The changes of level which occurred during the glacial epoch are shown by the deposits at Frankley Hill. In the clays and sands cut through by the Halesowen Railway only a few erratics (felsites) were found; but on the summit of the section they are abundant and of large size (_e.g._, 4 × 4 × 2ft.) Professor Bonney, who has examined them, feels certain they must have come from Wales, having seen nothing like them in the Lake District. Their height is nearly 800ft. above the sea level. Were these erratics brought by land ice, the alteration in the physical geography of the country must have been enormous to have enabled a glacier to have moved downwards over this point; were they dropped from icebergs, the land must have been depressed to the extent of at least 900ft., to form a sea in which the bergs could have floated.
Turning to the _Middle Glacial Clays, Sands, and Gravels_, these may be seen more or less developed in almost every section cut through undulating ground; and they are occasionally twisted and contorted. In the immediate neighbourhood of Birmingham they are not fossiliferous.
At Ketley, near Wellington (Shropshire) however, fossiliferous sands and gravels occur, which I am inclined (provisionally) to assign to this period. They rest upon a bed containing erratic blocks of granite, and other rocks of northern origin; and I collected from them 13 species of mollusca. Only one species was peculiarly northern (_astarte borealis_) but all in the group have an arctic range of habitat. The elevation of these beds is about 357 feet above the sea.
At Fox Hall Field, New Lodge, Lilleshall (Shropshire) in a pit worked for sand, 463 feet above the sea, Mr. Woodward discovered 21 species of mollusca, three--viz., _Dentalium abyssorum_, _Natica affinis_, and _Astarte borealis_--being characteristically arctic and extinct in British waters.
_The Upper Boulder Clay_ is worked for bricks in many localities. It is distinguished from the Lower Boulder Clay, by having erractic blocks sparsely scattered through it. It is often very compact and tenacious. No fossils have as yet been found in it; unless indeed a clay derived from a drain in a street at Wolverhampton, in which I detected fragments of _Tellina balthica_, the spine of an _Echinus_, _Polymorphina lactea_, and _Polystomella crispa_, may be assigned to this division of the epoch.