As astronomers began to explore the physical nature of comets, they found that meteors came from dust left by comets. Major meteor showers such as the Leonids, seen here as they appeared on November 12, 1799, occurred as Earth plowed through a river of comet dust. In 1833 and in 1866 additional recurrences of a Leonid meteor 'storm' helped lead to the discovery of the parent comet from which meteors came. (From the Midnight Sky, by Edwin Dunkin, 1869).