The gymnast paused, poised like a Mercury on the high coping. “Yes,” said he. “Otherwise I shouldn’t be able to do it at all.” “I should think not, indeed! Has it any particular utility, that form of exercise?” “Certainly. It is in pursuance of a theory of self-defense.” “What in the world has wall-hopping to do with self-defense?” “I shall expound,” said the stranger in professional tones, taking a seat by the unusual method of letting himself down on one leg while holding the other at right angles to his body. “Do you know anything of jiu-jutsu?” “Very little.” “In common with most Americans. For that reason alone the Japanese system is highly effective here, not so effective in Japan. You perceive there the basis of my theory.” “No, I don’t perceive it at all.” “A system of defense is effective in proportion to its unfamiliarity. That is all.” “Then your system consists in stepping up on a wall and diving into obscurity on the farther side, perhaps,” suggested Sedgwick ironically. “Defense, I said; not escape. Escape is perhaps preferable to defense, but not always so practicable. No; the wall merely served as a temporary gymnasium while I was waiting.” “Waiting for what?” “For you.” “You have distinctly the advantage of me,” said Sedgwick, with a frown; for he was in no mood to welcome strange visitors. “To return to my theory of self-defense,” said the other imperturbably. “My wall exercise serves to keep limber and active certain muscles that in the average man are half atrophied. You are familiar with the ostrich?” “With his proverbial methods of obfuscation,” replied Sedgwick. The other smiled. “That, again, is escape or attempted escape. My reference was to other characteristics. However, I shall demonstrate.” He rose on one foot with an ease that made the artist stare, descended, selected from the roadway a stone of ordinary cobble size, and handed it to Sedgwick. “Let that lie on the palm of your hand,” said he, “and hold it out, waist high.” As he spoke he was standing two feet from the other, to his right. Sedgwick did as he was requested. As his hand took position, there was a twist of the bearded man’s lithe body, a sharp click, and the stone, flying in a rising curve, swished through the leafage of a lilac fifty feet away. “How did you do that?” cried the artist. The other showed a slight indentation on the inside of his right boot heel, and then swung his right foot slowly and steadily up behind his left knee, and let it lapse into position again. “At shoulder height,” he explained, “I could have done the same; but it would have broken your hand.” “I see,” said the other, adding with distaste, “but to kick an opponent! Why, even as a boy I was taught—”