The Shark juggled the stone, which he still held. “Humph! This weighs more than twelve pounds, I’ll bet--may run up to fifteen,” said he. “But what am I figuring on? Why, the amount of force required to send it through the arc this stone described.” “Twelve to fifteen pounds!” jeered Step. “Seems to me you’re furnishing some of the unknown quantities yourself.” “I am,” said the Shark. “I admit it. I also admit that I can’t reach satisfactory results from such data. But the results I do get--subject to revision, of course--make me doubt that Tom Orkney could have done the job. When I have the stone weighed, and when I measure the distance across the room, and add a good estimate of the distance the thrower stood from the window, I believe I can plot a curve----” A chorus of shouts interrupted him. The non-mathematical members of the club would have none of such follies. Evidence? Wasn’t the cap evidence enough to convict Orkney? Stoutly the Shark maintained that one should not put too great faith in circumstantial evidence. “What! You’d put more in your old curves and calculations?” cried Step. “Every time!” vowed the Shark. Sam cut short the discussion. “Look here, fellows!” he said sharply. “I’m going to thrash Orkney, and there’s no more to be said about it.” “Well, thrash ahead!” growled the Shark. “I don’t object to the general proposition; but I am pointing out that you may be wrong as to your reason for thrashing him.” “I’ll risk that!” cried Sam hotly. “And I’ll even the score at the first chance I get.” This decision, warmly admired and praised by the club, seemed to be in a fair way for accomplishment on Monday when Sam, walking alone to school, met Orkney at a street corner. Meditation had cooled his anger, but had not lessened his determination to have a speedy accounting. He put himself in Orkney’s path, and gave him monosyllabic greeting. “Huh!” It must be confessed that there was a distinctly challenging note in Sam’s growl. “Huh!” responded Orkney. In fairness it is to be stated that he betrayed no sign of anxiety; and instead of halting, stepped aside and passed the boy holding the center of the walk. Sam turned, and overtook him in three long strides. Then they moved on together, but with a space of three or four feet between them. Orkney gazed straight before him. The sullenness of his expression may have been a trifle more marked than usual. Sam, studying him from the corner of an eye, decided that his enemy was merely playing a waiting game. There was a moment’s silence. Then said Sam, very grimly: “This thing has got to stop--see?” The tone was more impressive than the words. Orkney stopped, and inspected the other coolly. “Has, eh? Well, what might ‘this thing’ be?” he inquired. “You know well enough!” “Guess again. I don’t.” “You do.” A dull red showed in Orkney’s cheeks. “That’s the same thing as telling me I don’t tell the truth.” “Does sound like it.” “Mean to call me a liar?”