meiitioiiod spot, Ix'iijfi' niiicli nioro midci' iIh' iiiflnfiKM' of tlio pression 

 wliifh makes itself telt in the ]I. M. polder. 



At only 1125 M. noi-th-east of the wel! at Hille.uom, but 3üü M. 

 within the HaarIeinmeniieerj)older, at "Eert-den-Koniiig'', a well 

 has beeji sunk down to '2(13 AI. r^ A. P., in whieh on April 2'J^^ , 

 (before tlie heavy i-ains of the last weeks of that month), the level 

 of the water was 2.57 Al. f A. P. The cause of such a difference 

 is some 1500 M. greater proximity of the centre of the Haarlem- 

 mermeer polder. In the midst of that polder, at Adolfslioeve, on 

 the east Hoofdweg, 890 M. southwest of the Yijfliuizer Dwarsweg, 

 I saw the water ascend only to 4.70 M. ~ A. P. in a well, deep 

 34 AI. — A. P., sunk down below a bank of clay, slightly less deep. 

 Probably the rahis of a few days before, had raised the water a 

 decimeter above its dry weather level. At Hoofddorp I found on 

 May 8^11 1903 a level of 5.03 M. ^ A.P., in a well only 18.5 M. ^ 

 A. P. deep. x\lthough less deep than the other wells, also this was 

 sunk into the less fine sand, and near the top of the coarse-grained 

 sand, beneath the less permeable upper-soil <tf line sand and clay. 

 If the well had been sunk below the clay-l)ank and 34 M. r A.P. 

 deej), the ^\ater no doubt would have risen a little higher. So the 

 result is, that in the midst of the Haarlemmermeer polder, the under- 

 ground water, from under the deeper lying clay, caji ascend half a 

 metre above Summer Level (this being 5.20 M. t A. P.), on the other 

 hand, from under the clayey top-layer, it can rise but little above 

 it. The pression it accpiiretl in the dunes and in the surrounding, 

 shallower polders, on its way to the H. M. polder, is in the middle 

 of it, at 18.5 M. rA.P., almost entirely lost; and at 34 M. t- A.P. 

 reduced to about half a metre, so it can rise but little above 

 the surftice underground water, whereas at "Eert-den-Koning", the 

 ascending capacity of the water rising from 26 M. -f^ A.P. is 2.63 M. 

 above Summer Level, or about 1.50 M. above the grass-land of 

 the polder. The upper-soil, we nuist bear in mind is half permeable, 

 and on its way to the middle of the polder, the ^^ater gradually 

 loses more or less its ascending-capacity. Consequently also, the water 

 cannot horizontally move further east, for then it would ha^e to 

 moNe to parts, wdiere there is more pression. 



That indeed the difference in pression between the surrounding 

 higher parts and this deep polder, is the cause of the motion, 

 appeared from observations taken on other spots round the Haarlem- 

 mermeer polder, and in the deep polders more east, adjacent to it, 

 including the large Mijdrecht-polder. 



North-east of the Haarlemmermeer polder, in the Rieker-polder, 



