In which 1850 Wagner opera does the hero sing "Farewell, my beloved swan"?

Winfield Scott won the 1847 Battle of Churubusco during which war? The 1848 Treaty of Guadalupe Hidalgo, ending which war, added over 500,000 square miles to the U.S.? In 1846, poet Elizabeth Barrett secretly married which fellow poet? Which 1849 essay by Thoreau asks: "Unjust laws exist: shall we be content to obey them"? The 1850s trilogy by Tolstoy consisted of "Childhood", "Boyhood" and which work? Which 1851 novel is about a hunt for a white whale? In 1851, which fictional captain commanded the whaler Pequod? Which 1852 novel is subtitled "Life Among the Lowly"?