A little Scotch boy was sitting in his grandmother's kitchen. He was watching the red flames in the wide open fireplace and quietly wondering about the causes of things. Indeed, he was always wondering and always wanting to know.

"Grandma," he presently asked, "what makes the fire burn?"

This was not the first time he had puzzled his grandmother with questions that she could not answer. So she went on with her preparations for supper and paid no heed to his query.

Above the fire an old-fashioned teakettle was hanging. The water within it was beginning to bubble. A thin cloud of steam was rising from the spout. Soon the lid began to rattle and shake. The hot vapor puffed out at a furious rate. Yet when the lad peeped under the lid he could see nothing.

"Grandma, what is in the teakettle?" he asked.

"Water, my child—nothing but water."

"But I know there is something else. There is something in there that lifts the lid and makes it rattle."

The grandmother laughed. "Oh, that is only steam," she said. "You can see it coming out of the spout and puffing up under the lid."

"But you said there was nothing but water in the kettle. How did the steam get under the lid?"

"Why, my dear, it comes out of the hot water. The hot water makes it." The grandmother was beginning to feel puzzled.

The lad lifted the lid and peeped inside again. He could see nothing but the bubbling water. The steam was not visible until after it was fairly out of the kettle.

"How queer!" he said. "The steam must be very strong to lift the heavy iron lid. Grandma, how much water did you put into the kettle?"

"About a quart, Jamie."

"Well, if the steam from so little water is so strong, why would not the steam from a great deal of water be a great deal stronger? Why couldn't it be made to lift a much greater weight? Why couldn't it be made to turn wheels?"

The grandmother made no reply. These questions of Jamie's were more puzzling than profitable, she thought. She went about her work silently, and Jamie sat still in his place and studied the teakettle.

How to understand the power that is in steam, and how to make it do other things than rattle the lids of teakettles—that was the problem which James Watt, the inquisitive Scotch boy, set himself to solve. Day after day he thought about it, and evening after evening he sat by his grandmother's fireside and watched the thin, white vapor come out of the teakettle and lose itself in the yawning black throat of the chimney. The idea grew with him as he grew into manhood, and by long study he began to reason upon it to some purpose.

"There is a wonderful power in steam," he said to himself. "There was never a giant who had so much strength. If we only knew how to harness that power, there is no end to the things it might do for us. It would not only lift weights, but it would turn all kinds of machinery. It would draw our wagons, it would push our ships, it would plow and sow, it would spin and weave. For thousands of years men have been working alongside of this power, never dreaming that it might be made their servant. But how can this be done? That is the question."

He tried one experiment after another. He failed again and again, but from each failure he learned something new. Men laughed at him. "How ridiculous," they said, "to think that steam can be made to run machinery!"

But James Watt persevered, and in the end was able to give to the world the first successful form of the steam engine. Thus, from the study of so simple a thing as a common teakettle, the most useful of all modern inventions was finally produced.