The room seemed full of physical apparatus for the most part of outlandish appearance to Carton, he and his two fellow-journalists looking alertly around them. Upon the table before them, just inside the casement through which the brilliant sunlight was streaming, rested a squat cabinet of black metal, but inches square, with a small metal framework on it and with connections to what seemed small batteries and a row of three switches. Dr. Grantham was drawing their attention to this when the door behind them opened and another entered, an impeccably-dressed older man whose white head and genial countenance the reporters recognized instantly as that of Dr. Calvin Ellsworth, America University's very prominent president. He waved Grantham back as the latter turned toward him. "Don't let me interrupt, Grantham," he adjured him. "I just wanted to be a spectator like the rest." Dr. Grantham nodded in understanding, and turned back to the reporters. "To describe understandingly what I am going to show you," he told them, "you must understand something of the principle involved in this. I can make invisible, and that may seem a strange thing to many, who have not ever stopped to wonder just why matter is visible at all." "Why is it, then? Why do we see a house? We see it for two reasons, its obstruction and reflection of light. The light-rays come to us from all around it, but not from behind the house because they are stopped by it. The house, then, is an area of comparative darkness to us, and so is outlined against the light. Also light is reflected from all sides upon it and to our eyes." "But suppose that the light-rays behind, instead of being stopped by the house, curved round it? Then we would see what was behind the house, with ease, and the house itself would be quite invisible to us, granted that light striking it from all sides did not really strike it but curved around it. Then if I want to make a house, or a tree, or a stone, invisible, all I need to do is to deflect the light-rays around it in such a way that they will curve around and avoid it instead of ever striking it." "Can that be done? In principle, it has been possible for years, for years ago we learned that light does not always travel in straight lines but can be deflected to one side or another by certain forces. Einstein's discoveries showed that, it being photographically confirmed after his theory that the light-rays of stars curve in toward the sun in passing it in space. If there is a force that will attract light-rays and make them curve in toward an object, why not a force that will repel the light-rays and make them curve outward to avoid an object?" Sought for Years