Very much as a painter half closes his eyes so that some salient unity may disengage itself from among the crowd of details, and what he sees may thus form itself into a whole; very much on the same principle, I may say, I allow a considerable lapse of time to intervene between any of my little journeyings and the attempt to chronicle them. I cannot describe a thing that is before me at the moment, or that has been before me only a very little while before; I must allow my recollections to get thoroughly strained free from all chaff till nothing be except the pure gold; allow my memory to choose out what is truly memorable by a process of natural selection; and I piously believe that in this way I ensure the Survival of the Fittest. If I make notes for future use, or if I am obliged to write letters during the course of my little excursion, I so interfere with the process that I can never again find out what is worthy of being preserved, or what should be given in full length, what in torso, or what merely in profile. This process of incubation may be unreasonably prolonged; and I am somewhat afraid that I have made this mistake with the present journey.