15 



361 



Table 9. 



Specira of III''' order. 



I 





1 V _ in 













diameter 

 of central 



mn 



o •^ a3 CIS "a 



number of 



differences 



used 



square of 



mean error 



(m. e.)2 





weight 





image 











^2 ^5 







observed 



smoothed 



reduced 



mm 



ß 





/.2 



m-2 



m-2 



m-2 



■14 



+ 31 









— 



8 







•15 



+ 25 







— 



— 



12 







•16 



+ 21 



10 



1008 



23 



16 



2 



•17 



+ 18 



4 



736 



31 



22 



4 



•18 



+ 15 



18 



762 



30 



27 



8 



•19 



+ 12^ 



16 



311 



74 



33 



14 



•20 



+ 10 



34 



592 



39 



39 



22 



•21 



+ 8 



9 



355 



65 



46 



31 



•22 



+ 5- 



50 



464 



50 



53 



42 



•23 



+ 3^ 



26 



410 



56 



59 



52 



•24 



+ 2 



56 



369 



63 



63 



61 



•25 







18 



325 



71 



66 



66 



•26 



— 1- 



30 



201 



115 



68 



67 



•27 



— 3- 



13 



363 



64 



70 



65 



•28 



— 5 



20 



303 



76 



70 



60 



•29 



— 6- 



5 



137 



169 



71 



55 



•30 



— 8 



22 



508 



45 



71 



48 



•31 



— 9^ 



10 



327 



71 



71 



42 



•32 



— 11 



26 



234 



99 



72 



36 



•33 



— 12 



7 



531 



43 



72 



30 



■34 



-13- 



32 



444 



52 



72 



25 



•35 



-14- 



10 



220 



105 



72 



19 



•36 



— 16 



24 



177 



131 



73 



15 



•37 



— 17 



5 



713 



32 



73 



12 



■38 



— 18^ 



22 



339 



68 



73 



9 



■39 



— 19^ 



6 



204 



113 



73 



6 



•40 



-20^ 



16 



274 



84 



73 



3 



■41 



— 22 



4 



148 



156 



73 



1 



•42 



— 23 



3 



423 



55 



73 







•43 



— 24 







— 



— 



— 







•44 



— 25 



1 



312 



74 



— 







•45 



-26- 



1 



312 



74 



— 







The spectra of the IIP'' order were measured on 1262 images, the total weight 

 of the resulting colour equivalents being 45766 m~^. 



10. Relation between Effective Wavelength and Colour Index. 



As normal colour indices the /h values of the Göttingen Actinometry were 

 chosen. These Ir values are meant to represent the differences between the photo- 

 graphic Göttingen magnitude and the visual magnitude on the Harvard scale. In 

 stead of simply giving the effective wavelengths in Angström units, as I have previ- 

 ously done, I have in the present paper reduced them all to the /h system of 

 colour indices. 



