ble exposures on
the same film," the Spaniard went on. "You know what I mean; when
a picture is shown of a person sitting by a fireside, say, and
above him or her appears a vision of other days."

"Oh, yes, we can tell you how that is done," Joe said, and the
rest of the evening was spent in technical talk.

"Well, what were you going to say about that collision?" asked Joe
of Blake when Mr. Alcando had left them, at nearly midnight.

"I don't think it's exactly safe to say what I think," was Blake's
response. "I think he is--suspicious of us," he finished in a
whisper. "Let's watch and await developments."

"But what object could he--"

"Never mind--now," rejoined Blake, with a gesture of caution.

Several busy days followed the sinking of the _Nama_. The moving
picture boys went through the Miraflores locks, making some fine
films, and then proceeded on to the Pacific Ocean breakwater, thus
making a complete trip through the Canal, obtaining a series of
pictures showing scenes all along the way. They also took several
views in the city of Panama itself.

Of course theirs was not the first vessel to make the complete
trip, so that feature lost something of its novelty. But the boys
were well satisfied with their labors.

"We're not through, though, by any means," said Blake. "We have to
get some pictures of Gatun Dam from the lower side. I think a few
more jungle scenes, and some along the Panama Railroad, wouldn't
go bad."

"That's right," agreed Joe.

So they prepared to make the trip back again to Colon.

Once more they were headed for the locks, this time to be lifted
up at Miraflores, instead of being let down. They approached the
central pier, were taken in charge by the electrical locomotives,
and the big chain was lowered so they could proceed.

Just as the lower gate was being swung open to admit them to the
lock, there was a cry of warning from above.

"What's that?" cried Joe.

"I don't know," Blake answered, "but it sounds as though something
were going to happen. I didn't have all those feelings for
nothing!"

Then came a cry:

"The upper gate! The upper gate is open! The water is coming down!
Put the emergency dam in place! Quick!"

Joe and Blake looked ahead to see the upper gates, which were
supposed to remain closed until the boat had risen to the upper
level, swing open, and an immense quantity of foamy water rush
out. It seemed about to overwhelm them.

CHAPTER XVIII