CHAPTER XII

ALMOST AN ACCIDENT

“What’s that big, long affair, jutting out so far from the locks?” asked Blake, when the tug had approached nearer.

“That’s the central pier,” the captain informed him.  “It’s a sort of guide wall, to protect the locks.  You know there are three locks at this end; or, rather, six, two series of three each.  And each lock has several gates.  One great danger will be that powerful vessels may ram these gates and damage them, and, to prevent this, very elaborate precautions are observed.  You’ll soon see.  We’ll have to tie up to this wall, or we’ll run into the first protection, which is a big steel chain.  You can see it just ahead there.”

Joe and Blake, who had gotten all the pictures they wanted of the approach to the lock, stopped grinding away at the handle of the camera long enough to look at the chain.

These chains, for there are several of them, each designed to protect some lock gate, consist of links made of steel three inches thick.  They stretch across the locks, and any vessel that does not stop at the moment it should, before reaching this chain, will ram its prow into it.

“But I’m not taking any such chances,” Captain Watson informed the boys.  “I don’t want to be censured, which might happen, and I don’t want to injure my boat.”

“What would happen if you did hit the chain?” asked Blake.  They had started off again, after the necessary permission to enter the locks had been signaled to them.  Once more Blake and Joe were taking pictures, showing the chain in position.

“Well, if I happened to be in command of a big vessel, say the size of the Olympic, and I hit the chain at a speed of a mile and a half an hour, and I had a full load on, the chain would stop me within about seventy feet and prevent me from ramming the lock gate.”

“But how does it do it?” asked Joe.

“By means of machinery,” the captain informed him.  “Each end of the chain fender goes about a drum, which winds and unwinds by hydraulic power.  Once a ship hits the chain its speed will gradually slacken, but it takes a pressure of one hundred tons to make the chain begin to yield.  Then it will stand a pressure up to over two hundred and fifty tons before it will break.  But before that happens the vessel will have stopped.”

“But we are not going to strike the chain, I take it,” put in Mr. Alcando.

“Indeed we are not,” the captain assured him.  “There, it is being lowered now.”

As he spoke the boys saw the immense steel-linked fender sink down below the surface of the water.

“Where does it go?” asked Blake.

“It sinks down in a groove in the bottom of the lock,” the captain explained.  “It takes about one minute to lower the chain, and as long to raise it.”