BRITISH POSTGLACIAL &> RECENT DEPOSITS. 445 



would happen from time to time, we need feel no surprise at 

 meeting with layers of peat and woody matter at various levels 

 in the estuarine and fluviatile deposits that overlie the ancient 

 forest-bed. It is also quite possible that some of those peat- 

 beds may really represent old land-surfaces or marshes, formed, 

 as Mr. Ussher remarks, "at different times and in different 

 places from alterations in river-courses or stoppages of drainage." 



5th, After a time another change took place in the relative 

 level of sea and land. The sea gradually retreated and left the 

 estuarine and marine deposits exposed. This alteration of level 

 seems to have been accompanied also by the return of conditions 

 favourable to the growth of large trees. The land must then 

 have stretched southward for a considerable distance. This 

 inference is necessitated by the presence of the oaks, elms, and 

 other trees of the so-called submarine forests of the present fore- 

 shores, and the upper bed of peat with tree-roots which is found 

 in certain stream-tin sections resting upon the surface of the 

 fluviatile and estuarine deposits. It is hardly possible that so 

 strong a forest-growth could have taken place in the immediate 

 vicinity of the sea. 



6th, The position now occupied by the submarine trees points 

 to a recent submergence, the proximity of the sea bringing about 

 conditions adverse to the growth of trees, and producing the 

 present general bare appearance of the Cornish coast-lands. 



I shall now ask my reader to take a brief glance at the 

 evidence supplied by the sunk forests and buried peat of the 

 Fenland. These have been described by many writers, and the 

 general facts have long been known, but it would seem from the 

 recent exhaustive exploration of the district by Mr. S. B. J. 

 Skertchly of the Geological Survey that some of the views 

 which have hitherto prevailed are not quite correct. The region 

 of the Fenland, as every one knows, extends inland to west and 

 south from the borders of the "Wash, so as to embrace an area of 

 more than 1000 square miles, the widest tract of level ground in 

 Britain. This great stretch of flat land consists of superficial 

 accumulations of silt and peat with underlying gravel, which 



