282 



Canadian Forestry Journal, December, 1915. 



earth or rocks from which it slides, 

 rushing onward with constantly in- 

 creasing velocity — forcing brooks 

 and rivers to overflow their banks, 

 often causing great destruction of 

 life and property. The rapid move- 

 ment of water from higher to lower 

 levels removes all the lighter and 

 more fertile parts of the soil, and 

 this is repeated until the mountains 

 and hillsides have lost the last rem- 

 nant of a fertile soil, and become 

 totally barren. Such lands can 

 never be of any great value for cul- 

 tivation, and for this reason, if no 

 other, they ought to be reserved and 

 kept covered with forests, as part of 

 the public domain. 



Effects of Bad Logging. 

 Slashing the forests from the 

 mountain slope results in: (1) In- 

 creasing and excessive floods; (2) 

 Lengthening of low water periods; 

 (3) Deposition of large quantities of 

 mountain debris, covering the lower 

 fertile lands. 



A British Columbia forest waterfall 

 showing the density of tree growth. 



Logging operations which have 

 been up to the present unfortunately 

 followed by fire, destroy the absorp- 

 tive layer of the soil, leaving noth- 

 ing to absorb or retain moisture. 

 Exploitation accomplished by the 

 modern methods of conservative 

 lumbering, under government super- 

 vision, will aim to overcome and 

 eliminate dangers to the dependent 

 agricultural interests. 



Observations made by German 

 Forest Officials show that of 100 

 m.m (4 in.) of water falling on for- 

 ested territory, 10.5% evaporates; 

 20% is arrested by the crowns of the 

 trees; 25% is absorbed by the forest 

 floor; and 44.5% soaks into the 

 upper layers of the soil. 



On the other hand, when the same 

 quantity of rain falls on open 

 ground, 68.5% evaporates and 31.5% 

 is held in the soil. 



The Director of the Yale Forest 

 School gives an example of the care- 

 ful comparison of the stream flow 

 of a forested area and a non-forested 

 area in the San Bernardino Moun- 

 tains. 



The forested area (under scienti- 

 fic forest management) which dur- 

 ing December had a run-off of 5% 

 of the heavy precipitation of that 

 month ; and during January, Febru- 

 ary and March of the following year 

 had a run-off of 2)7% of the total 

 precipitation, experienced a well 

 sustained stream flow of three 

 months after the close of the rainy 

 season. 



The non-forested catchment area, 

 which during December had a run- 

 off of 40% of the precipitation, and 

 which during the three following 

 months had a 'run-off of 90 per cent, 

 of the precipitation, experienced a 

 run-off in April (per square mile) 

 of less than one-third of the forested 

 catchment area, and in June the flow 

 of the non-forested area had ceased 

 altogether. 



On the Trent Watershed. 



In 1911, the Commission of Con- 

 servation had a survey made of the 

 Trent Watershed which covers an 



