A sense of the supernatural and the weird, bound up with a mysterious feeling of limitlessness and indefinitude that haunted him in his thoughts about this world and our earthly life.  The forms of another mysterious world, very near to this earth of ours, were seemingly present to his imagination.  From The Feeling for Nature in Scottish Poetry, Vol. 2, 1887.

Out of himself, so to speak, and soaring in that strange supersensible region whence forms and 'things of unearthly make' visited him with a thrilling and subduing power."  From The Feeling for Nature in Scottish Poetry, Vol. 2, 1887.