ly to reappear in the
swamps, regulating their speed by that of the travellers. The three men
were greatly surprised at this.

"You may observe," said Cortlandt, "that the surface of the impression
is depressed as you watch it, as though by a weight, and you can see,
and even hear, the water being squeezed out, though whatever is doing
it is entirely invisible. They must be made by spirits sufficiently
advanced to have weight, but not advanced enough to make themselves
visible."

Moved by a species of vandalism, Bearwarden raised his twelve-bore, and
fired an ordinary cartridge that he had not prepared for the dragons,
at the space directly over the nearest forming prints. There was a
brilliant display of prismatic colours, as in a rainbow, and though the
impressions already made remained, no new ones were formed.

"Now you have done it!" said Cortlandt. "I hoped to be able to
investigate this further."

"We shall doubtless see other and perhaps more wonderful things,"
replied Bearwarden. "I must say this gives me an uncanny feeling."

When they had completed a little over half their circle, they came upon
another of the groves with which Saturn seemed to abound, at the edge
of which, in a side-hill, was a cave, the entrance of which was
composed of rocky masses that had apparently fallen together, the floor
being but little higher than the surface outside. The arched roof of
the vestibule was rendered watertight by the soil that had formed upon
it, which again was overgrown by vines and bushes.

"This," said Bearwarden, "will be a good place to camp, for the cave
will protect us from dragons, unless they should take a notion to
breathe at us from the outside, and it will keep us dry in case of
rain. To-morrow we can start with this as a centre, and make another
circuit."

"We can explore Saturn on foot," said Cortlandt, "and far more
thoroughly than Jupiter, on account of its comparative freedom from
monsters. Not even the dragons can trouble us, unless we meet them in
large numbers."

Thereupon they set about getting fuel for their fire. Besides
collecting some of the dead wood that was lying all about, they split
up a number of resinous pine and fir trees with explosive bullets from
their revolvers, so that soon they not only had a roaring fire, but
filled the back part of the cave with logs to dry, in case they should
camp there again at some later day. Neither Cortlandt nor Bearwarden
felt much