Stanza 1 Summary

Get out the microscope, because we’re going through this poem line-by-line.

The splendour falls on castle walls
And snowy summits old in story:

Wait, what? The first line doesn't seem to make sense at first. How can "splendour," which is intangible (something you can't touch), "fall"?
"Splendour" seems to mean something a bit different here, though, like sunlight. Maybe we're supposed to imagine streams of light coming through between clouds.
So if this bright light is "fall[ing]" against the "castle walls," it must be coming in at an angle… so it must be sunrise or sunset. Which do you think it is? (Let's bear this question in mind later in the poem—there might be more clues.)
The sunlight, or "splendour," is streaming down and "falling" against the walls of a castle and against the snow-capped tops of mountains. Sounds like the speaker is in a valley somewhere, looking across at a castle and some snowy mountains.
But these aren't just any mountains—they are "old in story," which means that many tales have been written about them.
(Historical Note! Tennyson visited Ireland in 1848, just before writing "Splendour Falls." His inspiration was almost certainly a visit to a place in the mountains near Killarney called the "Eagle's Nest.")
There's a steady rhythm as we read this—the rhythm, or meter, is "iambic tetrameter." (Check out the "Form and Meter" section for more about what that means.)
The first line of this poem has two words that rhyme within the line: "falls" and "walls." That's called internal rhyme. Again, you should check out "Form and Meter" to learn more.

The long light shakes across the lakes,
And the wild cataract leaps in glory.

Now we're told that the sunlight is streaming across lakes.
The speaker says that the light "shakes." Weird, right? What would make light appear to "shake"? Maybe the water on the surface of the lakes is moving, causing the light to shimmer and "shake"? Or maybe the light is coming through tree branches that are moving in the wind? What do you think?
The repetition of the "L" sound at the beginning of "long," "light," and "lakes" is called alliteration—check out the "Sound Check" section for more about the sound effects here.
We're given another detail about the scenery: there's a waterfall, or "cataract," which is probably making a lot of noise as it falls, since the speaker calls it "wild."
The word "leaps" seems like a weird choice of words, and in combination with that word "wild," it seems like the waterfall is some kind of wild animal, "leaping" down the mountainside. Metaphor alert!
Line 3 has more internal rhyme ("shakes" and "lakes"), and line 4 introduces the first end rhyme of the poem—"glory" rhymes with "story" (line 2). Check out "Form and Meter" to learn more about the rhyme scheme.

Blow, bugle, blow, set the wild echoes flying,
Blow, bugle; answer, echoes, dying, dying, dying.

Suddenly we're not alone anymore! Or are we? A bugle (a kind of horn like a trumpet) is blown, and the notes echo across the valley and then fade, or "die," away.
The repetition of the word "dying" seems to imitate the echoes that the speaker is describing.
The speaker addresses the bugle directly, instead of addressing the person who is blowing it. Ladies and gentlemen, it's a textbook example of a poetic tool called apostrophe—Shmoop on over to the "Symbols" section to learn more about that.