It happens that one of my own plays has had a very curious history. It has appeared before the American public in two forms, so radically different that a description of the changes made, and of the reasons for making them, will involve the consideration of some very interesting laws of dramatic construction. I shall ask you to listen very carefully to the story, or plot, of the piece as it was first produced in Chicago in 1873. Then I shall trace the changes that were made in this story before the play was produced in New York five years later. And after that, to follow the very odd adventures of the same play still further, I shall point out briefly the changes which were made necessary by adapting it to English life with English characters, for its production at the Court Theater, London, in 1879. All the changes which I shall describe to you were forced upon me (as soon as I had decided to make the general alterations in the play) by the laws of dramatic construction; and it is to the experimental application of these laws to a particular play that I ask your attention. The learned professors of Harvard University know much more about them than I do, so far as a study of dramatic literature, from the outside, can give them that knowledge; and the great modern authorities on the subject--Hallam, Lessing, Schlegel and many others--are open to the students of Harvard in her library; or, rather, shall I say, they lie closed on its shelves. But I invite you today to step into a little dramatic workshop, instead of a scientific library; and to see an humble workman in the craft, trying, with repeated experiments--not to elucidate the laws of dramatic construction, but to obey them, exactly as an inventor (deficient, it may be, in all scientific knowledge) tries to apply the general laws of mechanics to the immediate necessities of the machine he is working out in his mind. The moment a professor of chemistry has expressed a scientific truth, he must illustrate it at once by an experiment, or the truth will evaporate. An immense amount of scientific truth is constantly evaporating, for want of practical application; the air above every university in the world is charged with it. But what are the laws of dramatic construction? No one man knows much about them. As I have already reminded you, they bear about the same relation to human character and human sympathies as the laws of nature bear to the material universe. When all the mysteries of humanity have been solved, the laws of dramatic construction can be codified and clearly explained; not until then. But every scientific man can tell you a little about nature, and every dramatist can tell you a little about dramatic truth. A few general principles have been discovered by experiment and discussion. These few principles can be brought to your attention. But after you have learned all that has yet been learned by others, the