One drops eight and a
quarter inches to the mile, and the other nineteen inches to the mile.

"But understand, we're talking now of the upper thread of the
Mississippi River, and of the Three Forks of our river--which isn't by
any means at its head, even measuring to the head of the shortest of the
three big rivers that meet here. Now, add three hundred and ninety-eight
miles to twenty-five hundred and forty-seven miles. See what you got?"

"That's twenty-nine hundred and forty-five miles!" exclaimed John. "Is
it that far from the head to St. Louis?"

"Yes, it is. And if you took the Lewis and Clark measurements to the
Forks it would be thirty-two hundred and forty-seven miles.

"And if we took their distances to the place where they left their
canoes--that's what they called Shoshoni Cove, where the river petered
out for boats--we'd have three thousand and ninety-six miles; two
hundred and forty-seven miles above here, as they figured it, and they
weren't at the summit even then. Now if we'd take their probable
estimate, if they'd finished the distance to the real head of the
Missouri, we'd have to allow them about thirty-two hundred and
forty-nine miles plus their overrun, at least fifty miles.

"Yes, if they'd have gone to the real source, they'd have sworn it was
over thirty-three hundred miles to St. Louis, and over forty-five
hundred miles to the Gulf. The modern measurements make it forty-two
hundred and twenty-one miles.

"So, young gentlemen, you can see that you are now coming toward the
head of the largest continuous waterway in the world. It is five hundred
miles longer than the Amazon in South America, and more than twelve
hundred miles longer than the river Nile, in Africa.

"Now, Meriwether Lewis did not know as much about all these things as we
do now, yet see how he felt about it, at his camp fire, not so far from
here:

"'The mountains do not appear very high in any direction tho' the
tops of some of them are partially covered with snow, this
convinces me that we have ascended to a great hight since we have
entered the rocky Mountains, yet the ascent has been so gradual
along the vallies that it was scarcely perceptable by land. I do
not believe that the world can furnish an example of a river runing
to the extent which the Missouri and Jefferson's rivers do through
such a mountainous country and at the same time so navigable as
they are. if the Columbia fur