"The Thirteenth Proposition of the First Book of Euclid," sighed the Spook, exactly as though he were giving out a text in Chapel. "Many of you seem to have found so much difficulty over this that I propose to run over it again, if you will kindly hold your tongues. Hold your tongue, Kingdon! Another word from you, Pedley, and you'll have whipping in front of you—or rather behind you!"
The little joke was a stock felicity of the Spook's, and it was received in the usual fashion. At first there was a little titter, but nothing more until the Spook himself was seen to wear a sickly smile; thereupon the titter grew into a roar, and the roar rose into a bellow, and the bellow into one prolonged and insolent guffaw which the cadaverous but smiling Spook seemed to enjoy as much as the smallest boy in his mathematical. Jan alone did not join in the derisive chorus; to him it sounded almost as though it were in another room; and the figure of the Spook, standing before his blackboard, holding up a piece of chalk for silence, had become a strangely nebulous and wavering figure.
"'The angles that one straight line makes with another straight line,'" began the Spook at last, in a voice that Jan could hardly hear, "'are together equal . . . together equal . . . together equal . . .'"
Jan wondered how many more times he was to hear those two words; his head swam with them; the Spook had paused, and was staring at him with fixed eyes and open mouth; and yet the words went on ringing in the swimming head, fainter and fainter, and further and further away, as Jan fell headlong into the unfathomable pit of insensibility.
He came to earth and life on a dilapidated couch in the Spook's study, where the Spook himself was in the
