The Danube to the Severn gave
The darken’d heart that beat no more;
They laid him by the pleasant shore,
And in the hearing of the wave.


There twice a day the Severn fills;
The salt sea-water passes by,
And hushes half the babbling Wye,
And makes a silence in the hills.


The Wye is hush’d nor moved along,
And hush’d my deepest grief of all,
When fill’d with tears that cannot fall,
I brim with sorrow drowning song.


The tide flows down, the wave again
Is vocal in its wooded walls;
My deeper anguish also falls,
And I can speak a little then.

The River Wye flows into the Severn near Chepstow, at Bleachley Point. On many days in the year, the incoming tide is so powerful it creates the Bore, a powerful wave rushing upstream against the current of the river. But even on ordinary days the tide is very strong. When it drives upstream it slows the discharge of the River Wye, forcing it to back up. This pressure is released when the tide turns and flows out.

Tennyson uses this tidal phenomenon to make an image of his grieving, which is compared in its more superficial state to the “babbling Wye” flowing into the larger stream. But his deeper grieving is compared to the silent, backed up, state of the Wye at high tide. This grieving is silent and has no outward expression, even in poetry.

This is a powerful metaphor for readers who can imagine a fairly unusual natural phenomenon. The Danube is mentioned at the start of this canto because Hallam died in Vienna.

I can agree with Tennyson about a level of grief which is beyond expression.