It is an instinct.

By and by you will just naturally KNOW one from the other, but you never will be able to explain why or how you know them apart' It turned out to be true.

The face of the water, in time, became a wonderful book--a book that was a dead language to the uneducated passenger, but which told its mind to me without reserve, delivering its most cherished secrets as clearly as if it uttered them with a voice.
And it was not a book to be read once and thrown aside, for it had a new story to tell every day.

Throughout the long twelve hundred miles there was never a page that was void of interest, never one that you could leave unread without loss, never one that you would want to skip, thinking you could find higher enjoyment in some other thing.

There never was so wonderful a book written by man; never one whose interest was so absorbing, so unflagging, so sparkingly renewed with every reperusal.