Writing a dirt clump and telephone essay

I was writing an essay in front of my professor, who was a kind of Boris Ustinov character. The essay was about how war is a class struggle against the poor, the solder being the victim. Suddenly I was using organic matter to create my words on a big sheet of paper. I knew what I was writing, but I was using green and brown pieces of dirt and plants as my letters. When I was done and ready to hand it in, the essay turned into a black telephone with little words all over it, like an art project. Suddenly what I was doing made sense. My professor seemed pleased.