1 6 I NT ROD UCTION. 



examined by Grisebach 1 , and those of the table-land of Upper Bavaria by 

 Sendtner 2 . Peat-bogs are formed only where Sphagna find facilities for 

 their free development, where, as the first condition, they have water at 

 command which was either free from lime from the first, or at any rate 

 which no longer contains lime in solution. It is true that according to 

 Grisebach, with whom most modern writers agree on this point, the Sphagna 

 by themselves produce only a very poor peat, which is known as moss-peat, 

 a loosely felted brown mass which never becomes true brown heavy peat. 

 But by their vegetation they enable other plants, the Ericas especially, to 

 thrive on the surface of the bog, and the remains of these plants give rise to 

 a true peat of a similar character to that of the peat from the lake-marshes. 

 A peat-bog of this kind always begins with a colony of Sphagna, which 

 growing upwards in compact masses die down below and thus raise the 

 surface, while they hold the water like a sponge. When the surface of the 

 bog has thus become convex, it begins to dry up and is covered with plants 

 which grow in clumps Erica, Betula nana, Scirpus caespitosus, and others. 

 The remains of these plants falling to the ground are enveloped by the 

 Sphagna, and are thus withdrawn from the influence of the air. In this 

 way an upper heavier layer of peculiar character is gradually formed, the 

 weight of which depresses the general mass of the bog, and more favourable 

 conditions of growth and a more copious supply of water are naturally 

 secured for the Sphagna. By the continuance of this process the moss-peat 

 is compressed, and sinks deeper and deeper in the bog beneath the weight 

 of the overlying and constantly growing mass. Grisebach found in the 

 bogs of Ems a thin layer of compressed moss-peat, the original Sphagnum- 

 bed, forming the base of the black peat. The deepest layers of these peat- 

 bogs are often found to contain large tree-stems only slightly macerated 

 and altered, and erect stumps of trees. In this case the peat-bog was 

 developed in a wet and wooded spot, and gradually destroyed the trees 

 and closed over their prostrate stems. We may observe this process going 

 on at the present day in our own mountain districts, in the Harz and in 

 Thiiringen ; forestry in these highlands 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. To put a stop to this process the administration is chiefly 

 and constantly engaged in draining and planting the ground, though trees 

 do not thrive at such an elevation and in such a soil, and they can never be 

 expected to repay their cost. 



Lignite or brown coal, of a brown, brownish black, rarely black colour, 

 and always streaked with brown, much richer in hydrogen and oxygen than 



Grisebach (1). s Sendtner (1). 



