122 
secretary's report. 
At the outset of the Glacial Period glaciers existed in Britain, 
the small coalesced to form large ones, and these began to pro- 
trude into shallow seas. But a new factor came into the case 
in the development on a corresponding scale of magnitude of 
an ice-sheet having its centre in the Scandinavian region. That 
ice-sheet gradually pressed across the North Sea, and as it 
advanced it began to interfere with the eastward flow of the 
glaciers that debouched into the North Sea. That put on a back 
pressure, and there was a great augmentation of the glaciers. 
The great ice-sheet pressed on the Yorkshire coast, and its 
effects could be traced to altitudes exceeding a thousand feet ; 
but there were some striking differences between the Lincolnshire 
Wolds and tlie Yorkshire Wolds. The Yorkshire Wolds did 
not seem to have been overridden, but the Lincolnshire Wolds 
were overtopped. Whether this was due to the Lincolnshire 
Wolds not being so high as the Yorkshire Wolds, or whether it 
was to be ascribed to different thicknesses of the different portions 
•of the ice-front, was matter for future consideration ; but he 
was strongly disposed to think that it was a case of differences 
of thickness. The sheet flowed through the Wash gap and 
penetrated across to the Midlands, in places even overtopping 
the watershed of the Trent and the Warwick Avon. The de- 
posits of this great invasion are well developed in Lincolnshire, 
though their precise relations are not easy to discover. During 
the shrinkage of the ice great lakes were held up in all the principal 
valleys. Evidences of such a system of lakes are seen along 
the whole of the eastern slope of the Wolds. The final Avith- 
drawal of the ice left Lincolnshire very different from prior to 
the Glacial Period, when the coastline ran along the eastern 
foot of the hills at Louth and near Alford. Many hundreds of 
square miles of land were added to Lincolnshire by the accu- 
mulation of glacial deposits on the old sea bottom. Mr. Jukes- 
Browne, who is so well known for the care he has displayed in 
the discussion, and in many cases the successful solution, of 
many of the problems of Lincolnsliire geology, has pointed to 
the fact that on the western side of the Wolds is a type of boulder 
clay which is known as the Chalky Boulder Clay, whereas there 
is on the east side of the Wolds no Clialkv Boulder Clay as such. 
