d he dodged into a thicket."

"Well," admitted Jimmie, "I did look back."

Ned, rather disgusted at the carelessness of the boy, walked on in silence
until the two came to the smooth slopes which led up to Gatun. There they
found the boys, waiting for them, eager for the story of the explosion,
and wondering at their long delay.

CHAPTER XVII.

THE WATCHER IN THE THICKET.

Between Tabernilla and Gamboa, a distance of about fifteen miles, the
restless Chagres river, in its old days of freedom, crossed the canal line
no less than fifteen times. At Gamboa the river finds a break in the rough
hills and winds off to the northeast, past Las Cruces and off into more
hills and jungles.

Where the river turns the canal enters the nine-mile cut through the
Cordilleras, which form the backbone of the continent. Here at the Culebra
cut, the greatest amount of excavation for the waterway is being done.
This cut ends at Pedro Miguel locks, which will ease the ships down into
the Pacific ocean.

Where the river turns to the northeast, at Gamboa, a wild and hilly
country forms both banks. The hillsides as well as the plateaux are
overgrown with dense vegetation. As in all tropical lands, the fight for
survival is fierce and merciless. Trees are destroyed by great creepers,
great creepers are destroyed by smaller growths, and every form of life,
vegetable as well as animal, has its enemy. Every living thing springs up
from the dead body of another.

Sheltered and half concealed from view in this wild country between Gamboa
and Las Cruces, on the day the Boy Scouts set out in their search for
Jimmie and Peter, there stood a house of stone which seemed as old as the
volcanic formation upon which it stood. It was said that the structure had
been there, even then looking old and dismantled, when the French began
their operations on the Isthmus.

This house faced the valley of the Chagres river, having its back against
a hill, which was one of the steps leading up to the top of the
Cordilleras. There was a great front entrance way, and many windows, but
the latter seemed closed. Few signs of life were seen about the place at
five o'clock that afternoon.

From a front room in the second story the sounds of voices came, and now
and then a door opened and closed and a footstep was heard on the
stairway. However, those who walked about the place seemed either going or
coming, for the house gained no added population because o