318 SIR F. W. DYSON, PROF. A. S. EDDINGTON AND MR. C. DAVIDSON ON A 



TABLE XI. Check Plates, Measures. 



The unit for x and y is 5 millimetres, which is approximately equal to 5'. The 

 differences Ax, Ay are given in units of the fifth place of decimals == 0"-003. The 

 centre of the plate is near x == 14, y = 14. 



Plate-constants were then calculated in the usual way, by the formula; 



Ax = aye -f- by -f- c 

 Ay = dx + ey +/ 



These were applied, and the residuals A&, A^y converted into arc are as follows : 



TABLE XII. Check Plates, Residuals. 



The mean residual without regard to sign is 0"-21, from which the probable error 

 of a determination of Ax or Ay is 0"-22. 



