110 PROBABLE ANTIQUITY OF PEAT. CHAP. vn. 



peat, enclosing trunks of flattened trees, have been thrown 

 up on the coast at the mouth of the Somme; seeming to 

 indicate that there has been a subsidence of the land and a 

 consequent submergence of what was once a westward con 

 tinuation of the Valley of the Somme into what is now a 

 part of the British Channel, or La Manche. 



Whether the vegetation of the lowest layers of peat differed 

 as to the geographical distribution of some of the trees from 

 the middle, and this from the uppermost peat, as in Denmark, 

 has not yet been ascertained ; nor have careful observations 

 been made with a view of calculating the minimum of time 

 which the accumulation of so dense a mass of vegetable matter 

 must have taken. A foot in thickness of highly compressed 

 peat, such as is sometimes reached in the bottom of the bogs, 

 is obviously the equivalent in time of a much greater thickness 

 of peat of spongy and loose texture, found near the surface. 

 The workmen who cut peat, or dredge it up from the bottom 

 of swamps and ponds, declare that in the course of their lives 

 none of the hollows which they have found, or caused by ex 

 tracting peat, have ever been refilled, even to a small extent. 

 They deny, therefore, that the peat grows. This, as M. Boucher 

 de Perthes observes, is a mistake ; but it implies that the 

 increase in one generation is not very appreciable by the 

 unscientific. 



The antiquary finds near the surface Grallo-Eoman remains, 

 and still deeper Celtic weapons of the stone period. But the 

 depth at which Roman works of art occur varies in different 

 places, and is no sure test of age ; because in some parts of 

 the swamps, especially near the river, the peat is often so fluid 

 that heavy substances may sink through it, carried down by 

 their own gravity. In one case, however, M. Boucher de 

 Perthes observed several large flat dishes of Roman pottery, 

 lying in a horizontal position in the peat, the shape of 

 which must have prevented them from sinking or penetrating 



