Note 17 — BOOK IV.
Reading edition
—Page 267, stanza xciii.
O'er the Black Valley, demon shadows fleet.
Cwm Idwal (in Snowdonia). "A fit place to inspire murderous thoughts,—environed with horrible precipices shading a lake lodged in its bottom. The shepherds fable that it is the haunt of demons, and that no bird dare fly over its damned waters."—Pennant, vol. iii. p. 324.