What are the historical and geographical refrences in Matthew Arnold's poem "Dover Beach"?

"Dover Beach", by 19th century poet Matthew Arnold, is an
elegy on the retreat of faith - under the twin assaults of science and rationalism
- from the contemporary world. Both the setting of the poem, and its historical
allusions undergird this theme. Arnold wrote the poem in 1851 during or shortly after he
and his new bride visited Dover Beach, located on the south coast of England, a mere 21
miles from the French port city of Calais. This geography appears in the poem in the
first stanza: 

readability="7">

The tide is full, the moon lies fair/Upon the
straits; on the French coast the light/Gleams and is gone; the cliffs of England stand;
/ Glimmering and vast...

In
the context of the explicit theme of the poem, this geography assumes a metaphorical
cast. As the light on the French coast winks in and out - "Gleams and is gone" - so
faith, once bright and constant, now shines spasmodically. Similarly, the white cliffs
of Dover merely glimmer with an uncertain light. And though they are imposing, in fact
they are made of chalk, a substance that easily erodes. These physical traits of Dover
Beach further develop the theme of weakening faith. Stanza 1 concludes with a reference
to the "grating roar of pebbles" producing, in the wave action of the sea, a "tremulous
cadence" with "an eternal note of sadness". Later, in Stanza 3, Arnold supplies the
prophetic meaning  for these sounds: They are the "melancholy, long, withdrawing roar"
of the "Sea of Faith" retreating from the world. In the second stanza, the poet
compounds the geographical references with a historical one. Sophocles, the author of
Antigone - where divine intervention plays a very small role in
"the turbid ebb and flow
of human misery" - also must have heard the same
thing.