MULDBJERG DWELLING PLACE—TROELS-SMITH 589 
in dilute nitric acid, in which they are slightly oxidized so that the 
sample falls apart, and the peat snuff can easily be washed away by 
pouring the sample into a fine-meshed sieve. By this treatment the 
seeds and fruits become air-filled and will ascend to the surface when 
poured into a soup plate, while the larger plant fragments sink to 
the bottom. With a fine brush the single seeds and fruits are col- 
lected on a watch glass and are later sorted according to species and 
placed in sample vials. By comparison with seeds and fruits of con- 
temporary plants the specimens are identified as to genus and species. 
Thus from study of each peat sample it is known, layer by layer, 
which plants were growing on the spot, and in what proportion. 
WOOD IDENTIFICATIONS 
Charcoal, twigs, and pieces of branches found during the excava- 
tion may also tell about the vegetation. Oak and beech are most 
easily determined, usually with the naked eye or with the aid of a 
good magnifying glass. But in most cases it is necessary to prepare 
a thin section of the wood, which is examined under a microscope at 
about 100-times magnification. In that way the fine structure of 
the plant tissue becomes visible, making it possible to determine the 
trees and shrubs from which the charcoal, sticks, and twigs originated. 
RESULT OF THE INVESTIGATIONS 
THE TWO CULTURE LAYERS—THE FLOATING ISLAND 
Through the excavation and the surveyed sections we have obtained 
a knowledge of the structure of the bog (figs. 9 and 17) : At the bottom 
of the section we find gyttja and mud sediments which were deposited 
inalake. Above it is a dark-colored layer 380 to 40 cm. thick consisting 
of plant remains, leaves, and fragments of branches. Fragments of 
pots, bones, flint chips, and charcoal occur scattered within this lower 
culture layer. This layer was also deposited in a lake but in low 
water near the shore. This is followed by a 40-cm.-thick layer which, 
at the bottom, is composed of light gyttja interwoven with fine plant 
roots. Upward the roots dominate and the deposit darkens. At the 
top of this layer the plant roots are partially transformed into a dark 
homogeneous peat mass. Thereupon follows a thin culture layer 
which has a dirty gray color from charcoal dust and broken shells, 
and here we find a great number of flint chips, small potsherds, and 
bits of bones (upper culture layer). At the top the series of layers 
ends with a thick peat layer interwoven with alder roots. 
The striking thing about this section is that it comprises two culture 
layers: a lower one deposited in water, and an upper one resting on 
peat which was formed in a bog. At first glance one would believe 
that the lower layer was older and the upper younger, and that they 
were separated in time by several hundred, perhaps thousand, years. 
