309 
JUNCTION OF THE SILURIAN ROCKS WITH THE OVERLYING? 
MOUNTAIN LIMESTONE, AT MOUGHTON FELL, IN RIBBLES- 
DALE. BY THE EDITOR. (SEE PHOTOGRAPH.) 
The photogi'aph issued with this years volume of 
proceedings, illustrates an important section exposed in the 
valley of the Ribble, nearly opposite the village of Horton. 
The Silurian rocks, composed of grits, slates and limestones, 
extend over a large area, bounded by the line of the Pennine 
Fault, running in a north and south direction, and that of 
the equally important series of Craven Faults which run 
eastward from Ingleton, their position being indicated by 
the precipitous Scars of Giggleswick, Attermire, Malham, 
Yordale and Kilnsey. Bounded on the west and south by 
these Faults, the Silurian rocks underlie all the highest moun- 
tains in Yorkshire, forming a tolerably even base, with a 
general dip to the north-east. Sections exposing the junction 
of these rocks with the superincumbent Mountain Limestone 
may be seen beneath Whernside and Ingleborough, in the 
Ingleton and Dale Becks, and in Clapdale ; underlying Cross 
Fell and Mickle Fell, they may be seen at High Cup Gill, 
and as shown by Mr. Dakyns, at the Pencil Mill, near 
Cronkley Scar. Penyghent, and the extensive Limestone 
Fells of Malham and Kilnsey also have a basement of Silurian 
Grits. Perhaps the finest section, showing the junction of 
the two formations, anywhere exposed, is the one chosen for 
the subject of this photograph. The Silurian Rocks have 
long been quarried, and are locally known as the Horton 
Flagstones; they are a bluish grey colour, rather coarse 
sti*ucture, and can be obtained of verv larije size. The flacks 
are inclined at a very sharp angle to the horizontal beds of 
limestone which lie above them, but if traced along the side 
of the hill, it will be observed that they do not dip uniformly 
