West of this mountain range rolled the waves of the last Cretaceous sea -- the vast marine water which divided the American continent. Perhaps a low coastal range separated it from the Gulf, and it probably extended, widening, to the arctic circle.

Between the Nebraska-Kansas range and the Ozarks there was an estuary, which might be called Topeka bay, and on the western shore of the sea were others, and into these the ebb and flow of tide and current carried spongelike woods, where water-logged and slimeburdened they settled down, and after ages they became coal beds.

Out in the expanse of the Central Ocean, there was an island, a hundred miles or more in length, along about the eastern border of the present Laramie plains. This Hartville island as we shall call it, was of igneous rocks, thrust edgewise up above the sea. Its western shore was of rugged wave-washed granite cliffs, and its eastern border was of crumbling Benton shales and greenhorn lime.

Tin- Benton series was fractured when this island was funned, it was the newest of the rock so broken. And the Niobrara chalk rockwas the first laid after the faulting of the world's crustal shell. In the rapidly shallow- ' ing sea that covered most of Nebraska's central plains, the Niobrara, the Pierre, and other shales were laid. Much of this part of the ocean for long year.-,, probably ranged in depth from one hundred to two hundred

fathoms. There the little grains of glauconite occurred from decomposition of organic matter contained in tiny foraminiferal shells. This hydrous silicate of potassium and iron is seventeen percent potash. The soil of Nebraska is fertile as a result.