WELLINGTON, Utah - Along Utah's Nine Mile Canyon lies what some call the longest art gallery in the world — thousands of prehistoric rock carvings and paintings of bighorn sheep and other wildlife, hunters wielding spears, and warriors engaged in hand-to-hand combat. But now, a dramatic increase in natural gas drilling is proposed on the plateau above the canyon, and preservationists fear trucks will kick up dust that will cover over the images. And they worry that one possible solution — a chemical dust suppressant — could make things worse by corroding the rock. "They're irreplaceable," said Steve Tanner, a...