26 KANSAS CITY REVIEW OF SCIENCE. 
while it is one of the largest, and apparently one of the oldest of rivers, it is, in 
truth, one of the youngest of this continent. When the St. Lawrence, the Cum- 
berland, the Ohio, and the Upper Mississippi had attained their full growth and 
supremacy over the countries now tributary to th m, the Missouri River was but 
in its infancy. When their systems of drainage were complete, all the vast terri- 
tory now tributary to the Missouri, which lies within the limits of four great geo- 
logical formations, namely, the Triassic, Jurassic, Cretaceous, and Tertiary, em- 
bracing a part of Iowa, the most of the States of Kansas and Nebraska, all of 
Colorado, and the Territories of Wyoming, Dakota, and Montana, were covered 
by an ocean. The Missouri River was then but little more than four hundred 
miles in length, and its drainage covered less than half of Missouri and Iowa, and 
but a small part of the eastern portions of Kansas and Nebraska, its headwaters 
being not remote from Omaha, Nebraska. Then great reptiles, from forty to 
ninety feet in length, sported in this vast expanse of ocean, which, with some 
interspersed islands, extended westward over the western plains and Rocky 
Mountain regions, covering the entire country now drained by the Missouri 
River westward and northwestward of Omaha. The eastern borders of Kansas 
and Nebraska formed a part of the ocean's eastern shore line, and it was no- 
where at a greater distance than two hundred miles from the eastern boundary 
of these States, the greatest distance being along the Kansas border. 
The Triassic and Jurassic formations were the first to emerge from this old 
western ocean. These formations are exposed along a narrow strip of country 
extending through Middle Kansas, and prolonged, perhaps, into Eastern Nebraska, 
but greatly widening to the south-west through the Indian Territory and Northern 
Texas. They added but little to the drainage of the Missouri River, and are 
conspicuous for the paucity of organic remains in them. Next, the Cretaceous 
formation emerged and became dry land. This added to the Missouri's drainage 
a broad belt of country extending across Kansas and Nebraska, and northward of 
Omaha, through Dakota Territory, increasing the river's length more than four 
hundred miles, and adding very materially to its western tributaries. This forma- 
tion is noted for the great abundance and gigantic proportions of its fossil reptiles 
and numerous invertebrate forms, as well as for several varieties of fossil wood, 
leaves, and plants, closely approximating present living species. Lastly, the 
Tertiary formation rose from the water, completing the Rocky Mountain system, 
and the drainage of the Missouri River to its present sources, '^'j the uprising 
of this formation the -remainder of Kansas and Nebraska, the most of Colorado, 
and the Territories of Wyoming, Dakota, and Montana were made tributary to 
the waters of the Missouri. But we must not associate these various elevations 
with great catastrophes, or suppose them sudden or violent, but, on the contrary, 
we have reason to believe them slow and gradual, requiring long ages in their ac- 
complishment. We must not, either, consider the Missouri, though among the 
youngest of rivers, so very young, counting its age by years, or comparing it, 
even, with man's duration upon the earth, for it has witnessed stupendous and 
long-continued changes since it attained its majority and was adopted, full-grown. 
