Then chase itself down Hill — (13)
This line also implies that the train has a measure of independence and a mind of its own.
[…] docile and omnipotent (16)
Yeah, yeah, yeah, we know. We've brought this quote up for every theme. It's for good reason – this is kind of the crux of the poem. The train is "docile," and does what it's supposed to do. However, it (and other new, mighty technologies like it) is also "omnipotent," which implies that it's more powerful than we ourselves are. That's a little creepy.