Jarvis shifted the nozzle to the other side and bathed the other leg, at the same time keeping a watch for the boss. The latter was nowhere in sight. He had gotten well out of harm's way, evidently knowing what was about to happen. Having bathed himself to his satisfaction Jarvis began playing the hose on the cinder pile. The first contact of the water threw up a great cloud of steam, followed by a sharp, hissing sound. Steve knew by the sound that the other pit was being wet down, but it did not occur to him, either, that there was any danger in the operation. In fact, he was too busy shoveling the cinders from his own pit to give much attention to what was going on in the other. Bob was humming softly to himself as he played with the stream, first sending it straight up into the air so that the spray covered a wide area by the time it reached the floor of the mill. No one chanced to get wet, however, save the two boys, Bob being the more so because he was right under the shower. Next he turned the stream straight into the pit, driving it down in one place, trying to bore a hole in the cinders and slag. "Say, Steve!" "What?" "What do you think about----" Puff! A slender column of black smoke shot up from the centre of the pit that Jarvis was watering down. The lad stared at it in surprise. "Look at the geyser!" he shouted. Boom! The ground under Bob Jarvis's feet rocked liked a cradle. A great, black column rose from under his very feet, lifting him from the floor and hurling the boy straight up into the air. CHAPTER V ON THE BRINK OF A VOLCANO Reverberating crashes rent the air. Workmen in that part of the mill were hurled violently to the ground. Yells and cries were heard on all sides. The interior of the mill was full of flying debris. Bob Jarvis had put too much water on the pit. The sudden contraction, down deep among the hot slag and cinders, had caused a tremendous explosion, wreaking disaster for many feet on either side of the pit. Kalinski, in all probability, knew what would happen when he gave Jarvis permission to soak down the cinders, and no doubt that was why the boss made such haste to get away from the spot. If he were not there, he could not be held responsible for what had occurred. Fire spurted from the miniature volcano. Crash after crash followed, as parts of furnaces close by toppled over, though fortunately the inside walls of the furnaces did not fall and liberate their tons of molten metal. Many lives would have been lost had that occurred. However, the disaster was serious enough as it was, and several men had been injured. The red light was displayed at the top of the open-hearth building, but this time it was another than Steve Rush who was hurrying to the scene to gather the facts and give orders for the care of the injured.