The train in Giuseppe De Nittis’s 1869 painting “The Train Passes” is there mostly by implication. A thick plume of white smoke or steam suggests the presence of an engine, and a small, dark form on the horizon seems to be its origin. But the bleak landscape of a few, spindly, leafless trees underscores the real subject: a world transformed by trains, coal and industry, and cities and countries brought into new intimacy by extensive networks of rail, roads and waterways.