“You bet I remember,” said Perry, “why, Uncle George, just for fun I made myself a model of it.” “Good thing to do, it’ll help you to remember. Now, in the States we haven’t any one place where all these various strata show up clearly one above the other, with great ledges exposed for exploration and working, as they are in the Fayum. But, all over Wyoming, in different valleys and at different parts of the Bad Lands, there are these same strata exposed for miles and miles. At one place, Perry, such as the Washakie formation, where I’m going first, all the rocks deposited since the time of the Upper Eocene Period, have been washed or weathered away, so that the Upper Eocene layers are exposed. It’s a Bad Land country, too, where the rocks are soft, where there is no fertile soil and no steady rainfall. So, when the cloudbursts come, the rain eats easily into the soft rocks and carves them into buttes and ravines. The sand-bearing winds cut them away still further, so there are hundreds of thousands of square feet exposed to the weather and erosion is always going on.” “Gee, what a chance!” cried Perry. “Why, you could go over a country like that every year and find something.” “You can travel over it after every rainstorm or windstorm, for that matter. Then, after I’ve spent a day or two at the Washakie, I’m going to the Bridger Bad Lands. They’ve been cut down a little further, so that all the Upper Eocene has been eroded and the Middle Eocene is exposed. So you see, Perry, in the Washakie formation we have a chance of finding the fossils of animals that lived in the Upper Eocene Period; and, a few miles away, in the Bridger Bad Lands, we can find the fossils of half a million years earlier. Then, in the Wasatch, there are two places I’m going to visit, the Wind River Valley and the Gray Bull River country; the Wind River exposes the top of the Lower Eocene Rocks and the Gray Bull the bottom layers. Then, if I can get time, I’ll go to New Mexico, where there has been more erosion and the rocks are cut away down to the Basal Eocene, and, after that, I plan to come back to Wyoming for the famous Laramie formation, which is cut down to the Cretaceous Period, or the Age of Chalk, and which has been our great hunting ground for the Dinosaurs.” “My Pteranodon was from the Age of Chalk.” “Certainly, Perry, but it was from a marine formation, earlier than the Laramie. You see the Cretaceous Ocean covered Kansas, but did not cover Wyoming. I want to make an exact map of the relations of these strata to each other so as to show clearly the way in which the rocks were laid down and to give a continuous picture of the life of the animals that lived during those times. You know well, Perry, that I’m always more interested in fossils for the sake of the ideas of primitive life that they give, than for fossils themselves.”