These chapters are for children, and I shall try to make the words large enough to command respect. In the hope that you are listening, and that you have confidence in me, I will proceed. Dates are difficult things to acquire; and after they are acquired it is difficult to keep them in the head. But they are very valuable. They are like the cattle-pens of a ranch—they shut in the several brands of historical cattle, each within its own fence, and keep them from getting mixed together. Dates are hard to remember because they consist of figures; figures are monotonously unstriking in appearance, and they don’t take hold, they form no pictures, and so they give the eye no chance to help. Pictures are the thing. Pictures can make dates stick. They can make nearly anything stick—particularly _if you make the pictures yourself_. Indeed, that is the great point—make the pictures _yourself_. I know about this from experience. Thirty years ago I was delivering a memorized lecture every night, and every night I had to help myself with a page of notes to keep from getting myself mixed. The notes consisted of beginnings of sentences, and were eleven in number, and they ran something like this: “_In that region the weather_—” “_at that time it was a custom_—” “_but in california one never heard_—” Eleven of them. They initialed the brief divisions of the lecture and protected me against skipping. But they all looked about alike on the page; they formed no picture; I had them by heart, but I could never with certainty remember the order of their succession; therefore I always had to keep those notes by me and look at them every little while. Once I mislaid them; you will not be able to imagine the terrors of that evening. I now saw that I must invent some other protection. So I got ten of the initial letters by heart in their proper order—I, A, B, and so on—and I went on the platform the next night with these marked in ink on my ten finger-nails. But it didn’t answer. I kept track of the fingers for a while; then I lost it, and after that I was never quite sure which finger I had used last. I couldn’t lick off a letter after using it, for while they could have made success certain it would also have provoked too much curiosity. There was curiosity enough without that. To the audience I seemed more interested in my fingernails than I was in my subject; one or two persons asked me afterward what was the matter with my hands. It was now that the idea of pictures occurred to me; then my troubles passed away. In two minutes I made six pictures with a pen, and they did the work of the eleven catch-sentences, and did it perfectly. I threw the pictures away as soon as they were made, for I was sure I could shut my eyes and see them any time. That was a quarter of a century ago; the lecture vanished out of my head more than twenty years ago, but I could rewrite it from the pictures—for they remain. Here are three of them: (Fig. 1).