Cryptogram from Frankenstein; or, the modern prometheus, chapter 24

When I quitted Geneva my first labour was to gain some clue by which I might trace the steps of my fiendish enemy. But my plan was unsettled, and I wandered many hours round the confines of the town, uncertain what path I should pursue. As night approached I found myself at the entrance of the cemetery where William, Elizabeth, and my father reposed. I entered it and approached the tomb which marked their graves. Everything was silent except the leaves of the trees, which were gently agitated by the wind; the night was nearly dark, and the scene would have been solemn and affecting even to an uninterested observer. The spirits of the departed seemed to flit around and to cast a shadow, which was felt but not seen, around the head of the mourner.

The sentence you are solving goes here.

I had begun my adjuration with solemnity and an awe which almost assured me that the shades of my murdered friends heard and approved my devotion, but the furies possessed me as I concluded, and rage choked my utterance.