"No wonder the men wanted horses now--they knew the river's end was near. And yet they were four hundred miles, right here, from the head of the Missouri!" Billy had his _Journal_ pretty well in mind, so he went on frying bacon. "Why, what you talking about, Billy? They made the Forks by July 27th, and by the end of August they were over the Divide, headed for the Columbia!" "Sure. And at the Two Forks, where the Red Rock River turns south, the other creek--Horse Prairie Creek that they took--only ran thirty miles in all. The south branch was the real Missouri, but they kept to the one that went west. That was good exploring, and good luck, both. It took them over, at last." "But, Billy, everybody knows that Lewis and Clark went to the head of the Missouri." "Then everybody knows wrong! They didn't. If they had they'd never have got over that year, nor maybe ever in any year. I tell you they had luck--luck and judgment and the Indian girl. Sacagawea kept telling them this was her country; that her people were that way--west; that they'd get horses. For that matter, there were strong Indian trails, regular roads, coming in from the south, north and west; but it wasn't quite late enough for the Indians to be that far east on the fall buffalo hunt at the Great Falls. It took them more than a month to figure out the trail from here to the top. But if they had started south, down the Red Rock----" "Tell me about that, Billy." "We're working too hard before breakfast, son! Go get the others up while I fry these eggs. If we don't get off the Fort Rock and on our way, somebody'll think we're crazy, camping up here." Soon they were all sitting at breakfast around the remnants of the little fire, and after that Billy went after the horses while the others got the packs ready. Jesse was excitedly going over with Rob and John some of the things which Billy had been saying to him. Uncle Dick only smiled. "First class in engineering and geography, stand up!" said he, as he seated himself on his lashed bed roll. The three boys with pretended gravity stood and saluted. "Now put down a few figures in your heads, or at least your notebooks. How high up are we here?" "Do you mean altitude, or distance, sir?" asked Rob. "I mean both. Well, I'll tell you. Our altitude here is four thousand and forty-five feet. That's twenty-five hundred and twenty feet higher than the true head of the Mississippi River--and we're not to the head of the Missouri by a long shot, even now. "And how far have we come, say to the Three Forks, just above here?" "That's easy," answered John, looking at his book. "It's twenty-five hundred and forty-seven miles, according to the last river measurements; but Lewis and Clark call it twenty-eight hundred and forty-eight miles."