100 THE DEVELOPMENT OF BRITISH FORESTRY 



111 all instances of large tree growth, the peculiar 

 conditions under which the trees have been growing must 

 be considered. Practically all localities have a local 

 climate of their own, good or bad as the case may be, 

 which may be quite distinct from the general climate of 

 the surrounding district. Deep valleys, ravines, and hol- 

 lows in hill ranges usually possess these local climates, the 

 chief features of which are shelter from prevailing wind, 

 and frequently exceptionally favourable soil conditions. 

 Observations confined entirely to the largest trees in any 

 district, therefore, may lead to quite erroneous conclusions 

 being formed as to the general suitability or otherwise of 

 the local climate for timber-growing, and probabl}' many 

 mistakes of this kind have been made in the past. 



But, apart from actual data, observations made in 

 different parts of the country will quickly convince one 

 that the growth of most trees in the British Isles is very 

 greatly affected by wind currents, a factor which has not 

 been so carefully recorded in meteorological observations 

 as rainfall and temperature. The more Avesterly the 

 aspect and isolated the tree, the higher the elevation and 

 the poorer the soil, the greater becomes the effect of wind, 

 and whilst its influence is felt all over Western Europe, it 

 would require a strong imagination, and a blindness to 

 actual facts to assert that the British Isles were not 

 more exposed to westerly Avinds than countries farther 

 east. If a strip of country be taken within fifty miles 

 of the western coast of Europe, starting at Jutland in 

 the north, and extending as far south as Gascony in 

 France, it Avould be no exaggeration to state that tree 

 growth on exposed sites in that belt is retarded from 20 

 to 50 per cent, from westerly winds alone. This may not 

 be due to the course or prevalence of the winds altogether 

 but partly to the salinity of the air, which is sufficiently 

 strong to turn the needles of conifers in winter, or the 



