on the air photos and the composition and appearance of vegetation. 
Ordinary water-transported sediments also have a smoother surface 
than till. The same is also valid for lacustrine and marine sediments. 
Lacustrine and marine accumulations with characteristic forms are 
restricted to beach ridges and to some extent wave-washed deposits. 
Especially in the mountain areas mass movement deposits are fairly 
common. Talus, huge accumulations of boulders, often more or less 
completely cover the steeper mountain slopes. The boulders have been 
broken off from rock outcrops in the mountains by frost action and 
have then fallen down to lower levels as a result of gravity. 
On mountain slopes are also found a very typical waveshaped pattern 
of solifluction ridges which are found in cohesive material; as a rule 
coarse-silty till replaced through frost action. 
In stone-filled depressions the ground is completely covered by boul- 
ders accumulated through frost heaving. On air photos such depressions 
can be confused with bogs. If, however, one observes carefully it is 
possible to distinguish that they normally have a very typical reticular 
structure and another photographic tone than the bogs. 
As a rule the bogs can be identified with a great precision on the air 
photos. They not only have their own particular grey tone but very 
often also a characteristic pattern of peat strings and small areas 
of open water, 
In conifer forests one can often distinguish areas with more or less 
sparse forest and a typical grey tone. The ground in these areas is 
embogged and in the field one will find that they have a 30—50 cm 
thick carpet of peat. Under the peat-layer there follows as a rule a soil 
with a high percentage of grain sizes not coarser than coarse silt 
(< 0,06 mm), either a watertransported sediment or a till. On the 
surface there is very often laying a concentration of boulders. 
Bearing in mind that about 1/5 of the surface of Sweden is covered 
by peat, in northern Sweden even more, this motivates the use of photo 
interpretation for surveying surficial deposits. 
Naturally it is not possible to get direct information about the grain 
sizes of the deposits through photo interpretation. However, there 
exists much indirect information the more skilfull the interpreter and 
the longer the scientific investigation has advanced. 
Some examples of relations between surficial deposits and their 
grain sizes will be given. 
The Rogen moraine is as a rule rich in boulders and consequently the 
dominant grain size is coarse. 
The Veiki moraine and probably very often also the drumlins have a 
medium boulder content and a higher percentage of fine material. 
Especially below the marine limit the material in eskers is well sorted 
sand and coarser material. In the high mountains however the material 
in eskers and also other glacifluvial deposits is normally less well sorted. 
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