h ran from the bench level to the foot of the dam. Here
he walked along the level of the great eddy, along the rocky shore,
examining the face of the vast concrete wall itself, gazing also as he
always did, with no special purpose, at the face of the wide and long
apron where the waters foamed over, a few inches deep, white as milk,
day and night.

Any attempt at the use of dynamite by any enemy naturally would be made
on this lower side of the dam. There were different places which might
naturally be used by a criminal who had opportunity. One of these,
concealed from the chance glance of any officer, was back under the
apron, behind the half-completed side columns of the spill gate, where
a great buttress came out to flank the apron. A charge exploded here
would get at the very heart of the dam, for it would open the turbine
wells and the spillway passage which had been provided for the
controlled outlet.

Ragged heaps of native rock lay along the foot of the dam, flanking the
edge of the great eddy eastward of the apron. Here often the laborers
stood and cast their lines for the leaping trout, which, wearied by
their fruitless fight at the apron, that carried them only up to the
insurmountable obstacle which reached a hundred feet above them,
sometimes were swept back to seek relief in the gentler waters of the
deep eddy, that swung inshore from the lower end of the apron.

Sim Gage saw all these scenes, so familiar by this time, as they lay
half revealed under the blaze of the great searchlight. It all seemed
safe now, as it always had before.

But when at length he turned back to ascend to the upper level, he saw
something which caused him to stop for just an instant, and then to
spring into action.

The power plant proper of the dam was not yet wholly installed, only
the dam and turbine-ways being completed. In the power house itself, a
sturdy building of rock which caught hold of the immemorial mountain
foot beneath it, only a single unit of the dynamos had been installed.
This unit had been hooked on, as the engineers phrased it, in order to
furnish electric light to the camp itself, for the telephone service of
the valley and for the minor machinery which was operated by this or
that machine shop along the side of the mountain. A cable from the
power house ran up to another house known as the lighting plant, which
stood in the angle between the street level and the dam itself. Here
was installed