CONDITIONS FOR THE GROWTH OF TREES. 49 



savants have only a very general value. Without taking ac- 

 count of the upper limits of cultivation, which varies singu- 

 larly in the high valleys in proportion to the industry, intelli- 

 gence, and social condition of the inhabitants, we may say 

 that the vegetation of the plain hardly exceeds three thousand 

 feet ; above this height the slopes where man has not violently 

 interfered to change the productions of the soil are naturally 

 covered by vast forests. Still, the great trees gradually dimin- 

 ish in height in proportion as we rise into a zone where the 

 air is rarer and colder ; their wood becomes harder and more 

 knotted ; and the hardy kinds, which venture not far from the 

 region of the snows, end by creeping on the ground, as if to 

 seek shelter between the stones. To the north of Switzerland, 

 the beech does not exceed the height of four thousand feet, 

 and the spruce-fir stops at six thousand feet. In the group of 

 Monte Rosa, the same forest growth, which approaches most 

 nearly to the zone of perpetual snow, ascends as far as six 

 thousand two hundred feet on the northern slope ; while on 

 the opposite side the larch, still hardier, attains its upper 

 limit at seven thousand two hundred feet. Higher still we 

 only find the fantastically twisted trunks of a few mugho pines, 

 rhododendrons, willow-herbs, and juniper-trees ; then all vege- 

 tation becomes more stunted, and is attached to the ground in 

 order to escape the icy winds, and to allow of its being covered 

 in winter with a protecting layer of snow up to the very edges 

 of the glacier and the white surface of the snows." 



