The Geological Features. 163 



hemisphere, during what is known as the Ice Age or 

 Glacial Period, must have been simply marvellous, 

 taxing the powers of the human imagination to con- 

 ceive of them. According to Sir Archibald Geikie, 

 "the high grounds of Britain were important enough 

 to have their own independent ice, which, as the striae 

 show, radiated outward, some of it passing westwards 

 into the Atlantic, and some of it eastward into the 

 North Sea." The mass of ice which thus moved over 

 Scotland, and south as far as Middlesex, at that period 

 was so great that the broad plains of Perthshire are 

 believed to have been filled up by it to a depth of 

 fully 2000 feet. The subject is too wide and technical 

 for any extended notice in a work such as the present ; 

 but there is now an extensive literature upon it, 

 notably Professor J. Geikie's classical work, 'The 

 Great Ice Age.' Several local geologists, also, have 

 described the glacial features of the Edinburgh dis- 

 trict, where, as we have already remarked, examples 

 of ice-action are numerous. The "deposits" of the 

 Glacial Period — the boulder-clay and drift — already 

 mentioned, are also numerous and well marked in 

 this district. Indeed, the greater part of the New 



