he right-hand fork
was roily, boiling, and rolling, exactly like the Missouri up which they
had come, whereas the other fork was clear. But Lewis said that this
showed that the Marias ran through plains country and did not lead close
to the Rockies, from which the water would run clearer; and they did
not want to skirt the mountains northerly, but to cross them, going
west.

"Lewis had an old English map, made by a man named Arrowsmith, based on
reports of a Hudson's Bay trader named Fidler, who had gone a little
south of the Saskatchewan and made some observations. Now look at your
_Journal_, and see what Lewis thought of Mr. Fidler.

"The latter marked a detached peak at forty-five degrees latitude. Yet
Lewis--who all this time has been setting down his own latitude and
longitude from his frequent observations--makes the Marias as
forty-seven degrees, twenty-four minutes, twelve and eight-tenths
seconds. He says:

"'The river must therefore turn much to the south between this and
the rocky mountain to have permitted Mr. Fidler to have passed
along the eastern border of these mountains as far south as nearly
45 deg. without even seeing it.... Capt. Clark says its course is
S. 29 W. and it still appeared to bear considerably to the W. of
South.... I think therefore that we shall find that the Missouri
enters the rocky mountains to the North of 45 deg. We did take the
liberty of placing his discoveries or at least the Southern
extremity of them about a degree farther North ... and I rather
suspect that actual observations will take him at least one other
degree further North. The general course of Marias river ... is 69
deg. W. 59'.'

"Lewis also figured that Fidler in his map showed only small streams
coming in from the west, 'and the presumption is very strong that those
little streams do not penetrate the Rocky Mountains to such distance as
would afford rational grounds for a conjecture that they had their
sources near any navigable branch of the Columbia.' He was right in
that--and he says those little creeks may run into a river the Indians
called the Medicine River. Now that is the Sun River, which does come in
at the Falls, but which Lewis had never seen!

"Again, the Minnetaree Indians had told him, in their long map-making
talks at the Mandan winter quarters, that the river near the Falls was
clear, as he now saw this stream. The Minnetarees told him the Miss