Hour after hour the big hole deepened until the Seabees ran into noxious gases. Then they donned gas masks and continued. Deeper and deeper the hole was driven, until the temperature at the hole's end was over a hundred degrees. The Seabees merely shortened working time and operated in relays so efficiently that no time was lost. Rick and Scotty got back to the hole as often as they could, but there was much doing elsewhere. The Hot Springs Hotel swarmed with scientists and observers, and there were heated conferences and late evaluation sessions. The Spindrift scientists were always in demand, and their faces grew gaunt as the days passed. The hole gave its own location because of the shock waves it sent through the earth to the recorders, and even Rick's untrained eye could see the traces slowly closing with the magma front. Earthquakes increased in frequency until Rick and Scotty felt as though the ground never ceased shuddering. The air became noisy with planes as the Military Air Transport Command began ferrying in troops. Flight after flight of huge transports roared in for a landing at the Calor airport, discharged the soldiers, and took off again at once. And still the diamond hunt continued. Then, at one o'clock in the afternoon, Hartson Brant called a halt. "The magma's moving up through the dike," he reported. "It's now or never. Captain Montoya, we will ask the troops to clear the area. Commander Jameson, withdraw all men and equipment except those necessary for the final packing. Dr. Cantrell, please be ready to place the charge at dawn tomorrow." The final phase of the operation swung into action. The troops gathered at Redondo and marched shoulder to shoulder southward along the mountain slopes. They herded the diamond seekers before them, sometimes with enough roughness to overcome protests, but mostly with little difficulty. They herded the population entirely around El Viejo, and established a perimeter from Calor northward, with the population confined to a narrow segment of the island along the seaward side. Loud-speaker trucks roamed along the perimeter, reassuring the people. Military disaster units cooked huge quantities of food and prepared thousands of gallons of coffee and reconstituted milk. American soldiers played with cute little San Luzian kids and--after the diamond seekers became convinced they had never had a chance to find diamonds--the whole affair became one big picnic. But it was a picnic with overtones of fear. Rick and Scotty watched the placement of the nuclear explosive--a simple steel can, from the outside--in the big hole. They watched the remaining handful of Seabees load tons of rock in after it. Only the wires connecting the device to a radio firing unit on the beach gave evidence that an explosion equal to ten thousand tons of TNT was about to take place. Rick asked, "Won't all those rocks keep the volcano from erupting?"