504 
MINUTES OE PROCEEDINGS OE 
the top of the next shade below, we shall have the distance apart in plan, or 
horizontal equivalent for three contours of 50 feet, given on the left hand 
side of the scale, but the horizontal equivalents for one contour only on the 
opposite side—viz. for 5°, 3°, and 2°. The inner column on the scale 
gives the approximate gradients or numerical value of the base in terms of 
the perpendicular for each incline. 
The scale of shade, printed on paper, is pasted on the flat side of a box¬ 
wood protractor,* so that the bevelled edge can be applied to any position 
of the plan, and the inclination—and hence the number, thickness, and 
distance apart of the hachures to depict that inclination—ascertained. A few 
lines—as ab, cd, ef, &c. (Fig. 2) —may be drawn in pencil at right angles to 
Pig. 2. 
the contours, or in the direction water would take to trickle down the hill. 
These lines, termed guiding lines, will be of great assistance as regards the 
directions of the hachures; as each hachure, when passing over a watercourse, 
watershed, or guiding line, should be drawn at right angles to it. 
In Fig. 2, if the scale of shade be applied to the guiding line at ab , the 
inclination at that spot will be found to be 35°, as the line ab coincides with 
the horizontal equivalent for 35° on the scale. In like manner, the inclinations 
at cd , ef, gi, and gb, can be found, and the number of hachures, and their 
distance apart, marked off in pencil along each of these guiding lines, the 
scale of shade being kept opposite the draughtsman to guide him in copying 
the thickness of the hachures. After a little practice, the draughtsman will 
get so accustomed to the handwriting, so to speak, resulting from copying 
carefully the scale of shade at first, that he can trust almost entirely to 
memory, and obtain a tolerably accurate representation of the ground. 
It has been shewn that the scale of shade is adapted to the 6 inches to 
* Can be bought at Elliott’s, Strand; or Boddy’s, Woolwich, price Is. 9d. 
