130 THE DEVELOPMENT OF BRITISH FORESTRY 



the peat are favoured by the saturation of the ground 

 along its edges.' 



There is little doubt that the process described above 

 has been going on in Britain, and the result is seen in the 

 heaths of the south and east of England, the mountain 

 peat of the hill ranges, and the bogs of Scotland and 

 Ireland. Whether the climate has materially altered 

 since the trees whose remains are still found under peat at 

 2000 to 2500 feet above sea-level were growing or not is a 

 matter of opinion, but from records of temperature at high 

 elevations given elsewhere, it is evident that the climatic 

 conditions are all that are required to favour the growth 

 of peat at the present day, wherever soil conditions, such 

 as impervious subsoil, or the absence of alkaline bases, 

 bring about stagnation and acidity. Under a crop 

 of trees the shading of the ground would lower the 

 temperature of the surface soil sufficiently to retard the 

 rapid decomposition of humus produced from the leaf- 

 fall, while the evaporation of surface moisture would be 

 checked, and the soil maintained in a more or less 

 saturated condition from the heavy annual rainfall of 

 forty to sixty inches, which is more or less general at 

 high elevations. Under the shade of trees it is said 

 that the summer temperatures at a depth of two feet 

 are lower by T to 5° F. as compared with those in the 

 open field, while in winter they are slightly higher in the 

 forest than outside it. 



While these conditions are gradually brought about, 

 and the accumulation of peat above the tree limit 

 proceeds, the constant soakage of acidulated water down 

 the hillsides would gradually result in the death and 

 decay of the upper belt of trees, which were already 

 growing on a surface buried under a layer of raw 

 humus. This process can be seen going on in high- 

 lying plantations to-day, and can only be checked by 



