On some important Facts connected with the Boulders and Drifts of the Eden Valley, and their Bearing on the Theory of a Melting Ice-sheet charged throughout with Rock-fragments
Authors: Mackintosh D. 
Published: October 2009

Abstract

I
n
this paper the main object of the author was to defend generally received opinions, especially as regards the great glacial submergence, in opposition to the theory announced in the Quart. Journ. Geol. Soc. for last February (vol xxxi. p. 55). He brought forward a number of facts and considerations founded on repeated observations* which extended over part of the Lake-district and neighbouring plains, not apparently examined by Mr. Goodchild, though included in his theory. He stated that he had not found it safe to rely on a comparison of hand-specimens (as Mr. Goodchild has partly done), but that boulders, especially of granite, syenite, and felspathic rocks, require to be traced back to their sources. He maintained that the dispersion of Criffell granite boulders is so interwoven with that of boulders of porphyry and syenite from the mountains of the Lake-district as to be incompatible with the theory of transportation by currents of land-ice, and that the limitation of Criffell boulders along the north and west borders of the Lake-district mountains to a few hundred feet above the present sea-level is inconsistent with the idea of a boulder-charged ice-current 2400 feet in thickness. He likewise called attention to the interweaving of Criffell with Shapfell granite in the lower part of the Eden valley, as being inexplicable by upper and under currents of land-ice. He remarked that Mr. Goodchild has not directly referred to the dispersion of numerous boulders of Shapfell granite over ground at least 1300 feet above the sea, as far south as Milnethorpe. He defended the idea of a special, though not abruptly commencing, dispersion of surface-blocks of Shapfell granite (contrary to his first impressions), and thought that the limited altitude (1500 feet?) they have reached on Stainmoor is opposed to the theory of an ice-current “charged
throughout
with rock-fragments of all sizes” and attaining a thickness of 2300 feet; while an ice-current only 1500 feet in thickness (above the present sea-level) on Stainmoor, could not have spread out like a fan, and carried boulders as far as Royston, the coast of Holderness, Sedgefield near Durham, and over the East-Moorland hills. The author believes that some of Mr. Goodchild's sections are abnormal, while others which exhibit very complicated phenomena are paralleled in the maritime drifts in the plains of Cumberland, Lancashire, and Cheshire. The eskers of the Eden valley are similar in structure to those which contain sea-shells on the Welsh borders and elsewhere. They generally show traces of having been
pilled up
rather than
thrown down
, as Mr. Goodchild supposes. The author denied that the sea cannot throw down clays at angles of from 15° to 30°, and stated his grounds for believing (with the Rev. M. H. Close) that the sudden disappearance of the ice-sheet can be better explained by the encroachment of the sea than by the sudden melting of the ice. But the author's main argument against Mr. Goodchild's theory was derived from the
purity
of the interiors of existing ice-sheets, as shown by Professor Wyville Thomson and other eminent authorities.