es Terres, of the old French fur-traders' dialect, are an extensive tract in the Dakotas, Wyoming, and northwestern Nebraska, between the North Fork of the Platte and the South Fork of the Cheyene rivers, west, south, and southeast of the Black Hills.
It lies mostly between long.
103° and 105° N., with an area as yet not perfectly defined, but estimated to cover about 60,000 square miles.
There are similar lands in the Green River region, of which Fort Bridger is the centre, and in southeastern Oregon.
They belong to the Miocence period, geologically speaking.
The surface materials are for the most part white and yellowish indurated clays, sands, marls, and occasional thin beds of lime and sandstone.
The locality is fitly described as one of the most wonderful regions of the globe.
It is held by geologists that during the geological period named a vast fresh-water lake system covered this portion of our continent, when the comparatively soft materials which compose the present