( 676 ) 
So it cannot astonish us that in 1805 A. P. Twenr’) makes mention 
of great dryness, making the birches in the plains amidst the dunes 
die at the tops, and that for three years there had been no water 
in places where in earlier times it always had been found, even in 
summer. “Considering that the sea does not be lower now than before, 
as shown by all circumstances, of which not the least certain 
is that the outlets of the inland waters are not improved in this 
part, this matter deserves double consideration by the naturalists”. 
In 1816 and still in 1828 a quite different state of things prevailed, 
as appears from the prize-essay on the making accessible of the valleys in 
the dunes along the coast of Holland by D. T. Gevers, ?) an answer to 
the question: where and how to drain the water from the plains 
in the dunes and at the same time facilitate the access to them, in 
order that they may no longer lie useless and uncultivated. This, 
namely, was imputed for the most part to the want of the necessary 
evacuation of the water. This inconvenience then was very great, 
and its removing indeed was the chief purpose of the large treatise. 
Concerning a following dry period in the dunes no direct infor- 
mation has come to my knowledge. It appears however that from 
1831 till 1840 the rainfall at Zwanenburg (Halfweg), that is very 
near the dunes, has been considerably below the average. *) 
Certainly the level of the ground-water in the dunes of the com- 
munes of Zandvoort, Bloemendaal and Velzen, as well as in the dunes of 
the province of South-Holland (cf. Vuycx, ].¢. p. 184) was very high 
about 1845, so that for instance people skated in the dune-plains 
near Zandvoort. 
On the contrary, about 1860, the ground-water in the dunes stood 
only little higher than in the present period which is get very dry ; the 
water holes which contain now but little water were sufficiently but not 
abundantly provided. Though after 1858 the water supplies to 
Amsterdam, from the dunes, became less than in the former years 
and remained so till 1864, yet it was necessary to make new water 
collecting canals. 
Then again follows a wet period, during which many plains and lower 
places in the dunes became marshy or were drowned in winter, 
frequented by a number of waterfowl (ducks, pool-snipes) and in some 
spots remained occupied by water even in summer, so that water- 
1) Wandeling naar de Zeeduinen van Wassenaar tot digt aan Scheveningen, p. 5. 
2) D. T. Gevers. Verhandeling over het toegangbaar maken van de duinvalleien 
langs de kust van Holland, uitgegeven door de Maatschappij ter bevordering van 
den Landbouw te Amsterdam opgerigt. Deel 18, Amsterdam 1826. 
5) Nederlandsch Meteorologisch Jaarboek voor 1878, p. 288. 
