PHYSICAL GEOGRAPHY 
170 
' Where the Yoredale series, by the extinction of its limestones and 
some of its gritstones, becomes almost wholly argillaceous, as in Ingle- 
borough and Fountains fell, the profile changes. Then the main lime- 
stone and underset limestone conjoined or separately project into their 
usual mural precipices, and below them a nearly uniform slope of 
many hundred feet in descent conducts to the Dent or Hardrow lime- 
stone, which may or may not form a prominent belt according to 
circumstances. This depends very much on the thickness of the sub- 
jacent plates. (See Section No. 1, and Outline of Ingleborough No. 21.) 
In Bolland and the country south of the Craven fault the Yoredale 
series, being almost wholly shale with interlaminated limestones, presents 
only sloping surfaces below the gritstone summits, or smooth rounded 
hills in all the large region between Ribblesdale and the border of the 
Yorkshire coalfield, where no gritstone appears. These rounded sur- 
faces of shale and limestone are also in many instances conformed to 
the interior dislocations of the strata. (See Outline No. 23 for the 
contrast of shale and gritstone hills in Craven.) 
The facility of waste and tendency to form insular hills caused by 
the great abundance of shale in the Yoredale series is the cause of 
much of the grandeur and variety of the Yorkshire dales. To this 
cause we must ascribe the extensive denudations of the Yoredale series ; 
the connexion of the dale heads of opposte drainages ; and the enormous 
depth of the valleys. This facility of waste has cleared those prodigious 
broad limestone surfaces, on which at wide intervals stand the cones 
of Ingleborough, Wharnside, and Penyghent, deriving from their in- 
sulated position and happy combinations a grand and beautiful effect 
in the landscape, often denied to far higher but less favourably situated 
mountains. 
The alternation of limestones, gritstones, and plates, which constitutes 
the essential character of the complete Yoredale series, is the cause of 
another beautiful feature in the scenery of the Yorkshire dales— the 
waterfalls. 
