PEAT. 613 



oolitic, of white, gray, bluish, blackish and other colors, — the dark 

 colors mostly due to the presence of carbon from animal or vegetable 

 decomposition. 



The origin of strata through organic growth or accumulation is 

 well illustrated in the history of peat beds and coral reefs ; and 

 this subject of life is therefore concluded by a brief description 

 of their modes of formation. 



1. Peat Formations. 



Peat is an accumulation of half-decomposed vegetable matter 

 formed in wet or swampy places. In temperate climates it is due 

 mainly to the growth of mosses of the genus Sphagnum. This 

 plant forms a loose turf, and has the property of dying at the extre- 

 mity of the roots as it increases above ; and it thus may gradually 

 form a bed of great thickness. The roots and leaves of other plants, 

 or their branches and stumps, and any other vegetation present, may 

 contribute to the accumulating bed. The carcasses and excrements 

 of dead animals at times become included. Dust may also be 

 blown over the marsh by the winds. 



In wet parts of Alpine regions there are various flowering plants 

 which grow in the form of a close turf, and give rise to beds of peat 

 like the moss. In Fuegia, although not south of the parallel of 56°, 

 there are large marshes of such Alpine plants, the mean tempera- 

 ture being about 40° F. 



The dead and wet vegetable mass slowly undergoes a change, 

 becoming an imperfect coal, of a brownish-black color, loose in tex- 

 ture, and often friable, although commonly penetrated with root- 

 lets. In the change the woody fibre loses a part of its gases ; but, 

 unlike coal, it still contains usually 25 to 33 per cent, of oxygen. 

 Occasionally it is nearly a true coal. 



An analysis afforded— Carbon, 58.09, hydrogen, 5.93, oxygen, 31.37, ashes, 

 4.61 = 100. But there are several substances present, including three or four 

 distinct resins and vegetable principles. It affords a number of important pro- 

 ducts by distillation, among them Paraffine. Traces of phosphates are present, 

 arising from animal decompositions. 



Peat-beds cover large surfaces of some countries, and occasionally 

 have a thickness of forty feet. One-tenth of Ireland is covered by 

 them ; and one of the " mosses" of the Shannon is stated to be fifty 

 miles long and two or three broad. A marsh near the mouth of the 

 Loire is described by Blavier as more than fifty leagues in circum- 



