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Presently the dazzling bar of iron was withdrawn, and the sparks began to fall at his feet.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?”