4i6 



Report S.A.A. Advancement of Science. 



in projection an imaginary circle of 360 degrees through the diameter 

 joining 90 degs. and 270 degs. This line is the surveyors' north 

 and south axis, whilst, by co-ordination, all points of survey must 

 be referred to an origin which lies at the intersection of an east and 

 west axis drawn at right angles to the north and south axis or to 

 a parallel thereto. The reference of the points of survey to this 

 origin is by means of ordinates and abscissae, having sign values 

 in accordance with the direction of their projection on to the axis of 

 co-ordination. We should thus cease to speak of a line " bearing 

 N 40 deg. E," and say that it is a line " whose angle of direction 

 is 130 degrees." The writer maintains that this is no pedantic 

 distinction, but is a true mathematical expression, and in accord with 

 the practice of the Land Surveyors of this Colony, who fix the north 

 direction as 90 degrees. 



After such a free criticism of other people's methods, it would 

 be invidious of the writer not to proffer both a method of procedure 

 and a method of calculation. But, in criticising, the writer has in 

 many cases made clear what he considers the best practice should be, 

 whilst, at the same time, he recognises that he is but criticising 

 information supplied to him, and not a method with which he has 

 been actually in touch. Therefore, it is possible that in putting 

 forward the following forms he may be including much which he 

 has failed to find in the copies of the six systems included in this 

 paper : — ■ 



I.— PROCEDURE. 



At 930 R. C. and L. Drive. 



21/5/06. 



6-47 



Sio 



5 60 



Note: R.C, L., etc., denotes whether station is right, right 

 centre, centre, left centre, or left of drive, cross-cut, etc. Inst.= 

 height of instrument below station plug in hanging of drive. Pb. = 

 length of plumb line at foresight. Tr. = height of track from rail 

 level to station plug at foresight. "A" "B" mean A and B 

 verniers. 



