but it was only a catspaw to this. Give me a clear offing and I don't care how much wind blows, but blow me if I want to get under any more lakes in the sky."
"We'll have to take whatever comes," returned Cosmo, "but I don't think there is much danger of running directly into many of these downpours as we did into this one. Now that we know what they are, we can, perhaps, detect them long enough in advance to steer out of their way. Anyhow, we've got a good vessel under our feet. Anything but an ark of levium would have gone under for good, and if I had not covered the vessel with the dome there would have been no chance for a soul in her."
As a matter of fact, the Ark did not encounter any more of the columns of descending water, but the frequent billows that were met showed that they were careering over the face of the swollen sea in every direction.
But there was another trouble of a different nature. The absence of sun and stars deprived them of the ordinary means of discovering their place. They could only make a rough guess as to the direction in which they were going. The gyrostatic compasses gave them considerable assistance, and they had perfect chronometers, but these latter could be of no use without celestial observations of some kind.
At length Cosmo devised a means of obtaining observations that were of sufficient value to partially serve their purpose. He found that while the disk of the sun was completely hidden in the watery sky, yet it was possible to determine its location by means of the varying intensity of the light.
Where the sun was a concentrated glow appeared, shading gradually off on all sides. With infinite pains Cosmo, assisted by the experience of the captain, succeeded in determining the center of the maximum illumination, and, assuming that to represent the true place of the sun, they got something in the nature of observations for altitude and azimuth, and Captain Arms even drew on his chart "Sumner lines" to determine the position of the Ark, although he smiled at the thought of their absurd inaccuracy. Still, it was the best they could do, and was better than nothing at all.
They kept a log going also, although, as the captain pointed out, it was not of much use to know how fast they were traveling, since they could not know the precise direction, within a whole point of the compass, or perhaps several points.