198 



Prof. 0. Pritchard. 



number, viz., those given in the following tables, and of which the 

 magnitudes are given in the " Uranometria Nova Oxoniensis." 



Fig. 1. 



The curve having been formed as described, and practically repre- 

 sented above, then for each integral magnitude, such as I^M^ D 2 M 3 , 

 the corresponding diameter 0D 2 OD 3 was read off the curve itself, and 

 the following equations of condition resulted. 



log 3 [0-47712] 



=fi- 



30-ooa 



55 



4 [0-60206] 



=/*— 



23*495 



55 



5 [0-69897] 



-f x ~ 



18-695 



5) 



6 [0-77815] 



=/*- 



14-885 



5) 



7 [0-84510] 





11-585 



55 



8 [0-90309] 



=fi- 



9-005 



55 



9 [0-95424] 



=/*- 



7-385 



A solution of these equations reduces the fundamental equation 

 (1) to- 



logy=log 12-82-0-02157^ (A) 



The other two plates, similarly discussed, but each being absolutely 

 independent in its results from the others, give — 



lo g2/ =log 12-63-0-0216aj (B) 



„ 2/=logll-69-0-0247^ (C) 



From this investigation it may be gathered that the magnitude of 

 the star which was commencing to form its photographic image on the 



