Issuing from a break in the outer cavern wall was a stream of blue flame. For several hundred feet around it no vegetation grew, the ground being covered with thin gray ash. Robin looked at the loudly hissing lance of blue fire. It probably was a breakthrough from some adjoining bubble, one filled with a gas of some inflammable sort. Somehow in the course of the breakthrough, this leakage had been set aflame. And there it was now, a burning gas jet, sharp and hot. At that moment, Robin knew he had the answer to his metalworking problem. He'd tried to melt the metal of the rocket over his fires but he had been totally unsuccessful. But this jet, this hot blue flame, this surely would do the trick! For him the space helmet was now a certainty. It might take time, but now it could be done. That and more was possible, for he had enough metal to make a few necessities like a decent frying pan and a pot to use for boiling and perhaps a water container for a really long exploration trip. That was the end of Robin's first "Stone Age" period and the beginning of his "Iron Age." _10. The Incredible Footprints_ Using the gas jet proved to be considerably more difficult than might have been supposed. It was hard to approach too closely to the thing without running the danger of getting scorched. Also, to hold metal in it long enough to allow it to melt or become pliable it was necessary to find a way of holding the object without getting burned. Robin did get several blisters before he finally worked out a system. Making himself a pair of thick rabbit-skin gloves lined with a thin coating of the ash from the area around the flame proved to be part of the solution. A pair of bone pliers proved to be another part, though the necessity of replacing these was continuous. Working patiently then, Robin managed to cut and work some of the sheets of metal from the rocket nose. He made himself a hammer of hard stone with which to pound some shape into his pieces and finally had fashioned for himself a serviceable, though crude, frying pan and other implements he needed. His next project was to be the space helmet, the first essential part of any space suit. He considered this a long time, planning just how to make it. He had a good sheet of metal for the job, but he didn't want to make any errors in working it, and he wanted to have as few seams as possible. Welding had thus far proved a task he had not mastered. He considered making the joints airtight by means of some sort of vegetable- or animal-fat product. Robin sat in his cave watching the rebirth of life in the bubble-world after one of the winter half-months and thinking. He watched his monkey, Cheeky, turning over rocks for Moonworms--although the little brown pet had never been able to eat them, he seemed to enjoy the hunting of these odd creatures. He watched the rabbits bounding around, listened to those he kept penned up in the next cave.