midnight
At eleven o'clock that night the workmen employed at the locks , the spillway , and the barrier of the Gatun dam found that their lights were not working satisfactorily and sent word back to the electric department that something was amiss . The electric department sent word back to the men in the excavations that the lights were all right so far as they were concerned , that they were doing their full duty efficiently , and that the men with the shovels , the dynamite and the dump cars might go chase themselves . This expression of fact and permission did not make it any lighter at the workings , but the men kept on , in the intermittent showers of illumination , and grumbled while they excavated and piled in the concrete . At last , just before midnight , the incandescence did not come back to the globes , and the men gathered in groups to discuss the matter and express heated opinions of the efficiency of the men in charge of the lighting plant . The workmen moved about here and there in the shadows and clambered like ants over the great bulk of the dam . No one looked to see that the men assembled in the workings all belonged there . At midnight four men who did not belong there entered the excavation which leads from the bottom of the lower lock to the sea-level channel into Limon Bay , which is a child of the Caribbean Sea .