( 739 ) 



them. My rosearelies were pi-incipallv limitcMl to the soul hern i)art 

 of' tlie Noi-(li-Ilollaji(l low-lands, iiicludiuf!; the dunes, and the adjacent, 

 parts of the jn'ovinees of Uti-eeht and of South-Holland. It is a 

 matter of course that also here I had to limit myself to the chief 

 points of the (juestion. 



In the last decemiia, lunidreds of Uorings have been done in the 

 polders, in the dunes and in the area between them by the corps 

 of military engineers ajid by othei's, with the object of making 

 fortifications or of obtaining fresh water. Down to a certain de[)th, 

 the constitntion of the soil is conseipiently pi-ett_y well known, and some 

 deeper borings have tolerably well ac([uainte(l us also with the 

 constitution of tlie soil at greater dejtth. Sand is the chief substance, 

 alternating with beds of always very im[)ure cla}'. Close to the 

 surface, pretty generalh, a zone is found of clayey sul)stances, (the 

 well-known "old sea-clay" of STARiN(i), over considerable areas, 

 covered with a layer of peat, which cla}', in the dunes, where that 

 peat is generally lacking, is covered with blowji sand. Under the 

 liner sand of the u[)per-soil, often mixed with clay, in which occur, 

 in large areas, deeper layers of peat, there is a zone of coai'se-grained, 

 often gravelly sand, not unfrequently containing pebbles. In the 

 west of the mentioned region, the top of that zone lies ab(jut 30 M. 

 ^- A P. deep, or a few metres higher; in the east, near Aalsmeer, 

 Sloten, Amstelveen, Mijdrecht, Wilnis, (Judhuizen, it rises to J 6 or 

 14 M. fA.P.; near lAluiden and Nigtevecht as high as 10 or 8 M. 

 -r A.P. and its reaches the surface further east. Uiuler Amsterdam and 

 both south-east and north-east of it, the soil, on the whole, is much 

 richer in clay. 



Also at greater depths, clay-beds occur, but nevei- as unbroken 

 layers, extending over great distances ; the most regular zone is 

 after all that of the so-called old sea-clay, near the surface. It is 

 besides of importance, that near our eastern frontiers much older 

 formations come to the surface, than have been found, some hundreds 

 of metres deep, under the lowlyhig lands in the west. This in itself 

 is a reason not to expect ai-tesian water, from Germany, in our 

 western sea-provinces, to some hundreds of metres below the surface, 

 at least. 



Of great signiticance for the |n-oblem is also Ihe fad lha(m(u-eor 

 less pure clay I'arely occurs. Whai is considered as such, on further 

 examination, (washing of a uunibei- of samples of diilerent origin, 

 and especially chemical analysis, which analysis Dr. N. Sciiookl 

 was kind enough to do at my reipiestj proved lo consist for ojdy 

 one thii'd of clay at the nu;)sl, genei-ally for much less, even for only 



49* 



