While he was tutor, Whitney made playthings for the children, and fixed many handy things for Mrs. Greene to use about the house. She told him he ought to make a machine that would take the seeds out of the bolls, or fluffy heads, of the cotton plant. Great machines had been contrived for spinning and weaving cotton, but it took a man or a woman all day to pick the seeds out of a pound of cotton wool. [Illustration: ELI WHITNEY, INVENTOR OF THE COTTON GIN.] Eli Whitney went to work to make something that would do what in those days seemed impossible. He not only had to invent a cotton-gin, as the new machine was called, but he was obliged to make tools for making the machine itself, and even tools for making the other tools. But within a short time he had invented and built a machine which worked quite well. Still he was not satisfied. He locked himself up in a room and worked day and night until he had built a perfect cotton-gin which would work very fast and would clear out all the fine cotton seeds. This was in 1793, while Washington was President, and Philadelphia was the capital of the United States. Whitney would not let any one but Mrs. Greene and a friend named Miller see the model, or pattern, of his cotton-gin until he could take out a patent for it. But before he could get money enough to have his gin patented, someone broke into his little shop and carried off his precious model. Then the poor inventor had to begin again and make another machine, to prove to the officials in the Patent Office that the cotton-gin was his invention, before they could make out for him the patent right, which said he was the only person allowed to make and sell that machine in the United States. Before he could get this patent he found that others were making, selling, and trying to get a patent for machines made like the stolen pattern. [Illustration: WHITNEY’S FIRST COTTON GIN.]