BRITISH MOSSES. 55 



with fir-trees standing on it, all without bark, and dead. 

 Of the cause of their death he says nothing. Fifteen 

 years after he found the whole place a Peat Moss or 

 "fog," the trees swallowed up, and the moss so deep 

 that in attempting to walk on it he sank in it up to his 

 armpits. 



This same process of destruction is still found to be 

 going on in the mountain districts in the Harz and in 

 Thuringia. "Forestry in these highlands," says Graf zu 

 Solms Laubach in his Fossil Botany, " is everywhere at 

 strife with the peat bogs, which, left to themselves, are 

 always growing, and by the advance of their margins eat 

 their way into the adjoining forests, and make irregular 

 gaps in them." 



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 which it 

 is mainly composed, and is highly absorbent of moisture ; 

 whilst the black peat has lost all, or nearly all, traces of 

 the minute structure of the cells, and is not only un- 

 absorbent of moisture, but is impervious to it. In fact, 



