You bring up a really good point L.M. -- he does both because, I think, he feels both. Walden, the book, is a document of an experiment. And for all the hype that he lives far out in the woods, he really doesn't. Nor does he claim to. He notes many times that the railroad is just on the opposite edge of the pond. And that he "wears a trail to town" in his two year living in his "house". -- He only refers to his residence there as "cabin" once, all other times he refers to it as a "house" which I feel is significant.
Anyway, I got distracted there. Thoreau does appreciate the train and the great human endeavor that it stands for. Sometimes. Other times, he wonders if all that beautiful human effort and energy couldn't be put to better purposes than transporting goods and services -- that maybe if we put such effort into living a more beautiful life, even if only for a couple of years, we the human condition would grow.
The train in Walden is a lot like the Internet of today. Sometimes we love it. Sometimes we hate it. But the truth of the matter is that we are conflicted about it. It's a guilty pleasure, a necessary evil, and a beautiful transport of fellowship and communication all at once. And I think that Thoreau is showing you not his final thoughts about technology and the wild, but the natural paths of his thinking about such things.
"Solitude" is a beautiful chapter too, by the way. I think tomorrow I'll quote some of my favorite lines.
My personal favorite chapter is "The Bean Field". I adore the wild/agricultural/mock-heroic flavor of the whole chapter. And the wonderful experimentation of it.

