November i8, 1897] 



NATURE 



61 



OUR ASTRONOMICAL COLUMN. 



The November Meteors (Leonios). — Although it was 

 known that the presence of the moon would hinder materially 

 the brilliancy of the display of the members of this particular 

 meteor swarm, many hoped that the weather at least would 

 compensate us for that of last year. We were, however, 

 doomed to disappointment, and clouds were the order of the 

 night, both in London and in many other counties where 

 observers were on the watch. Mr. Denning, writing from 

 Bristol on the 15th, observes lamentably, " . . . up to the 

 present time my results are negative. November 12 was cloudy 

 all night, November 13 cloudy, except for an interval of partly 

 clear sky between ilh. 30m. and I4h., and November 14 over- 

 cast all night." 



Saturday night (November 13) in London proved really a 

 first-class night for such observations, excepting, of course, the 

 presence of the moon. It is true that white fleecy clouds 

 occasionally came rolling up from the southward, but they 

 afforded a magnificent spectacle, and soon disappeared in the 

 north, leaving the sky brilliantly clear. Three facts were im- 

 pressed on one when watching the heavens : first, the dearth of 

 meteors ; second, the great number of stars visible considering 

 the brightness of the moon ; and third, the extreme mildness 

 and absence of dew. 



In a watch lasting more or less continuously from gh. to I7h. 

 o'clock, only twenty meteors were seen, fourteen of these being 

 estimated as Leonids, three Andromedes, and two Lyrids. 



The five most brilliant' Leonids were plotted directly on a 

 star chart (Mean Equinox 1870). Three of these, when their 

 trails were prolonged backwards, converged nearly to a point 

 giving the coordinates of the radiant point as 152°, -f 25", while 

 the other two apparently emanated from 171°, -(- 19°. The 

 details of each are as follows : — 



Nc, 



G.M. 

 Time 



Coords, 

 of end 



Coords, of 

 commence- 

 ment 



h. m. 00 (. 



I... 13 50 ... 177 + 4 ... 187 - 18 

 2... 14 10 ... 184 -I-26 ... 197 +33-4 

 3 .. 14 50 ... 143-4 +22 ... 123-4 + 13 

 4... 15 30 ... 156 -(-35 ... 161 -f- 45 



Colour 



Yellowish 

 Yellow- blue 



Remarks 



Very quick 



Verj' slow, 



nucleus, 



very wavy 



166 +11 ... 182 —8-9 ... Reddish tinge A trail near 



I head just 

 I before dis- 

 V appearance 



Number 5 was somewhat unusual, falling towards the 

 south-eastern horizon very slowly, that part of the trail close to 

 the head being distinctly wavy. It may be mentioned that two 

 cameras pointed first towards the Pleiades in the earlier portion 

 f)f the evening, and towards Leo when sufficiently high in the 

 sky, recorded not a single trail, although fourteen plates were 

 exposed for forty minutes each during the time of observation. 



Jupiter's Third and Fourth Satellites. — Prof. Bar- 

 nard has communicated to the Astr. Nach. (No. 3453) some 

 most interesting observations of the third and fourth satellites of 

 Jupiter, together with a set of drawings of these bodies made both 

 out of and at the time of transit. These observations are valu- 

 able, as they can be compared with those made by Mr. Douglass, 

 and described in the Astr. Nach. (No. 3432). That they differ 

 from these latter is only natural considering the difficulty of the 

 observations themselves, but that this difference is so great and 

 fundamental is very surprising. Mr. Douglass, it will be remem- 

 bered, found that the surfaces of these two satellites were covered 

 with series of fine dark lines, measuring less than o"'i, or about 

 200 miles, and similar somewhat to those surface markings as 

 observed at his observatory upon Mars, Venus, and Mercury. 

 Prof. Barnard, on the other hand, has failed altogether to see 

 these details, although he has employed the 36-inch Lick re- 

 fractor in the attempt ; the markings he observed always ap- 

 peared to be large and more or less diffused, with the exception 

 of the white polar caps which, as he says, are exactly like those 

 of Mars. In the case of the third satellite the cap is generally 

 situated at the north limb, although on one or two occasions 

 a white southern cap has been observed. Both caps of the 

 fourth satellite have been clearly distinguished, that at the north 

 being sometimes exceptionally large, covering a surface equal to 

 one-quarter to one-third of the diameter of the satellite. 



Most interesting are the appearances and apparent changes 



NO. 1464, VOL. 57] 



of form which these satellites undergo when 111 uausii. 1 nus, 

 as regards the third satellite the transit " was very remarkable. 

 The satellite appeared as a black or very dark spot on its disc, 

 and close to the south limb of the satellite was a small, round, 

 very white spot, fully as conspicuous as I have shown it. No 

 other details were seen on it." The drawing referred to above 

 shows the satellite's disc very nearly black, the spot measuring 

 about one-sixth of the diameter of the satellite being repre- 

 .sented nearly white. The observations of Prof. Barnard show 

 fairly conclusively that the changes in form of the discs as they 

 pass across the primary are only apparent, and not due to any 

 peculiarity of shape of the satellites themselves. In fact, he 

 himself is perfectly convinced that they are caused by the 

 relative intensities of the satellite's markings in their transit over 

 those of the primary. The peculiar feature of a double dark 

 spot, or an elongated white spot shown by the first .satellite in 

 transit, is due to the fact that this body has a bright equatorial 

 region and dark poles. When transiting across a bright portion 

 of Jupiter's disc, the satellite appears like a double dark spot, 

 and when over a dark portion like an elongated white one. 



The discrepancy between the forms of the surface markings 

 on these satellites, as seen by two such observers as Mr. Douglass 

 and Prof. Barnard, is indeed remarkable, and it would be of 

 interest to know what would be the result of an interchange of 

 instruments at the time of the next oppositions. 



Comet Perrine (October 16). — The following is a con- 

 tinuation of the ephemeris of Comet Perrine for the ensuing 

 week as computed by Herr. J. Moller {Astr. Nachr., No. 



3456) :— 



\2h. Berlin M. T. 



Decl. 



logr. 



log A. 



Br. 



1897. R..\. 



h. m. s. o / 



Nov. 18 ... 18 28 14 ... -H 64 430 ... 01436 ... 9-9896 ... o'9 



19 ... 26 I ... 63 53-0 



20 ... 24 3 ... 63 46 ... 01418 ... 99993 ... 08 



21 ... 22 18 ... 62 177 



22 .. 20 43 ... 61 32*3 ... 0"i403 ... 00089 ••• 08 



23 ... 19 17 ... 60 483 



24 ... 17 59 ... 60 57 ... 0-1388 ... 00184 ••• o'S 



25 ... 16 49 ... 5924-6 



26 ... 18 15 45 ... +58 44-8 ... 0-1376 ... 0-0278 ... 0-7 



The Variable Star j8 Lyr.'e. — If Argelander's formula 

 be used for the determination of the times of minima and 

 maxima of this variable star, it will be found that the.se times do 

 not exactly correspond with those now observed. Herr Panne- 

 koek has recently undertaken to investigate the cause of this dis- 

 crepancy, and has published his results in the Koninklyke 

 Akademie van Wet ensc happen te Amsterdam (vol. v. No. 7). 

 A brief account of the main results are, however, contributed 

 to the Astronomische Nachrichten (No. 3546). The improved 

 formula for determining the times of the principal minima is given 

 by Herr Pannekoek as 



1855 Jan. 6, 604 Greenwich M.T. -i- 12 90S009 E 



+ o 000003855 E^ o 000000000047 E', 



and he adds a table, which facilitates greatly this computation, 

 containing every twentieth minimum from E = - 500 (1837) 

 to E - -4- 1500 (1908). ■ 



To determine the amount, if any, of a variation in the light 

 curve, Herr Pannekoek divided the period of observation into 

 two parts, before and after 1870, and obtained two sets of mean 

 values for the mantissje of the principal points reckoned from a 

 principal minimum : 



ist ma.\. 2nd min. 2nd max. 



d. d. d. 



184.2-1870 ... 3-12 ... 5-40 ... 9-54 

 1870-1895 ... 3-32 ... 6-48 ... 973 



This showed that the difiFerence between the intervals from the 

 principal minimum in the case of the maxima was quite apparent, 

 while in the case of the secondary minimum it was comparatively 

 small. It is pointed out, however, that a possible cause may 

 be due to different methods of curve-drawing, some observers 

 drawing the curves .symmetrically, and others not. The curves, 

 he finds, further show small irregularities in intensity somewhat 

 of the same kind as those observed in rj Aquilre, which render 

 uncertain the times of first maximum and principal minimum. 

 Herr Pannekoek finds that only the variation in the time of the 

 maxima can be put down to causes other than those of errors of 

 observation and drawing. 



