488 TIDDEMAN : CARBONIFEROUS ROCKS IN UPPER AIRE-DALE. 
x\ltliougli the white hmestoiies, from their sporadic distribution, 
their physical structure, and their material, are evidently, if not 
coral-reefs, something formed in a kindred way, the black limestones 
show marked contrast to them in every way, and evidently have had 
a totally different origin. Most of these black limestones, which to 
the eye appear to be structureless, are found, when sliced and 
examined by the microscope, to be to a very large extent made up 
of Foraminifera and fragments of other organisms in a state of 
minute disintegration. Not that there is altogether a lack of larger 
and more perfect specimens, but these are not nearly so abundant as 
in the white limestones. Then the strongly marked bedding, so 
regular and parallel, the frequent alternations with thin beds of shale, 
and the wide and uninterrupted spread of these deposits, are all 
suggestive of deposition in waters which were not shallow, and in 
which similar conditions prevailed over wide areas. 
Without going further into the evidence here, we may say that 
it is highly probable that the black limestones are successive floors of 
the ocean bed of Carboniferous times, and that the white limestones 
are the islands wdiich dotted its surface. 
These conclusions are derived from minute examination of a 
wide area, and it now remains to apply them to a part of it, the 
Upper Aire Valley. The portion of the Aire Basin which I propose 
to allude to is that N. and N.E. from Skipton, containing the head 
waters of the Aire from Malham Tarn downwards and its tributaries, 
Winterburn Beck, Flashy Beck, Linton Beck, and Skipton Brook. 
If we take these areas in order from the South, as seen in one- 
inch maps, 60 and 61 (New Series) of the Geological Survey, we 
shall find that, after leaving that portion of the valley which cuts 
the Millstone Grit Series with its escarpments, we have (1) a great 
anticline which runs E.N.E. and W.S.W. from Skipton, passing by 
or near Bolton Abbey ; next (2) a syncline of which the centre lies 
near Gargrave, and wdiich brings down in its fold the Millstone Grits 
along a line from Flashy Fell, or Sharp Haw (pronounced Sharpa), 
to the Wharfe at Bolton Strid. (3) North of this comes another 
anticline, marked by the limestones running from near Otterburn to 
Grassington, also on the Wharfe. (4) A lesser anticline runs out 
