126 DAKYNS: GLACIAL BEDS AT BRIDLINGTON. 
are not so, but the greater part I believe to be simply incipient 
concretions. The chalky gravel overlying the whole comes 
on about half-a-mile south of Clough Bridge, over the Gipsey. 
It generally lies on an eroded surface of sand ; but at one 
spot most distinctly dovetails with the sand. This shews 
that it is of the same general age as the underlying beds ; 
and that the eroded surface of these was caused by contem- 
poraneous denudations. 
Too much importance has been attached to such cases 
of partial unconformity, as if a great difference of age in 
the over and underlying beds were thereby necessarily 
implied. Geologists from the West Biding, who have paid 
much attention to the rocks of the neighbourhood, must be 
acquainted with scores of cases where such instances of 
contemporary erosion occur among the carboniferous rocks ; 
but no one dreams of taking such for anything more than local 
variations, or expects to found universal divisions upon 
them. Amongst the glacial beds of Holderness, however, 
it seems to be thought that such cases imply great divisions, 
and must be of far-reaching extent. In fact, both too much 
and too little importance has been attached to divisions in the 
boulder clay series : too much in so far as certain divisions 
have been seized upon and made to mean enormous differ- 
ences of age ; too little in that other divisions of perhaps 
equal importance have been entirely neglected. Thus many 
writers have recognised three boulder clays, whereas in some 
places there are four divisions in one of their boulder 
clays, with a like number of unconformities, or of changed 
conditions, or of both, as for instance at Dane's Dike, and 
the High Stacks at Flamborough Head. 
Some writers, again, speak as if there was but one real 
boulder clay, the boulder clay, one and indivisible; and 
all other stony clays were mere remanie beds. The 
great purple boulder clay itself, with its scratched, and 
