“Think of being crushed between two steel gates, of six hundred tons each, eighty feet high, sixty-five feet wide and seven feet thick,” observed Joe.

“I don’t want to think of it!” laughed Blake.  “We are well out of that,” and he glanced back toward the closed and water-tight lock gates which had so nearly nipped the tug.

“Here comes the water!” cried the captain.  There was a hissing and gurgling sound, and millions of bubbles began to show on the surface of the limpid fluid in which floated the Nama.  The water came in from below, through the seventy openings in the floor of each lock, being admitted by means of pipes and culverts from the upper level.

As the water hissed, boiled and bubbled while it flowed in Blake took moving pictures of it.  Slowly the Nama rose.  Higher and higher she went until finally she was raised as high as that section of the lock would lift her.  She went up at the rate of two feet a minute, though Captain Watson explained that when there was need of hurry the rate could be three feet a minute.

“And we have two more locks to go through?” asked Joe.

“Yes, two more here at Gatun, and three at Miraflores; or, rather, there is one lock at Pedro Miguel, where we go down thirty and a third feet, and then we go a mile to reach the locks at Miraflores.

“There we shall have to go through two locks, with a total drop of fifty-four and two-thirds feet,” Captain Watson explained.  “The system is the same at each place.”

The tug was now resting easily in the basin, but some feet above the sea level.  Blake and Joe had taken enough moving pictures of this phase of the Canal, since the next scenes would be but a repetition of the process in the following two locks that would lift the Nama to the level of Gatun Lake.

“But I tell you what we could do,” Blake said to his chum.

“What’s that—­swim the rest of the way,” asked Joe, “and have Mr. Alcando make pictures of us?”

“No, we’ve had enough of water lately.  But we could get out on top of the lock walls, and take pictures of the tug going through the lock.  That would be different.”

“So it would!” cried Joe.  “We’ll do it!”

They easily obtained permission to do this, and soon, with their cameras, and accompanied by Mr. Alcando, they were on the concrete wall.  From that vantage point they watched the opening of the lock gates, which admitted the Nama into the next basin.  There she was shut up, by the closing of the gates behind her, and raised to the second level.  The boys succeeded in getting some good pictures at this point and others, also, when the tug was released from the third or final lock, and steamed out into Gatun Lake.  There was now before her thirty-two miles of clear water before reaching Miraflores.

“Better come aboard, boys,” advised Captain Watson, “and I’ll take you around to Gatun Dam.  You’ll want views of that.”