( 480 ) 
already described accurately *). So the knowledge of the elevation 
of the floor above A. P. must be of much importance. 
For Friesland and Groningen Mr. van Giffen has collected data 
about this, and for Oldenburg Prof. J. Martin (at Oldenburg). From 
this appears that for the north of the Netherlands no greater sinking 
than 7 j — ± 1 m. can be derived from these data, nay for many 
Mounds a sinking which is hardly appreciable, or no sinking at all. 
In the first half of the nineteenth century about 1845 Dr. Acker 
Stratingh and Dr. Westerhoff stated about the Mounds at Warffum, 
Uskwerd, and about the Groningen Mounds in general that their 
bottom lay from two to three meters below the level of the arable 
ground. The height of the arable ground round the Mound with 
yespect to A. P. was, however, not given, and in no case ascer¬ 
tained by levelling. 
Moreover Acker Stratingh and Westerhoff have very probably set 
down the foundation (the floor or bottom) of the Mound as too low. 
This foundation could be most easily ascertained between the layer 
of manure at the bottom of the Mound and the untouched ground. 
But it is just at these places that the floor probably lies deeper, for 
the manure at the bottom of the Mound often lies in dug holes. Such 
holes have, e.g., been found in the Mounds of Baaijum and of Dongjum. 
There the remains are found of fresh water basins overgrown with 
rushes and filled with manure. These basins must have been dug 
in the earth at the building of the Mounds. When later on the Mound 
was made higher (which took place with all of them), they were 
filled up with the manure of the cattle-keepers, as still happens in 
the Halligen. 1 2 3 ) 
We can now by no means derive the depth of the floor of the 
Mounds, and much less the extent of the lowering, from the accounts 
of Stratingh and Westerhoff. 
1 ) Gf. “Beschrijving over het tegenwoordig standpunt onzer kennis van de 
Nederl. Terpen”. E. J. Brill Leiden 1908 p. 144-145. 
2 ) The Halligen are oblong, unembanked islands (“kwelders”), now inhabited by 
cattle-keepers, who do not occupy themselves with agriculture. They were rais 
high enough by washed ashore silt and mud in former times to be protected from 
the flood and to be habitable. They lie along the Sleswick coast. On t ese 
islands “wurthen” have been raised. If one digs down to the bottom of the Moun 
one finds the remains of a fresh water basin (Fething) as described above over¬ 
grown with rushes and filled with manure. Why and when this happened, is uo 
known to me. These Wurthen or Mounds date from the preceding century, so e l 
are of recent date. 
