Lingogidda?

See, see the wide horizons glorious blaze!
The setting sun descending low,
Beyond the fervid mountain's brow.
And high Carnedda's top reflects the lingering rays:
But now yon russet heath attracts our eyes,
Where sable Lingogidda's vapours rise.

Here oft 'tis said
The wand'ring spirits of the dead,
By magic's awful art confin'd,
Th' affrghted hind and rustic dame
See glowing in the lambent flame,
Hear howling in the wind.

These are the closing lines of the poem Petraeia by the artist Thomas Jones of Pencerrig and published in a book of 1791 "Picturesque Guide to the Beauties of South Wales."

Now the reference to the Carneddau hills is clear enough and on a late summer evening the sun certainly does reflect from its brow as the painter says, but can anyone tell me about Lingogidda? I guess the poem refers to corpse candles, the spontaneous combustion of methane and phosphane you get over bogland and, no doubt, bogland around Pencerrig. Lingogidda? Llyn Gogidda? There's a verb gogyddio - which refers to making millstones but who knows?