MOUNTAIN SLOPES. 625 



produced by the pressure of the earth's contraction, and in such a mass as 

 our earth the elevations would naturally be very great. 



Professor Geikie has shown how, by a very simple experiment, the 

 contortion of mountain strata is effected by pressure. A number of cloths 

 or towels placed flat on a table represent the sedimentary rocks. Place 

 a board with a weight on the top, and the towels will remain flattened. 

 But by holding two boards at the sides and pressing them together (the 

 weighted board still remaining), we shall find the towels crumpled and 

 upheaved like the Jurassic strata shown in the illustration (fig. 712). 

 Professor Heim calls the central masses wrinkles of the earth's crust. So 

 the Alps were pressed up or heaved into the air, the weather rain, frost, 

 snow, and sunshine imparting the infinite variety of " Horn," " Needle," and 

 " Peak," so expressively applied in Alpine nomenclature ; the Matterhorn, 

 Wetterhorn, Weisshorn ; the Pic du Midi, Aiguille de Dru, Aiguille Verte, and 

 many other mountains in well-trodden 

 Switzerland will occur to the reader at 

 once. 



The slopes of mountains though 

 to the casual observer they may appear 

 very much the same are very different. 

 We sometimes find a long, easy ascent, 

 more usually a steepish inclination, 

 perhaps 20; in other places, such as 

 on the Matterhorn, an almost perpendi- 

 cular face. Forty-five degrees rise is very 

 steep, and 53 is the limit of any great 



mountain's Slope. Cliffs and precipices Fig. 712. -Anticlinal and synclinal curves of the 



.1 r . , ., , Jura Mountains. 



there are, of course ; witness the terrible 



fall from the Matterhorn to the glacier below thousands of feet with one 

 tremendous leap from the rock to the ice underneath ; but mountain slopes are 

 not precipices. As a rule, we find that one side of a mountain chain is steeper 

 than the opposite one. It i5 harder to climb up from Italy to Switzerland 

 than to ascend in the opposite direction. The Pyrenees are also steeper on 

 the south side. The Scandinavian mountains likewise are steeper in the 

 west. The Himalaya are steepest towards the sea, so are the Ghauts. 

 We here find a difference between the slopes of the NEW and OLD WORLDS. 

 In the former we have the less precipitous mountain slopes towards the east; 

 in the old world they are towards the north, and an inspection of a physical 

 map of the world leads us to the conclusion that the Atlantic and Pacific 

 Oceans are the boundaries of entirely different degrees of slopes. The Pacific 

 and Indian Oceans would appear to border the more precipitous mountain 

 sides ; the Atlantic and its connections those less steep. 



As a rule, we have the most elevated portions of the earth, mountains, 

 and high tablelands, in equatorial regions ; and within the torrid zone every 

 terrestrial climate is to be found, owing to the snows of the high mountains 



40 



