376 MR J. GEIKIE ON THE BURIED FORESTS 



mosses does not quite tally with that which is said to characterise the peat of 

 Denmark. In the Danish peat mosses the pine lies at the bottom, and is succeeded 

 in ascending order by the oak and beech. But in the bogs of England, oak and 

 pine occur, as in Scotland, on the same horizon, and in such a way as to show 

 that they must have grown contemporaneously in the same forest, the pine occu- 

 pying the higher levels and more gravelly soil. Above the oak and pine we often 

 find a second stratum of timber, consisting chiefly of birch and hazel. When, over 

 this, we come upon a third layer, its prevailing wood is generally alder*. Occa- 

 sionally, however, pine trees are met with in peat mosses at a lower level than 

 oak.f While it is not denied that in this succession of trees we may have evi- 

 dence of certain changes of climate, we ought to be careful that we do not attach 

 too much importance to what may in many cases be only a local accident. The 

 succession of trees may sometimes be explained by a change in the nature of the 

 soil alone. Thus, in some of those clayey depressions in the drift, which have 

 been occupied at one time by the oak, we have evidence of a subsequent irruption 

 of fresh water converting the grove into a marsh. When the oaks had succumbed 

 to these changed conditions, we find them succeeded in place by some other 

 species, such as the alder or willow : from which it does not seem necessary to 

 infer more than a mere local change of circumstances. This peculiar succession 

 of trees, however, appears to have so frequently recurred in the peat mosses of 

 England (if not in those of Scotland), that we are forced to conclude that pheno- 

 mena so general in their appearance must be due to some common and widely 

 acting cause. 



But, apart from the evidence supplied by a succession of trees, the geologi- 

 cal history of the peat mosses themselves is conclusive upon this point. The 

 phenomena they present indicates the former prevalence of an extremely humid 

 climate. During the continental period the atmosphere must have been moist 

 from excess of vegetation, but in the succeeding or insular condition this humi- 

 dity appears to have greatly increased. At what time such a climate first began 

 to characterise these regions, it is of course impossible to say ; but probably long 

 before the complete submergence of the area now covered by the German Ocean, 

 those changes had already been set in progress, which, in the course of ages, were to 

 result in the formation of many, if not by far the greater portion, of our peat mosses. 



The most continuous sheets of peat occur on the west side of our island, and 

 this fact is to be connected with the greater rainfall of the west as compared with 

 that of the east coast. It was over this rainy region that peat would first begin 



* Vide Timber Trees, Society for Diffusion of Useful Knowledge, p. 32. 



| Mr Sainter, in a letter to my colleague, Mr A. H. Green, describes the Danes' Moss, a 

 large peat bog near Macclesfield. In this moss, he says, " the Scotch fir is found at a depth of 

 about 20 or 25 feet. A few feet above this lies the larch, and then in ascending order come the 

 oak (Quercus Robur), birch, hazel, alder, and willow." This moss occupies a depression. 



