THE "GREAT ICE AGE." 179 



the world where the snow line touches or nearly approaches 

 the level of the sea. 



All such streams must have followed the slope of the hill- 

 sides upon which they rested and down which they flowed, 

 and thus the upper limits of glaciation afford no measure what- 

 ever of the thickness of the ice upon " the low grounds of 

 Scotland," or of any other glaciated country. As an example 

 I may refer to Mont Blanc. In climbing this mountain the 

 journey from the lower ice-wall of the Glacier de Bossons up 

 to the bergschrund above the Grand Plateau is over one con- 

 tinuous ice-field, the level of the upper part of which is more 

 than 10,000 feet above its terminal ice- wall. Thus, if we 

 take the height of the striations or smoothings of the upper 

 neve, above the low grounds on which the ice- sheets rests, and 

 adopt Mr. Geikie's reasoning, the lower ice-wall of the Glacier 

 de Bossons should be 10,000 feet thick. Its actual thickness, 

 as nearly as I can remember, is about 10 or 12 feet. 



Every other known glacier presents the same testimony. 

 The drawing of a Greenland glacier opposite page 47 of Mr. 

 Geikie's book shows the same under arctic conditions, and 

 where the ice-wall terminates in the sea. 



I have not visited the Hebrides, but the curious analogy of 

 their position to that of the Lofodens suggests the desirability 

 of similar observations to those I have made in the latter. If 

 the ice between the mainland and the Outer Hebrides was, as 

 Mr. Geikie maintains, " certainly more than 2000 feet in 

 thickness," and this stretched across to Ireland, besides unit- 

 ing with the still thicker ice-sheet of Scandinavia, these 

 islands should all be glaciated, especially the smaller rocks. 

 If I am right, the smaller outlying islands, those south of Barra, 

 should, like the corresponding rocks of the Lofodens, display 

 no evidence of having been overswept by a deep mer de glace. 



I admit the probability of an ice-sheet extending as Mr. 

 Geikie describes, but maintain that it thinned out rapidly sea- 

 ward, and there became a mere ice-floe, such as now impedes 

 the navigation of Smith's Sound and other portions of the 

 Arctic Ocean. The Orkneys and Shetlands, with which I am 

 also unacquainted, must afford similar crucial instances, always 

 taking into account the fact that the larger islands may have 

 been independently glaciated by the accumulations due to their 

 own glacial resources. It is the small rocks standing at con- 

 siderable distance from the shores of larger masses of land that 

 supply the required test conditions. 



