spectrally

adv

1. In a spectral manner; like a ghost.

   “Beyond the fence the forest stood up spectrally in the moonlight, and through the dim stir, through the faint sounds of that lamentable courtyard, the silence of the land went home to one’s very heart, - its mystery, its greatness, the amazing reality of its concealed life.”

2. In terms of a spectrum.

   “Nautilus come from deepwater where the light is spectrally blue and not very bright.”