an
counterbalanced by the greater power of the propeller in the denser
fluid. We shall soon see."

So saying, the professor set the engines in motion, and the _Flying
Fish_ began to glide smoothly yet soon with marvellous rapidity through
the water.

"My surmise was correct, you see," said the professor some ten minutes
afterwards, as he pointed to another gauge on the wall of the pilot-
house. "We are now running steadily at a speed of one hundred and fifty
miles per hour; and we have already travelled twelve miles from our
starting-point. The gauge is, as you see, self-registering, and shows
on that piece of paper the exact distance run through or along the
surface of the water (but not through the _air_) between any two given
points. When the ship's course is altered, or you desire for any other
reason to commence the register afresh, all you have to do is, press
that ivory knob, and the instrument will draw a line across the paper
and, at the same moment, spring back to zero."

The water, at the depth at which they were travelling, proved to be
almost as transparent as crystal, of a dark olive-green tint beneath
them, merging by imperceptible gradations to a faint greenish-blue
above; the surface being discernible by the shifting lace work of gold
incessantly playing over it where the sun's beams caught the ridges of
the faint rippling wavelets raised by the languid summer breeze. Even
small objects, such as medusae, and fragments of weed floating in mid-
sea, were distinguishable at a considerable distance; and fishing-boats
could be clearly made out at the distance of a mile. A very novel and
curious effect was witnessed when objects floating on the surface (such
as ships, fishing-boats, or aquatic birds) came into view, the submerged
portions of them being as clearly defined as though they were floating
in air, whilst the parts _above_ the surface were wavering and
indistinct. A flock of diving gulls, for instance, which they passed at
no great distance, presented the curious spectacle of little more than
dark dots furnished with pairs of quickly-moving webbed feet whilst they
floated on the placid surface; but directly a bird dived its whole body
became distinctly visible, with a long stream of air-bubbles trailing
behind it.

At length it became apparent that they were approaching a large fleet of
ships making their way up channel.

A smile passed over the professor's features as he gazed out at th