“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

THE BIG SLIDE

For a short space there was a calm that seemed more thrilling than the wildest confusion.  It took a few seconds for the rush of water to reach the Bohio, and when it did the tug began to sway and tug at the mooring cables, for they had not yet been cast off to enable it to be towed.

Blake rushed toward the lower cabin.

“Where are you going?” cried Joe.

“To get the cameras,” replied his chum, not pausing.  “This is a chance we mustn’t miss.”