I found myself in a long road of tall and unlit mansions, stretching away into the distance, its length surmisable alone by the thread of twinkling gas-lamps which lay in front.    From Wordnik.com.  [Alfred Hitchcock's Mystery Magazine]

Out of the tail of his eye, just before he and Sonntag came to grips, he had caught a glimpse of this surmisable third party.    From Wordnik.com.  [From Place to Place] Reference