Thoreau writes in his journal:
C. [William Ellery Channing] says that he followed the track of a fox all yesterday afternoon, though with some difficulty, and then lost it at twilight. I suggested that he should begin next day where he had left off, and that following it, up thus for many days he might catch him at last . . .
Minott says that a hound which pursues a fox by scent cannot tell which way he is going; that the fox is very cunning and will often return on its track over which the dog had already run . . .