Geological Observations on the Volcanic Islands, visited during the Voyage of H.M.S. Beagle is a book written by the English naturalist Charles Darwin. The book was published in 1844, and is based on his travels during the second voyage of HMS Beagle, commanded by captain Robert FitzRoy. It is the second book in a series of geology books written by Darwin, and also includes The Structure and Distribution of Coral Reefs, published in 1842, and Geological Observations on South America, published in 1846.