Of course, cutting holes into such rock is hard work. But Captain Noda and Lieutenant Mori have provided him with an unlimited supply of Chinese laborers. At first the chatter of their drills drowns out the sounds of the jungle. Later, as they burrow into the earth, it fades to a thick tamping beat, leaving only the buzzing drone of the air compressors. Even at night they work by the dim light of lanterns, which cannot penetrate the canopy overhead. Not that MacArthur is sending observation planes over Luzon in the middle of the night, but work lights shining up on the mountain would be noticed by the lowland Filipinos.