695 



CHAPTEK VI. 



DAMAGE TO TBEES BY ACID FUMES FROM 

 FURNACES, etc. 



1. Description of Injury.* 



WOODS long exposed to acid fumes from iron- smelting 

 furnaces, alkali and other chemical works and brickfields, or to 

 excessive coal-smoke in crowded cities, become continually 

 more and more sickly, and may eventually die. 



The needles of coniferous trees become discoloured at first on 

 the side from which the fumes come, turning yellowish, then 

 reddish, and finally falling off, probably owing to the action of 

 the acids on the chlorophyll. The buds at first escape injury, 

 but the twigs of the trees gradually die from the summit of the 

 trees downwards. In this way the crowns of the trees get 

 continually thinner, as if they had been attacked by the pine 

 beetle, and they eventually die. 



Broadleaved trees suffer in a similar way, the damage to the 

 leaves showing itself by larger or smaller reddish blotches, 

 which gradually spread over the leaf till it dies and falls off 

 the tree. The fact that most broadleaved trees are leafless 

 during winter, when there is most smoke, accounts for their 

 comparative immunity in London, whilst in Lancashire large 

 coal-fires go on burning all the year round. Then, in propor- 

 tion to the area, there is ten times as much coal burned at 

 St. Helen's as in London, and consequently vegetation suffers 

 much more in the former place. , 



* Vide " Journal of the Society of Chemical Industry," pp. 202206 and pp. 342 

 345. Lunge's " Manufacture of Sulphuric Acid Alkali," vol. i., p. 110 ; vol. ii., 

 pp. 182190. " Air and Rain," by Dr. R. Angus Smith, 1872. Hasenclever, 

 "Chemische Industrie," 1879. Von Schroder, Dr. Julius, and Reuss, Carl, 

 " Beschadigung der Vegetation durch Rauch und die Oberharzer Huttenranch- 

 schaden. ' ' Berlin, 1883. The best monograph on the subject. Journal of Royal 

 Hort. Soc., March, 1891, "Trees and Shrubs for Large Towns," Maxwell T. 

 Masters ; also " Effects of Urban Fog on Cultivated Plants," F. W. Oliver. 



