But there were regular intervals between each successive blaze of light; and these allowed him to observe. Little, gleaming robots, walking like human beings on broad, elastic-shod feet, and provided with metal arms, were rebuilding the battlemented wall with limestone quarried from the hillside. They worked with perfect efficiency, raising blocks into place, and applying a kind of mortar with spatulate-ended arms. But their movements for each operation were always identical, betraying not intellect but standardized mechanical perfection. And it was the same with the other machines and weapons. A gun--it didn't look so very different from a familiar artillery piece, except for its complex breech-loading mechanism, fired intermittently, without any crew to operate it. Watching, Perry concluded that its sighting and firing apparatus must be stimulated by certain sounds, movements, and lights, out there where the soldiers were entrenched. For when he heard a shout from the rear, or saw a cannon flash, or troops advancing from the trenches, there was always a volley of small, screaming shells, the latter directed with a precise, cold accuracy, that must depend on the spiritless exactness of instruments. And the result was massacre. Heat beam projectors, lensed boxes in their webwork supports, seemed to operate under the same kinds of stimuli, turning their faint, barely visible spears of heatwaves toward sudden light, noise, or movement. Searchlights swept the sky, probably drawn by motor sounds. And if they located a plane, the movement of its light-enveloped form was enough to attract the high-angling muzzles of slender guns that fired with soft pops, but reduced duralumin to powder. The aiming was always perfect. When the search beam was turned away from him, Perry got cautiously out of the water and dashed for the nearest bush. He crouched behind it, as the beam swept past him like a great eye. Then higher, to another bush. And so he advanced. Once, because he stumbled, he was caught in the open; but he threw himself flat and waited, cursing his clumsiness. But the blazing glare passed him, and no blasting death followed. Perhaps camera eyes had photographed his inert form; but mechanical, adding-machine brains had not enough reasoning powers to recognize him as an interloper, as long as he did not move. Perry breathed with relief, and continued his intermittent climb at each brief moment of darkness.