354 HYDROaRAPHICAL SURVEYING [chap. xv. 



The formula for this is — 



c time elapsed 



Correction = Cosec Sec lat., 



2 2 



where is liaK the change of declination in elapsed time. 



This correction is additive to the angle when the sun is 

 moving from the nearest pole, and subtractive when moving 

 towards it. 



Let us take the following example : 



At Xut A- © Pagoda A 360°. 



Alt. 



Times. 



Hor. Allele. 



h. m. e. 



8 20 14 



8 23 22 



4 02 13 



4 05 20 



15 05 30 



15 09 15 



193 24 30 



193 28 45 



Z. K. 



z.'k. 



Lat. 30° N. Declination corrected to Greenwich time of 

 a.m. observation 18° 14' N. 8un moving north. 



Mean a.m. Times 



P.M. „ 



Elapsed Time 

 h Elapsed Time 

 Yar of dec. in 1 hour 



h. m. s. 



8 21 48 



16 03 46 



7 41 58 



3 50 59 



37" -44 

 3-85 



A.M. angle 



P.M. 



Mean angle 



15 07 22 

 193 26 37 



208 33 59 

 104 16 59 



18720 

 29952 

 11232 



= 144144 



c 



Cosec. 

 Sec. lat. 



E. T. 



2-15866 



•07279 

 •06249 



2-29394 

 Cor. = 3' 17" 



196"-7 



Mean angle 



Anglo of South Point 

 Or bearing of Pagoda 



104 16 59 

 - 3 17 



104 13 42 

 S. 104 13 42 E. 



A number of similar sets, taken with different degrees as zero, 

 Avill give a very correct result, and though all instrumental errors 

 will not be eliminated, the majority of them will disappear. 



