(758) 



intermixing- with water, rirlier in salt, both from above and from 

 below, may consequently l)e hindered or iiirlhered l»y it, also the 

 oozing in of fresh water; the diiferent mixtures, as an olhei- conse- 

 quence, being able to move horizontally in the one or the other 

 direction, or be prevented to move at all, which explains the diiferent 

 levels they reach. 



The hypothetic currents can be dispensed with to explain the 

 existence of fresh water, bel u een 35 and 50 M. : /V.P., in the old 

 boriiig at Sloten, so often ui-ged in i>roof of powerful subterranean 

 water-currents of distant origin. Of the abo\e mentioned \vells in 

 the Rieker polder, those, most A\est, are only 800 M. east of tlie 

 boring of 1887. The diiferent levels observed in the wells at Sloten 

 can in reality be due only to local motion, in the direction of the 

 shallower polders (with their higher upper-pression) to the deeper 

 polders, where the pression from above is less powerful. The fresh 

 water, everywhere found there at great depths, down to 50 M. ^ A. P., 

 can lind its origin only in those shallow polders themselves. The very 

 position of the old boring at Sloten, at a corner of the shallow 

 Rieker polder, between two deep jwlders (the H. M. polder and the 

 Middelveldschen Akerpolder (S. 1.. f 4.20 M.)), explains the irregu- 

 larities of composition observed there in the vertical distribution of 

 water, and thus it is, with the l)oring near Diemerbrug, outside the 

 north corner of the deep Bijlmermeer polder (S.L. -f 4.20 M.). At about 

 250 M. ^ A.F. water of a somewhat lower standard of salt (mini- 

 mum 1J92 m.G. a Liter) was found; no fresh water, as Dahapsky 

 lately held forth. Considering what influences are at work in the 

 distribution of the water in our soil, one can but see natural 

 phenomena in all those deviations. 



Considering the geological condition of the pliu-e itself and of its 

 surroundings, the occurrence at Wijk-aan-Zee, both of fresh water down 

 to 31 M. ^ A. P. (47.8 m.G. chlorine) and of its getting l)rackish, ali-eady 

 at 50 M. -7- A. P. (351 m.G. chlorine) may be easily explained; also 

 the presence of a layer of fresh water, between the sea-water, in 

 the sub-soil of IJmuiden. 



In this discourse on some general features of the movement of 

 the underground water in our lowlands the question remains to be 

 settled, how it is that some shallow polders, of whicli the canals 

 and the ditches like those of other, deeper polders, are mostly tilled 

 with brackish water, can furnish fresh underground water. 



In the first place the answer will be that, by no means, all 

 surface waters of the polders are brackish. Even in the H. M. polder, 

 I found, also at dry seasons, in some places fresh surface water 



