Analysis of A Thought From The Rhine

I heard an Eagle crying all alone
Above the vineyards through the summer night,
Among the skeletons of robber towers:
Because the ancient eyrie of his race
Was trenched and walled by busy-handed men;
And all his forest-chace and woodland wild,
Wherefrom he fed his young with hare and roe,
Were trim with grapes which swelled from hour to hour,
And tossed their golden tendrils to the sun
For joy at their own riches:-So, I thought,
The great devourers of the earth shall sit,
Idle and impotent, they know not why,
Down-staring from their barren height of state
On nations grown too wise to slay and slave,
The puppets of the few; while peaceful lore
And fellow-help make glad the heart of earth,
With wonders which they fear and hate, as he,
The Eagle, hates the vineyard slopes below.

On the Rhine, 1851.