106 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [DcC. 5, 



Fig. 2. — The Matterhorriy as seen from the Riffelherg. 



E, E, indicate the line of erosion. 



9000 feet ; there is a thick covering of snow round it, which con- 

 ceals the line of erosion and makes it appear to be higher than it 

 really is. 



There is no distinct lower limit to the abraded or rounded portion 

 of the mountains, but the upper limit of the abrasion is usually well 

 marked by a change in the outline of the hill-sides from a moderate 

 to a steeper slope, similar to the indentation produced on a coast by the 

 waves beating against a cliff*. The nearly uniform height of this 

 re-entering angle produces a tolerably level line round the mountains, 

 which I shall speak of as the line of erosion. It is best seen when 

 the observer is at a distance, or, if near, is only a few hundred feet 

 helow it, when a horizontal line may often be traced by the eye round 

 every one of the mountain-tops within its reach ; this is nowhere 

 more remarkable than in the view from the top of the Splugen Pass. 

 When standing on the level of the line of erosion, it is often more 

 difficult for the eye to follow it ; slight inequalities in the ground 

 which are near at hand concealing or interfering with the view. This 

 makes it difficult to measure the height of the erosion within 1 00 or 

 200 feet, even under favourable circumstances. But there are spots 

 free from this difficulty : whoever has ascended from Zermatt to the 

 Kiffelberg must remember the distinctness with which the conical 

 Riffelhorn rises from the flat at the top of the rounded Riffelherg : 

 the line of erosion is there as well marked as at the foot of a sea- 

 cliff, being (by my aneroid) between 9000 and 9100 feet above 

 the sea. 



When the observer is more than 1000 feet below the line, it will 

 require a practised eye to estimate its height within 500 feet ; and 

 the result will be merely a rough guess, which will usually prove to 

 be below the truth. In the following statements I have pointed out 

 those measurements which are most to be relied on ; but in general, 



* Some excellent profiles of cliffs and beaches have been given by Mr. Godwin- 

 Austen, Quart. Journ. Geol. Soc, vol. vii. pp. 118, 120, and 124. 



