208 The Scottish Naturalist. 



extensive erosion in an epoch corresponding to the second forest 

 period. Once more the sea invaded the land, and a humid 

 climate prevailed ; and then the third well-marked terrace of 

 coarse gravels was accumulated. 



The latest geological change to which I shall refer was the 

 final retreat of the sea to its present level. My early investiga- 

 tions into the history of our peat-mosses led me to conclude that 

 in our day the rate at which these bogs are wasting away under 

 the influence of sub-aerial agents much exceeds their rate of 

 growth. And Professor Blytt has formed the same opinion with 

 regard to the peat-bogs of Scandinavia. I do not, of course, 

 mean to affirm that peat-mosses are everywhere becoming disin- 

 tegrated, and weathering away. In many places where they are 

 favoured by their position, and by climatic conditions, they seem 

 to be flourishing ; but, looked at generally, there can be no doubt 

 that this is exceptional. And the final disappearance of 

 our bogs, through the action of the weather, is only a question of 

 time. Should present conditions continue, our hills must by-and- 

 bye become entirely divested of any peaty covering. We appear, 

 therefore, to be living under drier conditions than obtained when 

 the trees of the second forest-epoch were being slowly entombed 

 by the the upward growth of the bog-plants. Are these less 

 humid conditions the result of natural causes, or have they been 

 brought about by the drainage operations of our agriculturists ? 

 These operations must undoubtedly have influenced the result, 

 but many considerations lead to the conclusion that they are not 

 the sole cause of the present drying up and shrinking of our bogs. 

 I think it can be shown that the wide denuded channels and 

 hollows by which our hill-peat is so frequently traversed, existed 

 long before our present systems of drainage became general. The 

 bogs of hills and hill-slopes had been broken up, and hollows and 

 gutters washed out in them in early historical times ; for they are 

 mentioned, by old writers, as the hiding-places of thieves and 

 desperadoes ; and they also formed a more or less secure retreat 

 for hunted Nonconformists in the unhappy times of the Solemn 

 League and Covenant. I incline, therefore, to the opinion that 

 the general waste of our peat-mosses had set in long before the 

 work of our farmers could have begun to tell, that, in short, this 

 waste is an evidence of change of climate induced by natural 

 causes. 



