1036 Geological Society : — 



2. ' The G-lacial G-eologv of East Lancashire.' By Albert Jowett,. 



D.Sc, f.g.s. 



The area dealt with comprises the western slopes of the Pennines, 

 from Bculsworth Hill to Blackstone Edge, and their westerly 

 offshoot, the Possendale highland, which separates the basin of the 

 Kibble from that of the Irwell and Mersey. 



Three types of drift have been recognized : — 



(1) Local drift, consisting of materials which can be found in situ in the 



neighbourhood, chiefly Coal Measures and Millstone Grit. 



(2) Eibblesdale drift with Carboniferous Limestone, chert, and Silurian 



grit, as well as local material. 



(3) North-western drift which, in addition to any or all of the above- 



mentioned constituents, contains igneous rocks from the Lake 

 District and the South- West of Scotland. 



The distribution of the drift and the evidence of striated rock- 

 surfaces suggest the invasion of this area by an ice-sheet which 

 reached up to the Pennine watershed, and projected ice-lobes acros 

 it through the gaps at Widdop, Glorple, Cliviger, and Walsden. 



A small unglaciated region occurs a few miles south-west of 

 Todmorden. 



In the north-eastern portion of the area the general direction of 

 ice-movement was from north to south ; in the west it was from 

 north-north-west to south-south-east, but on the south of the 

 Bossendale highland the direction of flow curved round towards 

 the east-north-east, and ultimately, in the neighbourhood of 

 Bochdale, towards the north. 



The local drift is believed to have been produced by the over- 

 lapping of 200 feet or so of clean ice, which formed the upper 

 portion of the ice-sheet, beyond the limits reached by the ice 

 containing erratics. No evidence of local glaciation has been found. 



The limit of the north-western drift rises at the rate of about 

 4 feet per mile from Blackstone Edge towards the Irish Sea : 

 therefore, when at its maximum, the ice-sheet was jDrobably over 

 2000 feet above present sea-level in the middle of the Irish Sea 

 in this latitude. 



Extensive systems of glacier-lakes and drainage-channels were 

 produced on the retreat of the ice, and for some time the drainage 

 on the west of the Pennines in the Ribble and Irwell basins escaped 

 eastwards into the Yorkshire Calder. 



It is probable that the north-western ice arrived in this area 

 later, and disappeared earlier, than the Bibblesdale ice. 



Some local fluctuations in the ice-sheet occurred, but there is no 

 evidence for more than one Glacial Period. 



February 4th. — Dr. Aubrey Strahan, F.E.S., President, 

 in the Chair. 



The following communications were read : — 

 1. 'The Lithologv and Composition of Durham Magnesian 

 Limestones.' By Charles Taylor Trechmann, B.Sc, F.G.S. 



The present communication is the result of a somewhat close 



