132
The Wireless Operator
He asked permission to look around, and the captain told him to go where he liked, but cautioned him not to take too great liberties.
Henry stepped ashore and ran over to the dry dock. He was more amazed than ever when he stood on the edge of it and looked down into it. It was, indeed, a great hole in the ground—an excavation hundreds of feet long and many yards wide. The sides were made of massive masonry, built up like steps, of huge blocks of granite. The dry dock was as deep as a tall house is high. In shape it was long, and would have been rectangular had its inner end been square instead of rounding. The other end, the square end, was what interested Henry, for when he came to examine it, he found it was nothing but a water-gate. It was a great steel structure, tremendously braced to make it strong, though at first glimpse it seemed much like the rest of the wall. This steel end or gate held the water out, for, of course, the dry dock opened into the harbor. It was so made that water could pour through open ports, filling the dock. Then the gate itself could be swung outward to one side, so that a ship could enter the dock, and when the gate was once more swung in place and the openings closed, pumps were put at work and all the water pumped out, leaving the ship propped up securely on keel blocks. Thus the workmen