Final answer:
Henry Wadsworth Longfellow's second wife, Frances Appleton Longfellow, died from severe burns after her dress caught fire in their home on July 10, 1861.
Step-by-step explanation:
Henry Wadsworth Longfellow's second wife, Frances Appleton Longfellow, tragically died after her dress caught fire in their home. Frances, often referred to as Fanny, suffered severe burns from the tragic accident on July 9, 1861. Despite Henry's desperate attempts to extinguish the flames, her injuries were too extensive. Fanny passed away the next day on July 10, 1861. This devastating incident deeply affected Longfellow, and it influenced his subsequent works, reflecting on the themes of life, loss, and coping with grief.