52 
HitfTS fO TRAVELLERS. 
sun, when on the meridian, is north or south of the observer. Wlieii 
the sun is near the zenith this method would be of little use. 
To find the Meridian by the Sun, ivithout instrum:nU . 
Having levelled a piece of ground of sufficient size, plant a rod in a 
truly perpendicular position, testing it with a plumb-line, and at an hour 
or two before noon (say 10.30) mark accurately the extremity, C, of the 
shadow, B C, thrown by the rod when the sun is in the position S; then 
from the base, B, of the rod as a centre, with the radius B C, the length 
of the shadow, describe the circle, DCF, upon the ground. As the sun's 
altitude increases, the shadow of the rod will fall within the circum¬ 
ference of the circle, and will gradually grow shorter until noon; after 
which, as the sun's altitude decreases, the shadow of the rod will grow 
lender until, at last, when the sun has attained the position S', it will 
reach the circumference of the circle at the point D. Divide the arc 
C D, into two equal parts, and from E, a point equi-distant from C and 
D, draw a line through the centre B, and that line will coincide, approxi¬ 
mately, with the true meridian. 
