Poetry and Science.--The Paper Nautilus and the Sail.--Montgomery’s “Pelican Island.”--The Nautilus replaced by the Velella.--The Sailing Raft of Nature and Art.--Description of a Velella Fleet off Tenby.--The Natural Raft and its Sail.--The Boats of Nature and Art.--Man’s first Idea of a Boat.--The Kruman’s Canoe and the _Great Eastern_.--Gradual Development of the Boat....