The tug did not occupy a whole section of the lock, for they are built to accommodate vessels a thousand feet long. To economize time in filling up such a great tank as that would be the locks are subdivided by gates into small tanks for small vessels.
"It takes just forty-six gates for all the locks," explained Captain Watson, while Blake and Joe were getting their camera in position, and the men at the locks were closing certain water valves and opening others. "Each lock has two leaves, or gates, and their weight runs anywhere from three hundred to six hundred tons, according to its position. Some of the gates are forty-seven feet high, and others nearly twice that, and each leaf is sixty-five feet wide, and seven feet thick."
"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.