L. If it were divided into no more than three, on the outside of it, Isabel, it would be a fine world to live in; and if it were divided into three in the inside of it, it would soon be no world to live in at all. DORA. We shall never get to the crystals, at this rate. (Aside to MARY.) He will get off into political economy before we know where we are. (Aloud.) But the crystals are divided into three, then? L. No; but there are three general notions by which we may best get hold of them. Then between these notions there are other notions. LILY (alarmed). A great many? And shall we have to learn them all? L. More than a great many--a quite infinite many. So you cannot learn them all. LILY (greatly relieved). Then may we only learn the three? L. Certainly; unless, when you have got those three notions, you want to have some more notions;--which would not surprise me. But we'll try for the three, first. Katie, you broke your coral necklace this morning? KATHLEEN. Oh! who told you? It was in jumping. I'm so sorry! L. I'm very glad. Can you fetch me the beads of it? KATHLEEN. I've lost some; here are the rest in my pocket, if I can only get them out. L. You mean to get them out some day, I suppose; so try now. I want them. (KATHLEEN empties her pocket on the floor. The beads disperse. The School disperses also. Second Interlude--hunting piece.) L. (after waiting patiently for a quarter of an hour, to ISABEL, who comes up from under the table with her hair all about her ears and the last findable beads in her hand.) Mice are useful little things sometimes. Now, mousie, I want all those beads crystallized. How many ways are there of putting them in order? ISABEL. Well, first one would string them, I suppose? L. Yes, that's the first way. You cannot string ultimate atoms; but you can put them in a row, and then they fasten themselves together, somehow, into a long rod or needle. We will call these "NEEDLE-crystals." What would be the next way? ISABEL. I suppose, as we are to get together in the playground, when it stops raining, in different shapes? L. Yes; put the beads together, then, in the simplest form you can, to begin with. Put them into a square, and pack them close. ISABEL (after careful endeavor). I can't get them closer. L. That will do. Now you may see, beforehand, that if you try to throw yourselves into square in this confused way, you will never know your places; so you had better consider every square as made of rods, put side by side. Take four beads of equal size, first, Isabel; put them into a little square. That, you may consider as made up of two rods of two beads each. Then you can make a square a size larger, out of three rods of three. Then the next square may be a size larger. How many rods, Lily? LILY. Four rods of four beads each, I suppose. L. Yes, and then five rods of five, and so on. But now, look here; make another square of four beads again. You see they leave a little opening in the center.