grew more oppressive and the heat was like the breath of a
furnace. Ballard smoked another pipe on the bungalow porch, and when the
declining sun drove him from this final shelter he crossed the little
mesa and descended the path to the ravine below the dam.

Here he found food for reflection, and a thing to be done. With the flow
of the river cut off, the ground which had lately been its channel was
laid bare; and recalling Gardiner's hint about the possible insecurity
of the dam's foundations, he began a careful examination of the newly
turned leaf in the record of the great chasm.

What he read on the freshly-turned page of the uncovered stream-bed was
more instructive than reassuring. The great pit described by Gardiner
was still full of water, but it was no longer a foaming whirlpool, and
the cavernous undercutting wrought by the diverted torrent was
alarmingly apparent. In the cut-off tunnel the erosive effect of the
stream-rush was even more striking. Dripping rifts and chasms led off in
all directions, and the promontory which gave its name to the Elbow, and
which formed the northern anchorage of the dam, had been mined and
tunnelled by the water until it presented the appearance of a huge
hollow tooth.

The extreme length of the underground passage was a scant five hundred
feet; but what with the explorations of the side rifts--possible only
after he had gone back to the bungalow for candles and rubber
thigh-boots--the engineer was a good half-hour making his way up to the
great stop-gate with the rising flood on its farther side. Here the
burden of anxiety took on a few added pounds. There was more or less
running water in the tunnel, and he had been hoping to find the leak
around the fittings of the gate. But the gate was practically tight.

"That settles it," he mused gloomily. "It is seeping through this
ghastly honeycomb somewhere, and it's up to us to get busy with the
concrete mixers--and to do it quickly. I can't imagine what Braithwaite
was thinking of; to drive this tunnel through one of nature's compost
heaps, and then to turn a stream of water through it."

The sun was a fiery globe swinging down to the sky-pitched western
horizon when the Kentuckian picked his way out of the dripping caverns.
There were two added lines in the frown wrinkling between his eyes, and
he was still talking to himself in terms of discouragement. At a
conservative estimate three months of time and many thousands of dol