1891.] on British Mosses. 247 



spread of the wings of the Koman eagle, the phenomenon in question 

 is of far wider extension. They never conquered Denmark, or 

 Norway, or Ireland, or the islands of Scotland: in Scotland, and 

 even in England, their operations could never have covered the whole 

 country ; and as regards some of our peat mosses, we know that they 

 must have existed long before the Roman invasion ; for at least on the 

 borders of Sedgmoor we have traces of their using peat for fuel as it 

 is used there at the present day. 



Still humbler agents have been invoked, in the supposition that 

 the beaver and other rodents were the authors of the destruction of 

 the forests. So far as I can judge, the cause suggested seems inade- 

 quate to the effect. 



Again, changes in climate have been suggested. But, although 

 there may be some evidence from the succession of the trees of a 

 gradual amelioration in the climate, we know of no evidence of 

 changes of so sudden and violent a character as would destroy the 

 existing forests over large areas. Moreover, with few exceptions, the 

 trees of the destroyed forests are such as are now found wild, or will 

 grow easily in the spots where they lie buried. 



The overthrow by storms has, again, been suggested as the cause 

 of this wholesale destruction ; and the fact that in some of the peat 

 bogs of the West of Scotland the trees that have fallen lie to the 

 north or north-east, and in some of those in Holland to the south-east, 

 in the direction of the prevailing winds in those countries respec- 

 tively, affords some reason to believe that wind has given the coup de 

 grace to the dying trees, and determined the direction of their fall. 

 But it is much more likely that this was the work of the wind, than 

 that successive forests should have been swept from the face of vast 

 tracts of Europe by the agency of wind alone. Moreover, in some 

 cases the trunks as well as the bases and roots of the trees are found 

 standing or buried in the bogs. 



Allowing that some or all of these agencies may have had their 

 part in the destruction of the forests, I believe that the growth of 

 Sphagnum has been the greatest factor in the work of destruction. 

 " To the chilling effect of the wet bog mosses in their upward growth 

 must be attributed," says Mr. James Geikie, " the overthrow of by far 

 the greater portion of the buried timber in our peat bogs " (Trans. 

 Koy. Soc. Edin., xxiv. 380). 



But, it will be said, assuming that this may be the case with one 

 growth of forest, how about the successive destruction of successive 

 forests ? The answer is, I believe, to be found in the curious change 

 which peat undergoes, and which converts it from a substance highly 

 absorbent of water into one impervious to it. 



The section exposed by a peat-cutting in, I believe, almost all 

 cases exhibits two kinds of peat, the one known variously as red 

 peat — or red bog, or fibrous bog, or in Somersetshire as white turf — 

 which lies at the top, and the other, a black peat, which lies at the 

 bottom. The red peat retains visible traces of the Sphagnum of 



