MOETIMER : OEIGIlSr OF CHALK DALES. 
41 
and that the band is well seen in most of the quarries along- the 
Wold edg-e in Lincolnshire. Its stratigraphical position is near the 
somewhat indefinite line, which separates the grey chalk from the 
white chalk ; and I am not aware that it has been found at any other 
horizon. To disturbances only can we moreover attribute the almost 
innumerable beds of fullers earth, which exist throug-hout the whole 
thickness of the chalk. Some of these beds, 1 to 3 in. in thickness, 
are, like the black band, probably due to subterranean movements 
affecting- the bed of the ocean and troubling the waters, the smaller 
ones, some of which are hardly sufficient to separate the laminae of 
chalk which they divide, are, as mentioned in a previous paper of 
mine, undoubtedly due to ordinary ocean storms, acting on, and 
breaking up more or less the forming chalk below ; during the 
succeeding calms seams of fullers earth were deposited, which thus 
produced the innumerable laminae observed throughout the chalk 
formation, To no other cause can these fine divisions be attributed. 
If a section be drawn from Acklam on the western edge of the 
chalk, to Hornsea on the eastern coast-line, we shall find the base of 
the chalk to be 1,400 ft. higher at the former place than it is at the 
latter. Though part of this great difference may be due to chalk 
having been deposited in a basin-shaped hollow, upheaval has 
been an important factor in placing the beds along its elevated 
outcrop it their present position. An interesting feature is attached 
to the most elevated portion of this outcrop. The valleys on its 
outer edge, are sharply defined, whilst the hill tops show compara- 
tively little trace of denudation. But along the inner margin of the 
out-crop, the valleys are greatly widened, and the hill tops are much 
planed down, the material being carried down to lower ground 
(lowering hill and filling up dale) and producing a level appearance ; 
strikingly in contrast with what is observed on the outer and 
elevated side of the out-crop This great difference of appearance 
cannot be due to subaerial denudations, or Ave should have the outer 
side of the out-crop, which most probably, was the first to emerge 
from the cretaceous sea, quite as much if not more denuded than 
the inner. What then have been the causes that have acted so 
unequally upon the inner and the outer sides of the out-cropping 
