his eyes glued fast to a periscope. "Maybe a sky patrol," thought the
man of the earth; "a cop on the lookout for aerial smugglers, like as
not."

And then came another of those terrifying stops. This time, as soon as
he could collect his senses, the engineer saw that the machine had
landed approximately in the middle of the canon, and presumably among
the boulders in its bottom. For all about it were the tops of gigantic
rocks, most of them worn smooth from water action. And, as soon as the
engine stopped, Smith plainly heard the roar of water right at hand. He
could not see it, however. Why in the name of wonder didn't the fellow
look down, for a change?

The craft began to move. This time its motion was smoother arguing an
even surface. However, it had not gone far before, to the engineer's
astonishment, it began to move straight down a slope so steep that no
mechanism with which Smith was familiar could possibly have clung to it.
As this happened, his adopted eyes told him that the craft was located
upon one of those enormous boulders, in the center of a stream of such
absolute immensity that he fairly gasped. The thing was--colossal!

And yet it was true. The unseen machine deliberately moved along until
it was actually clinging, not to the top, but to the side of the rock.
The water appeared to be about five yards beneath, to the right. To the
left was the sky, while the center of that strange vision was now upon a
similar boulder seemingly a quarter of a mile distant, farther out in
the stream. But the fellow at the periscope didn't change position one
whit!

It was so unreal. Smith deliberately ignored everything else and watched