FOREST PROTECTION 151 



(2) if tall specimens are no more affected than short 



specimens; or if the trees die from below; 



(3) if the dying trees- are affected with a fmigus-disease 



(e. g. White Pine blight and Chestnut blight) 

 or an insect disease causing the death of the 

 trees outside the smoke region; 



(4) if death and discoloration are confined to one species 



only; 



(5) if the owner of the forests, allowing indiscriminate 



logging, or allowing forest fires to rage, is guilty 

 of contributory negligence; 



(6) if discoloration is caused by late frost, or draught, 



or leaf fimgi; 



(7) if the death rate within the smoke r^on is no greater 



than the death rate without, under otherwise 

 equal conditions (of geology, soil-fertility, as- 

 pect, forest fires, desiccation, storms, insects, 

 fungi and prior treatment of forests); 



(8) if dying and living trees are normally covered with 



tree mosses, algae and lichens; 



(9) if the death rate at the windward edge of the for- 



ests is not lai^er than the death rate in the in- 

 terior; 



(10) if the size of the annual rings of accretion is not ab- 



normally small; 



(11) if there are at hand, in the affected region, other 



plausible causes of discoloration and of death. 



Pbeventive Measures. 



1. In the source of damage: 



(a) Dilution of fiunes 



by emission into the upper atmosphere from 

 mountain tops or from high smoke-stacks; 



by accelerated conversion of SOj into S0»; 



by artificial draught increasing the rapidity of 

 dilution; 



by manufacture of sulphuric acid. 



(b) Other means suggested: 



by running smelter plants at night (possible in 

 pygmean operations only); 



by discontinuing operations in May, June and 

 July (impossible where himdreds of workmen 

 depend on continued employment); 



