The boys assented to this.
Billy went on, his finger now on the map in turn.
“Take Clark along in here on the Gallatin, near this ranch, say July 15th, about one month ahead of our date now. He is going east with his party. He has got the Indian girl and some horses and some good men. All right. On July 15th he starts across the Divide, heading for the Yellowstone Valley.
“Naturally, he found that plumb easy. He struck into one of the creeks that run down into the Yellowstone. It was only nine miles down that to the Yellowstone River itself, and they hit that just a mile below where it comes out of the Rockies from up yonder in Yellowstone Park, where we all were only yesterday.
“Clark had the easiest end of it, in some ways. He said he had to go only forty-eight miles from the Three Forks to hit the Yellowstone. If he had poled a canoe up the Gallatin, he would not have had to portage over eighteen miles.
“Those are the distances that Clark estimates, but for once he underestimates, I don’t know why. Wheeler points out that from Three Forks to Livingston is fifty-four miles, and Clark came down off the Divide at a place just above Livingston. Anyhow, I’ll bet he was glad when he saw the old Yellowstone Valley. He had horses now, you see, and he was hitting the trail hard.
“He went down the north side of the Yellowstone, and by July 17th he was down as far as Big Timber and Boulder River. I suppose they would have kept on downstream on horseback, but one of their men, Gibson, got snagged in a fall from his horse, so somewhere near the mouth of the Stillwater they concluded to make some canoes, so that Gibson could ride by boat.
“Now, on July 21st, along comes a nice party of Crows and steals twenty-four of their horses. They hunt a couple of days for the horses, but can’t find them—trust the Crows for that! So the canoes are mighty useful. They built two of them twenty-eight feet long and about two feet in the beam and lashed them together, so they had quite a craft.
“On July 24th, about the time Gass and his men were making the portage at the Great Falls, Clark took to the boats, but he put the rest of the horses in charge of Pryor, Shannon, and Windsor.