SUPP1.EMENTAL EEPOET — HANGING EOCK DISTRICT. 941 



above the lowest point (using any convenient scale); 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 a, perpendicular to the last mentioned line, and eall this 

 line A ; draw a meridian through the highest point, then the angle 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 line A for a base 

 and the diflference 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 oases 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 quotient is the natural tangent of the angle of the dip." 



