228 Account of the Climate, 8fc. of the North of France. 



The period at which the land began thus to encroach upon 

 the sea, is lost in the lapse of ages, — all that we can discover 

 from history is, that this encroachment had made considerable 

 progress anterior to the age of Julius Caesar. No fossil shells 

 are found in the soil, but trees, similar to those found in Hol- 

 land, have been dug out sixteen feet below the surface. The 

 cause of this formation of land, and consequent repulsion of 

 the sea, seems to be the successive accumulation of alluvial 

 matter brought down by the rivers,— including, perhaps, the 

 Rhine, the Meuse, and the Scheie!, along with the action of 

 the North Sea on the coast of Holland. Gravelines, built at 

 the mouth of a river, was, at the beginning of the last century, 

 bathed by the sea, and is now distant from it about three 

 miles. 



The surface of the country is but very little elevated above 

 the level of the sea at low water ; and when the sea is full, the 

 land is so much below it, that were it not for the artificial em- 

 bankments along the shore, and if the sluices were not regu- 

 larly shut at Calais, Gravelines, Dunkirk and Fort Nieulay, 

 the whole country would be inundated. Hence it is that the 

 rivers and canals do not flow during high water, a pheno- 

 menon which always attracts the attention of strangers, more 

 especially when unacquainted with the cause. 



Strictly speaking, there is but one river that passes through 

 this country, which is named the Aa, and which has its origin 

 near Reuti in Artois, about six leagues to the S. W. of St 

 Omer. Passing through the last mentioned town, its direc- 

 tion is towards Gravelines, and about a league beyond that 

 place, it reaches the sea, — its whole course not being less than 

 sixty or seventy miles. At different parts, as in the vicinity 

 of St Omer, the bed of the river has been raised many feet 

 above the surrounding fields, so that it is impossible to divine 

 what its original distribution may have been. At Watcn it 

 gives off a branch called the Cohne, which runs N., passes 

 Bergue, and enters the sea at Dunkirk. A second branch 

 goes toward Bourbourg, which it surrounds and crosses, and, 

 with the Colme, reaches the sea at Dunkirk. About two cen- 

 turies ago these branches were enlarged, (being then only 

 small streams,) so as to form two canals for the purpose of na- 



