o sharp; but
it has work to do, or it wouldn't be there. That section o' railroad
iron on top must be to hang the boat by,--a traveler,--when she's out
o' water.

"And the fan-wheel on the nose--what's that for? If it's a speed or
distance indicator, the dial's inside, out o' sight. There's no
exhaust, so the motive power can't be steam. Clockwork or electricity,
maybe. Mighty fine workmanship all through! That square door is fitted
in for keeps, and she must ha' cost a heap. Now, as she has horizontal
rudders, she's intended to steer up and down; and as there's no way to
get into her or to stay on her, and as she can't be started from the
inside or steered from the outside, I take it she's a model o' one o'
those submarine boats I've heard of--some fellow's invention that's got
away from him. Guess I'll try that lever and see what happens. I'll
bury the propellers, though; no engine ought to race."

He pushed the craft into deeper water, pointed it shoreward, and
cautiously lifted the curved blade to a perpendicular position, as high
as it would go. Nothing happened. He lowered it, raised it again,--it
worked very easily,--then, leaving it upright, he threw the long brass
lever back into the slot. A slight humming came from within, the
propellers revolved slowly, and the craft moved ahead until the bow
grounded. Then he followed and lifted the lever out of the slot to its
first position, shutting off the power.

Delighted with his success, he backed it out farther than before and
again threw back the brass lever, this time with the curved blade down
flat on the hull. With the sinking of the lever into the slot the
mechanism within gave forth a rushing sound, the propellers at the
stern threw up a mound of foam, and the craft shot past him, dived
until it glanced on the sandy bottom, then slid a third of its length
out of water on the beach and stopped, the propellers still churning,
and the small wheel on the nose still spinning with the motion given it
by the water.

"Air-pressure!" he exclaimed, as he shut it off. He had seen a line of
bubbles rise as the thing dived. "An air-engine, and the whole thing
must be full o' compressed air. The brass lever turns it on, and if the
steel blade's up it gives it the slow motion; if it's down, she gets
full speed at once. Now I know why it's blade-shaped. It's so the water
itself can push it down--after she starts."

He did not try to launch it; he waited until the tide f