( '5» ) 



containing only 78, 60, 35.5 niG. of rhlorine ;i Liter. Holes made 

 in the midst of deep-polder meadows often till with fresh water, 

 even when a long period of ahsolnte dry weather precedes the 

 digging of them ; so in the Purmer-polder, near the above mentioned 

 deep well, on May 13^'i 1903, the water in snch a hole, dng abont 

 1.80 M. deep, contained only 72.6 m. G. chlorine a Liter, the 

 adjacent ditch water having 407 m.O. Near Hoofddorp, in the 

 H. M. polder, in the midst of the Slaperdijk, 250 M. sonthwest of 

 the Hoofdvaart, after weeks of dry weather, in a hole, the Corps 

 of military engineers had dug, down to 0.40 M. below^ polder-level, 

 water oozed in, wdiich contained not more than 102 m.G. chlorine 

 a Liter, still that dike (the summit of which is about = A. P.) 

 over all its length stretches between two canals 10 a 15 M. wide, 

 only 40 M. apart and always füled with brackish water, lorl.5M. ' 

 deep. The water of those canals at that moment contained 511 m.O. 

 of chlorine a Liter. The level of the water that had gathered in 

 the hole, was 0.11 M. higher than that in the canals and at that 

 time they w^ere even considerably higher than they had been the 

 last month. But those are deep polders, in which the vertical motion 

 of the underground water is from below upward. What to think 

 now of the w^ater that penetrates the soil of the shallow polders? 

 The extent of the land, in the polders, generally exceeding that of 

 the water at least 25 times, and the level of the underground Avater 

 in vsiiny seasons, being considerably higher than the neighboui-ing 

 ditch water, consequently the fresh water will filter down, in a far 

 greater proportion than the brackish, the surface of which forming 

 but an insignificant portion of that of the fresh water fallen in the 

 meadows. The water of the canals ("boezemwater") consequently can 

 but little add, in those rainy seasons, to the salt-standard of the 

 underground water. In the dry season, on the other hand, the land 

 drying out, water must be let in ; the soil is then absorbing brackish 

 water from the canals. In fact, however, even such shallow polders, 

 as the Rieker polder and those of Purmerend, which possess fresh 

 underground water below the recent more or less impermeable strata, 

 have brackish nnderground water near the surface, all the year round. 

 Ne\'ertheless, to my opinion, a great number of phenomena point to 

 the supposition of the deep fresh underground water, found in some 

 of our shallow^ polders, which ha\e brackish underground Avater 

 near the surface, being due to rainfall on the spot itself, or at a 

 comparative short distance. This question will be the subject of a 

 further communication. 



Considering the facts communicated here, in connection with others, 



