IV THE ICE AGE AND ITS WORK 87 



The next illustration (Fig. 20) shows a rock mass poised 

 on the very edge of a cliff, in the pass of Llanberis, a 

 position it could hardly have reached by any other means 

 than ice-carriage. 



Two other figures, from Falsan's La P4riode Glaciaire, 

 show still more curious positions. The first (Fig. 21) is 

 one of the great train of erratics near Monthey, Bas Valais, 

 over 500 feet above the Rhone, standing on end upon a 



Fi({. 19. — Silurian erratic on limestone, ingleborough. 



heap of smaller blocks. The other is a mass of triassic 

 breccia, perched on the top of two other blocks partially 

 buried, and is perhaps the most fantastic work of the 

 glaciers yet discovered. Its position, five miles north- 

 west of Chambery, is now over 160 miles from the nearest 

 glacier (Fig. 22). 



The Teaching of British Erratics. 



The study of our British erratics has been assiduously 

 pursued for many years past by a committee of the British 



