AND PEAT MOSSES OF SCOTLAND. 375 



marks of fire, or adze and hatchet, may be considered to have had their growth 

 materially aided, if not always primarily caused, by the obstruction of the pros- 

 trate trees. But the peat bogs which have supplied such proofs of human agency 

 bear only a small proportion to the mosses where no such traces have been 

 detected. In most cases, both roots and trunks tell distinctly their story of 

 natural decay. In the many mosses which I have visited, the trees were invari- 

 ably found in such a state as plainly showed that natural decay had preceded 

 their overthrow. 



Are we to suppose that the peat only began to grow after those trees had thus 

 yielded to decay ? Did the fall of the trees, by choking the drainage, only then 

 bring about the requisite conditions for the increase of Sphagnum and its allies ? 



In a favourable climate, trees, which have given way before tempest or old 

 age, are quickly replaced by seedlings, and thus the gap caused by their over- 

 throw is gradually filled up Why then, we may ask, was not this the case with 

 the ancient forests of Scotland ? It seems strange that the death of the trees, 

 instead of being succeeded by the appearance of another generation, should 

 invariably give rise to a peat moss. The explanation of this anomaly ought to 

 be attributed to a change of climate. From some cause or other, the conditions 

 requisite for the continuous growth and succession of forest trees no longer existed 

 to the same extent. The nature of the great trees embedded in many of our peat 

 mosses points, as already remarked, to the former prevalence, over these regions, 

 of a somewhat excessive or continental climate ; and (following other authors) 

 I have sought to connect this period with the continental condition of Britain that 

 followed upon the close of the glacial epoch. Ere long certain changes ensued, 

 with a marked effect upon the vegetation. The succession of trees revealed by 

 several peat mosses seems to warrant us in concluding that the severity of the 

 climate which had nourished the hardy Scottish pines began at length to give 

 way. The most obvious cause of this change must be referred to the new geogra- 

 phical position of the country. The gradual separation of these lands from the 

 continent must have been followed by as gradual an amelioration of climate. 

 Whether, apart from the changes arising from oscillations of level, there may not 

 have co-existed some cosmical cause sufficient of itself to have brought about an 

 alteration of climate, can only be conjectured in the present state of the evi- 

 dence.* 



It is worth noting that the succession of trees revealed by some English peat 



* I have confined my remarks on this subject to the peat mosses of our own country, where 

 the appearances presented may be explained, as stated above, by a change from continental to insular 

 conditions. If, however, the alteration of climate referred to was also in great measure due to cos- 

 mical causes, the proofs are no doubt to be found in continental peat mosses. As I do not know 

 these turbaries from personal observation, I am unable to say whether the greater proportion of 

 their buried timber has fallen from natural causes or otherwise. It may be surmised, however, that 

 'narks of natural decay will probably occur most abundantly in the maritime regions. 



VOL. XXIV PART II. 5 I 



