"Feats on the Fiord" is indeed a book written by Harriet Martineau and is the third book in her series "The Playfellow." The series is a collection of stories aimed primarily at children, meant to both entertain and educate. Martineau was a prominent social theorist and writer in the 19th century, known for her works on political economy, sociology, and fiction.In "Feats on the Fiord," Martineau takes readers on a journey to Norway, where they encounter a variety of adventures and experiences. The story likely features themes of friendship, courage, and exploration, as well as insights into Norwegian culture and customs.As with Martineau's other works, "Feats on the Fiord" may also contain moral lessons and social commentary, reflecting Martineau's interests in education and social reform.