was due
the entire design of the wonderful ship, undertook, at Sir Reginald's
request, to point out to Lady Elphinstone a few of the most remarkable
characteristics of the structure; and accordingly, when her ladyship had
exhausted her wonder at the enormous proportions of the _Flying Fish_,
Herr von Schalckenberg conducted his hostess forward and into the space
between the starboard bilge-keel and the bottom of the ship, where there
was just sufficient room for a tall man to stand upright close to the
inner face of the bilge-keel. At a certain point in the tunnel-like
passage the professor came to a halt, and remarked--

"Now, Lady Olivia, kindly favour me with your attention. Although you
cannot distinguish it, there is a trap-door here, giving ingress to the
interior of the ship, and as it is possible that you may at some time or
other wish to make use of it when none of us are at hand to help you, I
should like to show you how the door is to be opened or closed. Now, in
the first place, you will observe that there is a vertical and also a
horizontal joint in the plating, meeting just here--it is the only
junction of the kind in this passage-way, so you cannot possibly mistake
it. Now, kindly take notice of these vertical and horizontal rows of
rivet-heads, and especially of this particular rivet that is common to
both rows. There is nothing whatever to distinguish it from the others,
is there? No. But if you will place your finger upon it, thus, and
push firmly to the left, thus, you will see what happens."

And, as the professor spoke, a section of the polished silver-like
plating of the ship's bottom folded gently out until its outer edge
rested upon the ground, forming a kind of sloping gangway, by means of
which it was easy to enter the yawning aperture that now appeared in the
ship's bottom.

"Supposing, however," continued the professor, "that you are leaving the
ship, and wish to close the trap-door behind you, all that you have to
do is to push the rivet back into its original position, and the
mechanism operating the door at once responds, closing the flap, thus,
and leaving no indication whatever of its existence. Now, Lady Olivia,
let me see whether you can open the flap."

Thus invited, Lady Elphinstone laid her finger upon the rivet-head and
gave it a vigorous push to the left, upon which the flap folded out as
before, and von Schalckenberg, taking her ladyship's hand, led her with
old-fashi