CHAPTEE II 



THE SANITARY INFLUENCE OF FORESTS 



The protection afforded by forests or even by belts of trees 

 makes life more bearable in districts where cold and humid 

 winds prevail. Crops are enabled to grow which would 

 not otherwise succeed ; and domestic animals enjoy 

 vigorous health, fatten, and produce an increased supply of 

 milk (1). Very few persons, not excepting scientific men 

 interested in ecology, have recognised the full severity of 

 the effect on all living things of humid winds conveying 

 air at a low temperature and persisting for a long period 

 of time. The eftect of such winds on trees themselves is 

 most marked. Their stems are greatly shortened in height, 

 becoming under extreme conditions unable to rise above the 

 ground, as is well seen on the west coast of Scandinavia, 

 Denmark, Holstein, Scotland, and Ireland. It is not the 

 cold alone of the mountain summits or of the Arctic plains 

 that stops tree growth, but the combined effect of wind, wet, 

 and cold. 



In regions of extreme cold, if the air is still, there may 

 occur large forests as in Siberia. Trees exposed to winds 

 are not only lessened in height, but are also altered in 

 shape, as they produce branches which grow best on the 

 leeward side ; and assuming what may be designated the 

 ' flag ' form, they indicate the direction of the prevailing 

 wind, which may be determined by the feeble or absent 

 growth on the windward side. The injuries to trees, which 

 are commonly ascribed to salt spray (2), are probably due 

 entirely to strong wind, as may be ascertained by examina- 

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