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various angles, some being almost prostrate. The 
rocks below (Gneiss and Mica Schist) are in- 
clined so that the edges retard the movement, 
which would otherwise be quicker and more 
dangerous. 
Theobald tells us that in the summer of 1861, 
at the time of the melting of the snow, he was on a 
geological excursion near the Schwarzhorn in the 
Grisons when he gradually became aware of a 
strange roaring and crushing noise all round him. 
At first he paid little attention to it, but he at 
length found that the whole surface on which he 
stood was slipping downwards. He escaped as 
quickly as he could, but the movement continued, 
and about a quarter of an hour afterwards a great 
mass, 20 to 30 paces in length, precipitated itself 
over a precipice.* 
Earth Pyramids. 
Whenever we have a deposit of comparatively 
loose material with hard blocks, or layers, there is a 
tendency to form earth pyramids, owing to the 
looser material being here and there protected by 
a more or less tabular block of hard substance. 
** Beitr. z. Geol. K. d. Schw., L. 11. 
