﻿18 J. R. Dakyns — Glacial Origin of Terraces. 



Slieet.^ This paper will doubtless call fortli a number of equally 

 elaborate answers : and this is well. But if Mr. Goodchild has a 

 fine goose fattened on the Limestone terraces of Wensleydale, I have 

 an equally fine gander reared on Gritstone terraces in Derbyshire : 

 and if a frozen sauce of regelated snow from wintry storms of the 

 Great Ice Age is good for one, it is equally good for the other. 

 Dropping metaphor, there is no difference between terraces, mainly 

 of limestone, in Wensleydale, and other ten'aces, chiefly of grit, that 

 are found over all the Millstone Grit area of South Yorkshire and 

 Derbyshire, saving that while limestone predominates in the one, 

 beds of grit do in the other. If an ice-sheet carved out the terraces 

 of the Limestone Dales, it equally did those of the rest of Yorkshire, 

 Derbyshire, and, may I not add, of Cheshire and Stafi"ordshire ; yet 

 no sober-minded man. looking at these terraces, over so large an area, 

 rising and falling with every change in the inclination of the beds, 

 but ever following the dip and keeping to the bedding-planes, could 

 possibly suppose that they Avere carved out by ice-sheets. What in 

 the name of reason is to cause a great grinding ice-sheet, of whose 

 vaunted powers we have heard so much of late, to keep to a bedding- 

 plane ; much more to rise and fall with the dip of the beds? Add 

 to this all-sufficient objection to Mr. Goodchild's theory the fact that 

 over a great portion of this terraced area there is not a particle of 

 drift or a single ice-scratch, that has j^et been discovered, to bear 

 witness to the fact of any ice-sheet having been there at all. 



The fact that the terraces conform to the bedding is to my mind 

 conclusive against the Glacial Erosion theory ; but, as Mr. Goodchild 

 actually thinks this an ai'gument in favour of his theory, allow me 

 to ask him how he reconciles this accommodation of glacial action to 

 differences of hardness with the power of ice to smooth and round 

 off gnarled crystalline rocks, or to scoop out rock-basins in tough 

 Silurian slates quite irrespective of degrees of hardness. It seems 

 quite clear that ice cannot behave at one and the same time in such 

 opposite ways ; if it is guided in its course by such differences of 

 hardness as occur between limestone and sandstone, or these and 

 shale, it cannot scoop out rock-basins in total disregard of such 

 differences ; and if it can scoop out such rock-basins, it will not be 

 so aifected in its course as to carve out bedding terraces. 



As for the lines of swallow-holes along the junction of the lime- 

 stone with the overlying shale, the fact that these exist only along 

 this line of junction, and are not equally to be found over the bare 

 surface of the limestone, is no argument against the shale bank 

 having been eaten back by ordinary atmospheric agencies ; for it is 

 just to the very presence of the shale that the marked lines of 

 swallow-holes owe their existence ; the actual hole in the limestone 

 is generally a very insignificant matter, mostly a mere ordinary 

 joint. The marked swallow-holes are in the shale itself, and are due 

 to the soft shale crumbling away and falling into the open joints 

 below, and so giving rise to a funnel-shaped hollow much wider at 



1 " Glacial Erosion," by J. G. Goodchild, Geol. Mag., July, 1875, Dec. II. 

 Vol. II. p. 323. 



