( 704 ) 



1700, 1 intend lo pnblish them here as a continuation to the earlier 

 reports of the "Comittee for the subsidence of the land." 



My results have been chiefly derived from the heights of the water 

 in the Y before xlmsterdam, recorded from 1700 to 1860 at each hour 

 of the day and at each half hour during the night in the town's 

 tidal station situated at the present fish market near the "Nieuwe 

 Markt." Part of them occur in two communications of Stamkart 

 (Verslagen en mededeelingen der Kon. Akad. van Wetenschappen 

 Afd. Natuurkunde, 15^ deel 18B3, p. 59—69 and 17^ deel 1865, 

 p. 261—303) and some in Stamk art's posthumous papers in keeping 

 of the Academy. 



The way in which these observations were made is described as 

 follows by Dr. Stamkart in his paper in Vol. XVII p. 273. The 

 tidal station was erected above the water; in the wooden floor of 

 one of the rooms was a hole through which a gauging rod carrying 

 a mark of the A. P. (zero of Amsterdam) was plunged vertically into 

 the water so far until a notch of the rod caught on the wooden 

 floor. The height to which the gauging rod was wetted showed the 

 level of the water with regard to the zero on the gauge. 



In order to draw reliable conclusions about the level of the North- 

 sea on our coast based on the results of the water-level in the Y, it 

 is necessary to in\'estigate whetlier during the period under conside- 

 ration variations have occurred in the influx and the outflow of the 

 water of the Y before Amsterdam, owing to changes in the depth and 

 width of the canals leading from the Northsea to the Y. It is very 

 probable that these variations may produce opposed effects on the 

 high and the low water and hence give rise to greater variations 

 in the difference between high and low water than in the mean 

 sea level. The variations of these differences in the succeeding years 

 will therefore be a good standard of the changes in the canals. 



From the tide tables of the town's tidal station we derive the 

 following differences between high and low water during 58 years. 



