n a scientific 
t nothing of 
it and iden- 
ey. 
rance of any 
CS, 
y is not jus- 
| quality can 
nguage very 
ictionary he 
terpretation 
erial photo- 
Imost daily. 
rs should be 
ery interest- 
cople astray. 
)0,000 aerial 
ation is still 
intelligence 
cult science. 
hink I have 
ear what is 
an show me 
ette stub in 
ven position 
nber X, the 
onan Doyle 
ey does not 
fferences in 
in shade of 
d so much 
d wind; the 
et up rules. 
nature has 
f centuries, 
terpretation 
by photo- 
thus make 
"wn techni- 
my opinion 
inbelievable 
ay will one 
  
  
      
Fig. 1. Portion of a vertical 
aerial photo mosaic, scale 1/ 
50,000, showing Dutch territo- 
ry in which soils exhibit varia- 
ble resistance to erosion. Com- 
pare with fig. 2. 
Fig. 2. Same area as fig. 1, on 
which density of dots indicates 
degree to which soil resisted the 
working of the water, formed 
barriers or cliffs, or consisted 
of dunes built up by water or 
wind. Areas containing few or 
no dots are those in which 
water caused erosion of thc 
soil, forming of rivers, lakes or 
moors, and in some cases, des- 
truction of rivers. 
  
Of course, such a publication will meet with objections. As Prof. Scher- 
merhorn once said: *Be careful; after you have been dead for many years, 
people will still curse you because you told them things they did not like to 
hear.” 
However, this should not prevent us from making progress. I should like 
to illustrate my methods with some slides, showing parts of the Dutch territory 
colored in red and blue on black maps scale 1 : 50.000. 
Blue means that the aerial photographs show that in a given period water 
did its work there: erosion of the soil, forming of rivers, lakes or moors, 
destruction of rivers. 
Red means that the photographs show that this soil resisted the working 
of the water, formed barriers or cliffs, or consisted of dunes, built up by water 
or wind. The red/blue map given as an annex, shows clearly the great impor- 
tance of the mapping of these features; a single photograph only gives a slight 
impression of what happened. 
Eprror’s NOTE: Because of difficulties involved in the reproduction of Mr. 
von Drabbe's maps in color it has been necessary to substitute annotated pho- 
tography instead. It is recognized and regretted that the effectiveness of his 
illustrative material is thereby somewhat diminished.