274 
SCENERY OF SWITZERLAND. 
bat of comparatively little value; the slopes generally 
bear dry grass and heather, while the flat ground is 
marshy. 
High Alpine plants are often found on moraines, 
not so much from any peculiarity of the soil, as be- 
cause of its coming from the heights. 
Screes are generally bare from the continuous 
movement, which does not give plants time to 
grow. 
Rockfalls. 
Falling stones constitute one of the greatest 
dangers of the Alps. Tyndall was injured, and 
Gerlach killed by one. Many couloirs cannot be 
ascended without much risk, and the ancient 
passage up Mont Blanc, first discovered by Balmat, 
has been abandoned for another longer, but safer, 
route. Many of the steeper valley sides, as, for in- 
stances, those between Martigny and the Lake of 
Geneva, are furrowed by stone streams, which, like 
those of water, have their collecting-ground above 
their regular channel, and a cone of deposit below, 
which, however, stands at a steeper angle than that 
of a torrent. Many rock-faces have a continuous talus 
or scree of fallen stones at the base, which takes an 
angle of about 30°, and in some cases has almost 
