482 
PHYSICAL HISTORY OF THE CARBONIFEROUS ROCKS IN UPPER AIRE-DALE. 
BY R. H. TIDDEMAN, M.A., F.G.S., OF THE GEOLOGICAL SURVEY. 
During the last few years the rocks in tliis area have been 
mapped in considerable detail by the Geological Survey, and the 
results which are coming out seem likely to thi'ow much light upon 
the physiography of Carboniferous seas and perhaps upon the genesis 
of some limestones of other ages. 
It was always a puzzle to those geologists wdio knew the ground 
how it came to pass that the well-known and very persistent series of 
the several limestones of the Yoredale Beds ran with such regularity 
over the great area of the Yorkshire dales and yet were not recognizable 
over the area of Bowland and the southern part of Craven. 
Until the area of which we now speak was carefully surveyed, 
it was assumed that there was a rapid transition of type in the 
Carboniferous Rocks between Clitheroe and the big fells north of 
Settle and Malham, but as to the cause of such a rapid change no 
explanation was forthcoming. Even Professor Phillips, who knew 
the country perhaps best of any among the old pioneers of Geology, 
often expressed himself to me as quite unable to account for it. If 
there is one thing more clearly brought out than another by the 
mapping in detail of this ground, it is this, that there is absolutely 
no transition from one type to the other. The two types run un- 
changed in their respective areas and with complete discordance with 
each other, quite up to a common boundary where the differences are 
rather accentuated than smoothed down. They might be Jews and 
Samaritans, agreeing in nothing save a common boundary to their 
territories and a determination to have nothing to do with one 
another. 
The line of demarcation is given by the Craven Faults, and more 
particularly by that which runs by the south end of Malham Tarn 
and that which passes between Malham Cove and Malham. 
With these preliminary remarks we may introduce a table 
showing the rocks in the two areas and their principal divisions and 
thicknesses. 
