( 484 ) 
A graveyard of urns, in which many coffins lie, showing the shape 
of trees, presents an “Oer *) soil” of pure gray clay. It is noteworthy 
that the younger tree-coffins lie deeper. The older urns with burned 
remains, which were found in it, lie close to the surface and date 
from the 3 rd century. 
So if these Mounds in Oldenburg sho^v a sinking of the ground, it 
is certainly smaller than 1 m. 
If we now summarize the results of the investigations, they teach 
us that: 
Some Mounds have shown a post-glacial sinking of ± 3 m., which 
took place before the beginning of our era. 
The calculations about the lowering of the beach at Domburgare 
still quite uncertain, because this situation depends on the influence 
of different other factors. The same thing applies to the beach at 
Katwijk. 
In Zealand the situation of the basis or floor of the Mounds 
teaches us but little about the lowering. The floors in Walcherenlie 
from 0.10 m. — A. P. to ± 0,80 m. -f A. P., certainly to 0.50 
m. -f- A. P. They only allow the assumption of a slight lowering. 
Reynold and Venema’s calculations on the lowering of the Dollard- 
polders must be rejected. 
It follows from the heights of the floors in the Mounds of Fries¬ 
land, . Groningen, and Oldenburg, that the lowering is only a few 
decimeters, or that there is none at all. 
A lowering in the Mound of Farmsum of 0.65 m. may be ascribed 
to a shrinking of a thick layer of peat binder the Mound. 
From the data of the gauges at Amsterdam and elsewhere in the 
Netherlands Ramaer has derived a lowering of ± 1.5 mm. a year 
during the preceding century, but according to van de Sande Bakhuyzen 
no reliable result can be derived from these data about the lowering 
of the ground in the last hundred years. 
We must further call attention to the uncertainty that prevails as 
to whether the sinking of the ground in the north of the Netherlands 
has been the same as in the south, and in the east the same as in 
the west. 
But on this point we have not yet any data layirtg claim to the 
least certainty with regard to Zealand, South- and North Holland, 
Friesland, Groningen, East-Friesland, Oldenburg, Holstein and Sleswick, 
which would point to this. 
x ) “Oer” is a layer of sand, containing still more oxyde of iron than the 
“knik” soil, and hardened by it. 
