Is it the absence of direct sunshine, the oblique, halfhearted way the frail light falls, that makes this island float in and out of focus, like a dream, on the opaque waters of the vast Pearl River Delta? You have to cross a bridge to get there, a solid concrete arch over the slow khaki- colored canal separating Shamian island from the ancient, crowded alleys of Guanghzhou alongside it. Many of the city’s over ten million bustling inhabitants trade in much the same way as t