BOGS AND FENS 19 



ally abandoned, and lapsed into wastes of scrub and 

 copsewood. 



The fens and bogs of Britain played likewise a large 

 part in the attack and defence of the country in Roman 

 and later times. They were of two kinds. One series 

 lay on the coast, especially of sheltered inlets, and 

 were liable to inundation by high tides. The most 

 notable of these was the wide tract of low, swampy 

 land at the head of the Wash, our Fenland — an area 

 where, secure in their amphibious retreats, descendants 

 of the Celtic population preserved their independence 

 not only through Roman but through Saxon times, 

 if indeed, as Mr. Freeman conjectures, outlying settle- 

 ments of them may not have lingered on till the 

 coming of the Normans. The other sort of fens were 

 those formed in the interior of the country by the 

 gradual encroachment of marshy vegetation over tracts 

 previously occupied by shallow sheets of fresh water, 

 and over flat land. It was in these swamps that the 

 Caledonians, according to the exaggerated statement of 

 Xiphiline, concealed themselves for many days at a 

 time, with only their heads projecting above the mire. 

 At a far later period the peat-bogs of the debateable 

 land between England and Scotland formed an impor- 

 tant line of advance and retreat to the freebooters of 

 the border, who could pick their way through sloughs 

 that to less practised eyes and feet were impassable. 



One of the distinguishing features among the topo- 

 graphical changes of the last few hundred years has 

 been the disappearance of a vast number of these fens 

 and bogs. In some cases they have been gradually 

 silted up by natural processes ; but a good many of 



