52 
SCENERY OF SWITZERLAND. 
being so easily accessible and so often visited, must 
have been struck by this fact; and must have noticed 
that the valleys are a far less important part of the 
whole district than they seem when we are below. 
The Matterhorn is obviously a remnant of an ancient 
ridge, which gives the peculiar straight line at the 
summit. The noble mass of the Bietschorn again, 
which forms such an imposing object as we look 
down the valley of St. Niklaus across the Rhone at 
Visp, is a part of the surrounding granite which has 
resisted attack more successfully than the rest of the 
rock. The mountain crests, solid as they look from 
a distance, are often covered by detached fragments, 
shattered by storms, and especially by frost. 
Mountain Ranges. 
The present temperature of the Earth’s surface 
is due to the Sun, that supplied from the original 
heat of the planet being practically imperceptible. 
The variations of temperature due to seasons, etc., 
do not extend to a greater depth than about 
io metres. Beyond that we find as we descend 
into the Earth that the heat increases on an average 
about 1° Fahr. for every 50 metres. * Even, there- 
* Agassiz, however, in the case of the Calumet Mine near 
Lake Superior, found a rate of i° Fahr. for every 223 ft. (Amer. 
fourn. of Science, 1895). 
