References to the land, sea, and sky show up six times in this poem's eighteen little lines, so you've probably already realized that nature is important in this piece. The potency of nature imagery here is also a little weird because, on the surface, the poem really isn't about nature at all. It's not some bizzare-o, bardic pagan song. In fact, the poem seems to have far more to do with Henry's psychological landscape than actual mountains or oceans. So, what gives, Mr. Berryman?
You don't have to read very far into this poem before some nature imagery smacks you over the head. Line 2 has flashing skies and yearning seas. But, um, last time Shmoop checked, seas can't yearn. At least not in the literal sense. They can slosh and splash and capsize boats, but… yearn? Here, Berryman is personifying the sea; he's giving it some of the snazzy qualities us human folk get to enjoy. And this poetic device allows Berryman to make a strong connection between the physical, natural world and the internal world of the speaker: his human emotions and human psyche.
Hey, remember that connection between nature and the human mind? Well, line 3 pretty much drives that point home. We "flash and yearn" just like the sky and sea "flash and yearn." Sweet.
Nature pops up yet again in the last stanza. We have "tranquil hills" which, to the speaker, "look like a drag." Now, let's consider how natural elements have been described in this poem so far; they "flash," "yearn," and are "tranquil." These descriptors all beautify the natural world. They're all, in a way, romanticizing nature by portraying it through a very human lens. Sound familiar? This is how nature is usually talked about in classic poetry and bad love songs, right? So, we think the way the speaker describes his surroundings reinforces his boredom not only with nature itself, but also with people's more general tendency to personify nature. And, since great literature is all about personification, dude's reinforcing his hatred for all that poetry and prose stuff too. It's all such a drag, man.
We'll get into Fido's significance later. For now, let's just consider the fact that this dog vanishes into the same three natural elements that have come up previously in the poem: the land, the sea, and the sky. The speaker is left behind to consider his surroundings, but, for some reason, some part of the dog remains with him. Even though the dog itself is no longer visible, there is something of its doggie-ness that remains with the speaker: its "wag."