Reports and Proceedings — Qeological Society of London. 281 



glacier had already reached its maximum extension, about 10 miles 

 below Zurich ; that the zonal subsidence continued throughout the 

 retreat of the ice ; and that the simultaneous formation of the lake- 

 basin should therefore be assigned to the end of the Glacial Period, 

 after which the original basin was, notably at its upper end, 

 restricted to its present dimensions by post-Glacial alluvia.- 



(7) In conclusion, the author shows that the same arguments 

 apply, in the main, also to the origin and age of the other principal 

 zonal lake-basins, which he illustrates by longitudinal sections. In 

 his view, the position and depth of these basins, as well as the 

 intervening ground, point to the probability that the bending took 

 place not only along one line, but along several, more or less 

 parallel, not always continuous lines within the zone between the Alps 

 and the Jura ; that the bending was by no means of uniform depth ; 

 and that, therefore, the Alps did not subside as a rigid mass, but 

 that the zonal bending along their edge merely extended locally for 

 some distance from the deepest points of the lake-basins along the 

 floors of the principal Alpine river valleys. 



2. ''On a Shelly Boulder-Clay in the so-called Palagonite 

 Formation of Iceland." By Helgi Pjetursson, Cand. Sci. Nat. 

 (Communicated by Prof. W. W. Watts, M.A., M.Sc, Sec. G.S.) 



There is no equivalent in the Tertiary basalt plateaux of Britain 

 of the great palagonite formation of Iceland, vv^bich Prof. Thoroddsen 

 has shown to be younger than the basalt formation of the latter 

 island. The basement layer of the breccia formation, resting 

 directly upon the basalts, contains glaciated blocks of all sizes, up to 

 6 feet and more in diameter. These ground-moraines are followed 

 by tufaceous sandstones, conglomerate, columnar basalts, other 

 ground-moraines, and volcanic tuffs and breccias. At Birlandshofdi 

 a shelly Boulder-clay, 70 to 80 feet thick, rests upon the fundamental 

 basalt, which here shows a glaciated surface. Unbroken shells are 

 very rare. Astarte borealis is the most common shell, and Saxicava 

 arctica and Mya truncata are less common, indicating that some of 

 the older moraines are of Pleistocene age. The author concludes 

 that volcanic activity did not pause in Iceland during the Glacial 

 Period, but that it was especially active at the beginning and the 

 close of glaciation, building up bulky hills of slags and ashes, some 

 of which have survived the Glacial Period as volcanoes, while others 

 have become extinct. Volcanic activity had died out in Britain at 

 this time, and hence the palagonite formation is unrepresented in 

 that country. 



II.— May 13th, 1903.— Edwin Tulley Newton, Esq., F.R.S., Vice- 

 President, in the Chair. The following communications were 

 read : — 



1. "On some Disturbances in the Chalk near Royston (Hertford- 

 shire)." By Horace Bolingbroke Woodward, Esq., F.R.S., F.G.S. 



A ' line of flexure ' is marked on the Geological Survey map from 

 Therfield, south-west of Eoyston, in Hertfordshire, to near Heydon 



