"I remember," he said at last, after staring hard at the unfortunate class, "we were going to talk about surface area." A broom swishing in the outside courtyard could be clearly heard over the silence.
"Forty-two minus six is thirty-four; thirty-four divided by two is ...?" He pointed to a small boy on the second row.
"Seventeen, sir," came the prompt answer, the boy bobbing to his feet and then sitting down again all in one motion.
"Seventeen," repeated Mendel, picking up his class roster and running his finger down to the appropriate number. "Kolreuter, how do you calculate the surface area of a cube?"
Not knowing the reason for his teacher's sudden and unexpected change in personality, the boy Kolreuter became disoriented, but arose to his feet and gave the best answer he could. "Please sir, you add together the areas of all four sides."
Mendel promptly turned on the boy, "And how many sides does a cube have?"
"Please sir, four sir."
"Is that right?" demanded Mendel of the boy sitting next to him.
"No sir, a cube has six sides sir," the second boy said correctly.
"So, in order to calculate the surface area of a cube you would have to add together the areas of all SIX sides, is that right?"
"Yes sir," answered the miserable Kolreuter.
"Think before you answer in future," Mendel said to him sharply. "Now a different question. What is the surface area of a sphere?" He looked around his class and pointed arbitrarily at a spotty youth trying to make himself look very small at the back of the room.
"Sir ... I ... it has something to do with ... er," he gave up at last, shaking his head and refusing to meet Mendel's eye.
After a pause, that to the members of the room seemed like an age, Mendel said, "Kolreuter, what is the surface area of a sphere?" His voice was low, but no one could mistake the tone.
"Please sir, you need to know the radius of the sphere."
"You do indeed. Now, assuming you know that radius what is the mathematical relationship between the radius of the sphere at the surface area?"
This was a most unusual teaching style for Brother Gregory, and it was the change in his manner that most affected the boys, particularly the one under questioning at the moment. Someone coughed at the back of the class and immediately tried to stifle a second noise.
"Well?"
Poor Kolreuter, who had no idea why Mendel was doing this, finally got his brain to work. He was an excellent student who, under other circumstances, would have been able to answer at once. "Please sir, to get the surface area of a sphere you square the radius and multiply the answer by four and by Pi."
"At last," snorted Mendel, "the surface area is obtained from the formula four - Pi - radius squared."
"True enough," said Makyatta interrupting at last from the side of the room. Like the class, he had no idea what had effected Brother Gregory, but, as a good teacher himself, he was determined to prevent the damage from going any further. "While you were out seeing the Headmaster, we were just reading about the surface area of a tree leaf. One particular fact interested me, the author pointed out that trees, with all their leaves, probably need all this surface area to exchange gasses with the air, just like we need lungs. What do you think?" He knew his ex-pupil well. All Mendel needed was a distraction and a different topic on which to focus his mind. It worked.