"_Val tas Winel yep frah?_" Carroll turned angrily. "Sell it to Tin Pan Alley," he snapped. "I've heard worse jangle songs!" He stamped off angrily to his room. CHAPTER VI _Proof_ Once in his room, Carroll gave way to a period of complete slump, both mental and physical. He just sat there and felt--not thought about--the sheer impossibility of a single man successfully fighting an entire inimical culture. The more he considered it the more he felt the futility of it all. The fact that he of all the teeming billions of Sol's heritage, was cognizant made it that more hopeless. Then out of that last, single, hopeless fact James Forrest Carroll took a new hope. For upon himself and himself alone rested the salvation of mankind! Regardless of what the world might think of him, regardless of life itself, he must carry on! And when he returned to confront Doctor Pollard he must have visible proof! The day dragged slowly. As usual, Kingallis did his studying, but found it hopeless because of Carroll's deep funk. Kingallis gave up and left Carroll, which was worse for Carroll because he had all those long hours in which to sit and stew. Evening came, and with it came more hope. Whatever it was that Carroll learned it was there and stuck tight. Whether valid or useless it was there. It seemed useful but he could not tell. For instance there was a concept of a circlet of silvery wire. This was mounted on a small cylindrical slug of metal that enclosed a bimorph crystal. The picture concept showed contour surfaces of force or energy that grew progressively fainter as they retreated from the circlet of wire. Not magnetism--for Carroll could see no energizing current. Not electrostatic field--for there could be no gradient. The word-concept for the thing was "_Selvan thi tan vi son klys vornakal ingra rol vou._" Well--whenever Carroll knew words he would know what the circlet of wire did--and why. But as he drew the diagram on a sheet of paper and labeled each part with a Terran symbol-system representing the alien sounds Carroll understood one other thing. No book is complete without an index! Wire recordings of text books are impractical otherwise. An engineer seeking information on the winding, packing fraction of a certain type of wire would not care to wade through four hours of facts. Of course he should know it already, for the facts would be indelibly impressed upon his mind. But there was the forgetting-factor that comes from disuse of any fact and doubtless this automatic means of education did not forever endow the owner with an eidetic memory of everything--never to be lost no matter how long the facts lie in disuse. But every text book has an index. And so Carroll sought the laboratory again that night and selected another roll at random. He placed it in the machine and, as he started it, hurled a thought into the machine.