BLUE-VIOLET LIGHT IN THE SOLAK CORONA ON AUGUST 30, 1905. 335 



The distances /t + A/i at which the corona lias the intensities t'+Ai are correlative 

 distances on corona [compare 5 (d) and (/)], where A/ = + AI-JT. 



The intensity formula for the corona ought to have been derived from the observed 

 values of h corrected by AA. 



As to the calculation of AA, I obtained the intensities of the corona from a diagram. 

 I drew six lines through C at intervals of 30 and marked off points at distances 

 (n + $)ir from C. I assume that the intensity of the corona belonging to a point thus 

 marked equals the mean intensity at all the points lying within a ring limited by 

 circles HIT and (n+l)ir and up to 15 from it. The intensity at the points was read 

 off the diagram and multiplied by f,/l2. The linear value of ir is, in unit of 10~ 3 

 solar diameter, 9'1 for screen 1, 6'5 for screen 2, 47 for screen 3, 3'2 for screen 4, 

 0'55 for full aperture. For screens 3 and 4 several rings were treated together. In 

 some directions the calculation had to extend as far as ring 80n. I calculated f by 

 the following formulae 



for large n, 



" 



J ffl ( n7r ) = 



., 1 \ 

 8nir/ 



4uir. 



For small values of u I interpolated the value of the integral from the table given 

 in MUELLER'S ' Photometric der Gestirne,' p. 166. 

 The result of the calculation is 



The systematic errors AA due to diffraction, and still more their functions t [see 

 5 (/)]> are ao sma ll compared with the accidental errors n of measurement, as 

 calculated from the residuals, that they can be neglected, and hence formula (D), 7, 

 gives the relative intensities of the corona. 



APPENDIX II. 



Comparison of Corona and Moon. 



The results contained in this section are not to be considered as an attempt to 

 standardise my eclipse plates, but they originated in a desire to give future observers 

 some ideas of the intensities with which they have to deal. 



