OF THE DISTRICT. 
169 
spicuous projection of the thinner underset limestone; a long slope 
succeeds, simple or slightly varied with rising undulations corres- 
ponding to the hard gritstones interstratified with shales; this ends 
above a single or double scar of the middle limestone, which is very 
conspicuous where thick, as in Addleburgh and Pen hill, but easily 
lost by the detritus of the superior rocks where it is thin, as above 
Hawes : below this is another slope to the Simonside limestone, which 
forms a smooth terrace ; another steep slope to the Hardrow scar lime- 
stone, which runs for miles along both sides of Wensleydale in a 
remarkable terrace, occasionally woody, always very abrupt and rocky 
at the edge, and based on a steep slope of plates leading to the broad 
floors of the lower limestone series. It seems unnecessary to offer 
any other explanation of the prominent and retiring parts of this 
profile, than that afforded by the consideration of the relative resistance 
offered by the different rocks to the atmospheric agency and watery 
currents which have modified the surface of the country ; the lime- 
stone is the most consolidated rock in the district and most capable 
of resisting the wasteful effects alluded to, hence its projecting scars : 
plate or shale is in this respect exactly the reverse, hence its soft 
uniform slopes : gritstone is of intermediate character and feature, 
but in the Yoredale series rocks of this nature are thin, much mixed 
with plate, and thus prevented, except in favourable circumstances, from 
appearing in a characteristic manner. Of the five limestone belts which 
encircle so many of the Yoredale mountains, the middle and lowest but 
one are the least constant : where these are indistinctly seen the interval 
between the upper or Cam belt of limestones and the lower or Hardrow 
scar limestone is enormous ; but in proceeding northward to Aldstone 
moor this interval contracts and the scar lime of that valley, equivalent 
to the black limestone of Dent and Hardrow scar, is not so far removed 
from the upper belt. The profiles of the hills in Aldstone moor follow 
the same law: the limestones almost always project, the argillaceous 
beds form obscure slopes, certain thick gritstones (as the Nattriss gill 
hazle particularly) occasionally rough angular edges. (See in illustra- 
tion of these remarks the Sections No. 1, 2, 3.) 
z 
