Reports cl; ProceediriJjs — Edimburfjli Geological Society. 141 



January 21, 1920.— Mr. E. B. Bailey, M.C., B.A., F.G.S., President, 



ill the Chair. 



1. " Evidence of the Retreat of an Ice-sheet to the South-East 

 of Edinburgh." By D. Anderson, M.A. 



Mr. Anderson referred to the work of Professor Kendall and E. B. 

 Bailey on the glacial channels in East Lothian, the principle of which 

 was that of marginal drainage along the edge of a retreating ice- 

 sheet. Mr. Anderson was led to look for similar evidence in Mid- 

 lothian. He then described the area Avhich he had surveyed, which 

 consisted of two ridges and the three valleys or stream-courses 

 by which these were marked out. The first is the Liberton- 

 C'raigmillar Ridge and the second that of Gilmerton ; the stream - 

 courses being those of the Braid Burn, the Burdiehouse Burn, and, 

 more remotely, the North Esk. After describing the main svirface 

 features of the district by reference to the map, and an allusion 

 to the contour of the main roads which cross the ridges in a south- 

 easterly direction from Edinburgh, he pointed out the geological 

 structure of the Liberton Ridge as belonging to the Upper Old Red 

 Sandstone System, while the Gilmerton Ridge consisted of the coal 

 and limestone series of the Carboniferous. The series of glacial 

 channels crossing the ridges were then described. A well-marked 

 one to the south-west is the Longloan Channel, so named from a 

 place which stands on its west edge. The height here is 450 feet, 

 consequently when the cutting began the impounding ice-mass 

 must have stood somewhat higher, and since Blackford Hill, the 

 Braids, Craiglockhart Hill, and Corstorphine Hill all reach 500 feet, 

 these heights may have risen like low islands above the surface of 

 the ice-lobe, somewhat back from its edge. The contour of the 

 Longloan Channel, as well as that of the others, was indicated by 

 sections kindly prepared by Mr. Mathieson of the Ordnance Survey 

 from measurements taken with this special end in view. The depth 

 here was 33 feet, and the "width 303 feet. Some four more channels 

 on this ridge were similarly described, the direction in which they 

 were taken being from south-west to north-east. After having 

 referred 'to certain other glacial phenomena on the Gilmerton Ridge 

 in connexion with the channels, he concluded by referring to one 

 which crosses the Liberton-Craigmillar height just at the place where 

 this is crossed by the Old Dalkeith Road. The lobe of the retreating 

 ice-sheet, which was the cause of the glacial channels described, 

 probably occupied the bed of the present Forth and constituted the 

 impounding barrier at the different heights ; and was, of course, the 

 mere shrunken remnant of a vast ice-sheet that had once enveloped 

 the whole country. 



2. " The Principles that regulate the Distribution of Particles of 

 Heavy Minerals in Sedimentary Rocks, as illustrated by the Sand- 

 stones of the North-Bast of Scotland." By Dr. Wm. Mackie, M.A. 

 Communicated by Dr. R. Campbell. 



