Figure 67. — Continuation of snow trail shown in figure 66. The trail in the upper right hand corner of this photograph joins 
the snow trail in lower left corner of figure 66. The tree in the center foreground is No. 1 1 of figure 65A. 
interpreted as resulting from an attraction to the 
vertical surface. That an additional phenomenon 
is involved may be seen from an examination of the 
position of trails with reference to barrier fences in 
figure 14. It will be recalled that these fences were 
constructed of inch mesh screen, a condition 
which may actually preclude the wall reaction 
itself. Nevertheless, in certain places trails did run 
adjacent to these fences. The critical place to note 
is the median barrier fence. It will be seen that 
trails existed all along the Food Pen side of the 
median barrier fence. A much smaller amount of 
trails existed along the area side of this fence and 
these trails were in general much farther from the 
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