An auburn-haired boy of twelve stood looking in at the door of a blacksmith shop and wondering why the smith sprinkled water on the fire. He stood with two girls and had an arm around each, but for the moment he had forgotten them both.

There have always been smithies, and children coming home from school have loved to look in at the open door, and doubtless there has been many a lad of whom the girls were so fond that they were willing to stand like tame fillies while he gazed into the shop like a wondering colt.

In such cases the young spectators were fascinated by the brawny courage of the smith, and by the danger of the sparks, but few would conclude that water will burn. This boy however did. He noticed that the sprinkling made the red flame sink back into the coals and then emerge whiter and brighter. The fire was certainly feeding on water.

Presently the dazzling bar of iron was withdrawn, and the sparks began to fall at his feet. The girls shrank back, and he laughingly drew them away.

Now this did not happen in a village but in the city of Chicago, and in the year 1905. Marvin Mahan was the third son of Chase Mahan, a mining engineer who was oftener away from home than at home. On this May afternoon, however, he happened not only to be in Chicago but to be engaged in writing letters in his den, which held minerals and chemicals and included most of the top story of an old house on the north side.

There the small boy easily found him. The afternoon sun was pouring through an open window on many a mineral of which Marvin already knew the name, but off in a corner a beam of it was running along a table on which lay a sieve of phosphor bronze. The boy stopped and gazed at that sieve.

“Well, son?”

“I’m looking at your rainbows.”

Marvin went over and slowly tilted the sieve toward the beam of light. The wires were pretty close together, about three hundred to the inch, and at an angle of thirty degrees the space between them was less than the diameter of the wire. Marvin raised and lowered the slope till suddenly a perfect spectrum of solar light appeared, and he turned grinningly toward his father.

Chase nodded and smiled.

“Some day, when I’m not making so much useless money, I’ll write a little paper about that. You have put your finger on a new way of measuring light-waves. But what the devil are you doing up here when you ought to be out with your nine?”

“I want to know what part of water burns?”

“Do you mean is burned?”

“Yes, dad.”

“Hydrogen.”

“Can I make some?”

“You can’t make anything. All you can do is to discover things that God Almighty put in the earth, and you are damned lucky if you can do that. I ought not to teach you to swear, but this letter I’m writing is to a self-made man who rather needs to be sworn at.”

“Aren’t you a self-made man, dad?”

“No! I came to this town bare-footed, but it’s only by the grace of God that I’m not in jail. You’ll be doing well if you keep out of jail yourself.”

“I will, dad, but can I turn some hydrogen loose?”

“Do you want to blow a hand off?”

“I don’t mind, if I can see how the meat looks.”

“Then go and ask Norah for a marmalade jar. Get a glass one, and wash the cork.”

Marvin was off like a flash.

Chase rose and paced the room, thinking about his children and thanking God they were no worse than they were. Every one of them except Helen was likely to pay dearly for the energy inherited from his own restless self. Augustus however was safely married without any serious explosion so far. Charles had not yet been expelled from college. Helen—sweet flower—was safe in her grave. Baby Anita was for the moment safe down stairs in her mother’s arms. But Marvin—this lovable twelve-year-old dare-devil—this imp of bottled lightning—what of him?

Marvin’s worst escapade thus far had been to lead his tender gang into a saloon and coax enough beer out of a law-abiding spigot to scandalize nine of the best families of the north side. That baseball team did not exactly go home drunk, but they all went home late, having slept off the beer on the lake shore.

His usual and lesser crime was to do all the arithmetic for the bunch and so gain time for sport. He had been punished in school and out of school for this misdemeanor, but he would never promise not to repeat it. What could a teacher say to a beautiful boy who smiled into her eyes and declared it “anti-social” not to help the other kids!

Marvin led everything and apparently had no desire to lead anything. He led because his brain was a little quicker, his foot a little swifter, his eye a little surer than those of any mate. He was the undisputed cockerel of the walk. As for girls—only God knew what he might be guilty of in the course of the next ten years.

Chase lamented that his own energy seemed so little tempered in Marvin by the mother’s steadiness. It was only in fits of abstraction that Marvin looked like the Helen Marvin whom Chase had loved these five and twenty years. The boy had some of the makings of a scientific genius—the quickness and accuracy of observation, the mathematical power, the swift intuition—but he seemed to lack the power of quiescence which permits a real genius to brood doggedly on a single problem.

Presently Marvin bounded up the steps, balancing the glass jar, with some water in it, on the back of his left hand. Chase explained that the process of separating water into two gases is electrical, and that the simplest way to get a current is to bring zinc and sulphuric acid together in the water. He said that both materials could be found in the room, and having said it returned to his writing.

There stood Marvin, left to his own devices, permitted to blow his eyes out if he so desired.

He rolled up a strip of zinc, dropped it into the water, and corked the jar. Then he punched a hole and inserted a small glass funnel to let the sulphuric in. It stood to reason that there should be another hole and a pipe to let the hydrogen out. He punched a second hole and inserted a piece of glass tubing.

So far, so good. It was the first time he had been allowed to monkey with the wonderful things in that corner of the den. He took down the bottle of sulphuric and pondered. If anything went wrong, dad would never let him try it again. If the acid made the water bubble and the hydrogen come out of the tube, would it be safe to light it like a gas jet? No, because there was no pressure and the flame would backfire into the jar.

He removed the tube and bent it in the flame of a bunsen burner. He thrust the short end back through the cork and ducked the other end into a bowl of water. Then he poured in a little acid and watched. Sure enough, bubbles began to rise and the glass grew warm, even hot Presently corresponding bubbles appeared on the surface of the bowl. He stirred in a little soap so that he could see them better, and they collected in iridescent masses.

Gosh, he had the stuff, but was it safe to touch it off? He sat down and ran his fingers through his chestnut curls and studied his apparatus. Flame could not possibly backfire through solid water. Hadn’t he figured this thing out himself? So he applied a match to the soap bubbles and was rewarded by a delightful fusillade—like a machine gun about a thousand miles away and ten years off. “Not dead yet, dad.”

“No, not yet,” smiled Chase Mahan.