144 THE DEVELOPMENT OF BRITISH FORESTRY 



natural soil below the peat, and that possibly similar 

 results might be obtained again if the peat were absent. 

 But such an answer does not explain the fact that trees 

 were growing upon the peat itself and subsequently died 

 out, nor why the peat took the place of natural forest at 

 some distant date, nor does it explain why trees planted 

 at similar elevations to-day, but on soils free from peat, 

 invariably fail, or grow into worthless scrub at the best. 



Geikie, Smith, LeAvis, and other investigators of peat 

 and moor formations have been able to trace indications 

 of varying climatic phases of the temperate, arctic, and 

 sub-arctic character, clearly suggesting that alternations of 

 dry and wet periods have taken place since the peat beds 

 of these islands began to form. In most beds two distinct 

 periods of forest growth are found, the lower indicating a 

 broad leaf, the upper a coniferous or pine type. Probably 

 the mountain-tree remains belong to the latter period, as 

 they are seldom covered by more than four or five feet 

 of peat, although much of it may have been denuded by 

 wind and rain. 



It is possible that the development of mountain peat in 

 the British Isles alone has been assisted by the heavy 

 autumn and winter rainfall, and the general absence of 

 snow and frost during the winter. Heavy rainfall at a 

 season of the year when most forms of vegetation are 

 dormant, and the surface more or less bare, favours the 

 washing out of soluble salts, whereas under a snow 

 covering the products of weathering would be preserved 

 near the surface until the following spring, and largely 

 utilised by growing plants. Mild winters and cool 

 summers also favour the growth of sphagnum, which is 

 seldom entirely checked by cold or drought, and quickly 

 fills up the drainage channels which are formed by heavy 

 rain storms, except where they run down the steeper 

 slopes, or carry streams of constant flow. 



