358 
HUGHES : rJfGLEBOROUGH. 
From below these Studfold sandstones the main mass of 
the Horton Flags, Acl, creep out, and, attaining a thickness of 
some 2,000 feet, occupy the whole of the eastern side of the valley 
as far north as Dove Cote and south nearly as far as Sherw^ood 
House. Owing to the rise of the synclinal axis as we follow 
it to the west, and a higher dip on its northern limb as seen at 
Arco Wood, the breadth of the mass is reduced under the lime- 
stone scar on the west of the Ribble to about three-quarters of 
a mile as compared with the two miles of ground which it and 
the overlying Studfold sandstones occupy where they disappear 
under the Mountain Limestone on the east of the valley. The 
Horton flags can be traced along the slope below the southern 
Fig. 2. 
(4R0UXD-PLAN SHOWING RELATION OF SILURIAN AND BALA SERIES 
BENEATH THE CARBONIFEROUS ROCKS. 
|'Ab4, Studfold Sandstone. Acl, Horton Flags. Ac2, Austwick Grits. 
A. Silurian Ac3, Pale Slate and Graptolithic Mudstone, with subordinate 
I limestones. Ac4, Basement Bed. 
B, Bala Beds. 
precipices of Moughton and the tip of the tongue formed by this 
syncHnal is protruded into the Crummack valley from beneath 
the western cliff of Mountain Limestone immediately below 
Studrigg Scar. 
The Austwick Grits crop out from beneath the Horton 
Flags. They are about a thousand feet in thickness, and from 
their massive, tough character and the occurrence in them of 
subordinate beds of softer material, they always give rise to 
marked features in the landscape. They can be traced by 
