"Hilderman's dead!" he said. "He made a full confession. It seems he is a German, and his name's von Hilder. He has lived most of his life in America. He is a brilliant physicist, and has done some big things with electricity and light. He was here to prepare the submarine base you found, and he also got on with a new invention--The Green Ray. Of course he didn't give the secret of that away, but we have the searchlight, and I have already tumbled to it partly. It is practically a new form of light. "It is formed by passing violet and orange rays through tourmaline and quartz respectively. The accident to Miss McLeod was their first intimation of its blinding properties, and to the end he knew nothing about the suffocation part of it. I find by experiment that when the two rays are switched on simultaneously the air does not become de-oxygenised, but when you put the violet ray first it does, and it remains so until the orange ray is applied. The effect that Hilderman imagined, and succeeded in producing, was a ray of light which should so alter the relative density of the air as to act as a telescope. He's done it, and it's one of the finest achievements of science. However, I have a piece of wonderful news for you." "What is it?" we both demanded at once. "The Secret of the Green Ray is ours, and ours alone. Hilderman has admitted that the reason why they did not clear it out at the first sign of suspicion was that, in their final calculations, they were unsure of their figures. That means, put popularly, that though he knew what he was trying to do, and how he meant to do it, the actual result was something of a fluke. It very often is with inventors. They had no drawings that they could rely on to make another searchlight by, so they were bound to take the whole thing back with them. They could send no figures, because the relative distances and other quantities baffled them. They could not take the searchlight back in pieces, because if any piece had been broken they might not have been able to reconstruct the proportions with critical accuracy, as we say. So what was to have been Germany's hideous weapon of war is now ours. We have a searchlight which acts as a telescope, which will pierce the deepest fog, and which will dispel the most ungodly poisonous gases ever invented. You can see for yourself that no gas could make headway against the atmosphere you encountered the other day. Armies and navies will be absolutely powerless to advance against it. The green ray is the fourth arm of military power. So you see what you've done for your country, you lucky dog!" "_I!_" I cried. "I like that! I've had less to do with it than anyone. What about you, eh?--coming running up with a gunboat at the critical moment. How did you manage that?"