856 



MR HENRY BRJGGS ON 



average centring displacement remains ^ inch, and that greater precision can only 

 be attained by closer centring. 



500 FT. 

 LENGTH OF TRAVERSE LINES 



Fig. 3. 



1000 ft 



In relation (7), when either v, or the average angular error due to centring becomes 

 equal to or less than one-third of the other, it may be considered negligible, so far as 

 its effect on t is concerned.* 



Compare with S. J. Bolman's Discussion of the Precision of Measurements, New York, 1901, second edition, p. 69. 





