Page:A Treatise on Geology, volume 1.djvu/258

 242 lies very extensively under the plains of northern Germany. (Heiligoland is formed of wasting green sand.)

The green sand formation is more extensively spread than the chalk, for it is chiefly in this form that we recognise the cretaceous system about Dresden, in the Alps, in the Carpathians, and even the Pyrenees. On the Italian side of the Alps, the chalk is supposed to be represented by the scaglia of Genoa and Lombardy.

In North America, according to Dr. Morton and Professor Rogers, the cretaceous system is largely developed on the Atlantic coast in New Jersey, whence it may be traced locally through Delaware, Maryland, Virginia, North and South Carolina, Georgia Florida, Alabama, Mississippi, Tenessee, Louisiana, Arkansas, and Missouri. In the northern parts of this extensive range, yellow ferruginous and green sands, and some argillaceous beds, constitute the greater part of the system, as in the Carpathians, and are excessively rich in the green silicate of iron; they are covered by friable limestones and calcareous sandstones. Such green sands occur more rarely in the south-western tracts, and are there associated with, and finally superseded by, very thick cretaceous and compact shelly limestones, apparently superior in position, which rise into bold hills. It is curious that, for a great part of this range, the green sands are separated from the primary strata more inland by a narrow belt of tertiary and alluvial deposits. "By specimens brought from time to time from the interior of the continent, it would appear to occur abundantly on the Missouri, far across towards the Rocky Mountains."

Physical Geography.—In England, the range of the chalk is one of the most conspicuous features of the eastern and southern counties, in which it forms a noble chain of hills, still partially left (as, perhaps, they all should have been) open for sheep-pasture. These