DRAINAGE. 



611 



and the lateral drains only to the same height as the latter 

 has been reduced in the remainder of the area. 



iii. In the first place, evaporation over the whole area is 

 increased by the action of the sun and winds on the exposed 

 water in the collecting trenches. In the second place, the 

 surface having become drier and warmer by the drainage, 

 increases the evaporation, and favours the capillary ascent of 

 water from the sub- 

 soil ; it also warms 

 the air near the sur- 

 face of the ground. 



The results of this 

 process must be 

 favourable to the 

 growth of plants. 

 By the gradual dry- 

 ing up of the surface, 

 peat-mosses and sour 

 grasses disappear 

 and the chemical and 

 physical condition of 

 the soil improve. 

 The formation of 

 peat ceases ; the de- 

 composition of the 

 humus becomes 

 normal. Lichens 



Fig. 279. Kaiser's method of drainage. 



disappear from the stems. Danger from frost is diminished. 

 Annual shoots, hitherto short, become longer. The water is 

 thus utilised for the service of the forest. 



The above method was tried in 1883 and subsequent years 

 in the Bavarian Eoyal forest of St. Oswald on peaty areas, 

 it is represented in Fig. 279. The collecting trenches were 

 dug in depressions and other places where the peat was 

 wettest. The lateral feeders were 30 to 45 centimeters wide 

 and deep, quite deep enough for young spruce to become 

 rooted above the subsoil water. The excess water was con- 

 ducted from the collecting trenches by little trenches a few 

 centimeters deep into a small watercourse named Seige, which 



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