...ackboard and was very impatient and indignant that I did not follow him as he made his lightning demonstration. I remained after the class had gone so as to have a talk with him, and I said to him: Professor Bartlett , I have a good mathematical mind, but I move slowly through a demonstration. If you hurry me or disconcert me I lose my chance. You are so familiar with this complicated work that it is very plai...