CASLLrs -- Jamie McKinnon may occasionally press the wrong button in his email program, but he really does know how to write letters to the editor. Another one to thank him for appeared today. It rebuts a Globe editorial saying pollution measures were too expensive, pointing out their wilful misunderstanding of the phrase "clean air is free." It's shorter and more cogent than two other letters making similar points. Obviously Jamie should be writing the editorials. (Wish he were.) Margaret Procter University of Toronto