692 D. MACKINTOSH ON SOME IMPORTANT FACTS CONNECTED WITH 



52. On some important Facts connected with the Boulders and 

 Drifts of the Eden Yalley, and their Bearing on the Theory of 

 a Melting Ice-sheet charged throughout with Mock-fragments. 

 By D. Mackintosh, Esq., F.G.S. (Bead June 23, 1875.) 



[Abstract.] 



In 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 dis- 

 persion of Criffell granite boulders is so interwoven with that of boul- 

 ders 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 hun- 

 dred 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 Eoyston, the coast of Holderness, Sedge- 

 field 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 Che- 

 shire. The eskers of the Eden valley are similar in structure to 

 those which contain sea- shells on the Welsh borders and elsewhere. 



* For detailed accounts of these observations see Geol. Mag. for October and 

 December, 1870, and June and July 1871. See also Quart. Journ. Geol. Sec. 

 for August 1873. 



