The Bamboo Dragonflies of Arashiyama   In a bamboo grove a man is carving bamboo to make dragonflies— their long tails counterweighting their paired forward-thrusting wings.   In the beginning, who imagined the balance and the buoyancy that could be achieved by means of mere weight and counterweight?   Yet stability depends on many matters, as the recently steady bamboo dragonflies discovered when I bumped them.   Even as they bob and wobble out of balance they look elegant— the bamboo dragonflies carved to match poise with counterpoise.   Andrew Lansdown