( 753 ) 



i. e. 0.04 M. ahoYQ avci-a^c I(>\\-li(l(> iiiarlv, and JJU) 31. bclow 

 high-lido mark. Oii Fchr. I.St»' 1903, at 4.20 |).ni., if hoiiig low-tide, 

 tlie quantity of cidoriue of tlie walcM- iii lliat well, was 291 hi.Ct. 

 the Liter. On Mairli ()"' J903, at 10.30 a.m., ahoiil three hours after 

 high-tide, the level of the water in that well was 0.93 M. -\- A. P. 

 or 0.76 M.. above the sea, at that nioment. 



Also ill the deej>er, coarse-grained sand-layers, there is a main 

 current of fresh water towards the sea. In a well in the dunes, 

 350 M. from the sea (low -water line), on the Kerkplein at Zandvoort, 

 sunk down to 28.3 jM. r A. P., the level of the water on the 14^'' of 

 April 1903 was as follows : 



At 4.30 p.m. 1.445 M. -f A.P. 

 ,, 5 „ „ 1.497 

 „ 5.25 „ „ 1.520 



So a distinct influence of the high-tide, which at IJmuiden rea che < 

 its highest level, J .43 31.-j-x\.P., at 4.55 p.m.; at Zandvoort presum- 

 ably 8 minutes eai'lier, is evident. 



The next day, in the same well — the dee[)er one of the two — 

 the level of the water was found to be : 



At 12 o'clock 1.28 M. + A. P. 

 ,, 12.35 p.m. 1.24 



Comparing the abo\e figures with those of the self-registering 

 tide-gauge at IJmuiden, it appeared that the influence of the tide 

 makes itself fell 40 minutes later in that well, situated 350 M. from 

 the sea. The sudden way in which the gradual rising of the water 

 stopped at 3.5 p. m. was found to correspond wilh the somewhat earlier, 

 change in the level of the sea, tiie difference in time corresponding. 



At Dmuideu, 1.30 |>.m., the low-tide level was obsei'ved to l)e 

 0.7(5 3[. ^-A.P.. So the walcr in ihc well was 1.95 M. higher. At 

 liigh-tide howe\eiv it \\as al that lime, but aboul 0.10 3J. abo\ethe 

 le\el of the sea. So the amplifiide of the tide inlliience in the Avell, 



50 

 Proceedings Royal Acad. Auibterdam. Vol. VI. 



