So George went to work. He did not neglect his school duties, but carefully prepared his daily lessons. When these were done he was ready to study agriculture. He did not know where to begin with books, so he asked questions. "Uncle Ben," he said one evening as the family was gathered around the library lamp, "how does it happen that a farmer sometimes raises tomatoes and sometimes potatoes? What does he do if he wants one rather than the other?" "Well, George," was the laughing reply, "I think that you have much to learn before you make a successful farmer. Don't you know that if he wants potatoes he plants potatoes?" "Why, I suppose so," said George. "Then if he desires apples, does he plant apples?" "Hardly," said his uncle. "Seeds would be better than entire apples." George was started and for the rest of the evening he asked no more questions, his whole attention being turned to the large encyclopedia on his knee. When next he plied his uncle with questions it was evident that he had already learned something. "When a farmer plants a potato, he puts it in a hole and covers it up. I have read that he plows the ground first. What does he do that for?" "For two reasons, I suppose," replied Uncle Ben. "The roots and sprouts grow better in a soil that has been softened. When the ground is unplowed, it is baked hard. Besides, plowing turns the soil over, brings new dirt to the top, and generally mixes it all together." "Oh, yes!" said George. "Then I must learn about plowing first." George obtained as good a knowledge of plows and tillage as was possible from books. In order fully to understand the subject, it would be necessary to see the plows and use them. But that could not come yet. The books told him that the earliest and simplest way to till the soil was with a spade. From them George learned, what most boys and girls know, what a spade was, and that a spade was all that was absolutely needed to soften the soil and prepare it for planting. To spade a piece of ground is slow work; it is also hard work. Could not some method be devised so that the spading or tilling could be done by horses or oxen? This led to the invention of the plow. This was made thousands of years ago. The kooloo plow, still in use in India, was one of the earliest and was very rude. It was made entirely of wood, the sharp part of the plow being like a thorn in shape, but very thick and strong. As the centuries went on, iron began to be used; and early in the history of iron it was applied to plows. They were still made of wood, but iron plates were placed over the wood, where the instrument tore into the ground. Later the plow itself was made of iron, leaving the handles still formed of wood. This iron plow would sometimes become covered with soil and so be almost useless. This was corrected by the use of steel shares instead of iron. This brought George to the modern plow.