She thought of the geometrical and historical difficulties in the way and sighed.
"A great deal will have to happen before I get there," David remarked light-heartedly, "but I mean to manage it somehow. Perhaps only Dobbin knows how much I think about it while I work here in my uncle's fields."
"Is that your uncle's house? " questioned Betsey, looking up at the big chimneys above the trees.
"Yes, and all this land is his, up to Somerset Lane. He is away a great deal and expects me rather to keep an eye on things, but of course I work on the farm too. There is really almost no one else to do it with all the labor crowding into the cities. I try to study by myself at night—but I don't get very far. There are some places where I think I will stick forever."
"Oh," exclaimed Betsey, suddenly seeing the explanation of that puzzling page that had fallen into her hands the night David's papers blew away, "do you find it hard to prove what is the volume of the frustum of a pyramid?"
"Do I?" returned David from the bottom of his heart. His freckled face crinkled into a delighted grin as he looked up at her. "Don't tell me that there is some one else who finds it as mysterious as I do! 'The frustum of a pyramid is
