This picture separates the two halves of Jerusalem (Plate 100 is of the same type.)
On page 330 of Erdman's The Illuminated Blake instead of making his own notes he extensively quoted page 397 of Lesnick's Forms; here are some extracts:
'Stones of fire' is mentioned near the end of Plate 49 and in the Prologue of Gates of Paradise 'To the Sexes':
"Mutual Forgiveness of each Vice
Such are the Gates of Paradise
Against the Accusers chief desire
Who walkd among the Stones of Fire"
From Plate 49:
"Learn therefore O Sisters to distinguish the Eternal Human
That walks about among the stones of fire in bliss & woe
Alternate! from those States or Worlds in which the Spirit travels:
This is the only means to Forgiveness of Enemies[.]"
The following two lines indicate that the speaker is a fallen one:
"Therefore remove from Albion these terrible Surfaces
And let wild seas & rocks close up Jerusalem away.."
In Lesnick's words, "This vision of the stones of fire...that must be removed is the center of the poem". Removing the vision, one falls.
Several prints of this plate title it Vala, Hyle and Scofield.
The spiked crown make Vala the whore queen. She is slumping and holding her head.
Hyle is a smaller version; Scofield is slumped, walking in chains.