NATURAL RESOURCES OF THE COUNTRY. 93 
twenty miles above Fort Union, and the line traces its course for some one hundred and eighty 
miles. Comparatively a small stream, it yet shows much the same features as the Missouri; 
has a wide, open intervale, half to four miles wide; is closed in on either side by the bluffs ter- 
minating the plains, which ascend as they recede from the river, the bluffs being very frequently 
cut with deep coulées, which can be traced five, ten, or fifteen miles into the interior. The river 
is plentifully supplied with cotton-wood, and its bottom-lands are flat and generally wide. At the 
first crossing of this river by the train, some fifiy miles above its mouth, the bed of the stream 
had a width of two hundred and twenty-five feet; the running water was but fifty feet wide and 
two and a half feet deep, with a sandy bottom, and banks of clay and sand rising some fifteen 
feet above the water-level, unstable, and often displaced by the river in its annual floods. 
At the third crossing, by the winding of the wagon road, a little more than one hundred and 
eighty miles above its mouth, the river retained nearly the same width of bed and genera] 
features, but with no running stream, the water remaining in the depressions and holes in its bed. 
The bottom-lands, both of the Missouri and Milk rivers, are composed of clay and sand, of a 
nature to become soft and sloppy with the wet of spring, and on the dry season succeeding, becom- 
ing parched and cracked. The prairie and upland formations are remarkably undeviating in their 
character, consisting of a mixture of clay and sand, intermixed with smooth pebbles, extending 
below the surface only from one to three feet, and below all, the underlying coarse sandstone 
The clay washed by the rains finds its way into the coulées and the bottom of the river, leaving 
the exposed pebbles on the surface, deceiving one with the appearance of gravelly or stony knolls. 
This section does not offer the best, but will afford a fair material for road embankment. 
The tributary rivers on the north side for which bridges must be erected are Great Muddy 
river, Poplar river, and Porcupine river—all small streams, with an average width of sixty feet, 
and greatest depth three feet, at our several crossings. 
The Missouri and Milk river bottoms possess one peculiar feature, for which provision 
must be made in constructing a railroad. At short intervals, averaging not over eight miles for 
the whole river line, narrow canal-like channels are found generally extending from the coulées 
of the bluffs, for the greater part dry in summer, but in spring freshets are the sluices by which 
the water from the rain and snow finds its passage to the river. These channels or sloughs have 
an average width of twenty-five feet, with a depth of eight feet, and should be spanned with a 
simple timber structure to prevent the accumulation of water and injury to the road-bed. 
The high prairie plateau which the road attains on leaving Milk river reaches to the base of 
the Rocky mountains, and is marked with but little variation of surface. The same formation of 
clay and sand, with more or less admixture of pebbles, continues as on the prairies, running back 
from the Missouri and Milk rivers. There is a scarcity of wood and water. The soil at first 
possesses little fertility, scantily shaded with a short thin grass; gradually improving as the ap- 
proach is made to the mountains. Through this plateau the rivers Marias and Teton flow in deep 
channels, concealed from sight till one is close upon them, with bottoms fairly wooded with cotton- 
wood one-quarter to half a mile wide, and marked by the deep coulées intersecting their valleys. 
These two rivers, in the vicinity of the railroad line, are about two hundred and one hundred 
and twenty feet wide, and flow some two hundred feet below the general level of the prairie. 
The water is no longer muddy or milky, as in the Missouri, with its lower tributaries, but is 
clear and cool, flowing over a pebbly and sandy bottom. The passage of the Marias river 
is one of some difficulty and expense, owing to the depth of the river below the prairie. The 
Teton is crossed high up, and with less difficulty. Sun river is crossed near its source, and 
with ease. 
From the Great Muddy river to the base of the Rocky mountains there is a river line for two 
hundred and sixty-five miles, and the balance is of prairie. The earth-work in all this extent will 
not be heavy. An average embankment of eight feet will more than cover it. The material, as 
already stated, is a mixture of clay and sand, not a light loam, but easily broken up with the 
