( 749 ) 



The real existence of the a^)o^■c indicated motion, from the 

 shallow polders, north of the H. M. pokier, towards the latter, is 

 confirmed by observing' tiie level in a well, sunk down to 32.5 M. 

 r A. P. under the direction of Dr. Alkxandkk Klein, near the 

 "Huis de Vraag", between the Rieker polder and the Sloter Binnen- 

 and Middel veldsche combined Polders (Summer Level -r 2.15 M.), 

 not far behind the Vondel Park. On June 16^'' J 903, I found the 

 level to be 2.46 M. -f A.P. The well lies 31(X) M. from the H. M. 

 polder, or about 1800 M. further than well III. 40, in the Rieker 

 polder. So also here there is an inclination of about 1.8 : 10000. 



Also towards the polders Avhich lie eastward, adjacent to the 

 H. M. polder, and hydrologically one witii it, the motion of the 

 water, deep down, is from the higher to the lower ones. This was 

 sho^vJl by soundings, done on June 24^'^ 1903, in wells, all sunk 

 doAvn to about 30 i\I. > A.P. and belonging to foii'tifications south- 

 east of Amsterdam. There appeared to be an ini))elling force in that 

 deep water towards the Groot-Mijdrecht polder (where they keep the 

 water to a Summer Level of -7- 6.60 M.). 



The following small table, concerning observed levels on August 

 26fi' 1903, shows this: 



Distance to the Level, 

 Groot-Mijdrecht Polder in M. ~ A.P. 



Fort near Nigtevecht 7 KM. 1.775 



Mil. Post near Oostzijdsclien Watermill 5.5 ,, 2.01 



Fort near Abcoude 4.5 ,, 2.12 



„ „ De Winkel 2.5 „ 2.29 



„ „ Botshol 0.2 „ 4.43 



The fact that the inclination of the pression-line is specially great 

 here, near the deep polder, and also from Nigte\'echt to the Oost- 

 zijdsclien Watermill, nuist, I think, be attributed to the greater height 

 to which the gravel-diluvium rises in this ))art, a thing to which 

 attention has been called, already at the beginning of this pa|)er. 

 The influence of sui'face- water can therefore make itself felt comp- 

 aratively strongly, when locally rapid changes occur ; at Botshol, 

 on account of the neighbourhood of the dee])er poldei'. and at 

 Nigtevecht on acconiit of the rising of the u|)per-[>art ol' the deposit 

 of coarse grained sand, which at a comparative small distance, east 

 of Nigtevecht, at certain S|)Ots, even reaches the surface. The reason 

 being that the artesian regularitv of pression, to which the deep 



