While at community college, I took Differential Equations with Mr Shear. As he would write equations up on the chalkboard, coming to one that was particularly useful or profound, he would laugh through his nose with delight. I suppose he once worked as an engineer or physicist for the U. S. Army at their labs in Aberdeen; then, instead of retiring, he became a professor. He was a good professor. Mr Shear was quite old.
Mr Shear wrote on the chalkboard with a brass chalk holder, so that he wouldn't get chalk dust on his fingers. He posted his home phone number in the syllabus, with the note: "Call me if you have any questions about the homework. Do not call after 9 PM. I go to bed early because I am an old man.". One time, we had a take-home test, and when we got to class to turn it in, Mr Shear asked who had called him at 1 AM. He wasn't mad so much as amused.
One time, Mr Shear was lecturing, when some student made the mistake of asking him what logarithms are. Mr Shear gave the sort of prepared speech that all the old engineers have, about how we used to do everything using slide rules and tables of logarithms are quite useful when that's all you have.
"In fact," he continued, "during the Great Depression, there was a sort of Civilian Conservation Corps for mathematicians, except, instead of building parks and bridges and so on that didn't really need building, they worked out tables of logarithms to an unnecessary precision. These otherwise out-of-work mathematicians labored for years, calculating logarithms by hand. They filled volumes and volumes with these tables of logarithms. And do you know where these books are now?"
"No, where are they?" we asked.
"In the dumpster. We have calculators now!" He laughed through his nose, and went back to lecturing on the method of undetermined coefficients.