230 
Oliver and Tansley. 
guished as the line a, the line b, etc. For convenience in com¬ 
pleting the operation of squaring, the posts on the base line 
stations and those on the measured perpendiculars should respec¬ 
tively bear numbered and lettered cards conspicuously displayed 
with their surfaces parallel to the lines on which they are, so that 
they can be easily seen from the directions perpendicular to these 
lines. 
The rectangles between the perpendiculars are now completed 
by ranging a parallel, as at j (Fig. 77), and posts with numbered 
cards are planted at 100-foot intervals in the usual way. The final 
plotting of a rectangle into squares can now be carried out very 
rapidly by three persons, of whom one plants the corner posts whilst 
the other two act as linesmen on two adjacent sides of the rectangle, 
ranging the post to be planted against the corresponding posts on 
the other two sides. In Fig. 77 two rectangles are shewn, one of 
which has been plotted into squares. 
In actual practice the perpendiculars should be raised at 
intervals not exceeding 600 feet, whilst the employment of field- 
glasses is of great assistance in promoting the operation of 
plotting the ultimate squares. 
The posts which mark the corners of the squares are known 
by the designations of the lines whose intersections they occupy, 
e.g. 14h, 17b, (see fig. 77). As soon as the squares in a rectangle have 
been plotted out, the posts should be marked with their designations. 
Observance of this precaution will save much loss of time, worry 
and confusion throughout the survey, and its importance cannot be 
exaggerated. 
When the ranging of the squares is complete the existence of 
any inaccuracy will be manifest. If the posts of the verticals, 
parallels and diagonals, respectively, stand in proper alignment 
everywhere the preliminary work of the survey may be accepted 
with confidence. And it may be counted as a further merit of the 
system that if posts are removed by mischievous persons it is of 
little moment, for they can be replaced as a rule by simple ranging. 
• 
It is prudent, however, to ensure the permanence of the base line by 
cutting out pieces of turf at each of the 100-foot stations. 
Mapping the Squares. 
For the purpose of mapping, the rectangles are allotted to 
small parties of two or three members, one of whom acts as Sur¬ 
veyor. The latter is provided with a field-book consisting of leaves 
