should by so doing arrive precisely at P? on the 

 preliminary. 



1". COMPUTE CURVE DEFLECTIONS. PCi is 

 2 making the first sub-chord on the 6-degree 

 curve, 28 ft. The corresponding deflection is .28 x 

 3 = - = 50', i. e.. the tangent deflection 



for station 23 is 50 minutes. The deflection for 

 sub-chord at PC* is .99 x 240' = 238' = 3 58'. 

 The deflection for sub-chord at PTi is .99 x 180' = 

 ITS' = 2 58'. The deflection for sub-chord at 

 PTs is .58 x 2-KK = 139' = 2 19'. 



ALGORITHMS. To facilitate explanation the 

 foregoing computations have been put down in a 



Fig. 2. Design for Rulings on Computing Paper. 



rambling manner which makes the computed 

 quantiti-es hard to find when wanted. For a lon- 

 ger location tJhan this, economy of time and effort 

 requires that the routine computatibns be syste- 

 matically arranged, that like operations as well as 

 like quantities may be brought together. By this 

 means entering the data and making the computa- 

 tions in a short time become largely mechanical 

 processes, and at the end the computed quantities 

 stand in tabular order and may be quickly found 

 when wanted. For the computations of this ar- 



12 



