This book forms the last of three. The first published was "The Boats of the 'Glen Carrig' " ; the second, "The House on the Borderland" ; this, the third, completes what, perhaps, may be termed a trilogy; for, though very different in scope, each of the three books deals with certain conceptions that have an elemental kinship. With this book, the author believes that he closes the door, so far as he is concerned, on a particular phase of constructive thought.