176 



E. LANCASTER JONES 



problem of least-square adjustment must be governed by considera- 

 tions of the accuracy justified in the particular survey, and the most 

 economical method of executing the calculations involved. Adjust- 

 ment involving elimination of the correlates of the first-remove cells 

 on the lines of §§4 and 5, using equations (6) to (11), is a simple, 

 reasonably rapid process, readily applicable to any cell in any net- 

 work however complicated. When the network is homogeneous, i.e., 

 when all the cells are polygons of the same species and regular in ar- 

 rangement, the more rapid approximations discussed in §§6 and 7 

 may be used with advantage. Also when there are outstanding runs 

 or chains of cells equations (16) to (19) are easy to apply and give 

 very rapid approximations. 



Fig. 7 



For general purposes, the procedure of §§4 and 5 is recommended 

 as being simple, universally applicable and almost as rapid as any of 

 the subsequent processes when account is taken of all the stages of 

 the operation. As a test of this procedure, an adjustment made for a 

 network of 56 Eotvos gravity stations may be cited. The observations 

 were made in the course of a practical survey in Cumberland. The 

 stations are shown as open circles in Figure 7, where they are connected 

 by broken-line links to form 80 triangles numbered i to 85, numbers 

 26 to 30 being omitted. It is evident that the network thus formed is 

 typical of a large regional survey and that the procedure of linking 

 could be adapted to any group of stations, however numerous. From 

 the measured data of the gravity survey the increments in g were 

 calculated for every link, and from these the excesses were derived 

 for each triangle of the network. The excesses for the first ten triangles 

 are tabulated in Table VIII in convenient units which were subse- 

 836 



