probability of its truth. If he had told me of the existence of falls
one thousand feet high, I should have considered his story an
exaggeration of a phenomenon he had really beheld; but I did not think
that his imagination was sufficiently fertile to originate the story of
the existence of a spouting geyser, unless he had really seen one, and I
therefore was inclined to give credence to his statement, and to believe
that such a wonder did really exist.

I was the more disposed to credit his statement, because of what I had
previously read in the report of Captain John Mullan, made to the war
department. From my present examination of that report, which was made
Feb. 14, 1863, and a copy of which I still have in my possession, I find
that Captain Mullan says:

I learned from the Indians, and afterwards confirmed by
my own explorations, the fact of the existence of an
infinite number of hot springs at the headwaters of the
Missouri, Columbia and Yellowstone rivers, and that hot
geysers, similar to those of California, exist at the head of
the Yellowstone.

Again he speaks of the isochimenal line (a line of even winter
temperature), which he says reaches from Fort Laramie to the
headwaters of the Yellowstone, at the hot spring and geysers of that
stream, and continues thence to the Beaver Head valley, and he adds:

This is as true as it is strange, and shows unerringly that
there exists in this zone an atmospheric river of heat,
flowing through this region, varying in width from one to
one hundred miles, according to the physical face of the