Again, another circumstance which might intervene to diminish the frequency of application of the memory referred to, as to the physical features or appearance of a book sought for, is where the shelf-arrangement is alphabetical, by authors' names, or by the names of the subjects of the books, if it is an alphabet of biographies. Here, the surest and the quickest guide to the book is of course the alphabetical order, in which it must necessarily be found. This memory of the aspect of any object once looked at, is further well illustrated in the very varied facilities for the spelling of words found in different persons. Thus, there are people who, when they once see any word (we will say a proper name) written or printed, can always afterwards spell that word unerringly, no matter how uncommon it may be. The mental retina, so to speak, receives so clear and exact an impression of the form of that word from the eye, that it retains and reproduces it at will. But there are others, (and among them persons of much learning in some directions) upon whom the form or orthography of a word makes little or no impression, however frequently it meets the eye in reading. I have known several fine scholars, and among them the head of an institution of learning, who could not for the life of them spell correctly; and this infirmity extended even to some of the commonest words in the language. Why this inaptitude on the part of many, and this extraordinary facility on the part of others, in the memorizing faculty, is a phenomenon which may be noted down, but not solved. That vivid mental picture which is seen by the inward eye of the person favored with a good memory, is wholly wanting, or seen only dimly and rarely in the case of one who easily forgets. So vital and important is memory, that it has been justly denominated by the German philosopher, Kant, "the most wonderful of our faculties." Without it, the words of a book would be unintelligible to us, since it is memory alone which furnishes us with the several meanings to be attached to them. Some writers on the science of mind assert that there is no such thing with any of us as absolutely forgetting anything that has once been in the mind. All mental activities, all knowledge which ever existed, persists. We never wholly lose them, but they become faint and obscure. One mental image effaces another. But those which have thus disappeared may be recalled by an act of reminiscence. While it may sometimes be impossible to recover one of them at the moment when wanted, by an act of voluntary recollection, some association may bring it unexpectedly and vividly before us. Memory plays us many strange tricks, both when we wake and when we dream. It revives, by an involuntary process, an infinite variety of past scenes, faces, events, ideas, emotions, passions, conversations, and written or printed pages, all of which we may have fancied had passed forever from our consciousness.