FOREST PROTECTION 141 



Par. 15. Protection Against Noxious Gases (Sulphurf umes) . 



By the term "siilphurf limes " are understood certain gases formed by 

 the oxidation of sulphur. Huge amounts of these gases are produced wher- 

 ever sulphur-bearing minerals are treated in the presence of atmospheric air. 



Contamination of the atmosphere is one of the evils adherent to civili- 

 zation, or, which is the same, adherent to an increase of population at cer- 

 tain centers. The breath of any man or any animal and, more than that, 

 the smoke rising from any building (dwellings as well as factories) contami- 

 nate the air. 



After Angus Smith, the atmosphere at Manchester, England, contains 

 a little less than the one-millionth part of SO 2 on the average of the year. 



The rain water investigations made by the same English author show 

 the rapid increase of sulphuric acid in rain water near industrial centers. 



The sulphur contained in common coal averages 1.7%, of which 1.2% 

 develop into noxious sulphurfumes. In other words, 85 tons of coal will 

 develop on the average 2 tons of noxious SO*. 



Since the consumption of bituminous coal in the United States is in 

 excess of 200,000,000 tons per annum, it appears that we send into the at- 

 mosphere (pre-eminently in the northeast) annually about 4,700,000 tons 

 of sulphurous acid, 



A. Nature of Damage to Leaves. 



There is not at hand, at the present time, any scientific explana- 

 tion of the strange physiological effect which sulphur fumes 

 exercise upon vegetation. 



After Prof. Naegeli, S0 2 checks the normal movement of the live 

 plasma in the leaves. 



Von Schroeder finds that the transpiration from the leaves is that 

 function which is most vitally reduced by inhalation of SO,. 



During night, transpiration from the leaves is naturally reduced 

 to a minimum, and it is interesting to note that there is little 

 difference in the evaporative function of leaves during night, 

 whether they be exposed to S0 2 or whether they be left in 

 an atmosphere free from SO, 



When the sun shines, the difference between the evaporation in 

 leaves exposed to SO 2 and in leaves exposed to a pure atmos- 

 phere is very striking. 



Reduced transpiration appears to be noticeable before discolora- 

 tion of leaves occurs in a sulphurous atmosphere. 



After von Schroeder, very small quantities of S0 2 continuously 

 acting produce the same final result (always in the glass case) 

 which large quantities will produce acting for short periods 

 only. This observation does not tally with the results of 

 Freytag's experiments made in the open air. 



