43 
Dr MacCulloch on Peat. 
water very unequally, the same tract will often be found to pre- 
sent considerable diversity of character. In some situations it is 
semifluid beneath, and covered with a matting of tenacious and 
half decomposed vegetables, or else it is interspersed with par- 
tial spots of the same nature, maintained by the firmness of the 
heath, or of the rushes which have established themselves in 
those places. In other situations it is intermixed in minute 
patches with mountain peat, according to peculiarities in the 
form of the surface, capable of determining the formation of 
these different varieties. 
Marsh peat occasionally forms a very imperfect stratum only, 
the roots of the rushes and grasses retaining much of their ori- 
ginal firmness, in which case it is sometimes known by the name 
of RuslHurf^ while, in other cases, a stratum of perfect peat is 
found beneath it ; an occurrence which takes place when a 
trembling bog has been accidentally drained ; or when, by the 
gradual accumulation of the peaty soil, the level has been so far 
raised as to cause a constant and natural drainage. It is in this 
species of peat that the Sphagnum palustre forms so conspicuous 
an ingredient, and this plant is indeed, from its nature, limited to 
the peculiar situations in which marsh-peat is formed. The 
other plants, which chiefly contribute to its formation, are in* 
eluded in the follomna^ list : 
a 
Erica vulgaris, 
tetralix. 
Myrica gale. 
Vaccinium oxycoccos. 
Eriophorum polystachium. 
vaginatum. 
Sehoenus albus, and others of 
this genus. 
Scirpus caespitosus, and o- 
thers of this genus. 
Pedicularis palustris. 
sylvatica. 
Orchis maculata. 
conopsea. 
Juncus, various species. 
CareXj various species. 
Aira aquatica. 
Aira caespitosa. 
Festuca fluitans. 
Caltha palustris. 
Hydrocotyle vulgaris. 
Lysimachia tenella. 
Menyanthes trifoliata. 
Ranunculus flammula. 
Comarum paliistre. 
Narthecium ossifragum. 
Pinguicula vulgaris. 
Drosera longifolia. 
anglica. 
rotundifolia. 
Triglochin palustre. 
Phalaris arundinacea. 
Arundo phragmites. 
Some of the Equiseta. 
The formation of Lahe peat is of a much more complicated 
nature than that of the two preceding kinds, and is moreover 
rendered additionally interesting, by its connection with that im- 
