The petrified prehistoric organisms are reason enough to visit Isle La Motte's Goodsell Ridge Preserve this summer. But there's another one: The 83-acre natural area on the Chazy Fossil Reef is hosting an evolutionary exhibit, "Walk Through Time." Created in 1996 by Sid Liebes, a scientist at Hewlett-Packard Labs, its 71 colorfully illustrated panels showcase 4.6 billion years of evolution of life on Earth. To help viewers put that mind-boggling time frame in perspective, the panels are spread over a 4,600-foot trail; each foot represents a million years. Scientist Jane Goodall, who has visited the traveling exhibit, called it "an unforgettable experience, awe-inspiring and humbling."