help for it.
My difficulty now was to get back through the lock; for though I waited
for quite three hours no boats came along. I saw the upper gates were
open, but how to get through the lower ones I could not conceive. I felt
sure that my only chance was to frighten the lock-keeper, and get him to
open the sluices, for I knew I could pass through them unobserved if
they were open, as I had done once before.

"In my diver's helmet was a thick glass face-piece. This had an opening,
closed by a cap, which could be unscrewed, and through which I could
breathe when above water, and also through which my voice would come,
causing a peculiar hollowness which I guessed would have a very
startling effect, especially as I myself would be quite invisible. I got
into the lock, and shouted to Pegg. I succeeded in frightening him; he
hurried to do what I ordered. He wound up the lower sluice, I shot
through under water, and so got back unseen. All yesterday I hesitated
about trying the experiment again, the risk was so great; but I knew
that Ridsdale was certain to see his bank-book soon, that my forgery was
in imminent danger of being discovered, also that you, Bell, were coming
upon the scene.

"Yes, at any risk, I must now go on.

"I repaired my light, and again last night passed through the lock on my
way up, by simply waiting for another boat. As a matter of fact, I
passed up through this lock under a skiff about eleven o'clock. My light
was now all right, I found the diamond case easily, and turned to pass
down the stream by the same method as before. If you had not been here I
should have succeeded, and should have been safe, but now it is all up."

He paused, and his breath came quickly.

"I doubt if I shall recover," he said in a feeble voice.

"I hope you will," I replied; "and hark! I think I hear the doctor's
steps."

I was right, for a moment or two later old Jimmy Pegg and Dr. Simmons
entered the cottage. While the doctor was examining the patient and
talking to him, I went out with Jimmy to have a look at the submarine
boat. By fixing a rope round it we managed to haul it up, and then
proceeded to examine it. It certainly was the most wonderful piece of
ingenious engineering I had ever seen. The boat was in the shape of an
enormous cigar, and was made of aluminium. It was seven feet long, and
had a circular beam of sixteen inches. At the pointed end, close to
where the occupant's feet would be, was an air cha