■484 TIDDEMAN : CARBONIFEROUS ROCKS IN UPPER AIRE-DALE. 
When further we consider how great is the discrepancy between 
the rocks of the two areas in series and in thickness — that the Craven 
Faults form the boundary, and that a sharp one, between tliem — that 
these two series proceed from that bounchiry with scarcely any change, 
one as far as the Tyne, and the other to the western limit of the 
Carboniferous Rocks or. the seaside plain of Lancashire — that the 
greater thickness is on the downthrow side of the fanlts — if we take 
all these points, I say, into consideration, it is impossible to come to 
any other conclusion than this : — 
That the Craven Faults were to a very considerable extent going 
on during the formation of these rocks and that they are responsible 
for the lack of agreement between the two series which were being 
simultaneously deposited in the two adjacent areas. 
This appears at first sight to be a rather large subject to be 
introduced into a description of the small valley of the Upper Aire, 
but it so happens that it was this valley in the neighbourhood of 
Malham together with the adjacent country ou either side, along the 
faults w'estwards to the Ribble and eastwards to the Wharfe, which 
gave the key to unlock the mystery to which I have alluded. I had 
long suspected that these faults had been at work in Carboniferous 
times, but until this particular piece of gTound lately fell to my lot 
to map, tlie actual demonstration was wanting. I then not only found 
my suspicions confirmed, but the uncompromising nature of the two 
adjacent types set forth in a manner most unmistakeable. 
If we are driven to the conclusion that the movements of the 
Craven faults and the consequent alterations of conditions of deposit 
were the causes of the two distinct series in the areas north and 
south of the faults, several interesting questions arise. We may 
expect that on the downthrow side we shall get a series of deposits 
of which a greater portion has been formed under deeper water 
conditions than we shall find on the upthrow, or rather lesser down- 
throw, side. 
Though doubtless the movements proceeded by fits and starts, 
and were not always at uniform rates, still there will be a greater 
number of beds representing shallow than deep water conditions. 
If we can ascertain which beds are which, we shall be able to 
