192 



BALDERSTOX 



GLACIAL ACTION NEAR INGLETON. 



some glacial action, the former being crossed obliquely and the latter 

 longitudinally by the course of the respective glaciers, but the signs 

 are doubtful, not that there is any lack of a manifestation of the 

 rounding and smoothing of the rock, but the exact agent is uncertain 

 and appears in a great measure to have been purely fluviatile, whilst 

 at the joints or veins, sometimes grooves, at others ridges, are con- 

 spicuous as the result of variation in the chemical agents, which in 

 their turn have brought about the slow decomposition of the upper 

 surfaces of the dyke. 



As in the case of Crummack Dale on the south-eastern slopes of 

 Ingleborough, so at Ingleton, a kind of Silurian ridge, which has 

 interposed itself in the way of the glacier, may be observed about 

 two miles above the village at this place, where the patches of green, 

 porphyritic rock appear : here, however, the rocks are massive, or if 

 showing indications of dip, denote it as only slightly deviating from 

 the perpendicular, whilst above Austwick the dip of the beds is in a 

 contrar)- direction and as much as 45° (N.E.) from the horizontal line. 

 These two ridges are fine situations, in situ, for viewing the direct 

 traces of glacial erosion ; the rocks, especially in Crummack Dale, 

 are in many parts reduced to an almost glassy smoothness, with 

 traces of striation in various places, and so high is the polish that it 

 is more easily detected by the foot than by the eye, as, when wet, it 

 is dangerous for a person to walk upon the inclined surfaces. 



The striation of the boulders at Norber is much more notable 

 than at Ingleton, where the smoothing and rounding of the somewhat 

 smaller masses is a stronger feature, speaking comparatively. At 

 Ingleton the story told is not so limited to one place, is not so con- 

 centrated, but, perhaps, on the whole gives a fuller history of general 

 glacial action. The Silurians of Crummack Dale are to a certain extent 

 of a more impressionable character than those which have been the 

 chief subject of erosion in the \'alley of the Doe, being of a somewhat 

 calcareous composition, effervescing with Ho SO 4, and not 'grits'— 

 although occasionally flecked with mica — as they have erroneously 

 been designated, yet sufficiently proof against the weather as to have 

 retained their lines and furrows for a protracted period : they appear 

 referable to the Coniston-Bala series, belonging to a portion of a fold 

 of the contorted strata now lying beneath the Carboniferous beds 

 somewhere about Chapel-le-Dale and Weathercote, the other portion 

 having been removed prior to the Carboniferous era, wdth the excep- 

 tion of the lower part, now buried below^ Ingleton and stratigraphically 

 above the Coniston limestone and shales here exposed, and appearing 

 again in the inverted flexure of the duplicature above Austwick with 

 these hard, calcareous Silurians actually overlying them. 



Naturalist, 



