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Astronomy. — ''Mutual occultations and eclipses of the satellites 

 of Jupiter in 1908." By Prof. J. A. C. Oudemans. 



SECOND PART. — ECLIPSES. 



(Communicated in the meeting of October 27, 1906). 



From occultations to eclipses there is but one step. 



Between the two phenomena there is this difference that, as has 

 been communicated on p. 305, the occultations have been observed 

 more than once, but that of tlie eclipses of one satellite hj another 

 we have but one, incomplete account given in a private letter of 

 Mr. Stanley Williams dated 7 December 1905. In his letter to us 

 he writes : "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'h August 1891 and was observed by Mr. J. Comas at 

 "Valls in Spain and by the writer at Hove. Mr. Comas' observation 

 "was published in die 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. 67, inch reflector, power 225. Definition 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 11''49'" a minute dark spot was seen 

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

 " "The shadow^s of satellites I. and II. were confounded together at 

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

 " "spot. At ll'i59''^ the two shadows were seen neatly separated, 

 ""thus, @® . The preceding shadow must^be that of II., the follow- 

 " "ing and )iiuch smaller one that of I.. At 12'ilO™ 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 

 " "the Red Spot Hollow, so that there could be no doubt of its 

 " "identity. It is on the north band of the north (south) equatorial 

 " "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 from my observation 

 "book. I take it that when satellite I. entered on the disc of Jupiter, 

 "it was already partly eclipsed by the shadow of II., so that it 

 "became lost to view immediately, instead of shining, as usual, for 



