You seldom see much critical contemporary social commentary in a book for the youngest story audience. It is very difficult to do without winding up as finger-shaking priggish. Bill Peet's often demonstrated sense of nonsense (Ella, Kermit the Hermit, Randy's Dandy Lions, et al) would naturally save him from such a stance. His subject is quite serious and will be an issue that tomorrow's voters will help decide if we are to survive. Dedicated to Rachel Carson, the simple story follows the forced departure of Shady Glade's population: ""half a dozen rabbits, a pair of possums, a single skunk, five green frogs, one bull frog and an old raccoon."" Their glade is laid waste by mindless machines sent out to expand the city's boundaries; their trees are torn up and their creek is stopped. A handy railroad bridge allows them to hop a passenger train which carries them so fast through the countryside they can't get off. The stops are all in cities where the streams are polluted by industry. Their luck holds and an emergency stop allows them to descend to an unspoiled spot like Shady Glade. The fun is all in the pictures, wonderfully colored as usual. The message and question about preservation will linger.