Another aspect of the transfer of magic in modern fiction to a scientific basis is that of second sight or supernatural vision. This motif still retains all its former effect of the unearthly, perhaps gaining more, since the scientific twist seems to give the idea that the ghostly power resides in the atoms and molecules and gases and machines themselves, rather than in the person who manipulates them, which is more subtly haunting in its impression. Second sight has been used as a means for producing uncanny effects all along the line of fiction. Defoe even used it in a number of his hoax pamphlets, as well as in his _History of Duncan Campbell_, and folk-lore is full of such stories, especially in the Highlands. The modern use of supernatural vision is based apparently on natural science, which makes the weird power more striking. _The Black Patch_, by Randolph Hartley, tells of an experiment in optics that produces a strange result. Two students exchange left eyeballs for the purpose of studying the effects of the operation, leaving the right eye in each case unimpaired. When the young men recover from the operation and the bandages are removed, they discover that an extraordinary thing has taken place. The first, while seeing with his right eye his own surroundings as usual, sees also with his left--which is his friend's left, that is--what that friend is looking at with his right eye, thousands of miles away. The severing of the optic nerve has not disturbed the sympathetic vision between the companion eyes, so this curious double sight results. In a quarrel arising from this peculiar situation, the first man kills the second, and sees on his left eye the hideous image of his own face distorted with murderous rage, as his friend saw it, which is never to be effaced, because the companion eye is dead and will see no more. Another instance of farsightedness is told in John Kendrick Bangs's _The Speck on the Lens_, where a man has such an extraordinary left eye that when he looks through a lens he sees round the world, and gets a glimpse of the back of his own head which he thinks is a speck on the lens. Only two men in the world are supposed to have that power.