( 439 ) 



Sterrenkunde. De Heer J. A. C. Oüdemans doet eene mede- 



deeling over: „Onderlinge bedekkingen en verduisteringen der 

 wachters van Jupiter in 1908." 



TWEEDE AFDEELING. — VERDUISTERINGEN. 



Medegedeeld in de vergadering van 27 October 1906. 



Om van de bedekkingen over te gaan tot de verduisteringen is 

 slechts één stap. 



Er is tusschen deze beide verschijnselen dit verschil, dat de be- 

 dekkingen, zooals boven, blz. 180, is medegedeeld, meer dan eens 

 zijn waargenomen, terwijl wij van die eener verduistering van den 

 eenen wachter door den anderen, slechts één, en dan geen volledig 

 bericht kennen uit een bijzonderen brief van den heer Stanley 

 Williams van 7 December 1906. Hij schreef ons namelijk „With 

 „regard to the heliocentric conjunctions there does seem to be one 

 .„observation of the rare phenomenon of the eclipse of a satellite 

 „in the shadow of another one on record. It occurred on the 14 th 

 „August 1901 and was observed by Mr. J. Comas at Valls in Spain 

 „and by the writer at Hove. Mr. Comas' observation was published 

 „in the French periodical L' Astronomie, 1891, p. 397 (read 398) 1), 

 „The following is an account of my observation. No particulars of 

 „this have hitherto been published. 



„ „1891 Aug. 14. 6 l / 2 inch reflector, power 225. Defmition good, 

 „ „but interruptions from cloud. Satellite I. transitted on the S. Equa- 

 „ „torial belt, (N. component). Immediately on its entering the disc 

 „ „it became lost to view. At ll h 49 m a minute dark spot was seen 

 „ „about in the position which the satellite should have then occupied. 

 „ „The shadows of satellites I. and II. were confounded together at 

 „ „this time, there seeming to be one very large, slightly oval, black 

 „ „spot. At ll h 59 m the two shadows were seen neatly separated, 

 „ „thus, $• . The preceeding shadow must be that of IL, the follo- 

 „ „wing and much smaller one that of I.. At 12 h 10 m satellite I. was 

 „ „certainly visible as a dark spot, much smaller than the shadow 

 „ „of either satellite. It had moved with respect to the shoulder of 

 „ „tlie Red Spot Hollow, so that there could be no doubt of its 

 „ „identity. It is on the north band of the north (south) ecpiatorial 

 ,, „belt 2). Satellite I. [This should evidently be II.] shines brightly 

 „ „on the disc near the limb. Definition good, but much thin cloud 

 „ „about." " 



.,The foregoing is an almost literal transcript froin my observation 



