THE oceans are big and broad. I believe two-thirds of the earth's surface is covered with water. What people inhabit this water has always been a subject of curiosity to the inhabitants of the land. Strange creatures come from the seas at times, and perhaps in the ocean depths are many, more strange than mortal eye has ever gazed upon.This story is fanciful. In it the sea people talk and act much as we do, and the mermaids especially are not unlike the fairies with whom we have learned to be familiar. Yet they are real sea people, for all that, and with the exception of Zog the Magician they are all supposed to exist in the ocean's depths.I am told that some very learned people deny that mermaids or sea-serpents have ever inhabited the oceans, but it would be very difficult for them to prove such an assertion unless they had lived under the water as Trot and Cap'n Bill did in this story.I hope my readers who have so long followed Dorothy's adventures in the Land of Oz will be interested in Trot's equally strange experiences. The ocean has always appealed to me as a veritable wonderland, and this story has been suggested to me many times by my young correspondents in their letters. Indeed, a good many children have implored me to "write something about the mermaids," and I have willingly granted the request.