THE GLACIAL PERIOD. 189 



stones in the till along the whole eastern seaboard south from 

 Aberdeenshire tell the same tale. They indicate the presence 

 in the area of the North Sea of some obstacle to the outflow of 

 the ice from Scotland, which, instead of going right out to sea, 

 was deflected and compelled to hug the Scottish shores in a 

 south-easterly direction. 1 



Thus are we driven to conclude that during the climax of 

 the Glacial Period all Scotland was drowned in a wide-spread 

 mer de glace, which coalesced in the north and east with a simi- 

 lar sheet of ice that crept outwards from Scandinavia. To the 

 west the Scottish ice, meeting with no impediment to its course, 

 overflowed the Outer Hebrides to a height of 1600 feet, and 

 probably continued on its path into the Atlantic as far as the 

 edge of the 100-fathom plateau, where the somewhat sudden 

 deepening of the sea would allow it to break off, and send adrift 

 whole argosies of icebergs. The height reached by the upper 

 surface of the ice that overwhelmed the Outer Hebrides enables 

 us to ascertain the angle of slope between those islands and 

 the mainland. This was 1 in 211, that is to say, the inclina- 

 tion of the surface of the ice-sheet was about 25 feet in the 

 mile — an inclination which would appear to the eye almost 

 like a dead level. 2 



I have been thus particular in my sketch of the salient 

 features of the general glaciation of Scotland during the cul- 

 mination of the Ice Age, because in describing them I am 

 practically describing the similar glacial phenomena of Ireland, 

 and a large part of England, of Scandinavia, Finland, Den- 

 mark, and Northern Germany. It will, therefore, not be neces- 

 sary to do more than give a brief sketch of the limits reached 

 by the great mer de glace in Northern Europe, so far as these 

 have been definitely ascertained by an appeal to such facts as 

 those I have mentioned in connection with the glacial phe- 

 nomena of Scotland. 



Glacial striae and boulder-clay have been followed over all 



Great Ice Age, p. 180. 

 2 J. Geikie, Quart. Journ. Geol. Soe., t. xxix. p. 861. 



