His patients near Portland, Oregon, know him as Dr. Clark, the man who has a nice parking spot and wears a clean T-shirt every day. Last summer, however, this particular dentist drew a thick line through one squeaky-clean work week on the calendar and then tried to convince a group of his skiing pals to do the same. He talked of roaming the untamed lands of the Northwest. The Columbia River, he told them, was lined with bald eagles, snow-capped mountains and Native Americans catching salmon. Then he mentioned plate-glass water that runs through some of the most scenic territory in North America.