Ill 
These two rocks resemble in character, thickness, and 
the distance between them, the Houghton Common and 
Brierley Eocks, and though the evidence is far from conclu- 
sive, there seems a strong probability that they are the same 
as these rocks. 
The plateau of Ackworth Moor Top is separated by the 
valley in which the village of Ackworth stands, from a 
corresponding tract of high ground at the eastern end of 
which is the village of East Hardwick. This hill is capped 
by a sandstone bed, and unless there be faults in the valley 
between, this rock must be the same as the Ackworth 
Ptock, and, therefore, probably the same as the Brierley 
Rock. 
Another valley separates the range of high land just 
described from the rising ground about Pontefract. In the 
latter we again find a couple of thickly bedded, softish, light 
brown sandstones. The upper is largely quarried in 
Pontefract, and forms the bold bluflp on which the castle 
stands ; the lower is a much less conspicuous rock. These 
two sandstones again so far resemble the Houghton Common 
and Brierley Rocks, that it is a reasonable conjecture to 
suppose them identical with those beds. 
The above scanty facts are all that we have to guide us in 
our attempt to puzzle out the geological structure of the 
district ; we recognise at three points a pair of sandstone 
beds which are much alike generally in thickness, character, 
and distance apart ; there is an a priori probability that the 
corresponding sandstones of each pair are detached portions 
of one and the same bed ; as far as the dip can be made out 
there is nothing in the lie of the strata to forbid this suppo- 
sition ; and we therefore have adopted it as the best of several 
explanations that have occurred to us. 
It is probable that the rocks over the whole of the 
district undulate gently in broad shallow folds ; in each basin 
