"I don't know!" Washington replied, as he dashed toward the engine
room.

The Mermaid, her forward flight checked, hung in the air, suspended,
neither rising or falling.

"Why don't we go on down?" the professor asked, hurrying to the tower.

"There has been an explosion-- an accident!" exclaimed Mark. "I guess
we can't go down!"

"But we must!" Mr. Henderson insisted, seizing the lever which should
have produced a downward motion. The handle swung to and fro. It was
disconnected from the apparatus it operated.

The ship was now stationary in the air, moving neither forward nor
backward, neither rising nor falling. Washington had stopped the air
pumps as soon as he learned something was wrong.

When Mr. Henderson saw the useless lever, which had controlled the
outlet of gas from the holder, he ran out on deck. One glance told him
what had happened. One of the electric wires had become
short-circuited,-- that is, the insulation had worn off and allowed
the current to escape. This had produced a spark, which had exploded
the gas which was in the pipe leading from the generator up into the
aluminum holder. Fortunately there was an automatic cut-off for the
supply of vapor, or the whole tank would have gone up.

As it was, only a small quantity had blown up, but this was enough to
break the machinery at the point where the lever in the conning tower