"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
"It is that force which for years I have sought and which I have finally found. It is an electromagnetic force which repels light-rays and by curving them around the zone of force can make all matter in that zone invisible. Understand, it does not blot out light in any way, it simply makes the light-rays detour around an object and so makes that object invisible."
"So much for theory. I have here a small cabinet of black metal in which is an apparatus for projecting this force upward for a few inches. Any small object placed on top of the cabinet will become invisible when the force from within is put into operation. If the force were more powerful, and radiated out in every direction instead of upward only, the cabinet itself and all around it would be made invisible."
Dr. Grantham cast a quick glance around and then picked from the table a small disk-shaped paper-weight of black, opaque glass.
"I shall endeavor to make this paper-weight invisible to your eyes—by placing it on the cabinet and using the force within to bend the light-rays around it."
He was turning with it to the little cabinet when Carton reached forth a hand.