lls, endeavoring to bring
into place the emergency dam.

It was a risky thing to do, but then Blake and Joe were used to
doing risky things, and this was no more dangerous than the
chances they had taken in the jungle, or in earthquake land.

On rushed the water. The tug rose and fell on the bosom of the
flood, unconfined as it was by the restraining gates. And as the
sturdy vessel swayed this way and that, rolling at her moorings
and threatening every moment to break and rush down the Canal,
Blake and Joe stood at their posts, turning the cranks. And beside
them stood Mr. Alcando, if not as calm as the boys, at least as
indifferent to impending fate.

Captain Wiltsey of the _Bohio_ had given orders to run the engine
at full speed, hoping by the use of the propeller to offset
somewhat the powerful current. But the rush of water was too great
to allow of much relief.

"There goes the emergency dam!" suddenly cried Blake.

"Gone out, you mean?" yelled Joe above the roar of waters.

"No, it's being swung into place. It'll be all over in a few
minutes. Good thing we got the pictures when we did."

Across the lock, about two hundred feet above the upper gate, was
being swung into place the steel emergency dam, designed to meet
and overcome just such an accident as had occurred.

These dams were worked by electricity, and could be put in place
in two minutes; or, if the machinery failed, they could be worked
by hand, though taking nearly half an hour, during which time much
damage might be done. But in this case the electrical machinery
worked perfectly, and the dam, which when not in use rested
against the side of the lock wall, and parallel with it, was swung
across.

Almost at once the rush of water stopped, gradually subsiding
until the tug swung easily at her mooring cables.

"Whew!" whistled Blake in relief, as he ceased grinding at the
crank of his moving picture camera. "That was going some!"

"That's what!" agreed Joe. "But I guess we got some good films."

"You certainly deserved to!" exclaimed Mr. Alcando, with shining
eyes. "You are very brave!"

"Oh, it's all in the day's work," spoke Blake. "Now I wonder how
that happened?"

"That's what I'd like to know," said Captain Wiltsey. "I must look
into this."

An inquiry developed the fact that a misplaced switch in some
newly installed electrical machinery that controlled the upper
lock gate was to blame. The lock machinery was designed to be
aut