Proto-Indo-European mythology also in the myths of the slaying of the nine-headed Lernaean Hydra by Heracles and the slaying of Python by Apollo. The story of Heracles's theft of the cattle of Geryon is probably also related. Although Heracles is not usually thought of as a storm deity in the conventional sense, he bears many attributes held by other Indo-European storm deities, including physical strength and a knack for violence and gluttony. The original Proto-Indo-European myth is also reflected in Germanic mythology. In Norse mythology, Thor, the god of thunder, slays the giant serpent Jörmungandr, which lived in the waters surrounding the
Greek mythology libretti for many of Handel's and Mozart's operas. By the end of the 18th century, Romanticism initiated a surge of enthusiasm for all things Greek, including Greek mythology. In Britain, new translations of Greek tragedies and Homer inspired contemporary poets (such as Alfred Lord Tennyson, Keats, Byron and Shelley) and painters (such as Lord Leighton and Lawrence Alma-Tadema). Christoph Gluck, Richard Strauss, Jacques Offenbach and many others set Greek mythological themes to music. American authors of the 19th century, such as Thomas Bulfinch and Nathaniel Hawthorne, held that the study of the classical myths was essential to the understanding of