BRIDGE CROSSING BY DAVE DRYFOOS He knew the city was organized for his individual defense, for it had been that way since he was born. But who was his enemy? * * * * * * * IN 1849, THE MIST THAT sometimes rolled through the Golden Gate was known as fog. In 2149, it had become far more frequent, and was known as smog. By 2349, it was fog again. But tonight there was smoke mixed with the fog. Roddie could smell it. Somewhere in the forested ruins, fire was burning. He wasn’t worried. The small blaze that smoldered behind him on the cracked concrete floor had consumed everything burnable within blocks; what remained of the gutted concrete office building from which he peered was fire-proof. But Roddie was himself aflame with anger. As always when Invaders broke in from the north, he’d