PEAT. 341 



a bed of clay containing marine remains. If it has 

 often been remarked, as if there was here also some 

 mystery, that the trees of such a deposit lie in one 

 direction, this is but the consequence of the prevailing 

 winds to which the fall of any such forest must be 

 attributed. In Lincolnshire, however, many of the 

 trunks are in their natural position : and I need only 

 further add, that if observers have described such de- 

 posits as if containing only trunks, branches, and 

 roots, they always comprise the usual marsh peat 

 which attends that of forests. And if such wood often 

 retains for a longtime its original vegetable character, 

 so, in other cases, it becomes more or less converted 

 into peat, acquiring a mixed chemical one ; while, as 

 I shall hereafter show, a longer continuance of the 

 same action of water converts it into lignite. 



Maritime peat appears to have been almost forgotten 

 by the writers on this subject ; but it is formed under 

 the sea, by the Zostera marina abundantly, while it is 

 produced in another manner by the plants of salt mar- 

 shes. It is abundant, under the former cause, where the 

 aestuary of a considerable river is a deep fiord; the ex- 

 tension of the shallow shores gradually also producing 

 a salt marsh, when the last species follows. When 

 purely submarine, it is often an important formation: 

 the banks of Zostera detaining sand, so as to produce 

 bars, and ultimately islands ; thus affecting the na- 

 vigation of shallow seas, and obstructing harbours; or, 

 reversely useful, by consolidating shifting bars and 

 banks. Thus also it often commences the foundation 

 of maritime plains; as, in Scotland, it is rapidly uniting 

 the islands of Barra and Vatersa. 



In these cases, it acts as the subaquatic lacustral 

 plants do in lakes, by detaining earth; while the semi- 

 maritime plants which follow, produce a marsh, and 



