is 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."

"We sure will!" cried Blake.

"Isn't it all wonderful!" exclaimed Joe, who was deeply impressed
by all he saw.

"It is, indeed!" agreed the Spaniard. "Your nation is a powerful
and great one. It is a tremendous achievement."

Aboard the tug they went around toward the great dam that is
really the key to the Panama Canal. For without this dam there
would be no Gatun Lake, which holds back the waters of the Chagres
River, making a big lake eighty-five feet above the level of the
ocean. It is this lake that makes possible the operation of a lock
canal. Otherwise there would have to be a sea-level one, and
probably you boys remember what a discussion there was, in
Congress and elsewhere, about the advantages and disadvantages of
a sea-level route across the Isthmus.

But the lock canal was decided on, and, had it not been, it is
probable that the Canal would be in process of making for many
years yet to come, instead of being finished now.

"Whew!" whistled Joe, as they came in sight of the dam. "That sure
is going some!"

"That's what it is!" cried Captain Watson, proudly, for he had had
a small part in the work. "It's a mile and a half long, half a
mile thick at the ba