THE DEAD PAST ARNOLD PO'rrERLEY, Ph.D., was a Professor of Ancient. History. That, in itself, was not dangerous. What changed the world beyond all dreams was the fact that he looked like a Professor of Ancient History. Thaddeus Araman, Department Head of the Division of Chronoscopy, might have taken proper action if Dr. Potterley had been owner of a large, square chin, flashing eyes, aquiline nose and broad shoulders. As it was, Thaddeus Araman found himself staring over his desk at a- mild-mannered individual, whose faded blue -eyes looked at him wistfully from either side of a low-bridged button nose; whose small, neatly dressed figure seemed stamped "milk-and-water" from thinning brown hair to the neatly brushed shoes that completed a conservative middleclass costume. Araman said pleasantly, "And now what can I do for you, Dr. Potterley?" Dr. Potterley said in a soft voice that went well with the rest of him, "Mr. Araman, I came to you because you're top man in chronoscopy." Araman smiled. "Not exactly. Above me is the World Commissioner of Research and above him is the SecretaryGeneral of the United Nations. And above both of them, of course, are the sovereign peoples of Earth." Dr. Potterley shook his head...