Which 1851 novel is about a hunt for a white whale?

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"? In which 1850 Wagner opera does the hero sing "Farewell, my beloved swan"? The 1850s trilogy by Tolstoy consisted of "Childhood", "Boyhood" and which work? In 1851, which fictional captain commanded the whaler Pequod? Which 1852 novel is subtitled "Life Among the Lowly"? Which 1852 American novel includes the line "Eliza made her desperate retreat across the river just in the dusk of twil… Which 1853 land deal brought the contiguous United States about to its present area?