Theodore Roethke - The Signals lyrics

Often I meet, on walking from a door, A flash of objects never seen before. As known particulars come wheeling by, They dart across a corner of the eye. They flicker faster than a blue-tailed swift, Or when dark follows dark in lightning rift. They slip between the fingers of my sight. I cannot put my glance upon them tight. Sometimes the blood is privileged to guess The things the eye or hand cannot possess.