260 H. W.Pearson — Oscillations of Sea- level. 



Data indicating a Period of Low Sea-level about the year 1175 a.d. 



Omar, who wrote about 1050 a.d., had satisfied himself that " the 

 extension of the sea had been greater at some former periods." He 

 was the author of a work, " The Retreat of the Sea." We can infer, 

 then, that he had observed indications of a recent recession of the 

 sea — in other words, he must have lived during a low-water period, 

 or at such time as the sea had already made great recession from the 

 high-water position of 875. Bede says the Channel between the 

 Isle of Thanet and balance of Kent was three furlongs wide in the 

 eighth century, and it is supposed it began to grow shallow about 

 1066 ("Principles," vol. i, p. 529). Dantzic at the same level now 

 as in the year 1000 ("Principles," vol. ii, p. 182). Heligoland in 

 1072 extended over a space of 900 square kilometres ("The Ocean," 

 p. 153). Island at the mouth of the Bay of St. Malo formed 

 a portion of the mainland in the twelfth century (" The Earth 

 and its Inhabitants," Europe, vol. ii, p. 251). 



Henry of Huntingdon says about 1134, "This fennie countrie 

 [the Fens, England] is passing rich and plenteous, finely adorned 

 with woods and islands." William of Malmsbury, who wrote about 

 the year 1140, says, "The Fens were a very paradise, the very 

 marshes bearing goodly trees which for tallness strived to reach up 

 to the stars " (" History and Antiquities of Boston," p. 660). " It 

 seems to show that Lincolnshire was then [time of William the 

 Conqueror, 1068] a fertile corn-bearing district " (" The Fenland 

 Past and Present," p. 98). We have already shown how this 

 paradise, this fertile corn-bearing district — these terms describing 

 the condition of this region during the low-water period — was later, 

 during the advance of the sea between the years 1250 and 1500, 

 submerged and devastated ; this devastation being contemporaneous 

 with the inundation of Holland. Dirk II received in 983 a broad 

 district that is now covered by the Zuyder Zee (Encyc. Brit., 

 vol. xii, p. 71). " There was [in the strait between the Isle of 

 Thanet and coast of Kent] a considerable passage for ships till 

 about the time of the Norman Conquest, very soon after which the 

 inhabitants began to reclaim the land that had been formerly under 

 water " (Wilson, "The Isle of Thanet Guide," p. 7). 



Data showing the High-Water Epoch of about 875 a.d. 



" In the time of Charlemagne the island [Heligoland] was not 

 much larger than now" ("Principles," vol. i, p. 559). In the year 

 800 the sea carried oif large quantities of soil from Heligoland 

 (" Gallery of Nature," p. 388). In the years 800 to 900 " Tempests 

 change the coasts of Brittany ; valleys and villages are swallowed 

 up" (loc. cit.). Channel between the Isle of Thanet and main- 

 land was three furlongs wide in the eighth century ("Principles," 

 vol. i, p. 529). In 660 the Ehine inundated the country ("The 

 Ocean," p. 153). " Some antiquarians maintain that the submarine 

 trees that occur along the coast between St. Malo and Cape La 

 Hogue are the relics of a broad belt of forest land, which was 



