16 
BLAKE : EAST YORKSHIRE. 
the substitution of limestone for shale, or of sandstone 
for grit, but each valley yields new developments, and no 
cliff is long like its neighbour. Its varied formations have 
not been neglected by geologists, and the materials for its 
general history are sufficiently abundant. 
The newer deposits on any area must of necessity take 
their character, to a greater or less degree, from the form of 
the ground produced by its earlier history. Where an axis 
of elevation is known to exist, we shall expect it to act as a 
barrier between the areas on either side of it, so that the 
deposits formed in them shall be different both in character 
and position ; or when such a difference is actually perceived, 
and an axis of elevation exists in a neighbouring district, we 
may safely conclude the extension of that axis into the area 
in question. Thus the great fold which bounds the Yorkshire 
coal field on the north, and brings up the older rocks in the 
neighbourhood of Harrogate, would seem to have been con- 
tinued to the east, and to have had its effect on all subsequent 
deposits. To the north of this east and west line is found a 
large development of newer rocks, whose character is peculiar 
to the district ; while to the south are the last remnants of 
another series of deposits, which here seem to find their 
northern limit, but which are extended southwards through 
Lincolnshire into the Home counties. 
This restriction of areas is of necessity most marked in 
the older portions of the series — for the amount of deposited 
material, the various changes of elevation that the country 
undergoes in process of time, must tend to obliterate the 
distinction ; and by the time the chalk was formed we shall 
not be surprised to find that it is recognisable no longer, or 
at least only so far as new axes of elevation seem always to 
have a tendency to follow the lines of old ones. 
The truth of these premises will come out most clearly, 
and the conclusions derivable from them will be most 
