Apostrophes at the beginning of stanzas in Byron's "The Giaour"

Question

My question is about Byron's The Giaour and the opening apostrophe at the beginning of a stanza. For example:

'His floating robe around him folding,
Slow sweeps he through the columned aisle;
With dread beheld, with gloom beholding
The rites that sanctify the pile
But when the anthem shakes the choir,
And kneel the monks, his steps retire;
By yonder lone and wavering torch
His aspect glares within the porch;
There will he pause till all is done -
And hear the prayer, but utter none
...

Why do some stanzas begin with an apostrophe, whereas others don't?

Answer 1

It's not an apostrophe but an opening quotation mark, paired with a closing quotation mark at the end of the stanza. If I am understanding rightly, this stanza is spoken by a monk into whose monastery the Giaour has come, and he is describing the Giaour's behaviour. (Hence e.g. his invocation of St Francis later in the stanza.)

In at least one early edition the typographical convention is different and more explicit, with every single line of the stanza preceded by a quotation mark.

(This isn't something you asked about but may also be worth mentioning: Some lines in this poem do in fact begin with apostrophes -- there are several beginning "'Tis". This is just an abbreviated version of "It is".)