244 GOODCHILD : GEOLOGICAL HISTORY OF UPPER SWALEDALE. 



seven principal beds of marine limestone (with others of lesser 

 importance), each of which is directly overlain by beds of a shaly 

 nature, and each, as a rule, is succeeded below by a bed of sand- 

 stone. All the true Yoredale strata are persistent over a very large 

 area, the Hmestones being so to an extent little short of marvellous ; 

 although, of course, minor local variations may here and there be 

 detected if carefully sought for. The total thickness from the base 

 of the Millstone Grit above to the top of the Mountain Limestone 

 below is subject to some variation, but 1,500 ft. may be safely taken 

 as a fair mean for the whole. 



Counting from above downward, the beds of limestone best 

 known may be stated as follows, those most persistent being dis- 

 tinguished by an asterisk : — Crow or Fell Top Limestone ; *Red 

 Bed Limestone ; "Main, Twelve Fadom, or Great Limestone ; 

 *Undersett Chert and Undersett Limestone or Four Fadom Lime- 

 stone ; *Third Sett or Three Yards Limestone ; *Fourth Sett or 

 Five Yards Limestone ; *Fifth Sett, Middle, or Scar Limestone ; 

 *Sixth Sett or Simonstone Limestone ; *Seventh Sett or Hardra 

 Limestone. Below follow the various subdivisions of the Mountain 

 Limestone, whereof the highest bed is seen in Wensleydale near 

 Askrigg, etc., and again in the long inlier on the south bank of the 

 Swale between Muker and Gunnerside. Above the Main Limestone 

 occurs a remarkable series of siliceous beds, which the present 

 writer described many years ago as of organic origin, and of the 

 same general nature as the siliceous deposits brought to light in the 

 course of the late deep-sea researches. These siliceous rocks (Main 

 Chert, Red Beds, etc.) play an important part in connection with 

 the mining industries of the district. When weathered these rocks 

 pass into rotten stone. 



Long after all the Carboniferous rocks had been deposited, the 

 whole region underwent considerable disturbance, and most of the 

 leading flexures, as well as the leading faults, including the Pennine 

 Fault, affected these rocks for the first time. It was at this period 

 that the initial tilting of the strata towards the north-east took place. 



At a later period came prolonged upheaval, accompanied by 

 enormous denudation, many thousands of feet of Carboniferous 

 rocks being stripped off, in course of time, from this area alone. 



Subsequently, the New Red (including under this term all the 

 post-carboniferous rocks of older date than the Rhajtics) were 

 spread out over the whole of the North of England. As the 

 so-called ' Permian ' is only the basement bed of the Jurassic Series, 

 it follows that these rocks also once extended continuously over the 

 whole of Swaledale. 



Naturalist, 



