An auburn-haired boy of twelve stood looking in at the door of ablacksmith shop and wondering why the smith sprinkled water on thefire. He stood with two girls and had an arm around each, but for themoment he had forgotten them both.
There have always been smithies, and children coming home from schoolhave loved to look in at the open door, and doubtless there has beenmany a lad of whom the girls were so fond that they were willing tostand like tame fillies while he gazed into the shop like a wonderingcolt.
In such cases the young spectators were fascinated by the brawnycourage of the smith, and by the danger of the sparks, but few wouldconclude that water will burn. This boy however did. He noticed thatthe sprinkling made the red flame sink back into the coals and thenemerge whiter and brighter. The fire was certainly feeding on water.
Presently the dazzling bar of iron was withdrawn, and the sparks beganto fall at his feet. The girls shrank back, and he laughingly drewthem away.
Now this did not happen in a village but in the city of Chicago, andin the year 1905. Marvin Mahan was the third son of Chase Mahan, amining engineer who was oftener away from home than at home. On thisMay afternoon, however, he happened not only to be in Chicago but tobe engaged in writing letters in his den, which held minerals andchemicals and included most of the top story of an old house on thenorth side.
There the small boy easily found him. The afternoon sun was pouringthrough an open window on many a mineral of which Marvin already knewthe name, but off in a corner a beam of it was running along a tableon which lay a sieve of phosphor bronze. The boy stopped and gazed atthat 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 thanthe diameter of the wire. Marvin raised and lowered the slope tillsuddenly a perfect spectrum of solar light appeared, and he turnedgrinningly toward his fa