"There is nothing mysterious about it, however, much as it differs from the old method. We use a tiny short-wave radio transmitter sealed in a tube of fused quartz. Here," he opened a compartment in the wail and took out a spare tube. "You will notice that point inside the tube— it is tipped with a radio-active material which emits a stream of electrons. The grid and plate are connected electrostatically for the feedback. The rate of oscillation is varied until it is of the frequency of white light and the movable adjustment is welded in place with a ray welder focussed through the quartz tube. We have other lamps on board that are adjusted to emit colored light ; and the searchlights we are using at the moment are infra-red. These rays are invisible but penetrate the mists well, and the reflected beams are picked up on the television plates around the shell of the vessel, being interpreted as white light on the screens before the control table. We are thus able to see where we are going and to view the ground, while to anyone without apparatus we are invisible. We have an adjustable light in another room if you care to examine it"