When a writer calls his work a Romance, it need hardly be observed that he wishes to claim a certain latitude, both as to its fashion and material, which he would not have felt himself entitled to assume, had he professed to be writing a Novel. The latter form of composition is presumed to aim at a very minute fidelity, not merely to the possible, but to the probable and ordinary course of man's experience. The former - while, as a work of art, it must rigidly subject itself to laws, and while it sins unpardonably, so far as it may swerve aside from the truth of the human heart - has fairly a right to present that truth under circumstances, to a great extent, of the writer's own choosing or creation . . . He will be wise, no doubt, to make a very moderate use of the privileges here stated, and, especially, to mingle the Marvellous rather as a slight, delicate, and evanescent flavor, than as any portion of the actual substance of the dish offered to the Public. He can hardly be said, however, to commit a literary crime, even if he disregard this caution.