2. When we have done anything very often, and have got into the habit of doing it, we generally take the various steps in the same order; in many cases this seems to be a _sine quâ non_ for our repetition of the action at all. Thus, there is probably no living man who could repeat the words of “God save the Queen” backwards, without much hesitation and many mistakes; so the musician and the singer must perform their pieces in the order of the notes as written, or at any rate as they ordinarily perform them; they cannot transpose bars or read them backwards, without being put out, nor would the audience recognise the impressions they have been accustomed to, unless these impressions are made in the accustomed order. 3. If, when we have once got well into the habit of doing anything in a certain way, some one shows us some other way of doing it, or some way which would in part modify our procedure, or if in our endeavours to improve, we have hit upon some new idea which seems likely to help us, and thus we vary our course, on the next occasion we remember this idea by reason of its novelty, but if we try to repeat it, we often find the residuum of our old memories pulling us so strongly into our old groove, that we have the greatest difficulty in repeating our performance in the new manner; there is a clashing of memories, a conflict, which if the idea is very new, and involves, so to speak, too sudden a cross—too wide a departure from our ordinary course—will sometimes render the performance monstrous, or baffle us altogether, the new memory failing to fuse harmoniously with the old. If the idea is not too widely different from our older ones, we can cross them with it, but with more or less difficulty, as a general rule in proportion to the amount of variation. The whole process of understanding a thing consists in this, and, so far as I can see at present, in this only. Sometimes we repeat the new performance for a few times, in a way which shows that the fusion of memories is still in force; and then insensibly revert to the old, in which case the memory of the new soon fades away, leaving a residuum too feeble to contend against that of our many earlier memories of the same kind. If, however, the new way is obviously to our advantage, we make an effort to retain it, and gradually getting into the habit of using it, come to remember it by force of routine, as we originally remembered it by force of novelty. Even as regards our own discoveries, we do not always succeed in remembering our most improved and most striking performances, so as to be able to repeat them at will immediately: in any such performance we may have gone some way beyond our ordinary powers, owing to some unconscious action of the mind. The supreme effort has exhausted us, and we must rest on our oars a little, before we make further progress; or we may even fall back a little, before we make another leap in advance.