CHAPTER XI.

NEWER PLIOCENE PERIOD.--BOULDER FORMATION.

Drift of Scandinavia, northern Germany, and Russia--Its northern origin--Not all of the same age--Fundamental rocks polished, grooved, and scratched--Action of glaciers and icebergs--Fossil shells of glacial period--Drift of eastern Norfolk--Associated freshwater deposit--Bent and folded strata lying on undisturbed beds--Shells on Moel Tryfane--Ancient glaciers of North Wales--Irish drift 121