"Sacks of which articles" in "Wuthering Heights"

In chapter 13 of Wuthering Heights by Emily Brontë, Isabella asks Joseph to find her a room to have supper in:

‘Here’s a rahm,’ he said, at last, flinging back a cranky board on hinges. ‘It’s weel eneugh to ate a few porridge in. There’s a pack o’ corn i’ t’ corner, thear, meeterly clane; if ye’re feared o’ muckying yer grand silk cloes, spread yer hankerchir o’ t’ top on’t.’

The ‘rahm’ was a kind of lumber-hole smelling strong of malt and grain; various sacks of which articles were piled around, leaving a wide, bare space in the middle.

What is the grammar here for "sacks of which articles"? Is it a relative clause? If so, why not just "sacks of which" without "articles“?

When you can’t figure out how a sentence works grammatically, a likely possibility is that you’ve got the wrong sense of a word, and in such cases looking in a dictionary is usually helpful. For example, you could use the free Wiktionary, where you would find:

which 3. (relative, formal outside certain phrases) Designates the one(s) previously mentioned.

He once owned a painting of the house, which painting would later be stolen. Yesterday, I met three men with long beards, which men I remember vividly. For several seconds he sat in silence, during which time the tea and sandwiches arrived. I'm thinking of getting a new car, in which case I'd get a red one.

In the passage from Wuthering Heights, plain “which” would have the same meaning, but the reason for using “which articles” is that, as noted in Wiktionary, this construction belongs to a formal register. In chapter 13, Isabella, who has been brought up as a member of the gentry, expresses her shock at the way she is treated by the residents of Wuthering Heights, and the contrast between her former way of living and her current situation. Isabella’s use of a formal register heightens the difference between her and the other characters, who speak in Yorkshire dialect.