4o0 Mr. Downing on the Drainage of Haarlem Lake. 



tions by which this result has been so successfully obtained. It will fa- 

 cilitate this end if we first consider some of the physical peculiarities of 

 Holland, its formation, the raiu-fall, evaporation, &c. It would be a great 

 mistake to suppose that this country is all a mere Delta of the Rhine ; the com- 

 parison of the coast-line of Holland with those of the Deltas of the Ganges, 

 the Mississippi, and the Nile, would, from the great difference in the contour of 

 the sea level, which they all, as compared with Holland, express, lead one to 

 suspect some corresponding difference in the character of their respective for- 

 mations. A more intimate knowledge of this country will, I think, confirm 

 the impression thus raised, at least as to all the more northern districts, in 

 which we find, prevailing over a large area, a dark peat, sometimes more than 

 30 feet deep, resting on sand or clay, the level of its surface being seldom above 

 mean tide level, and very frequently much below it. 



Nor is the river Rhine one of those that carries down to the coast any very 

 large proportion of sediment, as may be concluded from a comparison of it with 

 these other rivers, in reference to the weight of earthy matter in suspension: — 

 Oxus, 250 lbs. ; Yellow Sea, 50 lbs. ; Ganges, 22 lbs. ; Wear, in floods, 

 16 lbs. ; Mississippi, 6 lbs. ; Rhine, | lb. in 1000 gallons. 



In fact, so far from being a Delta, ever increasing by successive deposits, we 

 may regard this territory as the fragmentary relic of some larger region, which 

 has been devastated by the ocean, and is now only preserved in its present 

 outline by the unceasing care and industry of man. Many of these inroads 

 of the ocean are well-remembered historical facts ; the present inland arm of 

 the sea, called the Zuyder Zee, was the result of a terrible storm in 1 287, in 

 which 80,000 persons perished, and cattle innumerable ; and, ten years before, 

 the tract of land which now forms the Dollart was swallowed up ; and a long 

 list of similar disasters might be enumerated. 



Along the sea-board of the German Ocean the country is protected natu- 

 rally by a high ridge of sand-hills, which stretch along the coast from near 

 Dunkirk to the Helder. On every other part the waters are kept back by 

 immense sea-dykes; and not only on the sea-coast, but also on each bank of the 

 intersecting rivers, are these necessary. The annual cost of the maintenance 

 of the dykes, and the other necessary works, is about £600,000. From this 

 view of the relative position and levels of the land and water, we hardly re- 



