The chronometers of all the whale ships which sailed into Nantucket were brought to Mr. Mitchell to be “rated,” as it was called. Maria used to help her father with this; and at a very early age learned how to use a measuring instrument called the sextant. There was no school at this time where Maria Mitchell could be taught astronomy. Even Harvard University had no better telescope than her father’s. Maria, however, had an excellent teacher in him. Many scientists sought out Mr. Mitchell in remote Nantucket, and Maria had the benefit of their conversation. The years of Maria Mitchell’s girlhood passed quietly but happily. She went to two schools that her father taught, and then to a private school where she did very good work in mathematics. At sixteen years of age she began to teach. She gave up teaching, however, to become librarian of the Nantucket Athenæum, a position that she held for nearly twenty years. The library was open only afternoons and Saturday evenings. In the afternoons there were few visitors, so Miss Mitchell had plenty of time for reading and study. She went on with her studies in higher mathematics and worked out difficult astronomical problems. Whenever visitors came in and chatted, as they liked to do with this bright, interesting young woman, her book was dropped for knitting. Maria Mitchell never wasted a moment. Every clear evening was spent on the housetop observing the heavens. No matter how many guests there were in the parlor, Miss Mitchell would slip out and, lantern in hand, mount to the roof where the telescope was now kept. On October 1, 1847, there was a party at the Mitchell home. Maria, as usual, ran up to the telescope. Presently she hurried back and told her father that she had seen a new comet. Mr. Mitchell was convinced that she was right and he wrote to Harvard University, announcing the discovery. Maria Mitchell received for this discovery a gold medal offered sixteen years before, by the King of Denmark, to the first discoverer of a telescopic comet. This won world-wide distinction for Miss Mitchell. The next year another great honor came to the Nantucket girl. She was elected to the American Academy of Arts and Sciences. She was the first woman to be admitted to this important scientific society. Soon after this Miss Mitchell was asked to put her knowledge of astronomy to use on a work for navigators called the _American Nautical Almanac_. She was to watch the course of the planet Venus, and to make the tables which mariners need to guide them. For nineteen years she kept up this important work. It was quite natural that a woman who had watched ships pass her island home ever since childhood should long to travel. Miss Mitchell was especially eager to meet the great scientists of Europe. At last the happy time came for a European trip. Everywhere she was cordially received, and astronomers not only opened their observatories to her, but welcomed her in their homes.