CHAP. I.] STATION POINTER 27 



if this can be done without disturbing the coincidence of the 

 legs and all three points appreciably, the fix is bad. 



This is perhaps the most important thing for a beginner to 

 remember and to practise, as it is a practical test involving no 

 theory nor complications. 



Theoretically, one of the best positions is inside the triangle 

 formed by the objects, but in practice it is often impossible to 

 observe the large angles incidental to this position. 



Practically the beginner will find the following rules safe : — 

 1. Never observe objects of which the central is the farthest. 

 ■ 2. Choose objects disposed as follows : — 



{a) One outside object distant and the other two near, 

 the angle between the two near objects being not 

 less than 30° or more than 140°. The amount of 

 the angle between the middle and distant objects 

 is immaterial. 

 {h) The three objects nearly in a straight line, the angle 



between any two being not less than 30°. 

 (c) As before remarked, that the observer is inside the 

 triangle formed by the objects. 

 There are, nevertheless, cases v/here the middle object is very 

 distant, when the fix will be good enough for many purposes, 

 but such cases require a thorough grasp of the subject, and 

 should not be adopted by the beginner unless forced to it. 



1. The best fix is with one distant and two near objects, but Choice of 

 the angle between the latter should not be less than 30° or 40°. fQ^^^ ^ 

 The centre object must be either of the two near objects, and station 

 it is immaterial whether it be the nearer or farther of the two. Fixes. 

 The angle should be observed between the two near objects 



and between the distant object and the farther of the two 

 near ones 



2. With the centre object the nearest, a very good fix is 

 obtained ; but if it is very much nearer than either of the other 

 two, the whole angle should be observed and one of the others. 



3. With the centre object the farthest, caution is necessary. 

 If it is very much farther oS than the other two objects, a good 

 fix may be obtained if the observer's position Hes well away 

 from the circumference of the circle passing through the three 

 points ; but this will not be the case if the observer is nearly 

 on the line joining the two nearer objects. 



