I ought to explain why I, being a person without any of the scientific attainments that would fit one for the task, take it on me to write of dreams. It occurred to me that there were certain kinds of dreams common to nearly every one. Every one (using the word in a liberal sense, and not in the grudging spirit of the man who objected to ninety-nine ducks being spoken of as a round hundred) is familiar with the dream of falling over a precipice. A great many people know the dream that they are flying. Few have not dreamed that they have entered a polite assembly in a costume very much more appropriate to a Turkish bath than to their visionary surroundings, and there are many other common, generally familiar, dreams. And this being so, I was struck by the fact that no one seemed to have tried to find the common cause of each kind respectively of familiar dreams.