A growing number of dog owners are involving their dogs in various kinds of fun and athletic dog events. Get a dog's eye view of the world of frisbee, flyball, and agility trials. The north branch of the Potomac River was brought to the brink of death by acidic poison pumped up from the bowels of drowned, ancient coal mines. Witness its tale of rebirth. Get a close-up look at one of the most unusual critters on land or in the sea --- Neptune's steed, the seahorse.