I could see Nur An's fingers apparently feeling over the surface of something several inches above the top of the table. "By my first ancestor, it is still there!" he exclaimed. "It is wonderful," I exclaimed. "You did not even touch it; you merely made passes above it with the handle of a paint brush and it disappeared." "But I did touch it," insisted Phor Tak. "The brush was there, but you did not see it because it was covered by the substance which renders The Flying Death invisible. Notice this transparent glass receptacle in which I keep the compound of invisibility and all that you can see of it is that part of the rim which, by chance, has not been coated with the compound." "Marvellous!" I exclaimed. "Even now, although I have witnessed it with my own eyes I can scarce conceive of the possibility of such a miracle." "It is no miracle," said Phor Tak. "It is merely the application of scientific principles well known to me for hundreds of years. Nothing moves in straight lines; light, vision, electro-magnetic forces follow lines that curve. The compound of invisibility merely bows outward the reflected light, which, entering our eyes and impinging upon our optic nerves, results in the phenomenon which we call vision, so that they pass around any object which is coated with the compound. When I first started to apply the compound to The Flying Death, your line of vision was deflected around the small portions so coated, but when I coated the entire surface of the torpedo, the curve of your vision passed completely around it on both sides so that you could plainly see the bench upon which it was resting precisely as though the device had not been there." I was astounded at the apparent simplicity of the explanation, and, naturally, being a soldier, I saw the tremendous advantage that the possession of these two scientific secrets would impart to the nation which controlled them. For the safety; yes, for the very existence of Helium, I must possess them and if that were impossible, then Phor Tak must be destroyed before the secret of this infernal power could be passed on to any other nation. Perhaps I could so ingratiate myself with old Phor Tak as to be able to persuade him to turn these secrets over to Helium in return for Helium's assistance in the work of wreaking his vengeance upon Tul Axtar. "Phor Tak," I said, "you hold here within your grasp two secrets which in the hands of a kindly and beneficient power would bring eternal peace to Barsoom." "Heigh-oo!" he cried. "I do not want peace. I want war. War! War!" "Very well," I agreed, realizing that my suggestion had not been in line with the mad processes of his crazed brain. "Let us have war then, and what country upon Barsoom is better equipped to wage war than Helium? If you want war, form an alliance with Helium."