"flowed easily and felicitously, without any difficulty to lay hold of them or to find appropriate language" (which, by the way, is more than all would say who had read Scott's "Life of Bonaparte," and certainly more than can be said of his secretary, unless it really was a familiar experience with him to be unable to lay hold of his thoughts). "This was evident by the absence of all solicitude (miseria cogitandi) from his countenance. He sat in his chair, from which he rose now and then, took a volume from the bookcase, consulted it, and restored it to the shelf—all without intermission in the current of ideas, which continued to be delivered with no less readiness than if his mind had been wholly occupied with the words he was uttering. It soon became apparent to me, however, that he was carrying on two distinct trains of thought, one of which was already arranged and in the act of being spoken, while at the same time he was in advance, considering what was afterward to be said. This I discovered" (he should rather have said, "this I was led to infer") "by his sometimes introducing a word which was wholly out of place—entertained instead of denied, for example—but which I presently found to belong to the next sentence, perhaps four or five lines further on, which he had been preparing at the very moment when he gave me the words of the one that preceded it." In the same way the present writer has unconsciously substituted one word for another in lecturing, the word used always belonging to a later sentence than the word intended to be used. We have noticed also this peculiarity, that, when a substitution of this kind has been once made, an effort is required to avoid repeating the mistake, even if it be not repeated quite unconsciously to the end of the discourse. In this way, for example, the writer once throughout an entire lecture used the word "heavens" for the word "screen" (the screen on which lantern pictures were shown). A similar peculiarity may be noticed with written errors. Thus in a treatise on a scientific subject, in which the utmost care had been given to minute points of detail, the present writer once wrote "seconds" for "minutes" throughout several pages—in fact, from the place where first the error was made, to the end of the chapter. (See the first edition of Proctor's "Transits of Venus," pp. 131-136, noting as an additional peculiarity that the whole object of the chapter, in which this mistake was made, was to show how many minutes of difference existed between the occurrence of certain events.)
An even more curious instance of a mistake arising from doing one thing while thinking of another occurred to the writer fourteen years ago. He was correcting the proof-sheets of an astronomical treatise in which occurred these words: "Calling the mean distance of the earth 1, Saturn's mean distance is 9·539; again, calling the earth's period 1, Saturn's mean period is 29·457: now, what relation exists between these numbers 9·539 and 29·457 and their powers? The first is less than the second, but the square of the first is plainly greater than the second; we must therefore try higher powers," etc. The passage was
