July 02, 2004
#143 :: Glass Cutter
In seventh grade, we had Mr. Sletner. He was pear shaped, phlegmatic, probably 32 or 33, a lifelong science geek with a rather brittle demeanor. He assigned us to write a science fiction story one semester and I remember I wrote this very involved drama about astronauts marooned on the moon with no radio, no rescue and no weapons battling this huge bat creature from the sun. They finally defeated it by using compressed blasts of oxygen from the last of their air bottles to fire moon rocks at it, and eventually kill it. I was pretty proud of the hard science involved in the story, and my ballpoint-and-crayon illustrations. He gave me a C+ because my handwriting was so bad. For that reason, I didn't feel completely crushed by guilt when I was in his supply room one day after school by myself, and broke his sling psychrometer (a mercury-filled vessel with a wick that you swung in centrifugal circles) by accidentally smacking it against the black composite counter while swinging the thing around my head. Glass and beads of mercury all over the room. I sort of stuck it in the sink and vanished as fast as I could. Later that year (there was never any mention of the damaged equipment) he taught us about relative hardness, and how - short of diamonds - glass was one of the hardest substances on earth, harder even than steel. I still can't entirely figure out how a glass cutter works - I'm guessing the pressure causes glass' brittle surface to chip, scoring a line that later will snap when stressed by bending. But it's just a tiny little steel wheel with a sharp edge, mounted on a single pin (not even a bearing!) shoved through a cast piece of potmetal.