"I don't see how that is possible."
"I am going to make you a sketch which you can examine at leisure, that will show how he knows. Assuming that the earth has a crust—that is, the outside or cooled part, let the first sketch (Figure 10) represent this crust, before the mountains and valleys were formed. The slightly curved horizontal lines merely represent the different layers of the crust, such as rock, clay, coal, slate, and the like. When the cooling process took place the earth grew smaller within, so that the crust was forced together.
Fig. 10. Normal Crust of the Earth
"The second sketch (Figure 11) shows this crust forced together, so that when the upheaval took place, two mountain ranges, A and B, were formed, with a valley (C) between them, and the broken lines (D), where the crust separated, were exposed, and by that means examinations can be readily made way down into the crust, without ever leaving the surface of the earth."
As it was understood that the boys should take at least a day each week for hunting, particularly since such sport would develop expertness in the use of their weapons, an early start was made on the day selected, which was within a week of the time they returned home.
Ever since the disappearance of the boat left at the falls in South River, there was some anxiety on that score. It was a frequent topic of conversation, and after they left home it was by a mutual impulse that they wended their way south, taking a trail which was now familiar to them.