bor’ 
SUPPLEMENTAL REPORT—HANGING ROCK DISTRICT. 941 
above the lowest point (using any convenient seale); join the upper extremities of these 
lines and extend this connecting line till it meets the line passing through the feet of 
the perpendiculars ; from the point of intersection, draw a line to the lowest station ; 
from the highest station draw = perpendicular to the last mentioned line, and eall this 
line A; draw a meridian through the higkest point, then the angie between this meridian 
and the line A will be the direction of the dip. 
“‘To find the angle of the dip, make a right angled triangle, with the lino A for a base 
and the difference between the highest and lowest points, for the perpendicular; then 
the angle at the base is the amount of the dip. All this is to be done by simple measure- 
ment. If the dip per mile is required, divide the difference between the highest and low- 
est points in feet by the number of miles in A. But in all cases where the dip is but 
slight, it is better to divide the perpendicular of the last named triangle by the base, 
both in feet; the quetient is the natural tangent of the angle of the dip.” 
