Question

Which lines from matthew arnolds "Dover Beach" beat conveys a tone of serenity?

Answer 1

I'm a big fan of Matthew Arnold, including the poem Dover Beach. The first line actually conveys serenity: "The sea is calm tonight." More examples of serenity in the first stanza are as follows (slashes indicate line breaks):
"the cliffs of England stand, / glimmering and vast, out in the tranquil bay."
"Begin, and cease, and then again begin, / With tremulous cadence slow,  and bring / The eternal note of sadness in."

In the third stanza, you can find examples of serenity in the following:
"But now I only hear / Its melancholy, long, withdrawing roar, / Retreating, to the breath / Of the night-wind, down the vast edges drear / And naked shingles of the world."

In the fourth stanza, you can find examples of serenity in the following:
"The world, which seems / to lie before us like a land of dreams"

Hope this helps.