What if The Atlantic owned a train car? I wondered. Amtrak, I had just learned on the internet, allows owners of private railcars to lash onto runs along the Northeast Corridor, among other routes. “We should have a train car,” I slacked an editor. Moments later, it appeared on my screen, bright red with our magazine’s logo emblazoned in white, just like I’d ordered. It’s an old logo, and misspelled, but the effect was the same: A momentary notion—one unworthy of relating to someo...