Oil the Bnglitiuss of the Corona of April 16, 1893. 405 

 Table II. 



Measures of Plate 3a (large scale). 

 Exposure 50 seconds along four radii (N., S., E., W.), 



Distance from moon's 

 limb. 



Powers of 2 representing intensity of light. 



jS". 



S. 



E. 



W. 



Diy. 

















0-0 



i I 



O O 



/ o 



7 o 



10 



1 -6 





O £i 





• • 



20 



3 -1 



1 •'7 



/ y 







30 



4-7 





7 b 





/ o 



40 



6-2 





7 4 



'7 .« 



/ 



50 



7-8 



D 1 



D O 





ft .ft 



60 



9-4 



o o 



ft .Q 

 O O 







70 



iu y 





o o 





O 4 



80 



11-5 



4 4 



O 1 



O 



4 7 



90 



13-0 



3-8 



4-6 





4-2 



100 



15-6 



3 "4 



4-0 







110 



17-2 



3-0 



3-5 





3 -1 



120 



18-7 



2-8 



3-3 



3-3 



2-4 



130 



20-3 



2 -3 



2-8 





2-8 



\^ 



21 -8 



2-5 



2-7 





■ . : • 



150 



23-4 



2-2 



2-6 





2-3 



160 



25 -0 



2-2 



2-4 



2-5 



2-2 



170 



26-5 





2-3 





1 -8 



180 



28-1 



1-9 



2-0 







190 



29-6 





1-8 





i'V 



200 



31 -2 



1*8 



1-7 



1-9 



1-6 



210 



32-8 





.. 





1-7 



220 



34-3 



l*-5 









230 



35-9 









1-2 



240 



37 -4 



1-2 



** 



1-5 



1.4 



This table shows — 



(1) The accuracy of the method. The intensity of the light is 

 clearly determinable within an error of 0-1 or 0'2, i.e.^ of 2^'^ or 2^*^, 

 which are ratios of 1*07 and 1*15 respectively. 



(2) The intensity falls off in nearly the same manner in all four 

 directions. [It may be remarked that 1893 was near a sun-spot 

 maximum, and the corona of the kind approximating to symmetry all 

 round the limb.] Such differences as there are do not arise from the 

 excentric position of the sun behind the moon ; for the photograph was 

 taken after the middle of totality, when the moon would have advanced 

 towards the east, and hence the western radius should be brighter 

 than the eastern at the same distance from moon's limb ; whereas the 

 contrary is the case. Also there is a marked difference between the 

 N. and S. radii. 



VOL. LXVI. 2 H 



