102 
HINTS TO TRAVELLERS. 
position is the correct one. It will be seen that there is no point in C e g 
which fulfils this condition, but in the space A df i there is one point p, 
the perpendicular distances from which on to the rays A g, B h, and C i 
are proportional to the distances A p, B p, and C p. With a little 
practice, the position of this point can be estimated most accurately. In 
either case, having determined the approximate position of the point, lay 
the ruler over it and the most distant visible fixed point on the board, 
and turn the board in azimuth till that point is intersected and clamp it. 
The interpolation should then be repeated, when, if the point has been 
properly chosen, the rays will intersect on it; if any small error still 
remains, the process should be repeated. The rule of setting in azimuth 
by a distant point is one which should always be borne in mind, or the 
effects of errors in laying the rule over the points and in the accuracy of 
the assumed position are much minimized. 
