( 448 ) 



partie dn diamètre. Dans cette supposition la distance minima des 

 centres des deux onibres a du avoir lieu vers 11''47'" et Ie premier 

 contact vers 11''37'". Le premier satellite pénétra dans Ie disque de 

 la planète a 11^42"^ comme j'ai dit plus haut, done l'éclipse a com- 

 mence quand le satellite se prqjetait encore dans l'espace, cinq 

 minutes avant l'immersion. 



L'invisibilité de l'ombre d'Europe sur lo peut s'expliquer par la 

 mauvaise qualité des images. Toutefois, la pénombre et l'ombre du 

 II satellite ont été suffisantes pour diminuer notablement l'éclat du 

 premier. 



(2) The meaning evidently is that, as seen in an inverting tele- 

 scope the dark spot seemed to be situated on the North band of the 

 North belt, but that in reality it was on the vSouth band of the South 

 belt. It is well known that the so-called Red ^ipot is there situated. 



(3) The author does not refer here to the visibility of a shadow 

 of II on I. This may be explained, in my opinion, by irradiation and 

 diffraction. 



(4) According to the tables of Damoiseau, second part, the time of 

 the heliocentric conjunction of the two satellites is 23"45''^ civil time 

 Paris = 11"36'" Greenwich. In the Nautical Almanac of 1891 we 

 find the following data for 14 August : 



II Shadow. Ingress 10''51'^i M. T. Grw. 



I Transit ,, 11 33 ,, ,, ,, 



II „ „ 11 58 „ „ „ 



I Shadow. Egress 13 18 ,, ,, ,, 



If from the 1^' , 2"*^, 5'^^^ and 6''' line we compute the time at 

 which the shadows must coincide we get 11»31'". This result differs 

 by 5^ from that found just now. We have to consider, however, 

 that the two satellites went the same way, and that their relative 

 motion in five minutes, consequently also that of their shadows, was 

 very minute. 



Mr. Stanley Williams seems not to have perceived a shadow 

 before II '49" M. T. Greenwich; Mr. Comas already saw an oblong 

 shadow at ll''43^20' M. T. Greenwich. For the rest Mr. Stanley 



