e his head. A piece of rail had been
clamped across the metals to prevent the truck running over the edge.
Jake stood close by on the downward slope of the dam. Everything was
ready for the lowering of the next block, but they had a few minutes to
wait.

"That rib's a great idea," Jake remarked. "Tones up the whole work; it's
curious what you can do with a flowing line, but it must be run just
right. Make it the least too flat and you get harshness, too full and the
effect's vulgarly pretty or voluptuous. Beauty's severely chaste and I
allow, as far as form goes, this dam's a looker." He paused and indicated
the indigo sky, flaring lights, and sweep of pearly stone. "Then if you
want color, you can revel in silver, orange, and blue."

Dick, who nodded, shared Jake's admiration. He had helped to build the
dam and, in a sense, had come to love it. Any defacement or injury to it
would hurt him. Just then a bright, blinking spot emerged from the dark
at the other end of the line and increased in radiance as it came
forward, flickering along the slope of stone. It was the head-lamp of the
locomotive that pushed the massive concrete block they waited for. The
block cut off the light immediately in front of and below it, and when
the engine, snorting harshly, approached the edge of the gap somebody
shouted and steam was cut off. The truck stopped just short of the rail
fastened across the line, and Dick looked up.

The blast-lamp flung its glare upon the engine and the rays of the
powerful head-light drove horizontally into the dark, but the space
beyond the broken end of the dam was kept in shadow by the block, and the
glitter above dazzled his eyes.

"Swing the derrick-boom and tell the engineer to come on a yard or two,"
he said.

There was a patter of feet, a rattle of chains, and somebody called:
"_Adelante locomotura!_"

The engine snorted, the wheels ground through the fragments of concrete
scattered about the line, and the big dark mass rolled slowly forward. It
seemed to Dick to be going farther than it ought, but he had ascertained
that the guard-rail was securely fastened. As he watched the front of the
truck, Jake, who stood a few feet to one side, leaned out and seized his
shoulder.

"Jump!" he cried, pulling him forward.

Dick made an awkward leap, and alighting on the steep front of the dam,
fell heavily on his side. As he clutched the stones to save himself from
sliding down, a black mass plunged from