TOWN PLANTING 



cause of the destruction of the stonework has 

 been shown to be the presence in the air 

 of sulphur acids: the stone is converted into 

 sulphate of lime; in the process of its for- 

 mation this disintegrates the stone by ex- 

 pansion. The connection between smoke and 

 stone decay appears to be invisible gases 

 emitted from the smoke particles. 



If stonework suffers so at the hands of 

 smoke and sulphuric and other acids, what, 

 it may be asked, must the effect be on the 

 foliage of trees and shrubs particularly such 

 as are planted in the most smoke-infested 

 parts of our great towns and cities? When 

 compared with Continental cities Paris, 

 Brussels, or Berlin where tree culture is 

 carried out most successfully, the atmosphere 

 of British towns is impregnated to a far greater 

 extent with noxious fumes. Dry low-lying and 

 confined areas, particularly where excessive 

 heat and atmospheric impurities are present, 

 are decidedly the worst, while open and high- 

 lying districts, though in the centre of a town, 

 offer fewer difficulties. 



B2 



