HUGHES : INGLEBOROUGH. 
359 
Stainforth and Swartli Moor, they form the rugged slopes below 
the southern scars of Moughton, and they occupy 'nearly the 
whole of the floor of the valley of Crummack except a small 
part of the north end. 
Below these grits there is always a roughly-cleaved sand}^ 
mudstone, with subordinate grits, to which I have for conveni- 
ence of reference given the name Austwick Flags. This sub- 
division, which has a thickness of about 400 feet, varies much 
in general appearance, according as the cleavage coincides with 
the bedding or is transverse to it. We observe also considerable 
differences in composition and texture. There are in it some 
beds of tough grit, the larger of which give rise to important 
scenic features, as, for instance, that which, having a thickness of 
some 60 feet, accounts for tlie wild rocky scenerj^ in the beck below 
Capple Bank, or that which, with an apparent thickness of about 
20 feet, projects through the soil near tiie upper end of Moughton 
Lane. These beds, however, more commonly consist of a soft 
mudstone sphtting by cleavage and joints into small rhomboidal 
pieces, or readily breaking into slabs on wliich the bedding is 
sometimes indicated by faint lines and bands, or yielding rough 
flags when the bedding and cleavage coincide. 
They are best seen along their southern outcrop near South- 
waite and along the line of the road from Austwick to Crummack. 
The basement bed of the Silurian, i.e., of the Upper Silurian 
of the Survey, is the most interesting of the whole system. It 
is everjrwhere the horizon which presents the greatest difficulties. 
It is of small thickness, and therefore easily overlooked ; it 
consists of, and occurs among, alternations of deposits of different 
composition, texture, and structure, which are therefore apt to 
be either wholly removed or obscured by denudation. It is 
exceedingly variable, and is therefore difficult of identification 
where there is not a continuous exposure along which the changes 
of character may be traced. But it is the most worthy of careful 
examination, for it is the first accumulation of sediment under 
the new conditions which set in after the age of volcanic a,ctivity 
had passed away, and the full life of the Bala rocks had given 
place to a new group, among which very few of the abundant 
species of the earlier period are to be found. 
