dark mossy massiness

a terrific towering palisade of dark mossy massiness

From book 25, section 4 of Pierre. The full passage:

Cunningly masked hitherto, by the green tapestry of the interlacing leaves, a terrific towering palisade of dark mossy massiness confronted you; and trickling with unevaporable moisture, distilled upon you from its beetling brow slow thunder-showers of water-drops, chill as the last dews of death.

“unevaporable”… “slow thundershowers”… “last dews of death”