{ 742 ) 



Wilier, tlie lueaiib lu do so, jiltliongh liardly ever applied, ;iro evidcMit. 

 .lust tis on the siirFuce, it is the law of gravitation that also deep 

 below, gives to Ihe water its hoiizoiilal course. The direelion of that 

 motion, as caused Iw gra\ itation, can i)e demonstrated from the 

 inclination of the pression-line of Ihe water, deep l)elow, for that 

 motioncan hap[)en only from spots under greater, to tiiose of smaller 

 pression. The \ertical motion, under any given constitution of the 

 soil, can, as a rule, be inferred from the jtositive or negative character 

 of the j)rcssion l)elow, Avitli res|»ect to tlie level of the water on 

 the surface. 



When the water from the undergrouiul, freely rising in a lube- 

 well, remaijis below the level of that in Ihe upjier soil, that vei'tical 

 motion can take place only in a dowiiwai-d direction — if at 

 any rate, then and there, a motion in a ^■ertical direction on the 

 whole is possible, which is mostly the case. When, on llu^ other 

 hand, the level of the water, iu the tube-well rises highei' than that 

 of the surface-water, as is the case in the dee|t p(>lders, vertical 

 motion in a somewhat permeable soil, can take place only in aji 

 upward direction. The (puintity of chlorides in the watei', <letei'mined 

 as chlorine, furnishes us wiih an othci- indication of the direction 

 of that Aei'tical motion. 



So the observation of the height to which the water ascends in 

 the tnbe-wells and the mutual com|»arisou of the same, can teach 

 us much as to the direction in which the watei- moves. A great number 

 of those observations have enabled me to ascertain, that also deep 

 below, the motion of the underground water (unintluenced though it 

 remains by small irregularities), depends on the sha})e of the surface. 

 In short, the direction is from the dunes to the lower regions ; 

 from the higher to the deeper jiolders, and any great une\'enness of 

 the surface, makes its influence felt, already at a considerable distance. 

 In the dunes the deep underground water is under the highest 

 pressure ; in the deepest polders it ascends in the tube-wells to a 

 level some metres lower, although there it wells up above the 

 ground. Near a low-lying polder the water falls also in very deep 

 wells. So not only near the surface, but also deep below, there is 

 a motion from the dunes to those polders and also from the higher 

 to the lower polders. 



Before communicating the observations, on which those results are 

 founded, 1 must specially state, that there are influences, which for a 

 time may more or less change the pressicui of the water in the 

 underground, as it appears from the rise or fall in the wells. In the 

 tirst place uuisl be mentioned: rains, whicli make their influence felt 



