I glanced at MacDowell, who had gulped audibly. I said, "Keep going, guy. You're hot as a firecracker." "Well, seems like everything in motion makes an equal motion like itself, an' it don't matter whether what it acts on is still or movin'. An' if there's anything else actin' along with it, both movements is goin' to have a say in the showdown." * * * * * Me, I'm a publicity man, not a physicist. It was all a deep fog in my mind, but MacDowell's eyes were bulging. "Go on!" he ordered grimly. "Lastwise," drawled Hank, "'Pears like whenever there's a movement one way, there ought to be an equal kick-back 'tother way." He hesitated for a long moment. Then he shrugged. "Reckon that's all I can think of offhand." MacDowell repeated numbly, "That's all he can think of--offhand!" and staggered to his chair. He tottered for seconds, then dropped into it. "The product of a genius' thoughts for years. And he solves it in five minutes!" Then he snapped out of it, and was he sore! "You, Blakeson!" he yelled. "Yeah?" "This is one of your tricks! What do you mean by this outrageous imposter? You can't deceive _me_! This man has studied physics. He knows--" "Physics?" interrupted Hank eagerly. "Say, you're darn tootin' I've studied physics. An' take it from me, all these here now drugstore things ain't no good. You get you a batch of fresh wild-cherry saplings, bile 'em in water for a half hour, an' add--" "Quiet," I pleaded, "is requested for the sake of those who are asleep. Dr. MacDowell, I give you my word of honor Hank is just what he appears to be. A man of the soil, gifted with great talents. Or rather, _one_ great talent--that of common sense." "A--a moment!" MacDowell silenced me with an uplifted palm. "Mr. Cleaver, are you acquainted with the principles of Mendel?" "Nup!" acknowledged Hank cheerfully. "Perhaps, then, you'd be kind enough to derive an answer for this question? A man has a black dog and a white one. He mates them. The female whelps four puppies. Of the four, how many will you expect to be black, how many white?" Horse-sense Hank cast a sidelong glance at Helen, and blushed. But he didn't bat an eyelash. "This here now black hound, what color was his old man an' woman?" "They were also black." "An' 'tother one's mammy an' pappy was white?" "We will," said Dr. MacDowell weakly "assume that to be so." He knew he had lost again. And so he had. For Hank's answer was bland simplicity. "Why, then, them there pups would just natcherally hafta be all black." "H-how do you know?" demanded MacDowell faintly. "Just seems as if," said Hank. He scratched his head. "'Course," he said cautiously, "them there wouldn't be good show dogs, them pups. They wouldn't breed true wuth a damn. Next time they was mated, their pups would be mixed colors. I'd say 'bout three to one for the blacks."[1]